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Cited by 422Retinal Development and DisordersRetinal Diseases and TreatmentsRetinal Imaging and Analysis

The cell biology of the retinal pigment epithelium

Open access
Lakkaraju, Aparna, Umapathy, Ankita, Tan, Li Xuan, Daniele, Lauren, Philp, Nancy J., Boesze-Battaglia, Kathleen, Williams, David S.·2020·Progress in Retinal and Eye Research
DOI 10.1016/j.preteyeres.2020.100846PMC PMC8941496
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Abstract

The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.

AI snapshot

Written from the paper’s full text.

TL;DR

This review synthesizes RPE cell biology, emphasizing outer segment phagocytosis, LC3-associated phagocytosis, classical autophagy, organelle function, and metabolic coupling with photoreceptors. It argues that appropriate, well-polarized RPE models and live-cell imaging are essential for understanding RPE health and retinal disease.

Key findings

  • The RPE is a post-mitotic, polarized monolayer that supports photoreceptors; in the central human retina, ~33 photoreceptors are associated with each RPE cell, while the mouse central retina has >200 per RPE cell and peripheral ratios are ~12 in human and 100–120 in mouse.
  • OS phagocytosis follows a daily rhythm: rod OS phagosomes peak after light onset, cone OS phagosomes vary by species, and mouse/zebrafish RPE can show two peaks after light onset and lights-off. Phagosome degradation involves apical-to-basal migration, acidification, and proteases including cathepsin D and cysteine proteases; LAP recruits LC3B to ~30–45% of ingested phagosomes in vitro/in vivo, though GFP-LC3B overexpression yields 80–90%.
  • Autophagy and endolysosomal defects are linked to AMD and inherited retinal degenerations; RPE-specific loss of RB1CC1 causes RPE atrophy by 4 months, and RPE-specific Atg5 or Atg7 deletions produce retinal degeneration in 35–45% of mice between 8 and 24 months.
  • RPE metabolism is oxidative and coupled to photoreceptors: OSs are ~50% protein and 50% lipid by weight, and in human fetal RPE, ~50% of palmitate-derived acetyl-CoA is diverted to ketogenesis to produce β-hydroxybutyrate; Hmgcs2 transcripts are 30% higher and PGC-1 is 50% higher at 1.5 versus 9 h after light onset.

Methods

  • Narrative review integrating decades of published RPE cell biology, with no primary experimental data reported.
  • Discusses experimental preparations including RPE/choroid/sclera flatmounts, primary RPE cultures from rodent/pig/human sources, stem cell-derived RPE, and cell lines such as RPE-J, hTERT-RPE1, and ARPE-19, often on Transwell filters for polarization and live-cell imaging.
  • Main analysis is a synthesis of mechanisms across OS phagocytosis, LAP, classical autophagy, organelle biology, and RPE-photoreceptor metabolism, with emphasis on model selection and appropriate techniques.

Limitations

  • The paper states model limitations: flatmounts remain useful for only hours; primary human RPE has limited tissue availability and dedifferentiates with passaging; stem cell-derived RPE has inefficient transfection and limited passaging before failing to re-differentiate; ARPE-19 has genetic abnormalities and diminished differentiation with passage; in vitro metabolism does not recapitulate the in vivo RPE environment.
  • The paper identifies many open questions, including what distinguishes LC3-associated OS phagosomes, how autophagy is scaled to diurnal phagocytosis, how the organelle interactome changes with age/disease, and the need for in vivo RPE metabolic studies.
  • Evident from the text: as a narrative review, it does not conduct a systematic search or meta-analysis and reports no new experimental data; conclusions depend on cited studies and model-dependent findings.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.preteyeres.2020.100846

Cites

379 of 379 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

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  • Premisecitation

    Polarized expression of ion pumps and channels in the RPE helps regulate the environment around photoreceptors, which is important for photoreceptor electrophysiology and viability.

    “In addition to Na+/K+-ATPase, polarized expression of other ion pumps and channels help regulate the environment around the photoreceptors, which is important for photoreceptor electrophysiology and viability (Wimmers et al., 2007).”
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  • Premisecitation

    Electroporation or nucleofection yields transfection efficiencies of ~20-40% in primary RPE.

    “However, electroporation or nucleofection has been reported to yield transfection efficiencies of ~20–40% (Toops et al., 2014).”
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    • cites Toops et al., 2014 source

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  • Premisecitation

    In the human eye, each RPE cell takes care of ~30 photoreceptors.

    “In the human eye, each RPE cell takes care of ~30 photoreceptors (Osterberg, 1935), which places a unique burden on the degradative machinery of the cell.”
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    • cites Osterberg, 1935

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  • Premisereasoning

    Non-viral lipid-based gene transfection is less efficient in primary RPE due to their post-mitotic nature.

    “Second, non-viral lipid-based gene transfection is less efficient in primary RPE due to their post-mitotic nature.”
    Quote in the paperNot a substantial claim
  • Premisecitation

    Published protocols using directed approaches provide relatively efficient differentiation into cultures of cells reported to possess a wide range of RPE characteristics, including gene expression, polarized organization, and physiological and cell biological functions.

    “There are now published protocols using directed approaches that provide relatively efficient differentiation into cultures of cells, reported to possess a wide range of RPE characteristics, including gene expression, polarized organization, and physiological and cell biological functions (Idelson et al., 2009; Buchholz et al., 2013; Gong et al., 2015; Maruotti et al., 2015; Hazim et al., 2017).”
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    • cites Idelson et al., 2009 source

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    • cites Buchholz et al., 2013 source

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    • cites Gong et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Findingown data

    High passage-number cultures of RPE cells from human ESCs and iPSCs undergo dedifferentiation.

    “Although not explicitly reported in the literature, we have observed high passage-number cultures of RPE cells from human ESCs and iPSCs undergoing dedifferentiation.”
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    Findingown data

    ARPE-19 cells remain a widely used cell line, with ~170 papers published annually that mention "ARPE-19" or "ARPE19" in the title or abstract.

    “Nevertheless, the ARPE-19 cells remain a widely used cell line, with ~170 papers published annually that mention “ARPE-19” or “ARPE19” in the title or abstract (based on a current PubMed search), and, presumably, many others that still report experiments on the ARPE-19 cells, but may not mention the cell line by name in the abstract.”
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    Premisecitation

    Primary rodent RPE cultures can survive up to 10 days and are amenable to experimental manipulations including transfection, transduction, and live-cell imaging.

    “These cultures can survive up to 10 days and are amenable to experimental manipulations including transfection, transduction, and live-cell imaging (Gibbs et al., 2003).”
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    Interpretationreasoning

    A very high TER may be a characteristic of fetal RPE, and thus a potential drawback for modeling adult RPE.

    “Nevertheless, a very high TER may be a characteristic of fetal RPE, and thus a potential drawback for modeling adult RPE.”
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    Premisecitation

    Primary porcine RPE cultures grown on Transwell filters exhibit correct localization of tight junction markers such as ZO-1 and have a TER of ~400 Ω cm2 as early as 2 weeks in culture.

    “Primary porcine RPE cultures, grown on Transwell filters, exhibit correct localization of tight junction markers, such as ZO-1, and have a TER of ~400 Ω cm2, as early as 2 weeks in culture (Toops et al., 2014).”
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    • cites Toops et al., 2014 source

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    Premisecitation

    Humans and pigs share similarities with regards to their immune systems, which is an advantage for studying diseases with a strong immune component like AMD.

    “Moreover, an advantage of porcine eyes is that humans and pigs share similarities with regards to their immune systems, which is an advantage for studying diseases with a strong immune component like age-related macular degeneration (AMD) (Mair et al., 2014).”
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    Premisenone given

    A freshly-prepared RPE/choroid/sclera flatmount represents a close in situ approximation to in vivo RPE.

    “A freshly-prepared RPE/choroid/sclera flatmount represents a close in situ approximation to in vivo RPE.”
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    Premisenone given

    Certain genes associated with human disease, such as the three different human-specific isoforms of apolipoprotein E, are not expressed in mice, pigs, or cattle.

    “First, certain genes associated with human disease, such as the three different human-specific isoforms of apolipoprotein E, are not expressed in mice, pigs, or cattle, making it necessary to genetically modify these cells or to perform certain studies in human tissues.”
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    Premisecitation

    Primary RPE, iPS-RPE, and ES-RPE cells can form well-differentiated, RPE-like cultures, demonstrating a polarized epithelial organization, close approximation of native RPE gene and protein expression, and the ability to perform RPE functions such as ingestion and degradation of OSs over a time-course comparable to in vivo.

    “An important characteristic of primary RPE, iPS-RPE, and ES-RPE cells is that they can form well-differentiated, RPE-like cultures, demonstrating a polarized epithelial organization (Fig. 2), close approximation of native RPE gene and protein expression, and the ability to perform RPE functions, such as the ingestion and degradation of OSs over a time-course that is comparable to that in vivo (Mam”
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    • cites Strunnikova et al., 2010 source

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    • cites Blenkinsop et al., 2013 source

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    Interpretationreasoning

    Apical localization of Na+/K+-ATPase is likely important for spatial buffering of ions in the subretinal space and for depolarizing the photoreceptor plasma membrane during phototransduction.

    “Apical localization of Na+/K+-ATPase is likely to be important for spatial buffering of ions in the subretinal space and for depolarizing the photoreceptor plasma membrane during phototransduction.”
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    Premisecitation

    ESCs and iPSCs can spontaneously differentiate along the neural lineage and then to RPE cells, which are readily identified by pigmentation and cobblestone appearance.

    “ESCs and iPSCs can spontaneously differentiate along the neural lineage, and then to RPE cells, which are readily identified by virtue of pigmentation and cobblestone appearance (Kawasaki et al., 2002; Buchholz et al., 2009) (Fig. 4).”
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    • cites Buchholz et al., 2009 source

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    Interpretationnone given

    Crosstalk between lysosomal clearance of OSs, autophagic machinery, endosomal network, and oxidative metabolism is essential for maintaining RPE health and function.

    “As discussed below, crosstalk between lysosomal clearance of OSs, autophagic machinery and the endosomal network, as well as oxidative metabolism, is essential for maintaining RPE health and function.”
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    Premisenone given

    Flatmounts maintain many of their characteristics in culture medium for only a matter of hours, so many manipulations are not practicable.

    “A limitation of these flatmounts is that they maintain many of their characteristics in culture medium for only a matter of hours, so that many manipulations are not practicable.”
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    Premisecitation

    Addition of pyruvate in high-glucose DMEM causes ARPE-19 cells to recapitulate key features of RPE cells including RPE-specific differentiation markers, polygonal morphology, polar expression of proteins, extensive microvilli, the ability to phagocytose, and secretion of VEGF.

    “With the addition of pyruvate in high-glucose DMEM, it was shown that ARPE-19 cells recapitulated key features of RPE cells including RPE-specific differentiation markers, polygonal morphology, polar expression of proteins, extensive microvilli, the ability to phagocytose, and secretion of VEGF (Ahmado et al., 2011).”
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    Premisecitation

    ARPE-19 and D407 lines have genetic abnormalities, with triploidy in D407 and an abnormal karyotype in ARPE-19.

    “However, these cell lines have genetic abnormalities, with triploidy in the D407 line (Davis et al., 1995), and an abnormal karyotype (most notably, a loss of one copy of chromosome 15, and an unbalanced translocation between the chromosome 15q and 19q) in the ARPE-19 line (Fasler-Kan et al., 2018; Hazim et al., 2019).”
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    • cites Davis et al., 1995

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    • cites Hazim et al., 2019 source

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    Premisecitation

    Most animals (including mouse, rat, cat, hamster, Xenopus laevis, goldfish, rabbit, and chick) appear to be entrained to a circadian rhythm, which is cued by the light/dark cycle and persists even when the animal is maintained in absolute darkness, but not in absolute light.

    “Most animals (including mouse, rat, cat, hamster, Xenopus laevis, goldfish, rabbit, and chick) appear to be entrained to a circadian rhythm, which is cued by the light/dark cycle and persists even when the animal is maintained in absolute darkness (LaVail, 1976; Besharse et al., 1977; Grace et al., 1996), but not in absolute light (Teirstein et al., 1980).”
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    • cites LaVail, 1976 source

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    • cites Besharse et al., 1977 source

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    Premisecitation

    General disadvantages of stem cell-derived cultures include inefficient transfection (although not viral transduction) and the limited number of times they can be passaged before failing to re-differentiate fully into RPE cells.

    “General disadvantages of stem cell-derived cultures, like those of primary cultures, include inefficient transfection (although not viral transduction), as well as the limited number of times they can be passaged before failing to re-differentiate fully into RPE cells (Adijanto and Philp, 2014).”
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    • cites Adijanto and Philp, 2014

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    Premisenone given

    hTERT-RPE1 cells do not develop polarity and a "cobblestone" organization typical of well-differentiated RPE monolayers.

    “However, they do not develop polarity and a “cobblestone” organization that is typical of well-differentiated RPE monolayers.”
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    Premisecitation

    The model of choice is dictated by the scientific question; cells should be RPE-like with respect to characteristics that are central to the mechanisms to be studied.

    “The model of choice is dictated by the scientific question; to begin with, the cells should be RPE-like with respect to characteristics that are central to the mechanisms to be studied (Pfeffer and Philp, 2014).”
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    Premisenone given

    The overall process of phagocytosis involves a series of stages: binding between the OS plasma membrane and the apical membrane of the RPE, formation of a phagocytic cup around the distal OS, ingestion and transport into the cell, and degradation following interactions with endolysosomes.

    “The overall process of phagocytosis involves a series of stages. A prerequisite binding between the OS plasma membrane and the apical membrane of the RPE is followed by the formation of a phagocytic cup around the distal OS. The distal tip of the OS is then ingested and transported into the cell. The phagosome is degraded following interactions with endolysosomes, a process that appears to involve”
    Quote in the paperNot a substantial claim

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    Premisecitation

    Across species, rod OS phagosomes are most abundant just after light onset, whereas cone OS phagosomes, depending on the species, appear at the same time as rod OS phagosomes, or demonstrate a peak of phagocytosis just after lights-off, as in lizard, chicken, goldfish, and ground squirrels.

    “Across species, rod OS phagosomes are most abundant just after light onset, whereas cone OS phagosomes, depending on the species, appear at the same time as rod OS phagosomes, or demonstrate a peak of phagocytosis just after lights-off, as in lizard, chicken, goldfish, and ground squirrels (Young, 1977, 1978; Ruggiero and Finnemann, 2014).”
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    • cites Young, 1978

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    • cites Ruggiero and Finnemann, 2014

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    Premisenone given

    Immortalized or transformed RPE cell lines differ from RPE in vivo in that they must proliferate.

    “Immortalized or transformed RPE cell lines, of course, differ in one major respect from RPE in vivo; that is, they must proliferate.”
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    Premisecitation

    The pyruvate protocol for ARPE-19 differentiation required 3-4 months, whereas a more recent protocol achieved similar differentiation within 4 weeks through addition of nicotinamide instead of pyruvate.

    “These protocols required 3–4 months for RPE differentiation, whereas, a more recent protocol was able to achieve a similar level of differentiation within 4 weeks through the addition of nicotinamide instead of pyruvate (Hazim et al., 2019) (Fig. 5).”
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    • cites Hazim et al., 2019 source

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    Premisecitation

    In the frog, Rana pipiens, there is a strong dependency on external light stimuli to initiate OS phagocytosis; complete darkness prevents phagocytosis.

    “In other animals, like the frog, Rana pipiens, there is a strong dependency on external light stimuli to initiate OS phagocytosis; complete darkness prevents phagocytosis (Basinger et al., 1976).”
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    • cites Basinger et al., 1976 source

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    Premisecitation

    Expression of "RPE signature" genes is important; however, more importantly, the resulting proteins must be localized properly; e.g. the Na+/K+-ATPase should be in the apical membrane.

    “Expression of “RPE signature” genes is important (Strunnikova et al., 2010); however, more importantly, the resulting proteins must be localized properly; e.g. the Na+/K+-ATPase should be in the apical membrane (not basal as is the case in RPE-J cells).”
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    Premisecitation

    hTERT-RPE1 cells express some RPE-associated proteins and become pigmented in the absence of serum after 4 or 8 weeks in culture.

    “They have been reported to express some RPE-associated proteins (e.g. cellular retinaldehyde-binding protein [CRALBP]) and become pigmented in the absence of serum after 4 or 8 weeks in culture (Rambhatla et al., 2002).”
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    Premisecitation

    Disruption of the suprachiasmatic nucleus did not abrogate the daily schedule of the number of OS phagosomes, and cues for OS phagocytosis were concluded to be intrinsic to the eye.

    “A few studies found that disruption of this region did not abrogate the daily schedule of the number of OS phagosomes and concluded that cues for OS phagocytosis were intrinsic to the eye (Currie et al., 1978; Hollyfield and Basinger, 1978; LaVail and Ward, 1978; Tamai et al., 1978; Besharse and Dunis, 1983; Terman et al., 1993).”
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    • cites Currie et al., 1978 source

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    • cites Hollyfield and Basinger, 1978

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    • cites LaVail and Ward, 1978

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    Premisecitation

    Polarity and differentiation of RPE cultures are influenced by the source of the cells, plating density, and the substrate on which the cells are grown.

    “Polarity and differentiation are not only influenced by the source of the cells (transformed, primary, stem cell-derived), but also by plating density (Adijanto and Philp, 2014; Toops et al., 2014), and the substrate on which the cells are grown (Opas, 1989).”
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    Premisecitation

    Blockage of the rat pineal gland with reserpine prevented the sudden increase in phagosome number that occurs after light onset, suggesting some extraocular influence on circadian OS phagocytosis.

    “However, in his original paper, LaVail showed that blockage of the rat pineal gland with reserpine prevented the sudden increase in phagosome number that occurs after light onset (LaVail, 1976), suggesting some extraocular influence on circadian OS phagocytosis.”
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    • cites LaVail, 1976 source

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    Premisecitation

    Growth of ARPE-19 cells on extracellular matrix-rich membranes such as porcine lens capsule yields cells with improved phagocytosis and TER values reaching 200 Ω cm2.

    “The second method of ARPE-19 cell differentiation is the growth of cells on extracellular matrix-rich membranes such as porcine lens capsule (Turowski et al., 2004). Such cells have been reported to have improved phagocytosis and TER values reaching 200 Ω cm2.”
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    Premisenone given

    Many published studies have used poor culture conditions, so that the cell cultures bear little resemblance to an epithelium, let alone the retinal pigment epithelium.

    “However, a significant problem is that many published studies have used poor culture conditions, so that the cell cultures bear little resemblance to an epithelium, let alone the retinal pigment epithelium.”
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    Premisenone given

    A differentiated RPE cell's polarity characteristics include an apical membrane containing MERTK and αvβ5 integrin, an actin-rich apical domain, and a cell body with epithelial microtubule organization and organelle distribution.

    “An apical membrane, containing receptors such as Mer tyrosine kinase (MERTK) and αvβ5 integrin, an actin-rich apical domain, and a cell body, with an epithelial microtubule organization and organelle distribution, are all polarity characteristics of a differentiated RPE cell”
    Quote in the paperSubstantial claim

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    Premisecitation

    RPE-J cells routinely require pulses that are several hours long, with the binding phase requiring 2 h and subsequent ingestion another 2-3 h.

    “Studies utilizing RPE-J cells routinely require pulses that are several hours long, with one study noting that the binding phase requires 2 h and subsequent ingestion another 2–3 h (Finnemann et al., 1997).”
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    • cites Finnemann et al., 1997

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    Premisecitation

    In a netcasting spider, nearly all the phototransductive membrane is shed following dawn, and the rhabdomeres are essentially entirely resynthesized at dusk.

    “In a netcasting spider, which detects its prey by visual cues in dense rainforest at night, nearly all the phototransductive membrane is shed following dawn, and the rhabdomeres are then, essentially, entirely resynthesized at dusk (Blest, 1978).”
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    • cites Blest, 1978

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    Premisecitation

    Different classes of phospholipids may be effective ligands for RPE phagocytic receptors.

    “Early evidence suggested that different classes of phospholipids may be effective ligands for RPE phagocytic receptors (Effron et al., 1981).”
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    • cites Effron et al., 1981

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    Premisecitation

    External PS on OSs is bound by MFGE8 which serves as the ligand for αvβ5 integrin residing in the apical RPE.

    “External PS on OSs is bound by milk fat globule E8 (MFGE8) which, in turn, serves as the ligand for αvβ5 integrin, residing in the apical RPE (Finnemann et al., 1997).”
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    • cites Finnemann et al., 1997

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    Interpretationcitation

    Human, rat, and mouse RPE cells in culture can phagocytose OS membrane isolated from retinas of mice, rats, cows or pigs, with no obvious differences among species, suggesting mechanistic robustness across species.

    “However, human, rat, and mouse RPE cells in culture can phagocytose OS membrane isolated from retinas of mice, rats, cows or pigs, with no obvious differences among species, suggesting mechanistic robustness across species (Mazzoni et al., 2014)”
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    • cites Mazzoni et al., 2014 source

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    Premisecitation

    MFGE8 protein levels in the retina are highest around light onset and decrease thereafter, coinciding with the phagocytic burst.

    “MFGE8 protein levels in the retina are highest around light onset and decrease thereafter, thus coinciding with the phagocytic burst (Ruggiero and Finnemann, 2014).”
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    • cites Ruggiero and Finnemann, 2014

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    Premisecitation

    Primary rat RPE cultures exhibited specificity for phagocytosis of isolated rat OSs; compared with red blood cells, levels of OS binding and OS ingestion were 250 and 970 times greater, respectively.

    “Primary rat RPE cultures exhibited a specificity for phagocytosis of isolated rat OSs; compared with red blood cells, levels of OS binding and OS ingestion were 250 and 970 times, respectively, greater (Mayerson and Hall, 1986).”
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    • cites Mayerson and Hall, 1986

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    Premisecitation

    Phosphatidylserine is the classic 'eat-me' signal displayed by apoptotic cells and is recognized by surface receptors on various phagocytic cells.

    “phosphatidylserine (PS) has been widely studied as a phagocytic ligand; it is the classic ‘eat-me’ signal displayed by apoptotic cells and it is recognized by surface receptors on various phagocytic cells (Segawa and Nagata, 2015).”
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    • cites Segawa and Nagata, 2015

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    Premisenone given

    OS phagocytosis involves mechanisms that are specific for OSs.

    “- OS phagocytosis involves mechanisms that are specific for OSs.”
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    Interpretationreasoning

    With highly differentiated cultures, there appears to be a latency period prior to binding, likely due to extensive microvilli impeding the association of suspended OSs with RPE membrane receptors.

    “although, with highly differentiated cultures, there appears to be a latency period prior to binding, likely due to the extensive microvilli impeding the association of suspended OSs with RPE membrane receptors.”
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    Premisecitation

    Analysis of two locust species that migrate at night found that the rhabdomeral cross-sectional area was 5-fold greater at night than during the day, providing a concomitant increase in photoreceptor sensitivity at the expense of spatial resolution.

    “Analysis of two locust species that migrate at night found that the rhabdomeral cross-sectional area was 5-fold greater at night than during the day (Williams, 1982a, b), providing a concomitant increase in photoreceptor sensitivity at the expense of spatial resolution (Williams, 1983).”
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    • cites Williams, 1982a

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    • cites Williams, 1982b

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    • cites Williams, 1983 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In the center of a mouse retina, there are more than 200 photoreceptors for every RPE cell; the ratio decreases to ~12 in the periphery of the human retina and 100-120 in the periphery of a mouse retina.

    “In the central human retina, there are 33 photoreceptors associated with each RPE cell (Osterberg, 1935), and, in the center of a mouse retina, there are more than 200 photoreceptors for every RPE cell (Volland et al., 2015); the ratio decreases to ~12 in the periphery of the human retina and 100–120 in the periphery of a mouse retina (Volland et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Volland et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Most of the phototransductive membrane of nocturnal arthropods lasts half a day, a considerably shorter time than the 10-50 days for the disk membranes of vertebrates.

    “Most of the phototransductive membrane of nocturnal arthropods therefore lasts half a day, a considerably shorter time than the 10–50 days for the disk membranes of vertebrates (Young, 1967; Young and Bok, 1969).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Young, 1967 source

      Not checked in the free run.

    • cites Young and Bok, 1969

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning

    In arthropods, phototransductive membrane is microvillar and forms rhabdomeres, which are comparable to the outer segments of vertebrate photoreceptors.

    “In arthropods, phototransductive membrane is microvillar and forms rhabdomeres, which are comparable to the outer segments of vertebrate photoreceptors; the closely packed microvillar membrane provides an alternative way to form a structure that contains a high concentration of opsin and other phototransductive proteins.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Each OS phagosome contains densely packed membranes, but represents only 10% of the OS in mammals such as mouse and rat, and ~2% in the frog, Rana.

    “While each OS phagosome contains densely packed membranes, it represents only 10% of the OS in mammals, such as mouse and rat, and ~2% in the frog, Rana (Young, 1967; Young and Bok, 1969).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Young, 1967 source

      Not checked in the free run.

    • cites Young and Bok, 1969

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Arthropod photoreceptors typically degrade their own shed phototransductive membrane.

    “Arthropod photoreceptors typically degrade their own shed phototransductive membrane.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Lowering the temperature at which cells are fed OSs to 17-20 °C permits binding but blocks ingestion.

    “The timing of ingestion can be controlled by lowering the temperature at which cells are fed OSs to 17–20 °C (Hall and Abrams, 1987). This cooler temperature permits binding but blocks ingestion.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hall and Abrams, 1987

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Adult rat RPE expresses two different αv integrins, αvβ3 and αvβ5, although only αvβ5 facilitates OS binding and localizes to the apical surface.

    “Adult rat RPE expresses two different αv integrins, αvβ3 and αvβ5 (Finnemann and Rodriguez-Boulan, 1999), although only αvβ5 facilitates OS binding and localizes to the apical surface (Finnemann et al., 1997).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Finnemann and Rodriguez-Boulan, 1999

      Not checked in the free run.

    • cites Finnemann et al., 1997

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    ATP8A2 is localized to OS disk membranes and translocates PS and, to a much lesser extent, phosphatidylethanolamine, implicating the enzyme in maintaining PS asymmetry in the OS.

    “One such flippase, ATP8A2, has been localized to OS disk membranes and shown to translocate PS and, to a much lesser extent, phosphatidylethanolamine, implicating the enzyme in maintaining PS asymmetry in the OS (Coleman et al., 2009).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Coleman et al., 2009 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The vast majority of phototransductive membrane is turned over each day in nocturnal arthropods.

    “The vast majority of phototransductive membrane is turned over each day in nocturnal arthropods.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    MERTK is required for ingestion and is activated through αvβ5 integrin engagement and binding to Gas6/Protein S ligands.

    “- MERTK is required for ingestion and is activated through αvβ5 integrin engagement and binding to Gas6/Protein S ligands.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    TYRO3 and CD36 may be additional pathways mediating OS ingestion.

    “- TYRO3 and CD36 may be additional pathways mediating OS ingestion.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Release of a packet of disk membranes from the OS tip requires the RPE.

    “- Release of a packet of disk membranes from the OS tip requires the RPE.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    OS phagocytosis is arrhythmic, but not blocked in Mfge8−/− mice.

    “OS phagocytosis is similarly arrhythmic, but not blocked in Mfge8−/− mice (Nandrot et al., 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot et al., 2007 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    CD36 is not required for OS binding but is involved in phagosome engulfment, possibly as a signaling molecule, as antibodies against CD36 inhibited OS membrane ingestion by RPE cells.

    “The lipid receptor, CD36, is not required for OS binding but is involved in phagosome engulfment, possibly as a signaling molecule (Finnemann and Silverstein, 2001), as antibodies against CD36 inhibited OS membrane ingestion by RPE cells (Ryeom et al., 1996).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Finnemann and Silverstein, 2001

      Not checked in the free run.

    • cites Ryeom et al., 1996 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Actin rearrangement is required for formation of the phagocytic cup and phagosome ingestion.

    “- Actin rearrangement is required for formation of the phagocytic cup and phagosome ingestion.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    CD36 functions in OS membrane uptake during normal conditions, also recognizes oxidized phospholipids, and may be functionally advantageous under oxidative stress as an aid for the MERTK pathway.

    “Although CD36 functions in OS membrane uptake during normal conditions (Ryeom et al., 1996), it also recognizes oxidized phospholipids, such as oxidized PS and oxidized phosphatidylcholine, and may be functionally advantageous under oxidative stress (e.g., from intense light exposure) as an aid for the MERTK pathway (Greenberg et al., 2006; Sun et al., 2006).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Ryeom et al., 1996 source

      Not checked in the free run.

    • cites Greenberg et al., 2006 source

      Not checked in the free run.

    • cites Sun et al., 2006 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The interaction between αvβ5 and OS binding is specific as antibodies against the integrin block OS binding, but not the binding or uptake of latex beads.

    “The interaction between αvβ5 and OS binding is specific as antibodies against the integrin block OS binding, but not the binding or uptake of latex beads (Finnemann et al., 1997).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Finnemann et al., 1997

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    MERTK plays a key role in a variety of phagocytic events, including microglial phagocytosis, macrophage phagocytosis, and phagocytosis by Sertoli cells.

    “In general, MERTK plays a key role in a variety of phagocytic events, such as microglial phagocytosis to mediate synaptic pruning (Chung et al., 2013), macrophage phagocytosis to remove apoptotic immune cells (Scott et al., 2001), and phagocytosis of apoptotic germ cells and the residual body from maturing sperm by Sertoli cells in the testes (Breucker et al., 1985).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Chung et al., 2013 source

      Not checked in the free run.

    • cites Scott et al., 2001 source

      Not checked in the free run.

    • cites Breucker et al., 1985 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Due to defective phagocytosis and blockage of OS disk membrane turnover, the structure of OSs in RCS rats begins to deteriorate, leading to a complete loss of OSs within 3 months of age.

    “Due to defective phagocytosis, and thus a blockage of OS disk membrane turnover, the structure of OSs in RCS rats begins to deteriorate, leading to a complete loss of OSs within 3 months of age.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    In the absence of the β5 subunit, the daily rhythm of phagocytosis is lost and while OS ingestion is impaired, it is not absent, suggesting the existence of potential β5 compensatory mechanisms.

    “In the absence of the β5 subunit, the daily rhythm of phagocytosis is lost and while OS ingestion is impaired, it is not absent (Nandrot et al., 2004), suggesting the existence of potential β5 compensatory mechanisms.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot et al., 2004 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    IP3 was identified as a secondary messenger downstream of MERTK, as RCS rats do not exhibit the characteristic increase in IP3 levels upon OS phagocytic challenge.

    “For example, inositol triphosphate (IP3) was identified as a secondary messenger downstream of MERTK, as RCS rats do no exhibit the characteristic increase in IP3 levels upon OS phagocytic challenge (Heth et al., 1995).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Heth et al., 1995

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    TYRO3 exhibited gene dosage-dependent suppressive effects on the degree of retinal degeneration observed in Mertk−/− animals, but did not prevent it entirely, suggesting that MERTK is still indispensable.

    “Furthermore, TYRO3 exhibited gene dosage-dependent suppressive effects on the degree of retinal degeneration observed in Mertk−/− animals, but did not prevent it entirely, suggesting that MERTK is still indispensable.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    FAK operates downstream of αvβ5 integrin and shows a diurnal pattern of phosphorylation similar to that of MERTK, peaking after light onset and diminishing as phagosome degradation proceeds.

    “FAK operates downstream of αvβ5 integrin and shows a diurnal pattern of phosphorylation similar to that of MERTK, peaking after light onset and diminishing as phagosome degradation proceeds (Nandrot et al., 2004).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot et al., 2004 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The strength of retinal adhesion peaked 3.5 h after light onset, past the phagocytic peak.

    “The strength of adhesion peaked 3.5 h after light onset, i.e., past the phagocytic peak (Nandrot et al., 2006).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot et al., 2006 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Engagement of the αvβ5 integrin initiates a signaling cascade that triggers OS ingestion, predominantly mediated by MERTK, which is present in the RPE apical membrane.

    “Engagement of the αvβ5 integrin initiates a signaling cascade that triggers OS ingestion, predominantly mediated by MERTK (Gal et al., 2000), a member of the Tyro-Axl-Mer (TAM) ingestion receptor family, that is present in the RPE apical membrane (Prasad et al., 2006).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Gal et al., 2000 source

      Not checked in the free run.

    • cites Prasad et al., 2006 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Mutations in the human MERTK gene can lead to retinitis pigmentosa, rod-cone dystrophies, and cone-rod dystrophies.

    “Given the importance of MERTK to phagocytosis, mutations in the human MERTK gene can lead to retinitis pigmentosa, rod-cone dystrophies, and cone-rod dystrophies (Nandrot, 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot, 2014

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The RCS rat has a genomic deletion resulting in a truncated MERTK protein and lack of MERTK signaling.

    “before the identification of a genomic deletion in these animals that resulted in a truncated MERTK protein and lack of MERTK signaling (D’Cruz et al., 2000; Nandrot et al., 2000).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites D’Cruz et al., 2000

      Not checked in the free run.

    • cites Nandrot et al., 2000 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Although the extent of MERTK's requirement may differ among tissues, it plays a central role, directly or indirectly affecting the regulation of a wide variety of genes including those involved in cytoskeletal rearrangement and phagosome maturation.

    “Although the extent of its requirement may differ among different tissues, it nevertheless plays a central role, directly or indirectly affecting the regulation of a wide variety of genes including those involved in cytoskeletal rearrangement and phagosome maturation (Shelby et al., 2013; Penberthy et al., 2017).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Shelby et al., 2013 source

      Not checked in the free run.

    • cites Penberthy et al., 2017 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    β5−/− mice do not undergo retinal degeneration, but demonstrate vision loss from 6 months of age and accumulate fluorescent lipofuscin deposits.

    “β5−/− mice do not undergo retinal degeneration, but do demonstrate vision loss, as measured by electroretinograms (ERGs), from 6 months of age. They also accumulate fluorescent lipofuscin deposits, an inherent feature of the aging retina.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The presence of the MERTK ingestion receptor limits OS binding via αvβ5 integrin, such that transient reduction of MERTK expression or use of cells lacking MERTK results in excessive OS binding.

    “the presence of the MERTK ingestion receptor (discussed in the section 3.5.1) limits OS binding via αvβ5 integrin, such that transient reduction of MERTK expression or use of cells lacking MERTK results in excessive OS binding (Nandrot et al., 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nandrot et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    OS ingestion does occur in β5−/− mice, suggesting that the basal level of phosphorylated MERTK that persists is sufficient to mediate phagocytosis.

    “As noted in section 3.5, however, OS ingestion does occur in these mice, suggesting that the basal level of phosphorylated MERTK that persists is sufficient to mediate phagocytosis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Deletion of either Gas6 or Protein S alone does not affect retinal function in mice, but mice lacking both develop moderate to severe retinal degeneration, demonstrating that at least one ligand is required for MERTK activation.

    “While deletion of either ligand alone does not affect retinal function in mice (Hall et al., 2005; Burstyn-Cohen et al., 2012), mice lacking both Gas6 and Protein S do develop moderate to severe retinal degeneration, demonstrating that at least one ligand is required for MERTK activation (Burstyn-Cohen et al., 2012).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Hall et al., 2005 source

      Not checked in the free run.

    • cites Burstyn-Cohen et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Some mutant retinas also showed structures resembling drusen, and neovascularization of the RPE and photoreceptor layers.

    “Some mutant retinas also showed structures resembling drusen, and neovascularization of the RPE and photoreceptor layers (Jiang et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Jiang et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    OS phagosomes are highly motile, undergoing rapid bidirectional movements, while maintaining an overall bias towards the basal domain of the RPE.

    “It appears, then, that OS phagosomes are highly motile, undergoing rapid bidirectional movements, while maintaining an overall bias towards the basal domain of the RPE.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Upon OS feeding of cultured RPE, there is a brief burst of RAC1 activity together with colocalization of RAC1 with OS phagosomes.

    “Upon OS feeding of cultured RPE, there is a brief burst of RAC1 activity together with colocalization of RAC1 with OS phagosomes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    OS phagosomes mature by migrating from the apical to basal side of the RPE, while undergoing gradual acidification and degradation by hydrolases.

    “- OS phagosomes mature by migrating from the apical to basal side of the RPE, while undergoing gradual acidification and degradation by hydrolases.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    PI3K is required for OS engulfment, possibly due to a role in promoting phagocytic cup formation, while AKT is not required for ingestion and appears to restrict the size of the phagocytic cups and myosin-2 recruitment to the cup.

    “PI3K is required for OS engulfment, possibly due to a role in promoting phagocytic cup formation, while AKT is not required for ingestion, and appears to restrict the size of the phagocytic cups and myosin-2 recruitment to the cup (Bulloj et al., 2013).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Bulloj et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    ANXA2 localizes to the phagocytic cup and the early phagosome but dissociates from fully ingested phagosomes, mirroring the association kinetics of actin.

    “Consistent with its function, ANXA2 localizes to the phagocytic cup and the early phagosome but dissociates from fully ingested phagosomes (in vivo and in vitro) (Law et al., 2009), mirroring the association kinetics of actin.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Law et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    MERTK activation is neither required for nor affected by RAC1 activation and subsequent actin remodeling.

    “MERTK activation is neither required for nor affected by RAC1 activation and subsequent actin remodeling (Mao and Finnemann, 2012), consistent with the observation that actin is recruited to bound OS in RPE cells of the RCS rat (Chaitin and Hall, 1983b).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Mao and Finnemann, 2012

      Not checked in the free run.

    • cites Chaitin and Hall, 1983b

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    RAC1 inhibition prevents actin recruitment to the bound OS particle and therefore prevents ingestion.

    “RAC1 inhibition prevents actin recruitment to the bound OS particle and therefore, prevents ingestion.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    The frequency of stained OS tips was affected by the light exposure that the intact animal received prior to retinal dissection, suggesting that the opening of distal disks could be regulated by the RPE.

    “But, this, too, appears to be an event that could be regulated by the RPE, given that the frequency of stained OS tips was affected by the light exposure that the intact animal received prior to retinal dissection (while the OSs were still associated with the RPE) (Matsumoto and Besharse, 1985).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Matsumoto and Besharse, 1985

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    ANXA2 is a membrane-associated protein that regulates actin dynamics and binds signaling intermediates, serving as a direct or indirect linker between the phagosome membrane and actin cytoskeleton.

    “Annexin A2 (ANXA2) is a membrane-associated protein that regulates actin dynamics and binds signaling intermediates such as Ca2+, cholesterol-rich membranes, and phosphoinositides, serving as a direct or indirect linker between the phagosome membrane and actin cytoskeleton (Turowski et al., 2004; Law et al., 2009).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Turowski et al., 2004 source

      Not checked in the free run.

    • cites Law et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    This RAC1 activity is dependent upon αvβ5 integrin engagement by MFGE8 and is essential for phagosome ingestion.

    “This activity is dependent upon αvβ5 integrin engagement by MFGE8 and is essential for phagosome ingestion (Mao and Finnemann, 2012).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mao and Finnemann, 2012

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    Freshly isolated frog retinas incubated in Lucifer Yellow incorporated the dye into the distal tips of the OSs, suggesting that the opening of some distal disks to the extracellular space is an early step that leads to phagocytosis of the OS tip.

    “An earlier report showed that freshly isolated frog retinas incubated in the low molecular weight dye, Lucifer Yellow, incorporated the dye into the distal tips of the OSs, suggesting that the opening of some distal disks to the extracellular space is an early step that leads to phagocytosis of the OS tip (Matsumoto and Besharse, 1985).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Matsumoto and Besharse, 1985

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    OS phagosomes associate with subunits of both kinesin-1 and cytoplasmic dynein-1, which are plus- and minus-end directed microtubule motors, respectively, consistent with bidirectional motility along microtubules.

    “Demonstrated association with subunits of both kinesin-1 (Jiang et al., 2015) and cytoplasmic dynein-1 (Esteve-Rudd et al., 2018), which are plus- and minus-end directed microtubule motors, respectively, is consistent with bidirectional motility along microtubules.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Jiang et al., 2015 source

      Not checked in the free run.

    • cites Esteve-Rudd et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Phagosome acidification mediated by v-ATPase is required for protease activation.

    “- Phagosome acidification mediated by v-ATPase is required for protease activation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Detachment of retinas in frog eyecups in vitro prevents the release of the distal disks from the region of detachment, demonstrating that OS membrane shedding does not occur in the absence of the RPE.

    “it has been shown that the detachment of retinas in frog eyecups in vitro prevents the release of the distal disks from the region of detachment, demonstrating that OS membrane shedding does not occur in the absence of the RPE (Williams and Fisher, 1987).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Williams and Fisher, 1987

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The entry of phagosomes into the cell body region is retarded in Myo7a-null mice, as is the overall rate of OS phagosome degradation.

    “The entry of phagosomes into the cell body region is retarded in Myo7a-null mice, as is the overall rate of OS phagosome degradation (Gibbs et al., 2003).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gibbs et al., 2003

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    RAC1 is a small GTP-binding protein in the Rho family that destabilizes F-actin and facilitates its branching for the formation of the dynamic phagocytic cup.

    “RAC1 is a small GTP-binding protein in the Rho family of GTPases that destabilizes F-actin and facilitates its branching for the formation of the dynamic phagocytic cup.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    The RPE cytoskeleton and its motor proteins support rapid bidirectional motility of OS phagosomes, as well as basal migration, and are essential for normal phagosome degradation.

    “- The RPE cytoskeleton and its motor proteins support rapid bidirectional motility of OS phagosomes, as well as basal migration, and are essential for normal phagosome degradation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The mobilization of myosin-2 to the phagocytic cup was severely diminished in RPE cells from RCS rats, suggesting that while αvβ5 integrin converges on actin rearrangement pathways, MERTK signaling independently converges on the myosin force generation required for particle engulfment following phagocytic cup formation.

    “The mobilization of myosin-2 to the phagocytic cup was severely diminished in RPE cells from RCS rats, suggesting that while αvβ5 integrin converges on actin rearrangement pathways, MERTK signaling independently converges on the myosin force generation required for particle engulfment following phagocytic cup formation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    OS phagosomes in the RPE of Klc1−/− mice have impaired motility and are degraded more slowly.

    “OS phagosomes in the RPE of Klc1−/− mice (which lack a light chain of kinesin-1) have impaired motility and are degraded more slowly.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The lysosomal aspartyl protease cathepsin D is essential for phagosome degradation, together with cysteine proteases such as cathepsin S.

    “- The lysosomal aspartyl protease, cathepsin D, is essential for phagosome degradation, together with cysteine proteases such as cathepsin S.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Older Klc1−/− mice develop AMD-like pathology, such as slow loss of photoreceptor cells, complement hyperactivation, increased oxidative stress, and increased accumulation of neutral lipids such as lipoproteins and basal laminar deposits.

    “Older Klc1−/− mice develop AMD-like pathology, such as a slow loss of photoreceptor cells, complement hyperactivation, increased oxidative stress, and increased accumulation of neutral lipids such as lipoproteins and basal laminar deposits.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The RPE cytoskeleton and its associated motors are key for the overall basal movement of OS phagosomes in the RPE, and for the dynamic motility of phagosomes that appears to underlie their degradation.

    “Thus, the RPE cytoskeleton and its associated motors are not only key for the overall basal movement of OS phagosomes in the RPE, but also for the dynamic motility of phagosomes that appears to underlie their degradation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    These mice express mutant human ELOVL4 protein that mislocalizes to the OS, producing OS phagosomes with altered content which appear defective in their recruitment of motor linkers and motors, such as RAB7A and dynein.

    “These mice express mutant human elongation of very long chain fatty acids (ELOVL)-4 protein that mislocalizes to the OS, producing OS phagosomes with altered content which, in turn, appear to be defective in their recruitment of motor linkers and motors, such as RAB7A and dynein (Esteve-Rudd et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Esteve-Rudd et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Defective OS phagosome motility and degradation has been found in a mouse model of Stargardt macular degeneration (type 3), leading to phagosome accumulation, RPE pathogenesis, and photoreceptor cell death.

    “In a second example, defective OS phagosome motility and degradation has been found in a mouse model of Stargardt macular degeneration (type 3) (Esteve-Rudd et al., 2018), leading to phagosome accumulation, RPE pathogenesis, and photoreceptor cell death (Karan et al., 2005).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Esteve-Rudd et al., 2018 source

      Not checked in the free run.

    • cites Karan et al., 2005 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Phagosome degradation appears to involve a series of stages.

    “- Phagosome degradation appears to involve a series of stages.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Cells could be made to increase or decrease their phagocytic capacity by inhibiting or activating Rho kinase, which induced circumferential actin rearrangement or stress fiber formation, respectively.

    “Cells could be made to increase or decrease their phagocytic capacity by inhibiting or activating Rho kinase, which induced circumferential actin rearrangement or stress fiber formation, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    Anxa2−/− mice show phagosome accumulation in the apical microvilli, an observation not noted in wild type mice, strongly suggesting delayed phagosome ingestion in the absence of ANXA2.

    “Similarly, Anxa2−/− mice show phagosome accumulation in the apical microvilli (Law et al., 2009), an observation not noted in wild type mice, strongly suggesting delayed phagosome ingestion in the absence of ANXA2.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Law et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    In a Stargardt macular degeneration type 3 mouse model, mutant ELOVL4 mislocalizes from the endoplasmic reticulum to the photoreceptor OSs; when these mutant OSs were fed to wild-type primary mouse RPE cells, the resulting OS phagosomes associated with excessive RAB7A, and had affected motor protein recruitment and impaired motility, which likely underlies their observed slower degradation.

    “In a Stargardt macular degeneration type 3 mouse model, mutant ELOVL4 mislocalizes from the endoplasmic reticulum to the photoreceptor OSs. When these mutant OSs were fed to wild-type primary mouse RPE cells, the resulting OS phagosomes were found to associate with excessive RAB7A, and have affected motor protein recruitment and impaired motility, which likely underlies their observed slower”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Esteve-Rudd et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The monoclonal antibody 1D4 primarily detects phagosomes in the apical, but not basal RPE, indicative of early phagosomes.

    “For example, the monoclonal antibody, 1D4, whose epitope corresponds to the C-terminus of rod opsin (Molday and MacKenzie, 1983), primarily detects phagosomes in the apical, but not basal RPE, indicative of early phagosomes (Law et al., 2009; Esteve-Rudd et al., 2014; Wavre-Shapton et al., 2014).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Molday and MacKenzie, 1983

      Not checked in the free run.

    • cites Law et al., 2009 source

      Not checked in the free run.

    • cites Esteve-Rudd et al., 2014

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The acidification is mediated by the vacuolar type H+-ATPase (v-ATPase), and is required for the proper functioning of lysosomal proteases.

    “The acidification is mediated by the vacuolar type H+-ATPase (v-ATPase), and is required for the proper functioning of lysosomal proteases.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Deficient LAMP2 results in retarded OS phagosome degradation, and the accumulation of AMD-like deposits.

    “A recent report has shown that deficient LAMP2 results in retarded OS phagosome degradation, and the accumulation of AMD-like deposits (Notomi et al., 2019).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Notomi et al., 2019 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Phagosomal RAB7 and subsequent LAMP1 acquisition were compromised in cells treated with REP1 siRNA, leading to fewer fusion events with lysosomes, which, coupled with defects in phagosomal acidification, resulted in slower phagosome clearance.

    “Phagosomal RAB7 and subsequent LAMP1 acquisition were compromised in the cells treated with REP1 siRNA, thereby leading to fewer fusion events with lysosomes, which, coupled with defects in phagosomal acidification, resulted in slower phagosome clearance (Gordiyenko et al., 2010).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Gordiyenko et al., 2010 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisenone given

    The presence of RAB5 and early endosome antigen 1 (EEA1) indicate interactions with early endosomes, whereas RAB7 is a marker for late endosomes, and LAMP1 and LAMP2 are markers for lysosomes.

    “The presence of RAB5 and early endosome antigen 1 (EEA1) indicate interactions with early endosomes, whereas RAB7 is a marker for late endosomes, and the lysosome-associated membrane proteins, LAMP1 and LAMP2, are markers for lysosomes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    mcd/mcd mice display features reminiscent of geographic atrophy in AMD, including photoreceptor cell death, diminished ERG responses, accumulation of phagocytic material in the RPE, basal laminar and linear deposits, RPE pigmentary changes, and RPE cell atrophy and proliferation.

    “These mice display features reminiscent of geographic atrophy in AMD, such as photoreceptor cell death, diminished ERG responses, accumulation of phagocytic material in the RPE, basal laminar and linear deposits, RPE pigmentary changes, and RPE cell atrophy and proliferation.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Rakoczy et al., 2002 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Melanoregulin (MREG) is a small, highly charged protein that localizes to lysosomes.

    “Similarly, melanoregulin (MREG), a small, highly-charged protein that localizes to lysosomes (Frost et al., 2013), is important for cathepsin D maturation.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Frost et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    RPE from βA3/A1-crystallin knockout mice have decreased v-ATPase activity, elevated lysosomal pH, and decreased cathepsin D activity.

    “Indeed, RPE from βA3/A1-crystallin knockout mice have decreased v-ATPase activity, elevated lysosomal pH, and decreased cathepsin D activity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Caveolin-1 is recruited to maturing phagolysosomes and appears to be important for regulating lysosomal acidification and cathepsin D enzyme activity; increasing or decreasing caveolin-1 protein levels in vitro accelerated or decelerated phagosome degradation, respectively.

    “Additionally, the membrane organizer, caveolin-1, is recruited to maturing phagolysosomes and appears to be important for regulating lysosomal acidification and cathepsin D enzyme activity; increasing or decreasing caveolin-1 protein levels in vitro accelerated or decelerated phagosome degradation, respectively (Sethna et al., 2016), although the underlying mechanism remains unclear.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sethna et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Intravitreal injection of bafilomycin, a v-ATPase inhibitor, resulted in the accumulation of large phagolysosomes containing cathepsin D and with preserved opsin antigenicity, demonstrating that enzyme acquisition alone was not sufficient for opsin degradation.

    “Intravitreal injection of bafilomycin, a v-ATPase inhibitor, resulted in the accumulation of large phagolysosomes containing cathepsin D and with preserved opsin antigenicity, demonstrating that enzyme acquisition alone was not sufficient for opsin degradation (Deguchi et al., 1994).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Deguchi et al., 1994

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Alterations in endolysosomal marker association would likely indicate a defect in a particular maturation stage, which could contribute to inefficient OS phagosome degradation.

    “Alterations in endolysosomal marker association would likely indicate a defect in a particular maturation stage, which could contribute to inefficient OS phagosome degradation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Although lack of REP1 function appears to be compensated by REP2 activity in most tissues, the outer retina including the RPE requires REP1.

    “Although lack of REP1 function appears to be compensated by REP2 activity in most tissues, the outer retina including the RPE requires REP1.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Human iPSC-derived RPE cells from choroideremia patients, and human fetal primary RPE cells treated with REP1 siRNA, both demonstrate delayed OS phagosome clearance.

    “Moreover, human iPSC-derived RPE cells from choroideremia patients (Duong et al., 2018), and human fetal primary RPE cells, treated with REP1 siRNA (Gordiyenko et al., 2010), both demonstrate delayed OS phagosome clearance.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Duong et al., 2018 source

      Not checked in the free run.

    • cites Gordiyenko et al., 2010 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Bridge-like structures were described between phagosomes and organelles thought to be lysosomes in the rat RPE as early as 30 min after light onset.

    “‘Bridge-like structures’ were described between phagosomes and organelles thought to be lysosomes in the rat RPE as early as 30 min after light onset (Bosch et al., 1993).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bosch et al., 1993 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    These authors also demonstrate lysosome alkalinization in the albino Abca4−/− mouse and have recently shown that restoration of lysosomal pH with P2Y12 receptor antagonist prevents photoreceptor loss in these mice.

    “Moreover, these authors also demonstrate lysosome alkalinization in the albino Abca4−/− mouse (Liu et al., 2008) and have recently shown that restoration of lysosomal pH with P2Y12 receptor antagonist prevents photoreceptor loss in these mice (Lu et al., 2019).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Liu et al., 2008 source

      Not checked in the free run.

    • cites Lu et al., 2019

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    RAB GTPases mediate organelle trafficking and fusion, and facilitate interactions between phagosomes and endosomes.

    “RAB GTPases mediate organelle trafficking and fusion, and, in doing so, facilitate interactions between phagosomes and endosomes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Cathepsin D was the first lysosomal protease specifically investigated in the RPE.

    “Cathepsin D was the first lysosomal protease specifically investigated in the RPE.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    These phagosomes also possessed negligible cathepsin D staining, suggesting that they had not yet encountered lysosomes and that loss of the 1D4 epitope occurred during a prelysosomal and pre-migratory processing step.

    “These phagosomes also possessed negligible cathepsin D (lysosomal protease) staining, suggesting that they had not yet encountered lysosomes and that loss of the 1D4 epitope occurred during a prelysosomal and pre-migratory processing step.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    An intermediate step may exist between 1D4 epitope loss and cathepsin D acquisition, as EM studies revealed fewer associated cathepsin D particles in 1D4-negative phagosomes that retained a distinct disk structure than in phagolysosomes.

    “An intermediate step may exist between 1D4 epitope loss and cathepsin D acquisition, as EM studies revealed fewer associated cathepsin D particles in 1D4-negative phagosomes that retained a distinct disk structure than in phagolysosomes (Wavre-Shapton et al., 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wavre-Shapton et al., 2014

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    LC3B-II recruitment occurs on single-membraned phagosomes, unlike the double-membraned autophagosomes in classical autophagy.

    “In addition, LC3B-II recruitment occurs on single-membraned phagosomes, unlike the double-membraned autophagosomes in classical autophagy (Frost et al., 2015; Martinez et al., 2015; Klionsky et al., 2016).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Frost et al., 2015 source

      Not checked in the free run.

    • cites Martinez et al., 2015 source

      Not checked in the free run.

    • cites Klionsky et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Cathepsin L is detected at the transcript level in mouse RPE and can be upregulated in response to hyperoxia.

    “Cathepsin L has been detected at the transcript level in mouse RPE and can be upregulated in response to hyperoxia (Alizadeh et al., 2006).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Alizadeh et al., 2006 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Loss of LC3B results in age-dependent deposition of lipid-rich structures between the RPE and choroid, an increase in lipid peroxidation adducts, and increases in the pro-inflammatory lipid 7-ketocholesterol.

    “Loss of LC3B (Dhingra et al., 2018) results in age-dependent deposition of lipid-rich structures between the RPE and choroid, an increase in lipid peroxidation adducts, and increases in the pro-inflammatory lipid 7-ketocholesterol.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dhingra et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The Lc3b−/− mouse shows a decrease in LC3-mediated OS phagosome clearance, with no change in classical autophagy.

    “In contrast, the Lc3b−/− mouse shows a decrease in LC3-mediated OS phagosome clearance, with no change in classical autophagy (Dhingra et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Dhingra et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    After a single intravitreal injection of cysteine protease inhibitor, the inhibition is relieved within a week and phagosome counts in the RPE return to near control levels.

    “Cysteine protease inhibition of RPE cells in vivo, through a single intravitreal injection, has been shown to increase the accumulation of phagosomes and autofluorescent material (Ivy et al., 1989; Katz and Shanker, 1989; Okubo et al., 2000); although, the inhibition is relieved within a week, and phagosome counts in the RPE return to near control levels (Okubo et al., 2000).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Okubo et al., 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    LAP is distinguished from classical phagocytosis by the recruitment of lipidated LC3B (LC3B-II) to phagosomes.

    “It is distinguished from classical phagocytosis by the recruitment of lipidated LC3B (LC3B-II) to phagosomes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    LAP is an autophagosome-independent process and does not require the upstream components needed for initiating or regulating classical autophagy.

    “LAP is an autophagosome-independent process (Frost et al., 2015; Martinez et al., 2015; Klionsky et al., 2016), and does not require the upstream components needed for initiating or regulating classical autophagy.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Frost et al., 2015 source

      Not checked in the free run.

    • cites Martinez et al., 2015 source

      Not checked in the free run.

    • cites Klionsky et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The Atg5ΔRPE mouse exhibits elevated levels of oxidatively modified lipids, proteins, and DNA with occasional RPE hypertrophy.

    “The Atg5ΔRPE mouse also exhibits elevated levels of oxidatively-modified lipids, proteins, and DNA with occasional RPE hypertrophy (Zhang et al., 2017).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zhang et al., 2017 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    The Lc3b−/− mouse exhibits normal starvation-induced autophagy and delayed phagosome maturation.

    “The Lc3b−/− mouse exhibits normal starvation-induced autophagy and delayed phagosome maturation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Phagosome motility is determined by the organization of the cell's actin and microtubule cytoskeleton.

    “Phagosome motility is, in turn, determined by the organization of the cell’s actin and microtubule cytoskeleton.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Cathepsin B is identified in mouse, bovine, and human RPE, with some variation in protein expression at least in RPE from individual rats.

    “Cathepsin B has also been identified in the mouse (Alizadeh et al., 2006; Ahuja et al., 2008), bovine (Fröhlich and Klessen, 2001), and human (Hoppe et al., 2004b) RPE, although there appears to be some variation in the level of protein expression, at least in RPE from individual rats (Wassélius et al., 2003).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Alizadeh et al., 2006 source

      Not checked in the free run.

    • cites Ahuja et al., 2008 source

      Not checked in the free run.

    • cites Fröhlich and Klessen, 2001

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    LAP is distinct from classical autophagy both in initiation and function.

    “The recruitment of LC3B to maturing phagosomes requires proteins involved in classical autophagy; however, LAP is distinct from classical autophagy both in initiation and function.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Phospholipase A activity in the RPE was reported in the early 1980s.

    “Phospholipase A activity in the RPE was reported in the early 1980s (Zimmerman et al., 1983).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zimmerman et al., 1983 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    In the Atg5ΔRPE mouse, rod and cone photoreceptor functions are diminished, although no cell loss is apparent.

    “In the Atg5ΔRPE mouse, rod and cone photoreceptor functions are diminished, although no cell loss is apparent.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    LAP was first identified about a decade ago in studies on phagocytosis of pathogens and dead cells by immune cells.

    “LAP was first identified about a decade ago in studies on phagocytosis of pathogens and dead cells by immune cells (Sanjuan et al., 2007; Martinez et al., 2011) (Fig. 9).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Sanjuan et al., 2007 source

      Not checked in the free run.

    • cites Martinez et al., 2011 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    ULK recruits the ATG5-ATG12-ATG16L1 complex to mediate conjugation of phosphatidylethanolamine to LC3B.

    “ULK recruits the ATG5-ATG12-ATG16L1 complex to mediate conjugation of phosphatidylethanolamine to LC3B.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    mTORC1 negatively regulates autophagy by two distinct mechanisms in nutrient-replete or stress-free conditions.

    “mTOR Complex 1 (mTORC1), which includes mTOR, regulatory-associated protein of mTOR (RAPTOR), and mammalian lethal with SEC13 protein 8 (MLST8), negatively regulates autophagy by two distinct mechanisms in nutrient-replete or stress-free conditions.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Impaired autophagy is a feature of RPE from AMD donor tissue and multiple models of inherited retinal degenerations.

    “Impaired autophagy is a feature of RPE from AMD donor tissue and multiple models of inherited retinal degenerations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The resulting pro-inflammatory microenvironment leads to recruitment of microglia and contributes to RPE hypertrophy and loss of function (decreased c-wave).

    “The resulting pro-inflammatory microenvironment leads to recruitment of microglia and contributes to RPE hypertrophy and loss of function (decreased c-wave).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Non-polarized RPE respond to stereotypical autophagy inducers such as serum starvation, whereas well-polarized terminally differentiated primary RPE cultures do not.

    “First, whereas non-polarized RPE respond to “stereotypical” autophagy inducers such as serum starvation, well-polarized terminally differentiated primary RPE cultures do not (Toops et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Toops et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    These receptors have LC3-interacting regions (LIRs) that bind LC3 at the nascent autophagosome, resulting in ubiquitinated cargo being enclosed within the growing autophagosome.

    “These receptors also have LC3-interacting regions (LIRs) that bind LC3 at the nascent autophagosome, resulting in ubiquitinated cargo being enclosed within the growing autophagosome.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    LC3B-II promotes autophagosome closure after dissociation of ATG proteins.

    “At the final step, LC3B-II promotes autophagosome closure after dissociation of ATG proteins.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    p62 and other autophagic receptors bind ubiquitinated proteins and organelles tagged for removal.

    “p62 and other autophagic receptors bind ubiquitinated proteins and organelles tagged for removal.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Rubicon appears to function in balancing classical autophagy and LAP, by committing a cell to LAP while inhibiting classical autophagy.

    “Thus, Rubicon appears to function in balancing classical autophagy and LAP, by committing a cell to LAP while inhibiting classical autophagy (Wong et al., 2018).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wong et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Classical autophagy occurs at a basal, constitutive level in all eukaryotic cells, and is modulated by intrinsic and extrinsic stimuli.

    “Classical autophagy occurs at a basal, constitutive level in all eukaryotic cells, and is modulated by intrinsic and extrinsic stimuli.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Classical autophagy occurs at a basal, constitutive level in all eukaryotic cells.

  • May combine two claims.

    Premisenone given

    Basal autophagy in the RPE is not regulated by light exposure, but is triggered by OS disk membrane phagocytosis.

    “On the other hand, basal autophagy in the RPE is not regulated by light exposure, but is triggered by OS disk membrane phagocytosis.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    ATG9 delivers vesicles that provide membrane for autophagosome growth.

    “At the nascent autophagosome, ATG9 delivers vesicles that provide membrane for autophagosome growth.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Loss of MREG, an LC3B binding partner, contributes to a delay in phagosome maturation and lysosomal exocytosis, as well as basal laminar thickening in older mice.

    “Loss of MREG, an LC3B binding partner contributes to a delay in phagosome maturation (Damek-Poprawa et al., 2009) and lysosomal exocytosis, as well as basal laminar thickening in older mice (Frost et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Damek-Poprawa et al., 2009 source

      Not checked in the free run.

    • cites Frost et al., 2013 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    There are three principal routes of autophagy that differ primarily in the mechanism of cargo delivery to lysosomes: microautophagy, macroautophagy, and chaperone-mediated autophagy.

    “There are three principal routes of autophagy that differ primarily in the mechanism of cargo delivery to lysosomes: microautophagy, macroautophagy, and chaperone-mediated autophagy.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Fusion of autophagosomes with lysosomes requires microtubule-based transport, tethering factors, and SNARE proteins.

    “Fusion of autophagosomes with lysosomes requires microtubule-based transport, tethering factors, and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein [SNAP] receptor) proteins (Leidal et al., 2018; Levine and Kroemer, 2019).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Leidal et al., 2018 source

      Not checked in the free run.

    • cites Levine and Kroemer, 2019 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Polarized primary RPE do not upregulate autophagy in response to the non-specific mTOR inhibitor rapamycin, but respond to the specific mTORC1 inhibitor Torin-1.

    “Second, polarized primary RPE do not upregulate autophagy in response to the non-specific mTOR inhibitor rapamycin, but respond to the specific mTORC1 inhibitor Torin-1 (Toops et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Toops et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Activation of the ULK complex activates the VPS34 complex to initiate biogenesis of the double-membraned autophagosome.

    “Activation of the ULK complex (ULK1-ATG13-RB1CC1/FIP200) in turn activates the VPS34 complex (UVRAG-Beclin-VPS34-ATG14) to initiate biogenesis of the double-membraned autophagosome.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    mTORC1 phosphorylates and inactivates ULK1 and ULK2.

    “First, it phosphorylates and inactivates ULK1 and ULK2 (unc-51-like kinases 1 & 2).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationcitation

    The elevation of Rubicon levels in the RPE at light onset suggests that synchronized OS phagocytosis is required for Rubicon activation.

    “The observation that Rubicon levels in the RPE are elevated at light onset (Muniz-Feliciano et al., 2017) suggests that synchronized OS phagocytosis is required for Rubicon activation.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Muniz-Feliciano et al., 2017 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In autophagy, damaged organelles and cellular material are enclosed in a double-membraned autophagosome and delivered to lysosomes for degradation.

    “In autophagy, damaged organelles (e.g., mitochondria, lysosomes, peroxisomes) and cellular material (e.g., proteins, lipids, nucleic acids) are enclosed in a double-membraned autophagosome and delivered to lysosomes for degradation (Leidal et al., 2018; Levine and Kroemer, 2019).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Leidal et al., 2018 source

      Not checked in the free run.

    • cites Levine and Kroemer, 2019 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Conversion of non-lipidated LC3B-I to lipidated LC3B-II is necessary for its binding to the membrane and is regulated by ATG4, ATG7, and ATG10.

    “Conversion of non-lipidated LC3B–I to lipidated LC3B-II is necessary for its binding to the membrane and is regulated by ATG4, ATG7, and ATG10.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    The relevance of these in vitro studies to RPE in vivo is unclear since there is no evidence that post-mitotic RPE express EGFR on the apical cell surface.

    “Last, the relevance of these in vitro studies to RPE in vivo is unclear since there is no evidence that post-mitotic RPE express EGFR on the apical cell surface.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    LC3B-II recruitment is essential for autophagosome elongation and for recruitment of cargo to the autophagosome.

    “LC3B-II recruitment is essential for autophagosome elongation and for recruitment of cargo to the autophagosome.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    A growing body of evidence suggests that autophagy is crucial for maintaining RPE homeostasis, and impaired autophagy has been implicated in a plethora of retinal degenerations.

    “As discussed below, a growing body of evidence suggests that autophagy is crucial for maintaining RPE homeostasis, and impaired autophagy has been implicated in a plethora of retinal degenerations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In 6-month-old C57BL/6J mice RPE, the phagocytic peak occurs 30 min after light onset with a subsequent peak in LC3B-II and ATG5-ATG12 expression 2 h after light onset.

    “Based on current knowledge, it appears that there are two peaks of autophagy induction in response to OS membrane phagocytosis: in 6-month-old C57BL/6J mice RPE, the phagocytic peak occurs 30 min after light onset with a subsequent peak in LC3B-II and ATG5-ATG12 expression 2 h after light onset (Frost et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Frost et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    This was accompanied by the accumulation of p62/SQSTM1, damaged mitochondria, and lipid droplets with increased autofluorescence in the RPE, all indicators of impaired autophagic flux.

    “This was accompanied by the accumulation of p62/SQSTM1, damaged mitochondria, and lipid droplets with increased autofluorescence in the RPE, all indicators of impaired autophagic flux.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Yao et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The ability of a particular stimulus to induce autophagy, and the extent of induction, both depend on the differentiation status of the RPE.

    “Autophagy is known to be upregulated in the RPE in response to a variety of stressors (see below); however, it has become increasingly clear that the ability of a particular stimulus to induce autophagy, and the extent of induction, both depend on the differentiation status of the RPE.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Rubicon-deficient macrophages undergo normal levels of phagocytic uptake yet fail to recruit LC3B-II to phagosomes.

    “Rubicon-deficient macrophages undergo normal levels of phagocytic uptake yet fail to recruit LC3B-II to phagosomes (Kim et al., 2013; Martinez et al., 2015; Wong et al., 2018).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Kim et al., 2013 source

      Not checked in the free run.

    • cites Martinez et al., 2015 source

      Not checked in the free run.

    • cites Wong et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning

    Starvation and other cellular stressors inhibit mTOR, which relieves the block on ULK1 and ULK2 to initiate autophagy, and allows nuclear translocation of TFEB/E3 to induce transcription of lysosomal and autophagy genes.

    “Starvation and other cellular stressors inhibit mTOR, which relieves the block on ULK1 and 2 to initiate autophagy, and allows nuclear translocation of TFEB/E3 to induce the transcription of lysosomal and autophagy genes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Prolonged stress downregulates autophagy, which could send the cell into a spiral of increased debris, mitochondrial injury, and eventual metabolic reprogramming.

    “However, prolonged stress downregulates autophagy, which could send the cell into a spiral of increased debris, mitochondrial injury, and eventual metabolic reprogramming (Leidal et al., 2018; Levine and Kroemer, 2019).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Leidal et al., 2018 source

      Not checked in the free run.

    • cites Levine and Kroemer, 2019 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    HDAC6 also regulates the autophagy-dependent clearance of defective mitochondria, likely compromising lipid metabolism in Abca4−/− mice.

    “HDAC6 also regulates the autophagy-dependent clearance of defective mitochondria (Seigneurin-Berny et al., 2001), likely compromising lipid metabolism in Abca4−/− mice (discussed in more detail section 6).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Seigneurin-Berny et al., 2001 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Dynamic microtubules (marked by tyrosination) are required for efficient transport of autophagosomes, whereas stable microtubules (marked by acetylation) hinder autophagosome trafficking.

    “Dynamic microtubules (marked by tyrosination) are required for efficient transport of autophagosomes, whereas stable microtubules (marked by acetylation) hinder autophagosome trafficking (Toops et al., 2015; Mohan et al., 2019).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Toops et al., 2015 source

      Not checked in the free run.

    • cites Mohan et al., 2019 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Defective autophagy has been implicated in intractable age-related neurodegenerative diseases including Alzheimer's and Parkinson's diseases.

    “Defective autophagy has been implicated in intractable age-related neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases (Nixon, 2013).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nixon, 2013 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    These receptors have LIRs, which ensures the delivery of damaged mitochondria to autophagosomes.

    “These receptors have LIRs, which ensures the delivery of damaged mitochondria to autophagosomes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Live-cell imaging of RPE with lipofuscin bisretinoids showed significantly hindered autophagosome transport and impaired fusion with lysosomes.

    “Live-cell imaging of RPE with lipofuscin bisretinoids showed significantly hindered autophagosome transport and impaired fusion with lysosomes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    The antidepressant desipramine, which inhibits ASMase, decreased ceramide and restored autophagosome trafficking and autophagic flux in Abca4−/− RPE.

    “The antidepressant desipramine, which inhibits ASMase, decreased ceramide, and restored autophagosome trafficking and autophagic flux in Abca4−/− RPE.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Impaired autophagy in these diseases is accompanied by defects in other organelles/functions such as delayed phagosome maturation, lysosomal dysfunction, and endosomal abnormalities.

    “Impaired autophagy is accompanied by defects in other organelles/functions such as delayed phagosome maturation (Bietti’s, Batten, SLO (Wavre-Shapton et al., 2015; Hata et al., 2018; Ramachandra Rao et al., 2018)), lysosomal dysfunction (Stargardt, Batten, Bietti’s (Liu et al., 2008; Wavre-Shapton et al., 2015; Tan et al., 2016; Hata et al., 2018)), and endosomal abnormalities (Stargardt (Kaur et”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Wavre-Shapton et al., 2015

      Not checked in the free run.

    • cites Hata et al., 2018 source

      Not checked in the free run.

    • cites Ramachandra Rao et al., 2018 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    The ULK complex is upstream of ATG5 and ATG7 in the autophagy cascade, which might explain why mice lacking RB1CC1 in the RPE have a more severe phenotype compared to those lacking Atg5 or Atg7.

    “The ULK complex is upstream of ATG5 and ATG7 in the autophagy cascade, which might explain why mice, lacking RB1CC1 in the RPE, have a more severe phenotype compared to those lacking Atg5 or Atg7.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In Abca4−/− RPE, both autophagosome biogenesis and autophagic flux are inhibited.

    “In Abca4−/− RPE, both autophagosome biogenesis and autophagic flux are inhibited (Toops et al., 2015); however, in Batten, Bietti’s, and SLO diseases, autophagic defects manifest as an accumulation of LC3-positive autophagosomes and increased p62, suggestive of a block in autophagosome-lysosome fusion.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Toops et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    During mitophagy, mitochondria destined for degradation are tagged with ubiquitin, which is recognized by autophagy receptors such as p62 and optineurin.

    “During mitophagy, mitochondria destined for degradation are tagged with ubiquitin, which is recognized by autophagy receptors such as p62 and optineurin.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Decreased autophagy led to a secondary degeneration of photoreceptors, loss of scotopic and photopic vision, subretinal inflammation, and sub-RPE accumulation of oxidative stress markers in 8-month-old mice.

    “Decreased autophagy led to a secondary degeneration of photoreceptors, loss of scotopic and photopic vision, subretinal inflammation (microglial activation, complement activation), and sub-RPE accumulation of oxidative stress markers in 8-month-old mice.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Yao et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    SNAREs are critical components of cellular fusion machinery.

    “SNAREs are critical components of cellular fusion machinery.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The presence of mitochondrial fragments confirms studies showing increased mitochondrial DNA damage in AMD donor RPE, and likely indicates a failure of mitophagy.

    “The presence of mitochondrial fragments confirms studies showing increased mitochondrial DNA damage (Fisher and Ferrington, 2018) in AMD donor RPE, and likely indicates a failure of mitophagy, a selective autophagic mechanism for removing damaged mitochondria (Pickles et al., 2018).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fisher and Ferrington, 2018

      Not checked in the free run.

    • cites Pickles et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Abca4−/− RPE and in RPE from aged human donors, lipofuscin bisretinoids drive ceramide accumulation on the apical plasma membrane, resulting in enlarged early endosomes that act as conduits for complement C3 entry.

    “in Abca4−/− RPE and in RPE from aged human donors, lipofuscin bisretinoids drive the accumulation of ceramide - a cone-shaped lipid that promotes spontaneous negative curvature and inward budding - on the apical plasma membrane. This results in the formation of enlarged early endosomes from the apical surface, and these endosomes act as conduits for the entry of complement C3, as discussed above”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kaur et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    In later stages of AMD, increased C3 expression in the retina leads to increased generation of C3a fragments within the RPE and consequently chronically activates mTOR.

    “in later stages of AMD, increased C3 expression in the retina would lead to increased generation of C3a fragments within the RPE, and consequently, activate mTOR chronically.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The endosomal system can be co-opted to make the RPE susceptible to viruses and complement attack.

    “The endosomal system can be co-opted to make the RPE susceptible to viruses and complement attack.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Lysosomes in the RPE participate in calcium signaling and membrane repair in addition to their degradative functions, and these mechanisms are critical for maintaining RPE health and integrity.

    “lysosomes in the RPE perform various roles; in addition to their degradative functions, they participate in calcium signaling and membrane repair - mechanisms that are critical for maintaining RPE health and integrity (Liu et al., 2008; Tan et al., 2016).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Liu et al., 2008 source

      Not checked in the free run.

    • cites Tan et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Sema4A mutant proteins associated with human disease are mislocalized in the RPE, leading to defective endosomal sorting of prosaposins and CRALBP, which makes photoreceptors susceptible to degeneration.

    “Sema4A mutant proteins that are associated with human disease are mislocalized in the RPE, leading to defective endosomal sorting of prosaposins and CRALBP, which makes the photoreceptors susceptible to degeneration (Nojima et al., 2013).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Nojima et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Ceramide is increased in human brains as a function of age and in Alzheimer's disease, suggesting that a common mechanism could drive age-related early endosome defects in neurons and the RPE.

    “Recent studies show that ceramide is increased in human brains as a function of age (Park et al., 2018) and in Alzheimer’s disease (Filippov et al., 2012), suggesting that a common mechanism could drive age-related early endosome defects in neurons and the RPE.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Park et al., 2018 source

      Not checked in the free run.

    • cites Filippov et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    These include syntaxin-17 on autophagosomes and vesicle-associated membrane protein (VAMP) 7/8 on endolysosomal membranes.

    “These include syntaxin-17 on autophagosomes and vesicle-associated membrane protein (VAMP) 7/8 on endolysosomal membranes (Levine and Kroemer, 2019).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Levine and Kroemer, 2019 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In fish RPE, myosin-7a appears responsible for dispersion of melanosomes along apical processes in light, whereas in darkness retrograde movement out of apical processes appears to require myosin-2.

    “In fish RPE, myosin-7a appears to be responsible for the dispersion of melanosomes along the apical processes in the light (McNeil et al., 2004), whereas, in the dark, retrograde movement out of the apical processes appears to require myosin-2 (Barsoum and King-Smith, 2007).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites McNeil et al., 2004 source

      Not checked in the free run.

    • cites Barsoum and King-Smith, 2007

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Increased uptake of C3 in Abca4−/− RPE from the extracellular milieu into enlarged early endosomes enables the generation of intracellular C3a, and consequently sustained activation of mTOR.

    “Intracellular C3a is almost undetectable in healthy RPE, likely due to efficient recycling or degradation; on the other hand, increased uptake of C3 in Abca4−/− RPE from the extracellular milieu into enlarged early endosomes (discussed in detail below) enables the generation of intracellular C3a, and consequently, sustained activation of mTOR (Kaur et al., 2018).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kaur et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Early and recycling endosomes participate in RPE-photoreceptor communication and photoreceptor maintenance.

    “Early and recycling endosomes participate in RPE-photoreceptor communication and photoreceptor maintenance.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Peroxisomes provide a link between OS membrane phagocytosis and RPE metabolism due to β-oxidation of the very long chain fatty acids in ingested OS membranes.

    “peroxisomes, which provide a link between OS membrane phagocytosis and RPE metabolism due to β-oxidation of the very long chain fatty acids in the ingested OS membranes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    In the absence of a tapetum, the RPE contains melanosomes, which have a clear role in screening light.

    “In the absence of a tapetum, the RPE contains melanosomes, which have a variety of potential functions. A clear role for melanosomes in the RPE (as well as melanocytes of the skin) is in the screening of light.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductcitation

    A highly differentiated, tightly packed RPE monolayer is important for studies on polarized secretion of exosomes; poorly polarized cells make conclusions about directional exosome secretion meaningless.

    “A highly differentiated, tightly packed RPE monolayer is especially important for studies on polarized secretion of exosomes. Poorly polarized, loosely packed, or sparsely plated cells would allow intermixing of apical and basolateral media, and make any conclusions about directional exosome secretion meaningless (Klingeborn et al., 2017a).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Klingeborn et al., 2017a

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    In aging and early AMD, mTOR is well-regulated and autophagosome biogenesis is not heavily impacted.

    “In aging and early AMD, mTOR is well-regulated, and autophagosome biogenesis is not heavily impacted;”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    RPE melanosomes contain proteases including cathepsin D and have been observed to fuse with phagosomes, suggesting they may contribute to degradation of the phagocytic load.

    “RPE melanosomes contain proteases (Azarian et al., 2006), including cathepsin D, a major enzyme in the degradation of OS proteins (Hayasaka et al., 1975), and have been observed to fuse with phagosomes (e.g. Schraermeyer et al., 1999).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Azarian et al., 2006 source

      Not checked in the free run.

    • cites Hayasaka et al., 1975 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    In T-cells, C3 is internalized via early endosomes and cleaved intracellularly into active C3a and C3b fragments.

    “The mechanism points to an intriguing link between the complement pathway and autophagy in the RPE, and has parallels with the immune system: in T-cells, C3 is internalized via early endosomes and cleaved intracellularly into active C3a and C3b fragments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Melanosomes have been observed to move into the RPE apical processes in response to light onset.

    “Although more muted, melanosomes have been observed to move into the RPE apical processes in response to light onset (Futter et al., 2004).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Futter et al., 2004 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Abnormally enlarged early endosomes are seen in models of macular degeneration, suggesting a common etiology with other neurodegenerations such as Alzheimer's disease.

    “Abnormally enlarged early endosomes are seen in models of macular degeneration, suggesting a common etiology with other neurodegenerations such as Alzheimer’s disease.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Myosin-7a associates with RPE melanosomes by binding to MYRIP, which in turn binds to RAB27A on the melanosome surface.

    “myosin-7a associates with RPE melanosomes by binding to myosin-7a- and Rab-interacting protein (MYRIP) (El-Amraoui et al., 2002), which in turn binds to RAB27A on the melanosome surface (Futter et al., 2004; Gibbs et al., 2004; Kuroda and Fukuda, 2005; Klomp et al., 2007)”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites El-Amraoui et al., 2002 source

      Not checked in the free run.

    • cites Futter et al., 2004 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Increased RPE glycolytic flux resulting from sustained mTOR activation decreases the amount of glucose available to photoreceptors and could contribute to photoreceptor degeneration.

    “The resulting increase in RPE glycolytic flux decreases the amount of glucose available to photoreceptors, and could contribute to photoreceptor degeneration.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisereasoning

    A tapetum reflects light back through the photoreceptors, increases light absorption, and is found in animals active in low light environments.

    “A tapetum reflects light back through the photoreceptors (effecting “eyeshine” when light is shone in the eye at night), in contrast to the absorption of light by melanosomes. Tapeta are found among vertebrates and invertebrates. They increase light absorption (light not absorbed by the photoreceptors on the first pass through may be absorbed on the second pass through) and are thus found in an”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In cultures of mouse and human RPE cells, lack of myosin-7a results in inability to sequester melanosomes in the actin-rich apical domain; instead melanosomes undergo more rapid bidirectional movements along microtubules in the cell body.

    “In cultures of mouse and human RPE cells, lack of myosin-7a results in the inability to sequester melanosomes in the actin-rich apical domain; instead the melanosomes undergo more rapid bidirectional movements along microtubules in the cell body (Gibbs et al., 2004, 2010; Lopes et al., 2007; Jiang et al., 2019).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Gibbs et al., 2004 source

      Not checked in the free run.

    • cites Lopes et al., 2007 source

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning

    Pigmentation is a common but not universal characteristic of the RPE; the RPE in some animals lacks melanosomes completely or partially to make way for a tapetum lucidum.

    “Although pigmentation is a common characteristic of the RPE, it is not a universal one, as the RPE in some animals lacks melanosomes either completely or partially to make way for a tapetum lucidum.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    RPE lacking NHE8 have abnormally small recycling endosomes, and mice with an RPE-specific deletion of Slc9a8 show widespread retinal and RPE degeneration.

    “RPE lacking NHE8 have abnormally small recycling endosomes, and mice with an RPE-specific deletion of Slc9a8 show widespread retinal and RPE degeneration (Jadeja et al., 2015; Xia et al., 2015, 2018).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Jadeja et al., 2015 source

      Not checked in the free run.

    • cites Xia et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    C3a activates mTOR, which is essential for driving metabolic reprogramming and cell fate decisions.

    “C3a activates mTOR, which is essential for driving metabolic reprogramming and cell fate decisions (Hess and Kemper, 2016).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hess and Kemper, 2016

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Lysosomal hydrolases are activated by the highly acidic luminal pH (4.5-5.0), which is maintained by the v-ATPase on lysosomal membranes.

    “Lysosomal hydrolases are activated by the highly acidic luminal pH (4.5–5.0), which is maintained by the v-ATPase on lysosomal membranes (Mindell, 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Mindell, 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In HeLa cells, the position of lysosomes within the cell determines their luminal pH; peripheral lysosomes are less acidic than perinuclear lysosomes because they have less RAB7, leading to decreased recruitment of RILP and v-ATPase subunits.

    “Studies in HeLa cells show that the position of lysosomes within the cell determines their luminal pH; peripheral lysosomes are less acidic than those in the perinuclear region. This is because peripheral lysosomes have less RAB7, which leads to decreased recruitment of the RAB7 effector RILP (RAB-interacting lysosomal protein). RILP, in turn, is responsible for recruiting specific subunits of the”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Johnson et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Lysosomes in cultured human RPE from AMD donors were found to be enlarged and annular; whether this abnormal lysosome morphology is associated with decreased hydrolytic function is not yet known.

    “Lysosomes in cultured human RPE from AMD donors were found to be enlarged and annular; however, whether this abnormal lysosome morphology is associated with decreased hydrolytic function is not yet known (Golestaneh et al., 2017).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Golestaneh et al., 2017 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Seemingly contradictory findings could potentially be explained by lysosomal heterogeneity, i.e., all lysosomes are not created equal and exhibit significant structural and functional differences.

    “These seemingly contradictory findings could potentially be explained by lysosomal heterogeneity, i.e., all lysosomes are not created equal, and exhibit significant structural and functional differences.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Lysosomes perform multiple functions in the RPE: they help degrade phagocytosed and cellular material, act as signaling platforms, and maintain membrane integrity.

    “The studies discussed above add to the growing body of evidence that lysosomes perform multiple functions in the RPE – they help degrade phagocytosed and cellular material, act as signaling platforms, and maintain membrane integrity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In polarized RPE, calcium ionophores induce exocytosis at both the apical and basolateral domains because syntaxin 4 is non-polar; in MDCK cells, basolateral localization of syntaxin 4 restricts lysosome exocytosis to the basolateral domain.

    “In polarized RPE, calcium ionophores induce exocytosis at both the apical and basolateral domains (Xu et al., 2012), because syntaxin 4 is non-polar in the RPE (Low et al., 2002). This is in contrast to Madin-Darby canine kidney (MDCK) cells where basolateral localization of syntaxin 4 (Low et al., 1996) restricts lysosome exocytosis to the basolateral domain (Xu et al., 2012).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Xu et al., 2012

      Not checked in the free run.

    • cites Low et al., 2002 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Alternative splicing of LAMP2 results in three isoforms, LAMP2a, LAMP2b, and LAMP2c; patients with mutant LAMP2b and LAMP2c have milder phenotypes, whereas those with LAMP2a present with severe disease.

    “Alternative splicing of LAMP2 results in three isoforms, LAMP2a, LAMP2b, and LAMP2c. Patients with mutant LAMP2b and LAMP2c have milder phenotypes, whereas those with LAMP2a present with severe disease (Thiadens et al., 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Thiadens et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Lysosome exocytosis requires a population of peripheral lysosomes close to the plasma membrane, long-range microtubule-mediated transport for peripheral localization, and local depolymerization of the actin cytoskeleton for fusion.

    “Lysosome exocytosis requires a population of peripheral lysosomes in close proximity to the plasma membrane that can be rapidly deployed for fusion in response to membrane damage. Long-range microtubule-mediated transport is required for peripheral localization of lysosomes and local depolymerization of the actin cytoskeleton is essential for the fusion of membrane proximal lysosomes with the cell”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    Peroxisomes are numerous within the RPE and often found adjacent to mitochondria, consistent with the essential role of peroxisomes in β-oxidation of very long chain fatty acids and the lipid catabolic demands placed on the RPE by daily phagocytic uptake and degradation of OS disk membranes.

    “Peroxisomes are numerous within the RPE and often found adjacent to mitochondria, which is not surprising given the essential role of peroxisomes in β-oxidation of very long chain fatty acids (VLCFA) and the lipid catabolic demands placed on the RPE by a daily influx of VLCFA via phagocytic uptake and degradation of OS disk membranes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Fusion of lysosomes with the plasma membrane is a calcium-dependent process crucial for membrane repair, limiting pathogen entry, and clearing cellular debris.

    “Fusion of lysosomes with the plasma membrane is a calcium-dependent process crucial for membrane repair, limiting pathogen entry, and clearing cellular debris (Idone et al., 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Idone et al., 2008 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Peroxisome number, but not necessarily function, is elevated during ageing.

    “Peroxisome number, but not necessarily function, is elevated during ageing.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Rodent and fruit fly models of NPC disease have extensive cholesterol accumulation in the RPE and retinal neurons, increased lipofuscin, and progressive photoreceptor degeneration.

    “Rodent and fruit fly models of NPC disease have extensive cholesterol accumulation in the RPE and retinal neurons, increased lipofuscin, and progressive photoreceptor degeneration (Phillips et al., 2008; Claudepierre et al., 2010).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Phillips et al., 2008 source

      Not checked in the free run.

    • cites Claudepierre et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Patients with Danon disease have increased fundus autofluorescence and abnormal full-field ERGs, indicative of decreased lysosome function and loss of RPE function.

    “Patients with Danon disease have increased fundus autofluorescence and abnormal full-field ERGs, indicative of decreased lysosome function and loss of RPE function (Thompson et al., 2016).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Thompson et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Despite diurnal peaks in phagocytosis, peroxisome numbers are stable throughout the day in mouse RPE; however, catalase activity is elevated during the early morning hours when ingested phagosomes are highest, suggesting enzyme induction.

    “Surprisingly, despite diurnal peaks in phagocytosis and therefore peaks in substrate availability for β-oxidation, peroxisome numbers are stable throughout the day in mouse RPE. However, activity of the peroxisome antioxidant catalase is elevated during the early morning hours when numbers of ingested phagosomes are highest, suggesting enzyme induction (Daniele et al., 2019).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Daniele et al., 2019 source

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning

    The RPE is one of few epithelia that do not express AP-1B; in its absence, transferrin receptor and CAR are initially sorted to the basolateral membrane but upon endocytosis are transcytosed to the apical domain instead of being recycled back.

    “The RPE is one of few epithelia that do not express the clathrin adaptor protein AP-1B that is required for basolateral localization of both transferrin receptor and CAR. In the absence of AP-1B, these proteins are initially sorted to the basolateral membrane from the Golgi network, but upon endocytosis, are transcytosed to the apical domain instead of being recycled back to the basolateral”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In RPE with defective microtubule transport such as in the Abca4−/− mouse, lysosomes are sequestered in the perinuclear region; the resulting decrease in membrane proximal lysosomes prevents membrane repair after complement attack and makes the RPE susceptible to mitochondrial damage.

    “In RPE with defective microtubule transport such as in the Abca4−/− mouse, lysosomes are sequestered in the perinuclear region. The resulting decrease in membrane proximal lysosomes prevents membrane repair after complement attack, and makes the RPE susceptible to mitochondrial damage (Tan et al., 2016).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Tan et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Late endosomes mature into lysosomes, which are the major degradative compartments in the cell.

    “Late endosomes mature into lysosomes, which are the major degradative compartments in the cell.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The protein, lipid, and RNA content, stimulus for secretion, and machinery involved in exosome biogenesis and release are all cell type-dependent.

    “The protein, lipid, and RNA (mRNA and microRNA) content, stimulus for secretion, and machinery involved in exosome biogenesis and release are all cell type-dependent (for an in-depth discussion of our current understanding of exosome biology see van Niel et al., 2018).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites van Niel et al., 2018 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In normal RPE, complement attack accelerates CD59 recycling to the apical membrane to prevent MAC assembly; in the Abca4−/− mouse model of Stargardt disease, increased cholesterol prevents CD59 recycling and reroutes it to lysosomes, leading to increased MAC formation, increased intracellular calcium, mitochondrial fragmentation, and oxidative stress.

    “In normal RPE, complement attack accelerates CD59 recycling to the apical membrane to prevent MAC assembly. However, in the Abca4−/− mouse model of Stargardt disease, increased cholesterol prevents CD59 recycling in response to complement, and reroutes it to lysosomes. The resultant increase in MAC formation leads to increased intracellular calcium, mitochondrial fragmentation, and oxidative”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Tan et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    RPE-derived exosomes participate in inflammatory signaling and immune modulation; exosomes released by healthy RPE decrease inflammation and downregulate the immune response, whereas exosomes released by stressed RPE promote inflammation and activate immune cells.

    “a common theme that has emerged from these studies suggests that RPE-derived exosomes participate in inflammatory signaling and in immune modulation. Exosomes released by healthy RPE serve to decrease inflammation and downregulate the immune response, whereas exosomes released by stressed RPE promote inflammation and activate immune cells (Biasutto et al., 2013; Gangalum et al., 2016; Knickelbein”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Biasutto et al., 2013 source

      Not checked in the free run.

    • cites Gangalum et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Circadian clearance of OS phagosomes by the RPE occurs normally in the Abca4−/− model, suggesting that cathepsin D activity is not affected.

    “Circadian clearance of OS phagosomes by the RPE occurs normally in this model, suggesting that cathepsin D activity is not affected (Kaur et al., 2018).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kaur et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    Exosomes transfer proteins, lipids, and genetic material between cells, suggesting that they can participate in epithelial polarity, development, and tissue morphogenesis.

    “Exosomes transfer proteins, lipids, and genetic material between cells, suggesting that they can participate in epithelial polarity, development, and tissue morphogenesis (Lakkaraju and Rodriguez-Boulan, 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Lakkaraju and Rodriguez-Boulan, 2008

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Although cardiomyopathy is the most common symptom of Danon disease, approximately 70% of patients have retinal abnormalities including chorioretinal atrophy and cone-rod dystrophy.

    “Although cardiomyopathy is the most common symptom of Danon disease, ~70% of patients have retinal abnormalities. These include chorioretinal atrophy and cone-rod dystrophy.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Lysosomes in the RPE are likely heterogeneous, with location determining their structure, content, and therefore function.

    “Lysosomes in the RPE are likely heterogeneous, with location determining the structure, content, and therefore function.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Lysosome exocytosis prevents intracellular calcium increase and protects RPE mitochondria from fragmentation.

    “Lysosome exocytosis also prevents intracellular calcium increase and protects RPE mitochondria from fragmentation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Peroxisome biogenesis occurs by two distinct mechanisms: de novo synthesis or self-replication through growth and fission.

    “Peroxisome biogenesis occurs by two distinct mechanisms, de novo synthesis (Ma et al., 2011; Agrawal and Subramani, 2016) or, self-replication through growth and fission (Schrader et al., 2012).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Ma et al., 2011

      Not checked in the free run.

    • cites Schrader et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In de novo peroxisome synthesis, pre-peroxisomal vesicles bearing PEX16 and PEX3 bud from the endoplasmic reticulum and mitochondria, respectively, and heterotypic fusion establishes pre-peroxisomes competent to import other peroxisomal membrane proteins.

    “In de novo synthesis, mature peroxisomes are built incrementally, with the first step a budding of pre-peroxisomal vesicles bearing complementary proteins of the early import machinery, PEX16 and PEX3, from membranes of the endoplasmic reticulum and mitochondria, respectively (Schrader and Pellegrini, 2017; Sugiura et al., 2017). Heterotypic fusion of PEX3- and PEX16-bearing vesicles establish a”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Schrader and Pellegrini, 2017

      Not checked in the free run.

    • cites Sugiura et al., 2017 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Peroxisomes are degraded by regulated autophagy and to a lesser extent by peroxisomal LONP2-mediated proteolysis and lipoxygenase 15-mediated membrane disruption.

    “Peroxisomes are degraded by regulated autophagy (Deosaran et al., 2013; Nordgren et al., 2013) and to a lesser extent, peroxisomal Lon peptidase 2 (LONP2)-mediated proteolysis, and membrane disruption that is mediated by lipoxygenase 15 (Yokota et al., 2001; Yokota and Fahimi, 2009; Walker et al., 2018).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Deosaran et al., 2013

      Not checked in the free run.

    • cites Nordgren et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    PEX11β mediates peroxisome proliferation in the absence of external stimuli and facilitates peroxisome fission by promoting membrane deformation that depends on its self-dimerization.

    “PEX11β was shown to mediate peroxisome proliferation in the absence of external stimuli (Schrader et al., 1998). It facilitates peroxisome fission by promoting membrane deformation that depends on its self-dimerization (Bonekamp et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Schrader et al., 1998 source

      Not checked in the free run.

    • cites Bonekamp et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In aged human RPE, peroxisome number is increased but antioxidant and enzyme activity is reduced.

    “where peroxisome number is increased, but antioxidant and enzyme activity is reduced (Beier et al., 1993).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Beier et al., 1993 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Peroxisome proliferation is induced through stimulation of PPARα activity in response to oxidative stress following ischemic injury in neurons.

    “Peroxisome proliferation is induced through stimulation of peroxisome proliferator-activated receptor (PPAR) α activity in response to oxidative stress following ischemic injury in neurons (Young et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Young et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    DLP-1 has a shared function in peroxisomal and mitochondrial fission and is recruited to peroxisomes by MFF and FIS1 following PEX11β-mediated elongation.

    “DLP-1 has a shared function in peroxisomal and mitochondrial fission, and is recruited to peroxisomes by two mitochondrial-associated fission factors, mitochondrial fission factor (MFF) (Gandre-Babbe and van der Bliek, 2008), and mitochondrial fission 1 (FIS1), following PEX11β-mediated elongation (Koch et al., 2005; Itoyama et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Gandre-Babbe and van der Bliek, 2008 source

      Not checked in the free run.

    • cites Koch et al., 2005 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The RPE is oxidative and uses lactate produced by the photoreceptors and fatty acids from ingested OSs to fuel mitochondrial metabolism.

    “In contrast, the RPE is oxidative and uses lactate produced by the photoreceptors and fatty acids from ingested OSs to fuel mitochondrial metabolism (Adijanto et al., 2014; Adijanto and Philp, 2014; Kanow et al., 2017; Reyes-Reveles et al., 2017).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Adijanto et al., 2014

      Not checked in the free run.

    • cites Adijanto and Philp, 2014

      Not checked in the free run.

    • cites Kanow et al., 2017 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In aged versus young C. elegans, peroxisome number is increased and peroxisomal import efficiency is reduced.

    “A recent proteomic study of C. elegans also showed an increase in peroxisome number, and reduced import efficiency in aged versus young worms (Narayan et al., 2016)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Narayan et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Oxidants and ultraviolet light stimulate the elongation of peroxisomes in cultured hepatic cells.

    “Oxidants and ultraviolet light stimulate the elongation of peroxisomes in cultured hepatic cells (Schrader et al., 1999).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schrader et al., 1999 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In human fetal RPE, 50% of palmitate-derived acetyl-CoA was diverted towards ketogenesis to produce β-HB, while the remaining acetyl-CoA entered the TCA cycle.

    “A quantitative assessment of 13C-palmitate oxidation by human fetal RPE suggested that 50% of palmitate-derived acetyl-CoA was diverted towards ketogenesis to produce β-HB which was released apically, whereas the remaining acetyl-CoA entered the TCA cycle (Adijanto et al., 2014).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Adijanto et al., 2014

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In freshly isolated human RPE, expression of PPARα and PPARβ/δ was relatively high, while PPARγ was not detected.

    “Expression of PPARα and β/δ was relatively high in freshly isolated human RPE; however, PPARγ was not detected.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dwyer et al., 2011 source

      Not checked in the free run.

    • Rests on an assumption: Little is known of the role of PPARs in the regulation of RPE peroxisome homeostasis or proliferation.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PPARs are nuclear hormone receptors that respond to binding of endogenous fatty acids and fatty acid derivatives such as eicosanoids, by regulating expression of genes within diverse cellular pathways including lipid metabolism and inflammation.

    “PPARs are nuclear hormone receptors that respond to binding of endogenous fatty acids and fatty acid derivatives such as eicosanoids, by regulating expression of genes within diverse cellular pathways including lipid metabolism and inflammation (Kliewer et al., 1997; Chinetti et al., 2000).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Kliewer et al., 1997 source

      Not checked in the free run.

    • cites Chinetti et al., 2000 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    The RPE is the gatekeeper of the outer retina and regulates the flux of nutrients and oxygen between the choroid and the subretinal space.

    “The RPE is the gatekeeper of the outer retina, and regulates the flux of nutrients and oxygen between the choroid and the subretinal space.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Impaired peroxisome turnover during aging could result in the elevated peroxisome numbers that have been observed.

    “impaired peroxisome turnover during aging could result in the elevated peroxisome numbers that have been observed.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The specific mechanisms responsible for elevated peroxisomes in ageing and in AMD have not been elucidated in the RPE.

  • May combine two claims.

    Premisecitation

    Glucose is transported from the choroid to the subretinal space by GLUT1, which is expressed in the basolateral and apical membranes of the RPE.

    “Glucose, the major energy substrate of photoreceptor and Müller glial cells, is transported from the choroid to the subretinal space by the glucose transporter, GLUT1, which is expressed in the basolateral and apical membranes of the RPE (Swarup et al., 2019)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Swarup et al., 2019 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Glycolysis is low in the RPE so that glucose is spared for the outer retina.

    “Glycolysis is low in the RPE so that glucose is spared for the outer retina.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    PPARβ/δ is implicated in modification of AMD disease severity, but distinct effects of PPARβ/δ modulation depend on cell type.

    “Recently PPARβ/δ was implicated in modification of AMD disease severity, but distinct effects of PPARβ/δ modulation depended on cell type (Choudhary et al., 2016).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Choudhary et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Mitochondrial dysfunction could contribute to pathological changes in the retina.

    “Since mitochondria have roles in energy production, calcium regulation, and generation of metabolites that regulate gene expression, it is easy to understand how mitochondrial dysfunction could contribute to pathological changes in the retina.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Glycolysis is not required to support the metabolic needs of the RPE or for late-stage differentiation of the RPE.

    “This deletion did not impact differentiation or functional properties of the RPE, demonstrating that glycolysis is not required to support the metabolic needs of the RPE (Swarup et al., 2019) nor, as predicted from early in vitro studies, is it required for late stage differentiation (Adijanto et al., 2014).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Swarup et al., 2019 source

      Not checked in the free run.

    • cites Adijanto et al., 2014

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    A shift from oxidative to glycolytic metabolism leads to dedifferentiation of the RPE and a loss of expression of proteins required for RPE-specific functions.

    “In fact, a shift from oxidative to glycolytic metabolism leads to dedifferentiation of the RPE and a loss of expression of proteins required for RPE-specific functions.”
    Quote in the paperSubstantial claim
252 of 252

  • The paper relies on this without support.

    Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness.

    “Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness.”

  • The paper relies on this without support.

    The RPE is the primary caretaker of photoreceptor health and function.

    “The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function.”

  • The paper relies on this without support.

    The RPE forms a critical barrier between the retina and the systemic circulation and performs many essential functions to support the neural retina.

    “The retinal pigment epithelium (RPE) forms a critical barrier between the retina and the systemic circulation, and performs many essential functions to support the neural retina.”

  • The paper relies on this without support.

    New technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors.

    “In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors.”

  • The paper relies on this without support.

    OS phagocytosis is an important function of RPE cells.

    “Given that OS phagocytosis is an important function of RPE cells, measuring phagocytic capacity of these cells is a commonly-used metric.”

  • The paper relies on this without support.

    RPE cell cultures are disconnected from in vivo rhythms.

    “RPE cell cultures appear to be disconnected from in vivo rhythms, but are nevertheless amenable to experimentally-induced pulses of OS phagocytosis.”

  • The paper relies on this without support.

    Cysteine proteases are considerably more abundant than aspartyl proteases.

    “Cysteine proteases are considerably more abundant than aspartyl proteases.”

  • The paper relies on this without support.

    OS phagosomes have a high lipid content.

    “Given the high lipid content of OS phagosomes, it is not surprising that the RPE has the highest acid lipase activity of all ocular tissues (Hayasaka et al., 1977).”

  • The paper relies on this without support.

    Classical autophagy occurs at a basal, constitutive level in all eukaryotic cells.

    “Classical autophagy occurs at a basal, constitutive level in all eukaryotic cells, and is modulated by intrinsic and extrinsic stimuli.”

  • The paper relies on this without support.

    The specific mechanisms responsible for elevated peroxisomes in ageing and in AMD have not been elucidated in the RPE.

    “However, the specific mechanisms responsible for elevated peroxisomes in ageing and in AMD have not been elucidated in the RPE.”

  • The paper relies on this without support.

    Little is known of the role of PPARs in the regulation of RPE peroxisome homeostasis or proliferation.

    “However, little is known of the role of PPARs in the regulation of RPE peroxisome homeostasis or proliferation.”

  • The paper relies on this without support.

    No studies have demonstrated elevated peroxisome numbers or function as a result of PPAR regulation in RPE cells.

    “However, we are otherwise unaware of studies demonstrating elevated peroxisome numbers or function as a result of PPAR regulation in RPE cells.”
12 of 12

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Autophagosomes are assigned to the wrong section

    Minor

    The organelle overview directs readers to Section 4 for autophagosomes, but the paper says classical autophagy is discussed in Section 5. Section 4 covers LC3-associated phagocytosis, which it describes as autophagosome-independent.

1 of 1

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Related

Authors
Lakkaraju, A., Umapathy, A., Tan, L. X., Daniele, L., Philp, N. J., Boesze-Battaglia, K., & Williams, D. S.
Affiliations
  • University of California, San Francisco (US)
  • University of California, Los Angeles (US)
  • University of Pennsylvania (US)
  • Thomas Jefferson University (US)
Corresponding author
Williams, David S.
ORCID
Venue
Progress in Retinal and Eye Research
Publisher
Elsevier BV
Published
2020-09
Volume
78
Pages
100846
ISSN
1350-9462 (ISSN-L)
DOI
10.1016/j.preteyeres.2020.100846
PMC
PMC8941496
OpenAlex
W3007934773
Semantic Scholar
63c695d367d8f86b4997e021b2442387126d8b1b
Cited by
422
References
379
Citations by year
2026: 59 · 2025: 79 · 2024: 94 · 2023: 70 · 2022: 53 · 2021: 52 · 2020: 14
FWCI
4.52
Type
journal article
Language
en
Open access
Licence
Locations
  • Progress in Retinal and Eye Research (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
  • Scholarly Commons (University of Pennsylvania) (submittedVersion)
Funders
  • OS
  • NIH NEI (R01 EY023299, R01 EY026525, R01 EY012042, R21 EY029826, R01EY027442, R01EY013408)
  • Foundation Fighting Blindness grant
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Retinal Development and Disorders
  • Health Sciences › Medicine › Ophthalmology › Retinal Diseases and Treatments
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Retinal Imaging and Analysis
Keywords
retinal pigment epithelium, photoreceptor outer segment phagocytosis, autophagy, retinal disease, live-cell imaging

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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