Rett syndrome: a neurological disorder with metabolic components

In the paper

“Interestingly, lovastatin does not have a strong therapeutic effect on B6.Mecp2tm1.1Bird male mice, supporting the idea that elevated peripheral lipids may be a biomarker for those patients who may respond to statin drugs [188].”

What the sources say

• Disputed

  The Discussion argues against using elevated serum cholesterol to identify statin responders: it reports improved motor deficits with fluvastatin in female mice whose serum cholesterol was unchanged. It instead proposes investigating plasma 24S-hydroxycholesterol as a possible biomarker of brain cholesterol metabolism that might help identify patients for treatment; that is not a claim that elevated peripheral lipids predict response. (LLM, conf=0.86)

  Checked by a reasoning model — may be wrong.

  cites [188] Villani C, Sacchetti G, Bagnati R, Passoni A, Fusco F, Carli M, Invernizzi RW 2016 Lovastatin fails to improve motor performance and survival in methyl-CpG-binding protein2-null mice. Elife 5, e22409 (doi:10.7554/eLife.22409) 27892851 PMC5132339 sourceExperimental — accuracy not yet measured

In the paper

“However, MeCP2 may also facilitate transcriptional activation [77], chromatin compaction [78,79] and mRNA splicing [80,81], while also interacting with a host of other regulatory proteins involved in a variety of molecular pathways [81–84].”

What the sources say

• Supported

  The Abstract reports that MeCP2 can function as a transcriptional activator as well as a repressor in the mouse hypothalamus. It also reports MeCP2 binding with CREB1 at the promoter of an activated target, supporting the cited claim that MeCP2 may facilitate transcriptional activation. The other functions in the citing sentence have separate citations and are not attributed to this source. (LLM, conf=0.94)

  cites [77] Chahrour M, Jung SYY, Shaw C, Zhou X, Wong STCTC, Qin J, Zoghbi HYY 2008 MeCP2, a key contributor to neurological disease, activates and represses transcription. Science 320, 1224– 1229. (doi:10.1126/science.1153252) 18511691 PMC2443785 source
• Supported

  The citation to this paper supports the chromatin-compaction clause, not the separately cited claims about activation, splicing, or regulatory proteins. The Abstract and the section “Human MeCP2 Is a Unique Architectural Chromatin-binding Protein” report that MeCP2 compacted unmethylated nucleosomal arrays in vitro. (LLM, conf=0.94)

  cites [78] Georgel PT, Horowitz-Scherer RA, Adkins N, Woodcock CL, Wade PA, Hansen JC 2003 Chromatin compaction by human MeCP2: asssembly of novel secondary chromatin structures in the absence of DNA methylation. J. Biol. Chem. 278, 32 181– 32 188. (doi:10.1074/jbc.M305308200) 12788925 source
• Supported

  This source supports the chromatin-compaction portion of the sentence, to which citations [78,79] are attached. The Results section (‘MeCP2-R270X and MeCP2-G273X differ in their activity towards nucleosomal arrays’) reports that wild-type MeCP2 greatly facilitated oligomerization of nucleosomal arrays in an assay used to model compacted chromatin; the Introduction also describes MeCP2 compacting nucleosomal arrays in vitro. (LLM, conf=0.93)

  cites [79] Baker SA, Chen L, Wilkins AD, Yu P, Lichtarge O, Zoghbi HY 2013 An AT-hook domain in MeCP2 determines the clinical course of Rett syndrome and related disorders. Cell 152, 984– 996. (doi:10.1016/j.cell.2013.01.038) 23452848 PMC3641682 source
• Supported

  The Results section reports MeCP2-interacting proteins involved in transcriptional regulation, chromatin remodeling and RNA splicing. The Discussion states that the study provides strong evidence for MeCP2’s involvement in regulating RNA splicing. Transcriptional activation and chromatin compaction are assigned to other citations in the citing sentence, not to this source. (LLM, conf=0.92)

  cites [80] Li R et al. 2016 Misregulation of alternative splicing in a mouse model of Rett syndrome. PLoS Genet. 12, e1006129 (doi:10.1371/journal.pgen.1006129) 27352031 PMC4924826 source
• Supported

  For this source, the citing sentence attributes mRNA splicing and interactions with regulatory proteins to MeCP2; its activation and chromatin-compaction claims cite other sources. The Results show that MeCP2 affects splicing of a CD44 reporter, and the Discussion reports its interaction with YB-1, a protein involved in RNA processing (page numbers unavailable in our copy). (LLM, conf=0.92)

  cites [81] Young JI et al. 2005 Regulation of RNA splicing by the methylation-dependent transcriptional repressor methyl-CpG binding protein 2. Proc. Natl Acad. Sci. USA 102, 17 551– 17 558. (doi:10.1073/pnas.0507856102) PMC1266160 16251272 source

In the paper

“Consistently, MeCP2 represses transcription in a gene-specific manner, interacting with the co-repressor complexes mSIN3A and NCoR1/SMRT [70,76].”

What the sources say

• Partly supported

  The Results (page unavailable) confirm MeCP2’s interactions with both SIN3A and NCoR/SMRT and show repression of a reporter gene. The Discussion (page unavailable) describes silencing of specific genes as a possibility, alongside global inhibition of transcriptional noise; it does not establish gene-specific repression as a general fact. (LLM, conf=0.88)

  cites [70] Lyst MJ et al. 2013 Rett syndrome mutations abolish the interaction of MeCP2 with the NCoR/SMRT co-repressor. Nat. Neurosci. 16, 898– 902. (doi:10.1038/nn.3434) 23770565 PMC3786392 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [76] Nan X, Ng H-HH, Johnson CA, Laherty CD, Turner BM, Eisenman RN, Bird A 1998 Transcriptional repression by the methyl-CpG-binding protein MeCP2 involves a histone deacetylase complex. Nature 393, 386– 389. (doi:10.1038/30764) 9620804 source

In the paper

“Though Mecp2 null mice are asymptomatic prior to four weeks of age, there are subtle but consistent defects in transcription, ionotropic receptor signalling, and neuronal responsiveness during late embryogenesis and the perinatal period [122–124].”

What the sources say

• ?Not checked — no full text of the sourcecites [122] Bedogni F et al. 2016 Defects during Mecp2 null embryonic cortex development precede the onset of overt neurological symptoms. Cereb. Cortex 26, 2517– 2529. (doi:10.1093/cercor/bhv078) 25979088 source
• Partly supported

  The Abstract (page unavailable) reports subtle developmental differences from the first postnatal week despite an apparently normal phenotype, and the milestone results describe early reflex deficits in Mecp2-null mice. The paper does not establish defects in ionotropic receptor signalling or neuronal responsiveness, nor does it demonstrate that the reported deficits occurred during late embryogenesis; its transcription discussion does not establish a defect at that stage. (LLM, conf=0.88)

  cites [123] Santos M, Silva-Fernandes A, Oliveira P, Sousa N, Maciel P 2007 Evidence for abnormal early development in a mouse model of Rett syndrome. Genes Brain Behav. 6, 277– 286. (doi:10.1111/j.1601-183X.2006.00258.x) 16848781 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [124] Chao H-TT, Zoghbi HYY, Rosenmund C 2007 MeCP2 controls excitatory synaptic strength by regulating glutamatergic synapse number. Neuron 56, 58– 65. (doi:10.1016/j.neuron.2007.08.018) 17920015 PMC2198899 source

In the paper

“Altogether, multiple studies suggest that genes can be activated or repressed by MeCP2, depending upon the cellular context [77,89,90], suggesting that MeCP2 may be defined as a transcriptional modulator.”

What the sources say

• Supported

  The paper’s Abstract says MeCP2 regulates gene expression in the mouse hypothalamus and can function as both a transcriptional activator and a repressor. That supports the citing sentence’s characterization of MeCP2 as a transcriptional modulator. (LLM, conf=0.94)

  cites [77] Chahrour M, Jung SYY, Shaw C, Zhou X, Wong STCTC, Qin J, Zoghbi HYY 2008 MeCP2, a key contributor to neurological disease, activates and represses transcription. Science 320, 1224– 1229. (doi:10.1126/science.1153252) 18511691 PMC2443785 source
• Supported

  The Abstract describes MeCP2 as a modulator that can both increase and decrease gene expression. The Results also report MeCP2 binding to the promoters of an activated target and a repressed target, supporting the citing sentence's characterization. (LLM, conf=0.94)

  cites [89] Ben-Shachar S, Chahrour M, Thaller C, Shaw CA, Zoghbi HY 2009 Mouse models of MeCP2 disorders share gene expression changes in the cerebellum and hypothalamus. Hum. Mol. Genet. 18, 2431– 2442. (doi:10.1093/hmg/ddp181) 19369296 PMC2694691 source
• Supported

  The Background describes MeCP2 as a global transcription factor that can both activate and repress transcription. This supports the citing sentence’s description of MeCP2 as a transcriptional modulator. (LLM, conf=0.93)

  cites [90] Pacheco NL, Heaven MR, Holt LM, Crossman DK, Boggio KJ, Shaffer SA, Flint DL, Olsen ML 2017 RNA sequencing and proteomics approaches reveal novel deficits in the cortex of Mecp2-deficient mice, a model for Rett syndrome. Mol. Autism 8, 56 (doi:10.1186/s13229-017-0174-4) 29090078 PMC5655833 source

In the paper

“Importantly, cholesterol cannot cross the blood–brain barrier (BBB), so any cholesterol that the brain requires must be synthesized in situ [161].”

What the sources say

• ?Could not verify

  The Introduction discusses cholesterol in caveolar membranes and BBB transport generally, but does not say whether cholesterol crosses the BBB or whether the brain must synthesize its own. Searches for cholesterol crossing the barrier and synthesis in the brain found no passage addressing either point. (LLM, conf=0.76)

  cites [161] Zlokovic BV 2008 The blood-brain barrier in health and chronic neurodegenerative disorders. Neuron 57, 178– 201. (doi:10.1016/j.neuron.2008.01.003) 18215617 sourceExperimental — accuracy not yet measured

In the paper

“During the fasting cycle, the NCoR1/SMRT-HDAC3 complex maximally occupies hepatocyte chromatin, repressing the expression of genes involved in lipid synthesis and sequestration. However, during the feeding cycle, it releases chromatin, allowing for expression of its targeted loci [177].”

What the sources say

• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [177] Feng D, Liu T, Sun Z, Bugge A, Mullican SE, Alenghat T, Liu XS, Lazar MA 2011 A circadian rhythm orchestrated by histone deacetylase 3 controls hepatic lipid metabolism. Science 331, 1315– 1319. (doi:10.1126/science.1198125) 21393543 PMC3389392 sourceExperimental — accuracy not yet measured

In the paper

“Remarkably, treatment with either fluvastatin or lovastatin improves subjective health scores, motor performance (measured by rotarod and open field activity) and increases lifespan in 129.Mecp2tm1.1Bird male and female mutant mice when compared with control mice receiving a vehicle [156].”

What the sources say

• Partly supported

  The Results section (page unavailable) reports that fluvastatin improved subjective health scores, rotarod performance, open-field activity, and lifespan in male mutant mice versus sham-dosed controls. It reports rotarod and open-field improvements with lovastatin in males, but not improved health scores or lifespan. In females, it reports improved rotarod performance and survival through the fluvastatin trial, but not the full set of outcomes claimed for both drugs and sexes. (LLM, conf=0.90)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured

In the paper

“Consequently, the expression of Cyp46a1 is increased, indicating a heightened need for cholesterol turnover.”

What the sources say

• Partly supported

  The Results section reports that Cyp46a1 expression was 38% higher in P28 Mecp2 null mouse brains and interprets this as indicating a heightened need for neuronal cholesterol turnover. It describes the mice at P28 as displaying mild symptoms, however, not as pre-symptomatic. Page numbers were not supplied. (LLM, conf=0.88)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured

In the paper

“Triglycerides accumulate in the liver, and fatty liver disease develops, as indicated by pale liver.”

What the sources say

• Partly supported

  The Results section reports greatly increased liver triglycerides in symptomatic 129.Mecp2 null males by postnatal day 56, and the Discussion refers to fatty liver disease in these mice. The copy does not report pale liver as the indication of disease, so that detail is unsupported. (LLM, conf=0.83)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured

In the paper

“In support of this, Sqle, the suppressor of RTT-like phenotypes in mice, is a target of HDAC3, and its transcription increases approximately 170-fold in response to Hdac3 liver deletion [156,178].”

What the sources say

• Partly supported

  The Results identify a Sqle mutation that rescues Rett-like phenotypes in mice. The Discussion says Sqle promoter regions appear to be HDAC3 targets in the liver, but our copy does not report an approximately 170-fold increase in Sqle transcription after liver-specific Hdac3 deletion; it also frames the targeting as tentative. (LLM, conf=0.88)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured
• Supported

  The section on lipid and cholesterol biosynthesis reports an approximately 173-fold increase in Sqle expression in Hdac3-null livers. The histone-acetylation section also identifies Sqle among the genes de-repressed after Hdac3 inactivation, supporting its description as an HDAC3-regulated target. (LLM, conf=0.93)

  cites [178] Knutson SK, Chyla BJ, Amann JM, Bhaskara S, Huppert SS, Hiebert SW 2008 Liver-specific deletion of histone deacetylase 3 disrupts metabolic transcriptional networks. EMBO J. 27, 1017– 1028. (doi:10.1038/emboj.2008.51) 18354499 PMC2323257 source

In the paper

“Loss of MeCP2 decreases HDAC3 binding to DNA, resulting in hyperacetylated histones, and increases transcription of numerous lipid-regulating genes.”

What the sources say

• Supported

  The Results report that MeCP2 loss reduces HDAC3 binding near the Sqle, Fasn, and Cd36 transcription start sites and increases the activating histone-acetylation mark H3K27ac at those loci. The Results also report increased expression of multiple genes involved in fatty-acid and cholesterol metabolism in Mecp2-null mouse liver; the Discussion’s Figure 6 describes the same proposed sequence from reduced HDAC3 binding to aberrant transcription. (LLM, conf=0.92)

  cites [180] Kyle SM, Saha PK, Brown HM, Chan LC, Justice MJ 2016 MeCP2 co-ordinates liver lipid metabolism with the NCoR1/HDAC3 corepressor complex. Hum. Mol. Genet. 25, 3029– 3041. (doi:10.1093/hmg/ddw156) 27288453 PMC5181597 source

In the paper

“Additionally, CD1.Mecp2tm1.1Bird mice have an increase in serum triglycerides with no corresponding change in serum cholesterol [125].”

What the sources say

• Supported

  The Results and Discussion state that CD1 Mecp2tm1.1Bird/Y mice had unaltered cholesterol levels at pre- and post-symptomatic stages, while triglycerides were increased at P60, when symptoms were evident. The claim accurately summarizes that finding, though the observed triglyceride increase is specific to P60. (LLM, conf=0.94)

  cites [125] Gigli CC, Scaramuzza L, Gandaglia A, Bellini E, Gabaglio M, Parolaro D, Kilstrup-Nielsen C, Landsberger N, Bedogni F 2016 MeCP2 related studies benefit from the use of CD1 as genetic background. PLoS ONE 11, e0153473 (doi:10.1371/journal.pone.0153473) 27097329 PMC4838291 source

In the paper

“Remarkably, restoration of MeCP2 expression reversed symptoms: neurological assessments and overall health improved and 80% of TM-treated animals survived beyond 30 weeks of age (end of study).”

What the sources say

• Partly supported

  The passage describing the symptomatic male mice (indexed as Abstract; page unavailable) reports improved symptom scores after MeCP2 restoration and says five of six TM-treated animals survived well beyond the untreated mice’s maximum recorded lifespan of 17 weeks. It does not establish that 80% survived beyond 30 weeks of age or identify 30 weeks as the end of the study. (LLM, conf=0.86)

  cites [145] Guy J, Gan J, Selfridge J, Cobb S, Bird A 2007 Reversal of neurological defects in a mouse model of Rett syndrome. Science 315, 1143– 1147. (doi:10.1126/science.1138389) 17289941 PMC7610836 sourceExperimental — accuracy not yet measured

In the paper

“A number of conditional deletions in different subsets of neurons highlight the essential role of MeCP2 in neuronal function, yet their milder presentation suggests additional roles outside the CNS (reviewed in [143]).”

What the sources say

• Partly supported

  The Specific Spatio-Temporal Deletions section reports that forebrain-neuron Mecp2 deletion produces a milder phenotype and that deletion in other neuronal subsets causes neurological symptoms. It does not infer from those milder phenotypes that MeCP2 has roles outside the CNS. The Widespread Mecp2 Deletions section instead reports that brain-specific deletion in neuronal and glial lineages produces a phenotype similar to widespread deficiency. (LLM, conf=0.86)

  cites [143] Li W 2012 Beyond widespread Mecp2 deletions to model Rett syndrome: conditional spatio-temporal knockout, single-point mutations and transgenic rescue mice. Autism Open Access 2012(Suppl. 1), 5 (doi:10.4172/2165-7890.S1-005) 23946910 PMC3740402 sourceExperimental — accuracy not yet measured

In the paper

“Owing to decreased synthesis, brain cholesterol remains high, but not as high as at younger ages (smaller red arrow).”

What the sources say

• Partly supported

  The Results section reports elevated brain cholesterol at P56, when Mecp2 mutant males were severely symptomatic, along with downregulation of cholesterol-biosynthesis genes. But by P70, brain cholesterol in the null mice had returned to wild-type levels; the paper does not support saying it remained high at that later age. (LLM, conf=0.86)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured

In the paper

“Outside of the central nervous system, serum cholesterol is elevated, and expression of cholesterol biosynthesis genes is elevated in the liver.”

What the sources say

• Partly supported

  The Results section (‘Mecp2 null males have abnormal cholesterol metabolism’; page unavailable) reports elevated serum cholesterol and liver Hmgcr and Sqle expression in 129.Mecp2 null males at P56, when the mice were severely symptomatic. Liver gene expression was unchanged at P28, and the reported peripheral elevations were not seen in the B6 strain. The paper therefore supports the abnormalities, but not the claim that they occur in pre-symptomatic mice. (LLM, conf=0.90)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 sourceExperimental — accuracy not yet measured

In the paper

“Oxysterols can pass lipophilic membranes more easily than cholesterol, allowing for one-way egress across the BBB and into the body [163].”

What the sources say

• Partly supported

  The Discussion (page unavailable) says that 24S-hydroxycholesterol is readily secreted across the blood–brain barrier into circulation and then taken up by the liver. It does not establish that oxysterols generally cross lipophilic membranes more easily than cholesterol, or that passage across the barrier is one-way. (LLM, conf=0.85)

  cites [163] Lund EG, Guileyardo JM, Russell DW 1999 cDNA cloning of cholesterol 24-hydroxylase, a mediator of cholesterol homeostasis in the brain. Proc. Natl Acad. Sci. USA 96, 7238– 7243. (doi:10.1073/pnas.96.13.7238) 10377398 PMC22064 sourceExperimental — accuracy not yet measured

In the paper

“This mutation in Sqle improved RTT-like motor phenotypes, overall health and lifespan in Mecp2 null male mice [156].”

What the sources say

• Supported

  The Results section ('Whole exome sequencing reveals a stop codon mutation that confers rescue'; page unavailable) reports improved rotarod performance, open-field activity, and longevity in Mecp2-null male mice carrying the Sqle mutation. The 'ENU screen identifies five suppressors of Mecp2' Results section also reports health-trait rescue in the suppressor lines. The paper cautions that the Sqle mutation did not improve every symptom, but the claim does not assert that it did. (LLM, conf=0.90)

  cites [156] Buchovecky CM et al. 2013 A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat. Genet. 45, 1013– 1020. (doi:10.1038/ng.2714) 23892605 PMC3837522 source

In the paper

“Mice with a liver-specific deletion of Hdac3 display an increased expression of de novo lipogenesis enzymes due to a constitutively active transcriptional environment, resulting in fatty liver disease and elevated serum cholesterol [178,179].”

What the sources say

• Supported

  The section on lipid and cholesterol biosynthesis reports increased expression of fatty-acid synthesis enzymes after liver-specific Hdac3 deletion. The Discussion describes de-repression of metabolic genes with increased histone acetylation, while “Loss of Hdac3 disrupts metabolic homeostasis” reports liver lipid accumulation and significantly increased serum cholesterol. Together, these support the citing sentence’s account of the transcriptional and metabolic effects. (LLM, conf=0.87)

  cites [178] Knutson SK, Chyla BJ, Amann JM, Bhaskara S, Huppert SS, Hiebert SW 2008 Liver-specific deletion of histone deacetylase 3 disrupts metabolic transcriptional networks. EMBO J. 27, 1017– 1028. (doi:10.1038/emboj.2008.51) 18354499 PMC2323257 source
• Partly supported

  The Results sections on Hdac3-depleted fatty liver and metabolic rerouting report that liver-specific Hdac3 deletion increases expression of lipid-synthesis genes and causes hepatosteatosis. The paper describes derepression of lipogenic genes, but does not establish the claimed constitutively active transcriptional environment; no passage found reports elevated serum cholesterol (searched: cholesterol, plasma cholesterol). Page numbers were not available in our copy. (LLM, conf=0.86)

  cites [179] Sun Z et al. 2012 Hepatic Hdac3 promotes gluconeogenesis by repressing lipid synthesis and sequestration. Nat. Med. 18, 934– 942. (doi:10.1038/nm.2744) 22561686 PMC3411870 sourceExperimental — accuracy not yet measured

In the paper

“Similar to Mecp2 null mice and a liver-specific deletion of Hdac3, these mice develop dyslipidaemia, fatty liver and metabolic disease.”

What the sources say

• Partly supported

  The Discussion reports that liver-specific Mecp2 deletion causes fatty liver and increased serum cholesterol, supporting the dyslipidaemia and fatty-liver parts of the claim. But the Introduction says these mice remain insulin sensitive, so the paper does not support a broader claim that they develop metabolic disease such as insulin resistance; it reports insulin resistance in whole-body Mecp2-null mice instead. No page numbers are available in our copy. (LLM, conf=0.86)

  cites [180] Kyle SM, Saha PK, Brown HM, Chan LC, Justice MJ 2016 MeCP2 co-ordinates liver lipid metabolism with the NCoR1/HDAC3 corepressor complex. Hum. Mol. Genet. 25, 3029– 3041. (doi:10.1093/hmg/ddw156) 27288453 PMC5181597 sourceExperimental — accuracy not yet measured

In the paper

“Curiously, a dominant nonsense mutation was found in squalene epoxidase (Sqle), a monooxygenase and rate-limiting cholesterol biosynthesis enzyme, which requires an electron donor from mitochondria for its function [157].”

What the sources say

• Partly supported

  Section 2.2 (page unavailable) identifies squalene monooxygenase as an enzyme in sterol synthesis that requires an electron-transfer partner. It does not report a dominant nonsense mutation, a forward genetic suppressor screen, or findings in Mecp2-null mice. Its discussion of POR and a second microsomal reductase also does not support the citing sentence’s claim that the electron donor comes from mitochondria. (LLM, conf=0.84)

  cites [157] Porter TD 2012 New insights into the role of cytochrome P450 reductase (POR) in microsomal redox biology. Acta Pharm. Sin. B 2, 102– 106. (doi:10.1016/j.apsb.2012.02.002) sourceExperimental — accuracy not yet measured

In the paper

“Curiously, a dominant nonsense mutation was found in squalene epoxidase (Sqle), a monooxygenase and rate-limiting cholesterol biosynthesis enzyme, which requires an electron donor from mitochondria for its function [157].”

What the sources say

• Partly supported

  Section 2.2 identifies Sqle as squalene monooxygenase, an enzyme in sterol synthesis that requires an electron-transfer partner. It describes POR and a second, unidentified microsomal reductase—not an electron donor from mitochondria—and does not call Sqle rate-limiting. Page numbers are unavailable in our copy. (LLM, conf=0.90)

  cites [157] Porter TD 2012 New insights into the role of cytochrome P450 reductase (POR) in microsomal redox biology. Acta Pharm. Sin. B 2, 102– 106. (doi:10.1016/j.apsb.2012.02.002) sourceExperimental — accuracy not yet measured

In the paper

“To maintain homeostasis, cholesterol can be converted into the oxysterol 24(S)-hydroxycholesterol (24S-OHC) by the neuron-specific enzyme CYP46A1 (figure 4a) [162].”

What the sources say

• Partly supported

  The Abstract states that CYP46A1 converts cholesterol to 24(S)-hydroxycholesterol, and the Discussion links this pathway to maintaining brain cholesterol homeostasis. The paper reports expression in neurons of the adult brain, but also reports low-level expression in the liver and testis, so it does not establish that the enzyme is strictly neuron-specific. (LLM, conf=0.88)

  cites [162] Lund EG, Xie C, Kotti T, Turley SD, Dietschy JM, Russell DW 2003 Knockout of the cholesterol 24-hydroxylase gene in mice reveals a brain-specific mechanism of cholesterol turnover. J. Biol. Chem. 278, 22 980– 22 988. (doi:10.1074/jbc.M303415200) 12686551 sourceExperimental — accuracy not yet measured

In the paper

“The C57BL/6 J inbred strain and the 129/Sv substrains manage peripheral cholesterol metabolism differently, presumably due to differences in the transport of cholesterol breakdown products [172].”

What the sources say

• ?Could not verify

  The section on cholesterol flux through tissues outside the central nervous system describes peripheral cholesterol transport in mice generally, but does not compare C57BL/6J with 129/Sv or link strain differences to transport of cholesterol breakdown products. Searches for both strain names and that proposed mechanism found no passage addressing the claim. (LLM, conf=0.76)

  cites [172] Dietschy JM 2009 Central nervous system: cholesterol turnover, brain development and neurodegeneration. Biol. Chem. 390, 287– 293. (doi:10.1515/BC.2009.035) 19166320 PMC3066069 sourceExperimental — accuracy not yet measured

In the paper

“Interestingly, some RTT patients have bone abnormalities, severe gastrointestinal problems and biliary tract disorders [174–176].”

What the sources say

• Supported

  The citation to this bone-mass study supports the bone-abnormalities part of the sentence. The Discussion (page not provided) reports decreased bone mineral content and density in approximately half of the RTT females studied. The gastrointestinal and biliary conditions are not treated as claims attributed specifically to this source. (LLM, conf=0.91)

  cites [174] Shapiro JR et al. 2010 Bone mass in Rett syndrome: association with clinical parameters and MECP2 mutations. Pediatr. Res. 68, 446– 451. (doi:10.1203/PDR.0b013e3181f2edd2) 20661168 PMC3074246 source
• Partly supported

  The Discussion reports low bone mineral density and increased fracture risk in females with Rett syndrome, and the Results report scoliosis in 54% of the cohort. Our copy does not report severe gastrointestinal problems or biliary tract disorders in these patients, so it supports only the bone-abnormalities part of the sentence. (LLM, conf=0.88)

  cites [175] Motil KJ et al. 2011 Vitamin D deficiency is prevalent in girls and women with Rett syndrome. J. Pediatr. Gastroenterol. Nutr. 53, 569– 574. (doi:10.1097/MPG.0b013e3182267a66) 21637127 PMC3638258 sourceExperimental — accuracy not yet measured
• Supported

  The Study Design lists skeletal abnormalities and biliary tract disorders among the conditions assessed. The Results report gastrointestinal problems in the majority of the RTT cohort and biliary tract disease in a small number; the Discussion also describes serious complications, including gastric and intestinal perforations. Page numbers were not provided in the copy. (LLM, conf=0.91)

  cites [176] Motil KJ et al. 2012 Gastrointestinal and nutritional problems occur frequently throughout life in girls and women with Rett syndrome. J. Pediatr. Gastroenterol. Nutr. 55, 292– 298. (doi:10.1097/MPG.0b013e31824b6159) 22331013 PMC3393805 source

In the paper

“Additionally, both RTT patients and Mecp2 mutant mice present with metabolic syndrome [15,180], oxidative stress [27,29], cardiac defects [211,212], decreased bone density [174,213] and urological dysfunction [214,215].”

What the sources say

• Partly supported

  For the metabolic-syndrome portion of the sentence, “Considerations for Other Therapies that May Affect Metabolism in RTT Patients” explicitly describes metabolic-syndrome phenotypes in Mecp2-null mice. “A Subset of Rett Patients Display Dyslipidemia” reports elevated lipids in some RTT patients, but does not establish that RTT patients present with metabolic syndrome. No page numbers are provided in our copy. (LLM, conf=0.88)

  cites [15] Justice MJ, Buchovecky CM, Kyle SM, Djukic A 2013 A role for metabolism in Rett syndrome pathogenesis: new clinical findings and potential treatment targets. Rare Dis. 1, e27265 (doi:10.4161/rdis.27265) 25003017 PMC3978897 sourceExperimental — accuracy not yet measured
• Partly supported

  The Introduction and Discussion explicitly describe metabolic syndrome in Mecp2 mutant mice. For RTT patients, the Discussion reports abnormal cholesterol and triglyceride levels and glucose intolerance, but says systemic metabolic involvement remains a possibility requiring further examination; it does not establish that patients present with metabolic syndrome. The other conditions in the citing sentence have separate citations and are not assessed here. (LLM, conf=0.88)

  cites [180] Kyle SM, Saha PK, Brown HM, Chan LC, Justice MJ 2016 MeCP2 co-ordinates liver lipid metabolism with the NCoR1/HDAC3 corepressor complex. Hum. Mol. Genet. 25, 3029– 3041. (doi:10.1093/hmg/ddw156) 27288453 PMC5181597 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [27] Haas RH, Nasirian F, Hua X, Nakano K, Hennessy M 1995 Oxidative metabolism in Rett syndrome. 2. Biochemical and molecular studies. Neuropediatrics 26, 95– 99. (doi:10.1055/s-2007-979735) 7566465 source
• ?Not checked — no full text of the sourcecites [29] De Felice C et al. 2009 Systemic oxidative stress in classic Rett syndrome. Free Radic. Biol. Med. 47, 440– 448. (doi:10.1016/j.freeradbiomed.2009.05.016) 19464363 source
• Supported

  The citation is attached to “cardiac defects,” not to the other conditions in the sentence. The Abstract reports cardiac dysfunction in both RTT patients and animal models, and cardiac gene-expression and structural alterations in Mecp2-null mice. No page numbers are provided in our copy. (LLM, conf=0.92)

  cites [211] Hara M et al. 2015 Disturbance of cardiac gene expression and cardiomyocyte structure predisposes Mecp2-null mice to arrhythmias. Sci. Rep. 5, e11204 (doi:10.1038/srep11204) PMC4466896 26073556 source
• Supported

  This source is cited for the cardiac-defects portion of the sentence, not for the other listed conditions. The Introduction reports ECG and rhythm abnormalities in RTT patients, while the Discussion describes QTc prolongation and inducible ventricular arrhythmias in Mecp2-deletion mice. (LLM, conf=0.90)

  cites [212] Crosson J et al. 2017 Evaluation of QTc in Rett syndrome: correlation with age, severity, and genotype. Am. J. Med. Genet. 173, 1495– 1501. (doi:10.1002/ajmg.a.38191) 28394409 PMC5444992 source

In the paper

“RTT patients have increased oxidative burden and abnormal mitochondrial structure, while RTT animal models have defects in the mitochondrial respiratory chain [23,26,200–202] and oxidative changes in the brain [203].”

What the sources say

• ?Not checked — no full text of the sourcecites [23] Eeg-Olofsson O, Al-Zuhair AG, Teebi AS, Al-Essa MM 1988 Abnormal mitochondria in the Rett syndrome. Brain Dev.. 10, 260– 262. (doi:10.1016/S0387-7604(88)80010-X) 3218707 source
• ?Not checked — no full text of the sourcecites [26] Cardaioli E, Dotti MT, Hayek G, Zappella M, Federico A 1999 Studies on mitochondrial pathogenesis of Rett syndrome: ultrastructural data from skin and muscle biopsies and mutational analysis at mtDNA nucleotides 10463 and 2835. J. Submicrosc. Cytol. Pathol. 31, 301– 304. 10457616
• Partly supported

  The Discussion (page unavailable) reports earlier findings of abnormal mitochondrial structure in biopsies from RTT patients. It does not report increased oxidative burden in RTT patients; its mention of oxidative stress concerns other human disorders. The paper’s own respiratory-chain findings concern a mouse model. (LLM, conf=0.86)

  cites [200] Kriaucionis S, Paterson A, Curtis J, Guy J, MacLeod N, Bird A 2006 Gene expression analysis exposes mitochondrial abnormalities in a mouse model of Rett syndrome. Mol. Cell. Biol. 26, 5033– 5042. (doi:10.1128/MCB.01665-05) 16782889 PMC1489175 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [201] Gold WA, Williamson SL, Kaur S, Hargreaves IP, Land JM, Pelka GJ, Tam PPL, Christodoulou J 2014 Mitochondrial dysfunction in the skeletal muscle of a mouse model of Rett syndrome (RTT): implications for the disease phenotype. Mitochondrion 15, 10– 17. (doi:10.1016/j.mito.2014.02.012) 24613463 source
• ?Not checked — no full text of the sourcecites [202] Müller M, Can K 2014 Aberrant redox homoeostasis and mitochondrial dysfunction in Rett syndrome. Biochem. Soc. Trans. 42, 959– 964. (doi:10.1042/BST20140071) 25109986 source

In the paper

“Moreover, deletion of MeCP2 from glial cells induces a RTT-like phenotype, and re-introducing MeCP2 to astrocytes of Mecp2 null mice using GFAP-Cre improves symptoms and restores dendritic morphology [193,194].”

What the sources say

• Partly supported

  The paper reports that tamoxifen-induced MeCP2 re-expression using hGFAPcreT2 improved RTT-like symptoms and restored the number of apical dendritic branches (passages 2, 3, and 6). However, the rescue mice carried a Mecp2Stop allele, not a true null allele: the paper distinguishes them from Mecp2-/y mice and reports residual MeCP2 expression from the stop locus (passage 8). (LLM, conf=0.88)

  cites [193] Lioy DT et al. 2011 A role for glia in the progression of Rett's syndrome. Nature 475, 497– 500. (doi:10.1038/nature10214) 21716289 PMC3268776 sourceExperimental — accuracy not yet measured
• Partly supported

  The Introduction reports that re-expressing MeCP2 in astrocytes of RTT mice improves motor activity and behavior. It does not specify GFAP-Cre or report restoration of dendritic morphology; this paper's own rescue experiments instead use NG2Cre to target oligodendrocyte-lineage cells (Results, 'MeCP2 expression is restored specifically...'). (LLM, conf=0.86)

  cites [194] Nguyen MVC, Felice CA, Du F, Covey MV, Robinson JK, Mandel G, Ballas N 2013 Oligodendrocyte lineage cells contribute unique features to Rett syndrome neuropathology. J. Neurosci. 33, 18 764– 18 774. (doi:10.1523/JNEUROSCI.2657-13.2013) PMC3841446 24285883 sourceExperimental — accuracy not yet measured

In the paper

“Notably, six of these mutations in TBLR1 mapped to the WD40 domain of the protein and disrupted MeCP2-binding [150].”

What the sources say

• Partly supported

  The section “Disease-Associated TBLR1 Mutations Block MeCP2 Binding” (page unavailable) identifies six TBLR1 mutations and says all map to the WD40 domain. It demonstrates disrupted MeCP2 binding for two of those mutations, D369E and P444R, but does not establish that all six disrupt binding; the Discussion likewise says “at least two.” (LLM, conf=0.90)

  cites [150] Kruusvee V, Lyst MJ, Taylor C, Tarnauskaitė Ž, Bird AP, Cook AG 2017 Structure of the MeCP2–TBLR1 complex reveals a molecular basis for Rett syndrome and related disorders. Proc. Natl. Acad. Sci. USA 114, E3243– E3250. (doi:10.1073/pnas.1700731114) 28348241 PMC5402415 sourceExperimental — accuracy not yet measured

In the paper

“For example, the treatment of Mecp2 null mice with a protein-tyrosine phosphatase 1B (PTP1B) antagonist that was developed to treat Type II diabetes extended lifespan, decreased hindlimb clasping and improved motor performance [207].”

What the sources say

• Partly supported

  The Results section, “Inhibition of PTP1B improved survival in Mecp2 -/y mice” (page not provided), reports extended survival in male Mecp2-null mice. The paw-clasping and rotarod passages (“Volume 125 Number 8 August 2015,” page not provided) report those improvements in heterozygous female Mecp2 -/+ mice, not null mice. The cited passages also do not establish that the inhibitor was developed to treat type II diabetes. (LLM, conf=0.92)

  cites [207] Krishnan N, Krishnan K, Connors CR, Choy MS, Page R, Peti W, Van Aelst L, Shea SD, Tonks NK 2015 PTP1B inhibition suggests a therapeutic strategy for Rett syndrome. J. Clin. Invest. 125, 3163– 3177. (doi:10.1172/JCI80323) 26214522 PMC4563751 sourceExperimental — accuracy not yet measured

In the paper

“Not surprisingly, both RTT patients and Mecp2 mutant mice have abnormal responses to glucose tolerance tests, and mutant mice are also insulin-resistant [180,195].”

What the sources say

• Supported

  The Results section reports glucose intolerance and insulin resistance in Mecp2 mutant mice. The Discussion reports glucose intolerance in pediatric RTT patients. The copy does not specify the patient testing procedure, but its reported finding supports the claim’s description of abnormal glucose tolerance. (LLM, conf=0.86)

  cites [180] Kyle SM, Saha PK, Brown HM, Chan LC, Justice MJ 2016 MeCP2 co-ordinates liver lipid metabolism with the NCoR1/HDAC3 corepressor complex. Hum. Mol. Genet. 25, 3029– 3041. (doi:10.1093/hmg/ddw156) 27288453 PMC5181597 source
• ?Not checked — no full text of the sourcecites [195] Cooke DW, Naidu S, Plotnick L, Berkovitz GD 1995 Abnormalities of thyroid function and glucose control in subjects with Rett syndrome. Horm. Res. 43, 273– 278. (doi:10.1159/000184309) 7607612 source

In the paper

“Similarly, Trolox, a vitamin E derivative, normalized blood glucose levels, reduced oxidative stress and improved exploratory behaviour in Mecp2 mice [208].”

What the sources say

• Supported

  The Results (Systemic Parameters; page unavailable) report that Trolox abolished the blood-glucose difference between Mecp2−/y and wild-type mice. The Results (Lipid Peroxidation and Protein Carbonylation; page unavailable) report reduced markers of oxidative damage, and Behavioral Testing reports improved exploration in high-dose-treated Mecp2−/y mice. The glucose increase was a trend, and the exploration benefit was dose-specific. (LLM, conf=0.90)

  cites [208] Janc OA, Hüser MA, Dietrich K, Kempkes B, Menzfeld C, Hülsmann S, Müller M 2016 Systemic radical scavenger treatment of a mouse model of Rett syndrome: merits and limitations of the vitamin E derivative Trolox. Front. Cell. Neurosci. 10, 266 (doi:10.3389/fncel.2016.00266) 27895554 PMC5109403 source

In the paper

“Interestingly, wild-type neurons have abnormal dendritic morphology when co-cultured with MeCP2-deficient astrocytes, yet MeCP2-deficient neurons have normal dendritic morphology when co-cultured with wild-type astrocytes [192].”

What the sources say

• Partly supported

  The Results section (“RTT astrocytes cannot support normal neuronal growth”; page unavailable) reports abnormal dendritic morphology in wild-type neurons co-cultured with MeCP2-deficient astrocytes. The Results section (“RTT ACM cannot support normal neuronal growth”; page unavailable) also reports normal morphology in MeCP2-null neurons exposed to conditioned medium from wild-type astrocytes, but does not establish that result for co-culture with the astrocytes themselves. (LLM, conf=0.88)

  cites [192] Ballas N, Lioy DT, Grunseich C, Mandel G 2009 Non-cell autonomous influence of MeCP2-deficient glia on neuronal dendritic morphology. Nat. Neurosci. 12, 311– 317. (doi:10.1038/nn.2275) 19234456 PMC3134296 sourceExperimental — accuracy not yet measured

In the paper

“Known target genes of the complex in the liver include Sqle and other lipogenesis enzymes.”

In the paper

“Mecp2 mutant rodents recapitulate many hallmark symptoms of RTT and are the most widely accepted tool to study the disorder.”

In the paper

“Despite remarkable scientific progress since its discovery, the mechanism by which MECP2 mutations cause RTT symptoms is largely unknown.”

In the paper

“At four weeks of age, null mice begin to develop uncoordinated gait, hypoactivity, tremors, hindlimb clasping reminiscent of the hand stereotypies seen in RTT patients, and irregular breathing. These phenotypes progress in severity until death.”

In the paper

“MeCP2 is an abundant nuclear protein that was originally identified in a screen for proteins with methyl-DNA-specific binding activity. It is ubiquitously expressed throughout all human tissues, but is particularly abundant within neurons [52,53].”

What the sources say

• ?Not checked — no full text of the sourcecites [52] Tate P, Skarnes W, Bird A 1996 The methyl-CpG binding protein MeCP2 is essential for embryonic development in the mouse. Nat. Genet. 12, 205– 208. (doi:10.1038/ng0296-205) 8563762 source
• ?Not checked — no full text of the sourcecites [53] Lewis JD et al. 1992 Purification, sequence, and cellular localization of a novel chromosomal protein that binds to Methylated DNA. Cell 69, 905– 914. (doi:10.1016/0092-8674(92)90610-O) 1606614 source

In the paper

“In the central nervous system (CNS), MeCP2 is expressed at low levels prenatally, but progressively increases during neuronal maturation and synaptogenesis reaching its peak in mature, post-migratory neurons, suggesting a role for MeCP2 in maintaining neuronal maturation, activity and plasticity [54–57].”

What the sources say

• ?Not checked — no full text of the sourcecites [54] Cohen DRS, Matarazzo V, Palmer AM, Tu Y, Jeon O-H, Pevsner J, Ronnett GV 2003 Expression of MeCP2 in olfactory receptor neurons is developmentally regulated and occurs before synaptogenesis. Mol. Cell. Neurosci. 22, 417– 429. (doi:10.1016/S1044-7431(03)00026-5) 12727440 source
• ?Not checked — no full text of the sourcecites [55] Jung BP, Jugloff DGM, Zhang G, Logan R, Brown S, Eubanks JH 2003 The expression of methyl CpG binding factor MeCP2 correlates with cellular differentiation in the developing rat brain and in cultured cells. J. Neurobiol. 55, 86– 96. (doi:10.1002/neu.10201) 12605461 source
• ?Not checked — no full text of the sourcecites [56] Samaco RC, Nagarajan RP, Braunschweig D, LaSalle JM 2004 Multiple pathways regulate MeCP2 expression in normal brain development and exhibit defects in autism-spectrum disorders. Hum. Mol. Genet. 13, 629– 639. (doi:10.1093/hmg/ddh063) 14734626 source
• ?Not checked — no full text of the sourcecites [57] Kishi N, Macklis JD 2005 Dissecting MECP2 function in the central nervous system. J. Child Neurol. 20, 753– 759. (doi:10.1177/08830738050200091001) 16225831 source

In the paper

“Targets in the brain remain unknown.”

In the paper

“Despite this, metabolic parameters vary greatly within the RTT patient population and among different mouse strains indicating that genetic variation may play a large role in the penetrance of metabolic symptoms.”

In the paper

“RTT patients show abnormal neuronal morphology, but not neuronal death, giving legitimacy to the possibility that defective MeCP2-deficient cells can recover [144].”

What the sources say

• ?Not checked — no full text of the sourcecites [144] Armstrong D, Dunn JK, Antalffy B, Trivedi R 1995 Selective dendritic alterations in the cortex of Rett syndrome. J. Neuropathol. Exp. Neurol. 54, 195– 201. (doi:10.1097/00005072-199503000-00006) 7876888 source

In the paper

“The primary mechanism of action for statin drugs is to competitively inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), a rate-limiting step in cholesterol biosynthesis [181], effectively reducing the endogenous production of cholesterol.”

What the sources say

• ?Not checked — no full text of the sourcecites [181] Istvan ES, Deisenhofer J 2001 Structural mechanism for statin inhibition of HMG-CoA reductase. Science 292, 1160– 1164. (doi:10.1126/science.1059344) 11349148 source

In the paper

“As cholesterol synthesis is a resource-expensive process, current data suggest that newborn neurons must produce cholesterol in a cell-autonomous manner, but as they mature they outsource production to astrocytes (reviewed in [160,191]).”

What the sources say

• ?Not checked — no full text of the sourcecites [160] Pfrieger FW, Ungerer N 2011 Cholesterol metabolism in neurons and astrocytes. Prog. Lipid Res. 50, 357– 371. (doi:10.1016/j.plipres.2011.06.002) 21741992 source
• ?Not checked — no full text of the sourcecites [191] Pfrieger FW 2003 Outsourcing in the brain: do neurons depend on cholesterol delivery by astrocytes? Bioessays 25, 72– 78. (doi:10.1002/bies.10195) 12508285 source

In the paper

“As CNS-targeted gene therapy becomes a more realistic therapeutic approach, peripheral deficiency of MeCP2 must be considered more than ever as these symptoms are likely to persist following targeted genetic treatment to the brain.”

In the paper

“However, despite this progress, no single treatment has yet fixed every phenotype in Mecp2 mice or yet proved to effectively treat RTT symptoms.”