Microglia Sculpt Postnatal Neural Circuits in an Activity and Complement-Dependent Manner

In the paper

“Complement cascade components C1q and C3 localize to immature synapses and are necessary for the developmental pruning of retinogeniculate synapses (Stevens et al., 2007; Stephan et al., 2012).”

What the sources say

• Partly supported

  In the Results, C1q colocalizes with small synaptic puncta described as probably immature or undergoing elimination. C3 colocalizes with synaptic puncta in the postnatal dLGN, but those puncta are not specifically identified as immature. The Introduction and Discussion state that both C1q and C3 are required for developmental retinogeniculate synapse elimination. (LLM, conf=0.85)

  cites Stevens et al., 2007 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Stephan et al., 2012 source

In the paper

“recent studies suggest that microglia may play a role in synaptic remodeling and plasticity in the healthy brain (Davalos et al., 2005; Nimmerjahn et al., 2005; Paolicelli et al., 2011; Tremblay et al., 2010a; Wake et al., 2009; Schafer et al., 2012).”

What the sources say

• ?Not checked — no full text of the sourcecites Davalos et al., 2005 source
• ?Not checked — no full text of the sourcecites Nimmerjahn et al., 2005 source
• Supported

  The Abstract says microglia engulf synaptic material and play a major role in synaptic pruning during postnatal development in mice. The paper’s conclusion also links that pruning to synaptic and circuit maturation, supporting the hedged claim about remodeling and plasticity in the uninjured brain. Page numbers were not provided in our copy. (LLM, conf=0.92)

  cites Paolicelli et al., 2011 source

In the paper

“Previous work has suggested that sensory deprivation or pharmacological blockade of neuronal activity (i.e., TTX) results in reduced mitochondria in presynaptic terminals known to undergo subsequent elimination (Hevner and Wong-Riley, 1993; Tieman, 1984).”

What the sources say

• Partly supported

  The COW mRNA section (page unavailable) reports that mitochondrial volume fraction decreases in specific cortical regions after TTX treatment. It also says the authors’ data do not establish whether the number of mitochondria changes. The paper does not place the decrease in presynaptic terminals or link those terminals to subsequent elimination, and the cited passage does not address sensory deprivation. (LLM, conf=0.85)

  cites Hevner and Wong-Riley, 1993 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Tieman, 1984 source

In the paper

“Microglia were labeled using the CX3CR1+/GFP mouse line in which all microglia express EGFP under the control of fractalkine receptor, CX3CR1, expression (Figure 1, S1, and S5) (Cardona et al., 2006; Jung et al., 2000; Saederup et al., 2010).”

What the sources say

• ?Not checked — no full text of the sourcecites Cardona et al., 2006 source
• Partly supported

  The Results and Discussion describe the CX3CR1+/GFP reporter mouse and show GFP expression in its microglia. They state that all CX3CR1-expressing cells are GFP-positive, but do not establish that all microglia express CX3CR1 or EGFP; the claim’s universal qualifier is therefore unsupported. (LLM, conf=0.82)

  cites Jung et al., 2000 sourceExperimental — accuracy not yet measured
• Supported

  The Results section on CX3CR1 and CCR2 distribution (Figure 5; page not provided) identifies GFP-positive microglia in Cx3cr1GFP/+ mice throughout healthy and diseased brain tissue. The Discussion states that microglia invariably expressed CX3CR1 and that CX3CR1-GFP distinguishes resident microglia, supporting the described labeling approach. (LLM, conf=0.92)

  cites Saederup et al., 2010 source

In the paper

“these data are consistent with previous work demonstrating that such a competition results in decreased territory of the ‘weaker’ inputs and increased territory of ‘stronger’ inputs within the dLGN (Del Rio and Feller, 2006; Huberman et al., 2008; McLaughlin et al., 2003; Penn et al., 1998; Shatz, 1990; Shatz and Stryker, 1988; Stellwagen and Shatz, 2002; Stellwagen et al., 1999; Torborg and Felle”

What the sources say

• ?Not checked — no full text of the sourcecites Del Rio and Feller, 2006 source
• Supported

  In the Introduction’s discussion of eye-specific segregation in the LGN, the paper says competitive interactions between inputs from the two eyes are critical. It also reports that the more active eye wins more LGN territory, supporting the claim’s stronger-versus-weaker input comparison. (LLM, conf=0.92)

  cites Huberman et al., 2008 source
• ?Not checked — no full text of the sourcecites McLaughlin et al., 2003 source

In the paper

“Because pHrodo only fluoresces once it enters acidic compartments of lysosomes, any pHrodo-positive fluorescence within a microglia confirms phagocytosis of RGC inputs.”

What the sources say

• Partly supported

  The Results (page not available in our copy) state that pHrodo fluorescence increases as the compartment containing it acidifies. The Time Course of Phagosomal Acidification section (page not available) describes that acidification follows particle uptake in alveolar macrophages. The paper does not establish that pHrodo fluoresces only in lysosomes or that fluorescence in microglia confirms phagocytosis of RGC inputs. (LLM, conf=0.88)

  cites Deriy et al., 2009 sourceExperimental — accuracy not yet measured
• Partly supported

  The Results (page not provided) show that pHrodo-labeled cells become much brighter after macrophage engulfment as phagosomes acidify. But the paper also reports dim fluorescence before engulfment, so “only fluoresces once” is too absolute; it tests macrophages engulfing apoptotic cells, not microglia engulfing RGC inputs. (LLM, conf=0.88)

  cites Miksa et al., 2009 sourceExperimental — accuracy not yet measured

In the paper

“In the retina, spontaneous, correlated neuronal activity from both eyes (i.e., retinal waves) drives the elimination of synapses and segregation of inputs into eye-specific territories in the dLGN (Del Rio and Feller, 2006; Feller, 1999; Huberman et al., 2008; McLaughlin et al., 2003; Penn et al., 1998; Stellwagen and Shatz, 2002; Torborg and Feller, 2005).”

What the sources say

• ?Not checked — no full text of the sourcecites Del Rio and Feller, 2006 source
• ?Not checked — no full text of the sourcecites Feller, 1999 source
• Supported

  The Introduction reports that blocking stage II retinal waves in both eyes prevents eye-specific segregation in the LGN. It also states that stage III waves drive fine-scale retinotopic refinement and that blocking wave-induced spiking prevents normal elimination of retinogeniculate synapses. These are distinct developmental processes, but the review supports both parts of the claim. (LLM, conf=0.88)

  cites Huberman et al., 2008 source

In the paper

“In the immune system, C3 is cleaved into an activated form, iC3b, which covalently binds to the surface of cells or debris and targets them for elimination by macrophages via specific phagocytic receptor signaling (e.g., CR3) (Lambris and Tsokos, 1986; van Lookeren Campagne et al., 2007).”

What the sources say

• ?Not checked — no full text of the sourcecites Lambris and Tsokos, 1986
• Partly supported

  The “Complement C3 opsonization” section says C3 is first cleaved to C3b, which covalently binds a surface; subsequent cleavage of bound C3b produces iC3b. The receptor sections support iC3b recognition and phagocytosis through CR3, but the claim incorrectly presents iC3b as the direct product of C3 cleavage and the form that initially binds covalently. The discussion of cell-debris removal identifies CRIg as a possible receptor, rather than specifically CR3. (LLM, conf=0.88)

  cites van Lookeren Campagne et al., 2007 sourceExperimental — accuracy not yet measured

In the paper

“Previous work has demonstrated that microglia have the capacity to interact with synaptic elements in response to neurotransmitter release and/or sensory experience (Biber et al., 2007; Fontainhas et al., 2011; Nimmerjahn et al., 2005; Ransohoff and Perry, 2009; Tremblay et al., 2010a; Wake et al., 2009).”

What the sources say

• ?Not checked — no full text of the sourcecites Biber et al., 2007 source
• Partly supported

  The Introduction reports that microglial processes repeatedly contact nearby neurons, and the Discussion says neurotransmission rapidly regulates microglial morphology and behavior in retinal explants. The paper does not demonstrate that neurotransmitter release causes microglia to interact specifically with synaptic elements; it discusses synaptic pruning as a finding suggested by earlier studies. It does not test sensory experience. (LLM, conf=0.84)

  cites Fontainhas et al., 2011 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Nimmerjahn et al., 2005 source

In the paper

“using array tomography (AT), a powerful tool for high resolution imaging and quantification of synaptic density in vivo (Greer et al., 2010; Margolis et al., 2010; Micheva and Smith, 2007; Ross et al., 2010).”

What the sources say

• Partly supported

  The Results section describes array tomography as imaging ultrathin brain sections to visualize synapses in 3-D, and reports synaptic-puncta densities in mouse hippocampi. Experimental Procedures (Array Tomography) specifies 100 nm sections and synapse counting. The imaging was performed on fixed, excised tissue, however, not in vivo. (LLM, conf=0.84)

  cites Greer et al., 2010 sourceExperimental — accuracy not yet measured
• Partly supported

  The Results section (‘Ephexin5 negatively regulates excitatory synapse number’; page unavailable) reports using array tomography to quantify excitatory synapses in mouse hippocampus in vivo. The Experimental Procedures confirm use of the method, but our copy does not characterize its imaging resolution or describe it as a ‘powerful tool.’ (LLM, conf=0.82)

  cites Margolis et al., 2010 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Micheva and Smith, 2007 source

In the paper

“For example, MHC class I molecules, another class of immune molecules demonstrated to play a role in retinogeniculate pruning, have been shown to be activity-dependent, localized to synapses, and co-localized with C1q leaving the possibility that MHC class I molecules may play an upstream role in microglia-mediated pruning of synapses (Corriveau et al., 1998; Datwani et al., 2009; Goddard et al.,”

What the sources say

• Partly supported

  The section on activity-regulated genes reports that blocking neural activity reduces class I MHC expression in the LGN, supporting the activity-dependent part of the claim. The passages on neuronal protein expression and the proposed synaptic role do not establish localization to synapses, and our copy does not report co-localization with C1q. Page numbers were not available in the indexed passages. (LLM, conf=0.88)

  cites Corriveau et al., 1998 sourceExperimental — accuracy not yet measured
• Supported

  The Introduction reports that blocking neural activity downregulated neuronal MHCI mRNA, and the Discussion reports downregulation of both mRNA and protein. The Results (‘MHCI Immunostaining is associated with LGN synapses and C1q,’ Figure 4) show MHCI puncta associated with synaptic markers and C1q. The paper cautions that its imaging cannot resolve MHCI's precise position on the synaptic membrane, but the citing sentence does not make that more specific claim. (LLM, conf=0.91)

  cites Datwani et al., 2009 source
• ?Not checked — no full text of the sourcecites Goddard et al., 2007 source

In the paper

“Furthermore, microglia can contribute to synaptic plasticity in the adult CNS and, more recently, in the context of the normal developing hippocampus (Paolicelli et al., 2011; Pascual et al., 2011; Roumier et al., 2008).”

What the sources say

• Supported

  The paper reports that microglia engulf synaptic material in the developing mouse hippocampus (Abstract) and that reduced microglial numbers delay synaptic pruning and the maturation of synaptic plasticity (Synaptic Pruning by Microglia Is Necessary for Normal Brain Development). This supports the developing-hippocampus portion for which Paolicelli et al. is cited; the sentence also cites other papers for the adult-CNS context. (LLM, conf=0.91)

  cites Paolicelli et al., 2011 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Pascual et al., 2011
• Partly supported

  The Discussion reports altered adult hippocampal synaptic function after prenatal microglial activation, and describes enhanced long-term potentiation in mice with a mutation affecting a microglial gene. The Results also describe microglia in the developing hippocampus, but the paper does not establish that microglia contribute to synaptic plasticity during normal hippocampal development; its functional findings concern mutation or inflammation. (LLM, conf=0.87)

  cites Roumier et al., 2008 sourceExperimental — accuracy not yet measured

In the paper

“In addition to diseases associated with neurodegeneration, recent data from genome-wide association studies and analyses of postmortem human brain tissue have suggested that microglia and/or the complement cascade may also be involved in the development and pathogenesis of neurodevelopmental and psychiatric disorders (e.g., autism, obsessive compulsive disorder, schizophrenia, etc.) (Chen et al.,”

What the sources say

• Partly supported

  The Introduction (page unavailable) reports that genome-wide association studies implicate immune-related genes in susceptibility to psychiatric disorders, and the Discussion links defective microglia to pathological grooming in mice. The paper does not report analyses of postmortem human brain tissue or implicate the complement cascade, so it supports only part of the attributed claim. (LLM, conf=0.88)

  cites Chen et al., 2010 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Havik et al., 2011 source
• ?Not checked — no full text of the sourcecites Monji et al., 2009 source

In the paper

“Indeed, in a mouse model of glaucoma, a neurodegenerative disease associated with RGC loss and gliosis, C1q and C3 are highly upregulated and deposited on retinal synapses and C1q deficiency or microglial ‘inactivation’ with minocycline provide significant neuroprotection (Howell et al., 2011; Steele et al., 2006; Stevens et al., 2007).”

What the sources say

• Partly supported

  The research article (p. 6) reports early retinal upregulation of C1qa, C1qb and C1qc and says C1qa localizes to retinal synapses. Table 1 (p. 7) and Figure 8 (p. 11) show substantial protection in C1qa-deficient mice. Our copy does not establish C3 deposition on retinal synapses or neuroprotection from microglial inactivation with minocycline. (LLM, conf=0.89)

  cites Howell et al., 2011 sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites Steele et al., 2006 source
• Partly supported

  The Results report that C1q RNA increased in DBA/2J glaucoma retinas and that C1q protein localized to retinal synapses. They do not establish that C3 was upregulated or deposited there. The Discussion says testing whether C1q or C3 deficiency protects against glaucoma-related neurodegeneration is future work; the paper does not report neuroprotection from C1q deficiency or minocycline. (LLM, conf=0.89)

  cites Stevens et al., 2007 sourceExperimental — accuracy not yet measured

In the paper

“While in at least one other developing system local axonal retraction and synapse elimination appear to occur independent of microglia (Cheng et al., 2010), recent work describes a role for microglia at developing hippocampal synapses (Paolicelli et al., 2011).”

What the sources say

• Supported

  The Results section reports that developmental lamina-specific pruning showed no signs of glial engulfment and proceeded normally in mice lacking C1q, which the authors describe as important for microglia-mediated synapse elimination. The paper concludes that this refinement is glia-independent; it also describes axon arbor retraction and synapse elimination in this developing retinal system. Page numbers were not supplied in our copy. (LLM, conf=0.92)

  cites Cheng et al., 2010 source

In the paper

“While in at least one other developing system local axonal retraction and synapse elimination appear to occur independent of microglia (Cheng et al., 2010), recent work describes a role for microglia at developing hippocampal synapses (Paolicelli et al., 2011).”

What the sources say

• Supported

  The Abstract describes microglia engulfing synaptic material during synaptic maturation in the mouse hippocampus. The conclusion also reports that microglia eliminate synapses during development. (LLM, conf=0.94)

  cites Paolicelli et al., 2011 source

In the paper

“This increase in overlap was attributed to a significantly broader ipsilateral projection territory (Figure 7D) and a small, but not significant, increase in the contralateral projection territory (Figure 7E).”

In the paper

“immunohistochemistry for CR3 ligand, C3 was enriched in synaptic regions of P5 dLGN and downregulated by P9, an age when pruning is largely complete (Figure 6B)”

In the paper

“CR3, a high affinity receptor for activated C3 (Akiyama and McGeer, 1990; Perry et al., 1985), was specifically upregulated in microglia in the P5 dLGN and downregulated at later developmental time points (Figure 6A).”

In the paper

“engulfment of RGC inputs was developmentally regulated. During a developmental period of robust pruning (P5), engulfment was high (Figure 2B, Di). As few as 4 days later (P9), when much of the pruning is nearly complete, engulfment of RGC inputs was significantly reduced (Figure 2B,Dii).”

In the paper

“our EM experiments demonstrated that engulfed material as well as surrounding dLGN neuropil did not appear to have classic signs of axonal or synaptic degeneration such as multilamellar bodies, electron-dense cytoplasm, lack of synaptic vesicles within presynaptic terminals, etc.”

In the paper

“minocycline (P4–P8; 75 mg/kg) treatment during the peak of the pruning period resulted in reduced microglial phagocytic function (i.e., reduced RGC input engulfment) at P5 and a statistically significant deficit in eye-specific segregation at P10 (Figure S6C–E).”

In the paper

“Synaptic pruning is an activity-dependent developmental program in which a large number of synapses that form in early development are eliminated while a subset of synapses are maintained and strengthened (Hua and Smith, 2004; Katz and Shatz, 1996; Sanes and Lichtman, 1999).”

What the sources say

• ?Not checked — no full text of the sourcecites Hua and Smith, 2004 source
• ?Not checked — no full text of the sourcecites Katz and Shatz, 1996 source
• ?Not checked — no full text of the sourcecites Sanes and Lichtman, 1999 source

In the paper

“minocycline, an established inhibitor of microglial ‘activation’ (Buller et al., 2009)”

What the sources say

• ?Not checked — no full text of the sourcecites Buller et al., 2009 source

In the paper

“3D structural illumination microscopy (3D-SIM), a technique enabling 2X the resolution of light microscopy (Gustafsson, 2000), was used to assess the P5 dLGN of CX3CR1+/EGFP mice immunolabeled for VGlut2.”

What the sources say

• ?Not checked — no full text of the sourcecites Gustafsson, 2000 source

In the paper

“our data directly implicate microglia as mediators of anatomical pruning and identify CR3/C3-dependent signaling as an underlying molecular mechanism.”

In the paper

“Taken together, our data suggest that engulfed presynaptic elements were healthy, intact, and specifically engulfed by microglia.”

In the paper

“Microglia were identified by EM using criteria previously described including a small, irregular-shaped nucleus containing substantial amounts of coarse chromatin and a cytoplasm rich in free ribosomes, vacuoles, and lysosomes (Mori and Leblond, 1969; Sturrock, 1981).”

What the sources say

• ?Not checked — no full text of the sourcecites Mori and Leblond, 1969 source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Sturrock, 1981

In the paper

“While these studies describe microglia dynamics at synapses, a precise function and molecular mechanism(s) underlying microglia-synapse interactions in these brain regions was unknown.”

In the paper

“Only those brains with sufficient dye fills were analyzed (see Supplementary Methods for details).”

In the paper

“All analyses were performed blind with littermate controls.”