Cited by 1,379Neuroscience and Neuropharmacology ResearchNeuroinflammation and Neurodegeneration MechanismsPhagocytosis and Immune Regulation

The DOI matches its Crossref record; 40 of the 40 references it cites were found in a registry or an index; 10 of the 26 sources its claims cite were checked for support.

Astrocytes mediate synapse elimination through MEGF10 and MERTK pathways

Open access

Abstract

To achieve its precise neural connectivity, the developing mammalian nervous system undergoes extensive activity-dependent synapse remodelling. Recently, microglial cells have been shown to be responsible for a portion of synaptic pruning, but the remaining mechanisms remain unknown. Here we report a new role for astrocytes in actively engulfing central nervous system synapses. This process helps to mediate synapse elimination, requires the MEGF10 and MERTK phagocytic pathways, and is strongly dependent on neuronal activity. Developing mice deficient in both astrocyte pathways fail to refine their retinogeniculate connections normally and retain excess functional synapses. Finally, we show that in the adult mouse brain, astrocytes continuously engulf both excitatory and inhibitory synapses. These studies reveal a novel role for astrocytes in mediating synapse elimination in the developing and adult brain, identify MEGF10 and MERTK as critical proteins in the synapse remodelling underlying neural circuit refinement, and have important implications for understanding learning and memory as well as neurological disease processes.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This study shows that astrocytes actively engulf and eliminate synapses in the developing and adult mouse CNS, using the phagocytic receptors MEGF10 and MERTK. Loss of both pathways impairs retinogeniculate refinement and leaves excess functional synapses.

Key findings

  • Astrocytes engulfed synaptosomes in vitro and synaptic material in vivo; engulfed debris co-localized with the lysosomal marker LAMP2, and super-resolution (array tomography) and serial block-face EM showed intact pre- and postsynaptic elements inside astrocytes.
  • In vivo phagocytic index was reduced by about 45% in Megf10−/− and 58% in Mertk−/− dLGN astrocytes, and by roughly 85% in Megf10−/−;Mertk−/− astrocytes, suggesting the two receptors act in parallel.
  • Megf10−/−;Mertk−/− mice showed incomplete eye-specific segregation at P30 and, at P15–18, no fully refined dLGN neurons (versus 91% of wild-type neurons receiving 1–4 inputs); single-fiber responses were weaker, with each fiber contributing 16.3 ± 0.03% of total innervation versus 40.6 ± 0.07% in wild type.
  • Blocking retinal waves with epibatidine reduced astrocyte engulfment, and monocular epibatidine caused preferential engulfment of the weaker projection that was diminished in Megf10−/− and Mertk−/− backgrounds. In adult (1- and 4-month) somatosensory cortex, astrocytes engulfed both excitatory and inhibitory synapses.

Methods

  • In vitro engulfment assays using immunopanned astrocytes and microglia from wild-type, Megf10−/−, and Mertk−/− cortex incubated with tdTomato- or pHrodo-conjugated synaptosomes, quantified by imaging and FACS.
  • In vivo retinogeniculate assays in Aldh1l1-EGFP and CX3CR1-EGFP mice with intraocular CTB labeling, confocal imaging, a custom MATLAB algorithm to isolate engulfed debris, plus array tomography and serial block-face EM.
  • Electrophysiology on acute P15–18 slices (step-counting and minimal-stimulation fiber-fraction methods), eye-segregation analysis at P29–P30, epibatidine injections, and retinal wave recordings; statistics by ANOVA with Dunnett's tests, t-tests, and Kolmogorov–Smirnov tests.

Limitations

  • The paper notes that MERTK is expressed by microglia as well as astrocytes, and that Mertk−/− microglia showed a transient increase in engulfed debris at P4–P5, so microglia may partly compensate for reduced astrocyte phagocytosis; it also states that astrocyte engulfment is independent of C1q (data not shown).
  • The authors raise unresolved questions about how neural activity controls phagocytosis, whether astrocytes and microglia target different synapse types or circuits, and how astrocytes select which synapses to engulf.
  • Evident from the text: several key mechanistic claims (e.g., C1q independence, persistence of MEGF10/MERTK mRNA in adult astrocytes) rest on unpublished data or are not shown, and the relative astrocyte-versus-microglia contribution is inferred from per-cell-volume and cell-number comparisons rather than direct functional competition experiments.

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Integrity signals

Registry

Crossref · 10.1038/nature12776

Cites

40 of 40 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

34 Own result · 18 Own interpretation · 7 No full text of the sources · 3 Supported · 3 Partly supported · 1 Supported so far · 1 Couldn’t confirm · 1 Sources not found · 1 No basis given · accuracy not yet measured

Show all 55 claims

  • Probably not a substantial claim. 4
  • It may state two separate claims as one. 10
14 of 14
  • The paper relies on this without support.

    The mechanisms of developmental synapse remodeling other than those mediated by microglia are unknown.

    “Recently microglial cells have been shown to be responsible for a portion of synaptic remodeling, but the remaining mechanisms remain mysterious.”
  • The paper relies on this without support.

    One astrocyte ensheaths thousands of synapses.

    “Since astrocytes highly express phagocytic receptors as well as all their other interacting proteins listed above2, and one astrocyte has been shown to ensheath thousands of synapses, we hypothesized that astrocytes mediate synapse elimination within the developing and adult CNS through the MEGF10 and/or MERTK phagocytic pathways.”
2 of 2

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Metadata

Authors
Chung, W.-S., Clarke, L. E., Wang, G. X., Stafford, B. K., Sher, A., Chakraborty, C., Joung, J., Foo, L. C., Thompson, A., Chen, C., Smith, S. J., & Barres, B. A.
Affiliations
  • Stanford Medicine (US)
  • University of Michigan (US)
  • University of California, Santa Cruz (US)
  • Agency for Science, Technology and Research (SG)
  • Boston Children's Hospital (US)
Corresponding author
Chung, Won-Suk
Venue
Nature
Published
2013-11-24
Volume
504
Issue
7480
Pages
394-400
ISSN
  • 0028-0836 (ISSN-L)
  • 1476-4687
OpenAlex
W2125236750
Cited by
1,377
References
40
Citations by year
2026: 108 · 2025: 143 · 2024: 133 · 2023: 131 · 2022: 126 · 2021: 146 · 2020: 125 · 2019: 90 · 2018: 91 · 2017: 93 · 2016: 73 · 2015: 62 · 2014: 55 · 2013: 1
FWCI
31.20
Type
journal article
Language
en
Open access
Locations
  • Nature (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
  • RePEc: Research Papers in Economics (submittedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • National Institute of Mental Health (T32MH020016)
  • National Institute of Neurological Disorders and Stroke (NS069375, R01NS075252, P30NS069375, R21NS072556)
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development (P30HD018655)
Topics
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Immunology and Microbiology › Immunology › Phagocytosis and Immune Regulation
Keywords
astrocytes, synaptic pruning, synaptic engulfment, MEGF10, MERTK, phagocytosis, neural circuit refinement, microglia, glial cells, adult brain
MeSH terms
c-Mer Tyrosine Kinase, Animals, Astrocytes, Brain, Learning, Membrane Proteins, Mice, Transgenic, Neural Pathways, Phagocytosis, Proto-Oncogene Proteins, Retina, Synapses, Lateral Thalamic Nuclei, Receptor Protein-Tyrosine Kinases, Mice, In Vitro Techniques

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