Astrocytes phagocytose focal dystrophies from shortening myelin segments in the optic nerve of Xenopus laevis at metamorphosis

Elizabeth A. Mills, Chung Ha O. Davis, Eric A. Bushong, Daniela Boassa, Keun Young Kim, Mark H. Ellisman, Nicholas Marsh-Armstrong

Research output: Contribution to journalArticle

19 Scopus citations


Oligodendrocytes can adapt to increases in axon diameter through the addition of membrane wraps to myelin segments. Here, we report that myelin segments can also decrease their length in response to optic nerve (ON) shortening during Xenopus laevis metamorphic remodeling. EM-based analyses revealed that myelin segment shortening is accomplished by focal myelin-axon detachments and protrusions from otherwise intact myelin segments. Astrocyte processes remove these focal myelin dystrophies using known phagocytic machinery, including the opsonin milk fat globule-EGF factor 8 (Mfge8) and the downstream effector ras-related C3 botulinum toxin substrate 1 (Rac1). By the end of metamorphic nerve shortening, one-quarter of all myelin in the ON is enwrapped or internalized by astrocytes. As opposed to the removal of degenerating myelin by macrophages, which is usually associated with axonal pathologies, astrocytes selectively remove large amounts of myelin without damaging axons during this developmental remodeling event.

Original languageEnglish (US)
Pages (from-to)10509-10514
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
StatePublished - Aug 18 2015
Externally publishedYes



  • Glia
  • Lipid droplet
  • Mfge8
  • Thyroid hormone

ASJC Scopus subject areas

  • General

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