Journal
JOURNAL OF COMPARATIVE NEUROLOGY
Volume 520, Issue 18, Pages 4184-4203Publisher
WILEY
DOI: 10.1002/cne.23147
Keywords
Schwann cell; taste bud; sox10; pou3f1; egr2a; b
Categories
Funding
- DePaul University Undergraduate Research Assistantship
- National Institutes of Health [R01-DE016678, R15-HD064169]
- National Cancer Institute [P30-CA060553]
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Myelination is a cellular adaptation allowing rapid conduction along axons. We have investigated peripheral axons of the zebrafish maxillary barbel (ZMB), an optically clear sensory appendage. Each barbel carries taste buds, solitary chemosensory cells, and epithelial nerve endings, all of which regenerate after amputation (LeClair and Topczewski [2010] PLoS One 5:e8737). The ZMB contains axons from the facial nerve; however, myelination within the barbel itself has not been established. Transcripts of myelin basic protein (mbp) are expressed in normal and regenerating adult barbels, indicating activity in both maintenance and repair. Myelin was confirmed in situ by using toluidine blue, an anti-MBP antibody, and transmission electron microscopy (TEM). The adult ZMB contains similar to 180 small-diameter axons (<2 mu m), approximately 60% of which are myelinated. Developmental myelination was observed via whole-mount immunohistochemistry 46 weeks postfertilization, showing myelin sheaths lagging behind growing axons. Early-regenerating axons (10 days postsurgery), having no or few myelin layers, were disorganized within a fibroblast-rich collagenous scar. Twenty-eight days postsurgery, barbel axons had grown out several millimeters and were organized with compact myelin sheaths. Fiber types and axon areas were similar between normal and regenerated tissue; within 4 weeks, regenerating axons restored similar to 85% of normal myelin thickness. Regenerating barbels express multiple promyelinating transcription factors (sox10, oct6 = pou3f1; krox20a/b = egr2a/b) typical of Schwann cells. These observations extend our understanding of the zebrafish peripheral nervous system within a little-studied sensory appendage. The accessible ZMB provides a novel context for studying axon regeneration, Schwann cell migration, and remyelination in a model vertebrate. J. Comp. Neurol. 520:41844203, 2012. (c) 2012 Wiley Periodicals, Inc.
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