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Somite polarity and segmental patterning of the peripheral nervous system.

Authors
  • Kuan, C-Y Kelly
  • Tannahill, David
  • Cook, Geoffrey M W
  • Keynes, Roger J
Type
Published Article
Journal
Mechanisms of development
Publication Date
Sep 01, 2004
Volume
121
Issue
9
Pages
1055–1068
Identifiers
PMID: 15296971
Source
Medline
License
Unknown

Abstract

The analysis of the outgrowth pattern of spinal axons in the chick embryo has shown that somites are polarized into anterior and posterior halves. This polarity dictates the segmental development of the peripheral nervous system: migrating neural crest cells and outgrowing spinal axons traverse exclusively the anterior halves of the somite-derived sclerotomes, ensuring a proper register between spinal axons, their ganglia and the segmented vertebral column. Much progress has been made recently in understanding the molecular basis for somite polarization, and its linkage with Notch/Delta, Wnt and Fgf signalling. Contact-repulsive molecules expressed by posterior half-sclerotome cells provide critical guidance cues for axons and neural crest cells along the anterior-posterior axis. Diffusible repellents from surrounding tissues, particularly the dermomyotome and notochord, orient outgrowing spinal axons in the dorso-ventral axis ('surround repulsion'). Repulsive forces therefore guide axons in three dimensions. Although several molecular systems have been identified that may guide neural crest cells and axons in the sclerotome, it remains unclear whether these operate together with considerable overall redundancy, or whether any one system predominates in vivo.

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