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The branchial arches and HGF are growth-promoting and chemoattractant for cranial motor axons

Item Type:Article
Title:The branchial arches and HGF are growth-promoting and chemoattractant for cranial motor axons
Creators Name:Caton, A. and Hacker, A. and Naeem, A. and Livet, J. and Maina, F. and Bladt, F. and Klein, R. and Birchmeier, C. and Guthrie, S.
Abstract:During development, cranial motor neurons extend their axons along distinct pathways into the periphery. For example, branchiomotor axons extend dorsally to leave the hindbrain via large dorsal exit points. They then grow in association with sensory ganglia, to their targets, the muscles of the branchial arches. We have investigated the possibility that pathway tissues might secrete diffusible chemorepellents or chemoattractants that guide cranial motor axons, using co-cultures in collagen gels. We found that explants of dorsal neural tube or hindbrain roof plate chemorepelled cranial motor axons, while explants of cranial sensory ganglia were weakly chemoattractive. Explants of branchial arch mesenchyme were strongly growth-promoting and chemoattractive for cranial motor axons. Enhanced and oriented axon outgrowth was also elicited by beads loaded with Hepatocyte Growth Factor (HGF); antibodies to this protein largely blocked the outgrowth and orientation effects of the branchial arch on motor axons. HGF was expressed in the branchial arches, whilst Met, which encodes an HGF receptor, was expressed by subpopulations of cranial motor neurons. Mice with targetted disruptions of HGF or Met showed defects in the navigation of hypoglossal motor axons into the branchial region. Branchial arch tissue may thus act as a target-derived factor that guides motor axons during development. This influence is likely to be mediated partly by Hepatocyte Growth Factor, although a component of branchial arch-mediated growth promotion and chemoattraction was not blocked by anti-HGF antibodies.
Keywords:Branchial Arches, Chemoattraction, Cranial Motor Axons, Hepatocyte Growth Factor, Rat Embryo, Animals, Mice, Rats
Source:Development
ISSN:0950-1991
Publisher:Company of Biologists (U.K.)
Volume:127
Number:8
Page Range:1751-1766
Date:1 April 2000
Official Publication:http://dev.biologists.org/cgi/content/abstract/127/8/1751
PubMed:View item in PubMed

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