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Division of Molecular Neurobiology, MRC National Institute for Medical
Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
* Present address: GlaxoSmithKline Biologicals, Rue de l'Institut 89, B-1330
Rixensart, Belgium
Present addresses: Department of Clinical Genetics, Erasmus University, Dr
Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
Author for correspondence (e-mail:
vpachni{at}nimr.mrc.ac.uk)
Accepted 28 August 2002
The majority of neurones and glia of the enteric nervous system (ENS) are derived from the vagal neural crest. Shortly after emigration from the neural tube, ENS progenitors invade the anterior foregut and, migrating in a rostrocaudal direction, colonise in an orderly fashion the rest of the foregut, the midgut and the hindgut. We provide evidence that activation of the receptor tyrosine kinase RET by glial cell line-derived neurotrophic factor (GDNF) is required for the directional migration of ENS progenitors towards and within the gut wall. We find that neural crest-derived cells present within foetal small intestine explants migrate towards an exogenous source of GDNF in a RET-dependent fashion. Consistent with an in vivo role of GDNF in the migration of ENS progenitors, we demonstrate that Gdnf is expressed at high levels in the gut of mouse embryos in a spatially and temporally regulated manner. Thus, during invasion of the foregut by vagal-derived neural crest cells, expression of Gdnf was restricted to the mesenchyme of the stomach, ahead of the invading NC cells. Twenty-four hours later and as the ENS progenitors were colonising the midgut, Gdnf expression was upregulated in a more posterior region the caecum anlage. In further support of a role of endogenous GDNF in enteric neural crest cell migration, we find that in explant cultures GDNF produced by caecum is sufficient to attract NC cells residing in more anterior gut segments. In addition, two independently generated loss-of-function alleles of murine Ret, Ret.k and miRet51, result in characteristic defects of neural crest cell migration within the developing gut. Finally, we identify phosphatidylinositol-3 kinase and the mitogen-activated protein kinase signalling pathways as playing crucial roles in the migratory response of enteric neural crest cells to GDNF.
Key words: Neural crest, Cell migration, Enteric nervous system (ENS), Receptor tyrosine kinase (RTK), RET, Glial cell line-derived neurotrophic factor (GDNF), Mouse
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