Expression of ret in the chicken embryo suggests roles in regionalisation of the vagal neural tube and somites and in development of multiple neural crest and placodal lineages

In a screen for receptor tyrosine kinase genes regionally expressed in the developing hindbrain, we cloned and characterised the chicken ret gene. Data derived from studies of congenital human disease and from disruption of murine ret have demonstrated roles for ret in development of the kidney and enteric nervous system; the latter has been most well-studied in the avian embryo. In agreement with studies of the mouse embryo, we find expression of ret in both the intermediate mesoderm and the enteric nervous system. However, we additionally detect transcripts specifically in the vagal neural tube prior to the migration of enteric crest precursors, suggesting a possible earlier function in regionalisation of the neural tube and vagal neural crest. This spatial restriction in the neural tube is modulated by retinoic acid, but is not coordinately regulated with RAR-beta which shares a common anterior limit of expression with ret in normal embryos. Widespread expression of ret in placodal and neural crest derivatives raises the possibility of other roles in the development of the peripheral nervous system. In addition, ret may function in the spatial organisation of the epithelial somite, where it might play a role in the specification of anterior dermamyotome.