S21-05. Hedgehog signalling and cell diversity in the zebrafish myotome

sory and autonomic neurons, and craniofacial structures. Data compiled from vertebrates models suggest that a network of interacting transcriptional regulators and downstream effector genes confer properties like multipotency and migratory capacity to nascent neural crest cells. These regulatory interactions involve inductive signals (e.g. Wnt, BMP, FGF) that establish the neural plate border, by up-regulation of border specifier genes like Msx1/2, Pax3/7, and Zic. These border genes in turn up-regulate neural crest specifier genes like Slug/Snail, FoxD3 and the SoxE family. Finally, the neural crest specifiers turn on specific downstream targets that render the neural crest migratory and multipotent. We are testing linkages in this gene regulatory network in chick and lamprey by systematically perturbing a subset of the transcription factors involved in early neural crest specification and examining the effect on likely downstream target genes in order to establish interrelationships. In addition, we are isolating cis-regulatory regions of genes to identify neural crest enhancers, determine additional inputs to the network and determine which interactions are direct. The results suggest that a series of gene regulatory circuits are involved in the production of migratory neural crest cells in the early vertebrate embryos and that many of these events may be conserved to the base of vertebrates.