The major goal of this component project is to understand how two signaling pathways, Bmp and Wnt/B-catenin, work in combination to induce a specific tissue type, the neural crest. Neural crest cells arise from the lateral edge of the neural plate and then migrate throughout the body to form a variety of cell types including neurons and glia of the peripheral nervous system, cartilage, and pigment cells. While there is a large body of evidence to support a role for Wnt and Bmp signals in neural crest induction, how the two pathways cooperate has been largely unexplored. In this project, we will examine where and when these signals are needed using transgenic zebrafish that express activators and inhibitors of the Wnt/B-catenin and Bmp signaling pathways under control of a heatshock promoter. We will examine how signals are integrated by studying regulation of the pax3 promoter, a gene regulated by both signaling pathways. Finally, we will identify new target genes activated by both pathways involved in neural crest induction using a combination of microarray screening and in situ hybridization. We will systematically test the role of these genes in neural crest induction by mRNA misexpression and by using function blocking antisense morpholino oligonucleotides. These experiments should allow us to construct a genetic hierarchy of genes regulated by Wnt and Bmp signals that coordinate the formation of the neural crest. Dissecting how these signaling pathways integrate to direct embryonic processes should lead to eventual understanding and treatment of human inherited and developmental disorders.
