Wnts are secreted glycoproteins that act as ligands to activate receptor-mediated signal transduction. pathways involved in development, and in human cancers. In vertebrates two Wnt signaling pathways have been identified, the Wnt/B-catenin pathway and the Wnt/calcium pathway. Evidence in multiple systems suggests that the Wnt/B-catenin pathway regulates specific genes, and can be transforming. To date no systematic effort has been made to identify Wnt/B catenin-responsive genes in embryos of any organism. The Wnt/calcium pathway often antagonizes the Wnt/B-catenin pathway, and may act as a tumor suppressor pathway. Little is known of genes that may respond to this pathway. Our proposal is to systematically identify as many genes as possible that respond to both Wnt pathways in zebrafish embryos, using DNA microarrays, and suppressive PCR techniques. We will rely on activation and inhibition of each pathway, as well as analyzing gene expression in zebrafish in which the functions of specific Wnt genes are reduced by morpholino antisense oligonucleotides or gamma ray-induced deficiency. After confirming and characterizing Wnt-responsive genes, our data will be compared with the BMP-responsive genes of the Kimelman and Raible projects, in an effort to identify genes responding to both Wnts and BMPs. The collective project will thus provide important insights into combinatorial signaling leading to regulation of genes involved in development, and likely cancer.
