Neural crest cells are progenitors of diverse and numerous lineages in the vertebrate embryo, including the peripheral nervous system and the bones and cartilage of the head. Neural crest cells arise in the neural folds as the neurectoderm rolls into a neural tube, then migrate to a variety of distant sites in the periphery of the embryo. Despite the fundamental importance of the neural crest for vertebrate development, it is not known how these cells form. The goal of this proposal is to define the molecular events that generate neural crest cells. An arrayed cDNA library will be created from a pool of embryos at different stages of neural crest development. Neural crest-specific genes on the array will be identified by hybridizing subtracted, labeled cDNA made from tissues that are induced versus uninduced for neural crest. From this pool, regulators of neural crest cell identity will be identified by three criteria: l) sequence, 2) ability to induce neural crest when ectopically expressed by electroporation, and 3) expression pattern. In future work, genes identified by this technique will be functionally characterized in order to understand the cascade of events that gives rise to neural crest cells.