The evolution and elaboration of vertebrate neural crest cells.

Vertebrate neural crest cells are embryonic neuroepithelial cells that undergo an epithelial-mesenchymal transition, migrate throughout the embryo and form a wide variety of derivatives, including peripheral neurons and glia, pigment cells, and craniofacial cartilage, bone and teeth. Neural crest cell evolution and elaboration is intimately bound up with vertebrate evolution: the most primitive living vertebrates, lampreys and hagfishes, have most but not all neural crest derivatives. A torrent of recent molecular information has changed our understanding of vertebrate phylogenetic relationships, expanded our understanding of the gene circuitry underlying neural crest development, and given interesting information on the deployment of homologues of these genes in invertebrate relatives such as ascidians and amphioxus. New molecular insights into the evolutionary origin of cartilage, as well as into the nature and evolution of the cells and genes involved in tooth and bone formation, enable tentative hypotheses to be framed for the evolution of skeletal neural crest derivatives.