Developmental biology of melanocytes

Apart from embryonic stem cells (ESCs) in the blastocyst, neural crest stem cells (NCSCs) in vertebrate embryos represent the stem cell population in our body with the broadest developmental potential, generating most of the neurons and glia of the peripheral nervous system (PNS) as well as various nonneural cell types, such as smooth muscle cells in the outflow tract of the heart, craniofacial bone, and cartilage and, in particular, melanocytes in the skin. It is assumed that a third of all congenital birth defects are due to failures in neural crest development, illustrating the significance of this stem cell population. Moreover, processes underlying melanocyte development appear to be recapitulated, at least partially, during formation of melanoma, the most aggressive skin tumor. For instance, it has recently been shown that an embryonic NCSC gene expression signature is reactivated upon tumor initiation in a zebrafish model of melanoma, suggesting a functional involvement of a NCSC program in tumors originating from neural crest derivatives. Thus, to gain insights into melanoma biology, it is important to understand the mechanisms regulating NCSC and melanocyte development, as outlined in this chapter