In mammals (but not in chicks), the Kit receptor protein is critical in causing the committed melanoblast precursors to migrate on the dorsolateral pathway. This protein is found on those mouse neural crest cells that also express MITF—that is, the presumptive melanoblasts. Kit protein binds stem cell factor (SCF), which is made by the dermal cells. When bound to SCF, Kit prevents apoptosis and stimulates cell division among the melanoblast precursors. If mice or humans do not make sufficient amounts of Kit, the neural crest cells do not proliferate enough to cover the entire skin (see Figure 15.17C, D; Spritz et al. 1992). Moreover, SCF is critical for dorsolateral migration. If SCF is experimentally secreted from tissues (such as cheek epithelium or the footpads) that do not usually synthesize this protein (and do not usually have melanocytes), neural crest cells will enter those regions and become melanocytes (Kunisada et al. 1998; Wilson et al. 2004).
Kunisada, T. and 8 others. 1998. Transgene expression of steel factor in the basal layer of epidermis promotes survival, proliferation, differentiation, and migration of melanocyte precursors. Development 125: 2915–2923.
Spritz, R. A., L. B. Giebel and S. A. Holmes. 1992. Dominant negative and loss of function mutations of the c-kit (mast/stem cell growth factor receptor) proto-oncogene in human piebaldism Am. J. Hum. Genet. 50: 261–269.
Wilson, Y. M., K. L. Richards, M. L. Ford-Perriss, J. J. Panthier and M. Murphy. 2004. Neural crest cell lineage segregation in the mouse neural tube. Development 131: 6153–6162.