EFFECT OF THE STEEL GENE-PRODUCT ON MELANOGENESIS IN AVIAN NEURAL CREST CELL-CULTURES

Mutations at the Steel (Sl) and dominant white spotting (W) loci affec t three embryonic lineages: primordial germ cells, hemopoietic stem ce lls and neural-crest-derived melanocytes. The gene products of these l oci are a peptide growth factor, called here stem cell factor (SCF), a nd its tyrosine kinase receptor, the protooncogene c-kit. We have stud ied how chicken recombinant SCF affects the development of melanocytes from quail neural crest cells in secondary culture under defined cond itions. We observed that the total number of neural crest cells, of me lanocytes and of their precursors was higher in the presence than in t he absence of SCE Labelling with bromodeoxyuridine showed that SCF had a modest and transient mitogenic effect on the neural crest populatio n. SCF also enhanced the differentiation rate of melanocyte precursors , recognized by the ,,melanocyte early marker'' monoclonal antibody (M elEM MAb), and of melanocytes, since the proportion of both subpopulat ions significantly increased in the presence of SCE Finally, SCF incre ased the survival of the neural crest population since in its presence the total number of cells remained stable while it gradually declined in control cultures. Our results support the notion that SCF sustains the survival of the neural crest population and stimulates the rate o f the melanogenic differentiation process.