MUTATIONS AT THE W-LOCUS AFFECT SURVIVAL OF NEURAL CREST-DERIVED MELANOCYTES IN THE MOUSE

The development of melanoblasts in normally pigmented and dominant spo tting (W) embryos was followed by in situ hybridisation to TRP-2/DT mR NA, which labels migratory melanoblasts from 10 days post coitum. Nume rous melanoblasts migrate to the inner ear around 11 days. In contrast , few migratory melanoblasts are associated with the eye or skin at th is stage and melanoblast distribution within the trunk and tail is pat chy. The distribution of melanoblasts in 10.5-11-day-old W-v/W-v, W-sh /W-sh and W-41/W-41 mutants was similar to that in controls but melano blast density was lower and by 12 days was severely reduced. These res ults suggest that mutations of the c-kit receptor tyrosine kinase enco ded at the W locus do not alter early migration or differentiation of melanoblasts but severely affect melanoblast survival.