Melanocyte developmental genetics: Biphasic control of dopa oxidase activity by the E locus of the fowl

Aliquots of developing feather papillae isolates were measured for oxygen consumption before and after incubation in the substrate, L dopa. Net oxidation (dopa minus basal) indicated the amount of L dopa oxidized by melanocytes. The albino like mutant e(y)/e(y) c/c showed minimal net oxidation when compared to its counterpart e(y)/e(y) +(c) +(c). This shows that the c mutation severely restricts dopa oxidase activity. The eumelanic genotype (E/E) had high net oxidation at stage 34 which regressed to a low value by stage 38. The pheomelanic producing genotype (e(y)/e(y)) had a low net oxidation at stage 34 which progressed to a high value by stage 38. Dopa oxidase activity in the eumelanin and pheomelanin producing genotype (standard; +(E)/ +(E)) was biphasic. Cells from these embryos had a high net oxidation at both stages 34 and 38 and a low value at stage 36. High net oxidation at stage 34 in E/E and +(e)/+(e) seem associated with eumelanogenesis, while the high net oxidation at stage 38 in +(e)/+(e) and e(y)/e(y) is thought to be related to pheomelanogenesis. L dopa substrate utilization values were also completed for the heterozygote E(e(y) to determine if differences were detectable between this genotype and its respective homozygotes. The heterozygote net oxidation resembled E/E in pattern but at about one half the E/E values. The data are discussed in terms of the E locus as a possible control gene locus which determines whether eumelanin or pheomelanin is synthesized. (37 references)