Genes involved in regulating the melanocyte and melanoblast‐melanocyte populations in the epidermis of newborn mouse skin

Abstract

In the dorsal epidermis of both C57BL/10J and C3H/He mice, the number of melanocytes positive to the dopa reaction increased from birth to 3 or 4 days of age, and then gradually decreased and disappeared by 30 days of age. However, the number of melanoblasts plus melanocytes positive to the combined dopa-premelanin reaction remained constant until 3 or 4 days of age and then decreased in both strains. Despite the similarity of the change in these populations from birth on, there was a significant difference in the number of such cells between the two strains. Both melanocytes and melanoblasts in C3H/He were fewer than in C57BL/10J mice. The F₁, F₂, and backcross matings were performed in order to gain some information about the genetic basis of the difference. In the F₁ generation the offspring from reciprocal crosses exhibited intermediate values in both populations. The F₂ generation included the C3H/He type, F₁ type, and C57BL/10J type in a ratio of about 1:2:1 in both populations. Moreover, both reciprocal backcrosses gave ratios of parent type to F₁ type, which did not differ significantly from 1:1 in either population. These results indicate that the melanocyte and melanoblast-melanocyte populations in the dorsal epidermis of newborn mouse skin are controlled by semidominant genes.