Developmental interaction in the pigmentary system of mice

Abstract

Among mice with Jay's dominant spotting (WJ2/+), the size of white spots is reduced in yellow (el e) mice as compared with nonyellow (El−) mice. The size of white spots in AVY/−WJ2/+ mice is correlated with the extent of yellow pigmentation. Comparisons of phenotypes and their causative genotypes, noted in this study and others, suggest that some stage in the process of formation of yellow pigment, rather than the presence of yellow pigment or the specific genotype that determines its presence, may be responsible for the smaller spot size In white-spotted yellow as compared with white-spotted black mice. On the one hand, genotype does not always correlate with this interaction. Extension-locus and agouti-locus alleles may affect the size of white spots in WJ2/+ mice, but if the mice of a given genotype (Avy− are not yellow, then the spot size is not affected. On the other hand, embryological processes responsible for white spotting function pri marily in utero, while actual formation of pigment begins about at birth. These observations suggest that the interaction between white spotting and phaeomelanogenesis occurs at an intermediate developmental stage, and is neither due to a primary gene action nor directly dependent on the presence of phaeomelanin.