Golden: a novel coat color mutant in the wild mouse Mus caroli.

We identified a spontaneous pigmentation mutant in the wild mouse species Mus caroli. Mutant mice exhibit a golden coat color on the agouti background, easily distinguishable from the darker wild type. The golden phenotype segregates as an autosomal recessive, showing no linkage to the sex-linked enzyme marker glucose-6-phosphate dehydrogenase. Obligate heterozygotes are phenotypically indistinguishable from the wild type. At birth, homozygotes have poorly pigmented eyes, which darken with age to become indistinguishable from the wild type. Pigmentation of the ears, tail, and footpads is reduced in intensity. Preliminary studies indicate that the phenotype may be due to an alteration in the shape and pigmentation of the eumelanosomes. The viability and fertility of both heterozygotes and homozygotes, as measured by litter size, sex ratio, or frequency of survival to weaning, appear to be normal for M. caroli. Spectrophotometric analysis of hair samples from the mouse variant at the putative golden locus (gdn) suggests that this mutant is not homologous to at least six independent pigment mutants previously identified in M. musculus.