The agouti suppressor (As) coat color mutation in mice: developmental effects on the expression of agouti locus alleles.

The alleles at the agouti locus in the mouse determine whether eumelanin or pheomelanin is synthesized by the follicular melanocytes. The agouti suppressor (As) mutation, which is closely linked to the agouti locus, reduces the amount of pheomelanin produced by whatever agouti alleles are present in the animal's genome. Previous developmental studies have indicated that the agouti alleles exert their influence on the follicular melanocytes via interactions between the developing dermis and epidermis. Using the techniques of dermal-epidermal recombination of embryonic agouti suppressor (AsAw/AsAw), white-bellied agouti (Aw/Aw), yellow (Ay/a), viable yellow (Avy/Avy), black and tan (at/at), and nonagouti (a/a) mouse skin, the present study demonstrates that 1) the dermis is responsible for the development of regional pigmentation patterns in white-bellied agouti mice, and 2) the agouti suppressor mutation interferes with the expression of the white-bellied agouti allele by acting on the dermis as well as the epidermis. In addition, this study provides further evidence for the role of the epidermis in the expression of the agouti locus alleles.