epistatic variation
Steiner CC, Weber JN & Hoekstra HE 2007 Adaptive variation in beach mice produced by two interacting pigmentation genes. PLoS Biol 5:e219.
- here we identify genetic changes contributing to an adaptive difference in color pattern between two subspecies of oldfield mice (Peromyscus polionotus)
- two candidate genes, the melanocortin-1 receptor (Mc1r) and its antagonist, the Agouti signaling protein (Agouti), map to independent regions that together are responsible for most of the difference in pigmentation between subspecies
- a derived mutation in the coding region of Mc1r, rather than change in its expression level, contributes to light pigmentation
- beach mice have a derived increase in Agouti mRNA expression but no changes in protein sequence
- these two genes also interact epistatically
- the phenotypic effects of Mc1r are visible only in genetic backgrounds containing the derived Agouti allele
- cryptic coloration can be based largely on a few interacting genes of major effect
- epistasis is a property of particular alleles rather than of loci themselves
- thus epistatic interactions observed in the laboratory may differ from those seen in natural populations
