In other species: cattle , dog , horse , red fox , pig , sheep , jaguar , jaguarundi , American black bear , woolly mammoth , domestic cat , rabbit , domestic guinea pig , goat , Arctic fox , rock pocket mouse , oldfield mouse , gray squirrel , lesser earless lizard , little striped whiptail , water buffalo , domestic yak , alpaca , , reindeer , Geoffroy's cat , Colocolo , ass , Arabian camel , Mongolian gerbil , raccoon dog , fallow deer , zebu , lorises , antarctic fur seal

Categories: Pigmentation phene

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 266300 (trait) , 155555 (gene)

Links to MONDO diseases: No links.

Mendelian trait/disorder: unknown

Considered a defect: no

Key variant is published: no

Cross-species summary: The extension locus encodes the melanocyte-stimulating hormone receptor (MSHR; now known as MC1R). This receptor controls the level of tyrosinase within melanocytes. Tyrosinase is the limiting enzyme involved in synthesis of melanins: high levels of tyrosinase result in the production of eumelanin (dark colour, e.g. brown or black), while low levels result in the production of phaeomelanin (light colour, e.g. red or yellow). When melanocyte-stimulating hormone (MSH) binds to its receptor, the level of tyrosinase is increased, leading to production of eumelanin. The wild-type allele at the extension locus corresponds to a functional MSHR, and hence to dark pigmentation in the presence of MSH. As explained by Schneider et al. (PLoS Genet 10(2): e1004892; 2015), "The most common causes of melanism (black coat) mutations are gain-of-function alterations in MC1R, or loss-of function alterations in ASIP, which encodes Agouti signaling protein, a paracrine signaling molecule that inhibits MC1R signaling". Mutations in MC1R have been associated with white colouring in several species.

Molecular basis: By comparing the sequence at three coat-colour genes (MC1R, ASIP, and CBD103) in all-white and coloured coyotes from Newfoundland, Brockerville et al. (2013) provided data strongly implicating one or both of two mutations (P159Q or R306Ter) in the MC1R gene as being causative of white coat colour in these coyotes. Further work is required to confirm a causal mutation.