Genetic variation within coat color genes of MC1R and ASIP in Chinese brownish red Tibetan pigs

Abstract

Melanocortin receptor 1 (MC1R) and agouti signaling protein (ASIP) are two major genes affecting coat color phenotypes in mammals, and inactivation mutations in the MC1R gene are responsible for red coat color in European pig breeds. Conversely, the gain-of-function ASIP mutations block MC1R signaling and lead to the production of red pheomelanin. Chinese Tibetan pigs have three types of coat color phenotypes, including brownish red, solid black and black with patches of brownish red and white. Herein, we investigated variations of the MC1R and ASIP genes in Tibetan pigs. The results showed that the brownish red Tibet pig had the dominant black MC1R allele (E(D1)). No loss-of-function mutation in MC1R responsible for red coat color in European breeds was observed in this breed. No causal mutation for the red coat color phenotype was found in the coding sequence of the ASIP gene. A novel missense mutation c.157G > A was firstly identified in exon 2 of ASIP, which was further genotyped in 285 pigs from five Chinese breeds and three Western breeds having different coat color phenotypes. Nearly all pigs were GG homozygotes. In conclusion, no functional variant responsible for brownish red coloration was found in the coding region of MC1R and ASIP in Tibetan pigs.