Convergent changes in melanocortin receptor 1 gene are associated with black-headed coat color in sheep

As one of the most obvious phenotypic traits, the coat color of sheep is an ideal model to study the genetic mechanisms underlying coat color varieties of mammals. One distinguishable coat color is the black-headed type, such as the famous black-headed Dorper sheep from Africa and Bayinbuluke sheep from Asia. In this study, we compared the genome sequences of black-headed and all-white sheep to identify causative genes for the black-headed sheep, including black-headed Dorper vs. white-headed Dorper, as well as Bayinbuluke (black-headed) vs. Small-tailed Han (all-white). The most differentiating region between black-headed sheep and all-white sheep was found to harbor a haplotype covering melanocortin receptor 1 (MC1R) gene. The share of this haplotype by the black-headed sheep from Africa and Asia suggested that the convergent change in the MC1R region is likely to determine this unique coat color. Two missense mutations (g. 14251947T > A and g. 14252090G > A) within this haplotype of MC1R gene were found. We further analyzed whole genome sequence data of 460 worldwide sheep with diverse coat colors and confirmed the association between the MC1R haplotype with pigmentation variations. Our study provides novel insights into coat color genetics in sheep and expands our knowledge of the link between MC1R gene and varying pigmentation patterns in sheep.