Analysing the diversity of the caprine melanocortin 1 receptor (MC1R) in goats with distinct geographic origins

In humans, the variability of the melanocortin 1 receptor (MC1R) gene has been associated with geography, being mainly determined by the amount of exposure to sunlight. Studies performed in pigs have also evidenced the existence of a geographic component in the distribution of MC1R haplotypes, probably as a consequence of an ancient split between Asian and European wild boars. Herewith, we have partially resequenced the caprine MC1R coding region in 58 goats from distinct geographic locations i.e. Colombia, Italy, Spain, France, Greece, Romania, Iran and Africa. The resulting dataset was merged with 39 previously published caprine MC1R sequences and a median joining network was built. This phylogenetic analysis did not yield any evidence of a relationship between geography and the clustering of caprine MC1R sequences, a result that was confirmed by performing a Mantel test with a previously published dataset of nine goat breeds (N = 319) with available MC1R genotypes. The majority of caprine MC1R variation was non-synonymous (c.676A > G, c.748G > T, c.764G > A and c.801C > G) and predicted to have functional effects. An analysis of goat MC1R sequences with the PAML 4 software provided evidence that two SNPs (c.764G > A and c.801C > G) might evolve under positive selection. The apparent lack of any link between caprine MC1R variation and geography might be explained by a complex array of factors including artificial selection for pigmentation phenotypes and recent divergence amongst goat breeds.