Plumage color is an artificially and naturally selected trait in domestic ducks. Black, white, and spotty are the main feather colors in domestic ducks. Previous studies have shown that black plumage color is caused by MC1R, and white plumage color is caused by MITF. We performed a genome-wide association study (GWAS) to identify candidate genes associated with white, black, and spotty plumage in ducks. Two non-synonymous SNPs in MC1R (c.52G>A and c.376G>A) were significantly related to duck black plumage, and three SNPs in MITF (chr13:15411658A>G, chr13:15412570T>C and chr13:15412592C>G) were associated with white plumage. Additionally, we also identified the epistatic interactions between causing loci. Some ducks with white plumage carry the c.52G>A and c.376G>A in MC1R, which also compensated for black and spotty plumage color phenotypes, suggesting that MC1R and MITF have an epistatic effect. The MITF locus was supposed to be an upstream gene to MC1R underlying the white, black, and spotty colors. Although the specific mechanism remains to be further clarified, these findings support the importance of epistasis in plumage color variation in ducks.

Artificial selection affects phenotypes differently by natural selection. Domestic traits, which pass into the wild, are usually negatively selected. Yet, exceptionally, this axiom may fail to apply if genes, from the domestic animals, increase fertility in the wild. We studied a rare case of a wild boar population under the framework of Wright\'s interdemic selection model, which could explain gene flow between wild boar and pig, both considered as demes. We analysed the MC1R gene and microsatellite neutral loci in 62 pregnant wild boars as markers of hybridization, and we correlated nucleotide mutations on MC1R (which are common in domestic breeds) to litter size, as an evaluation of fitness in wild sow. Regardless of body size and phyletic effects, wild boar sows bearing nonsynonymous MC1R mutations produced larger litters. This directly suggests that artificially selected traits reaching wild populations, through interdemic gene flow, could bypass natural selection if and only if they increase the fitness in the wild.

Variation in coat colour genotypes of archaeological cattle samples from Finland was studied by sequencing 69 base pairs of the extension locus (melanocortin 1-receptor, MC1R) targeting both a transition and a deletion defining the three main alleles, such as dominant black (E(D) ), wild type (E(+) ) and recessive red (e). The 69-bp MC1R sequence was successfully analysed from 23 ancient (1000-1800 AD) samples. All three main alleles and genotype combinations were detected with allele frequencies of 0.26, 0.17 and 0.57 for E(D) , E(+) and e respectively. Recessive red and dominant black alleles were detected in both sexes. According to the best of our knowledge, this is the first ancient DNA study defining all three main MC1R alleles. Observed MC1R alleles are in agreement with calculated phenotype frequencies from historical sources. The division of ancient Finnish cattle population into modern Finnish breeds with settled colours was dated to the 20th century. From the existing genotyped populations in Europe (43 breeds, n = 2360), the closest match to ancient MC1R genotype frequencies was with the Norwegian native multicoloured breeds. In combined published genotype data of ancient (n = 147) and genotypes and phenotypes of modern Nordic cattle (n = 738), MC1R allele frequencies showed temporal changes similar to neutral mitochondrial DNA and Y-chromosomal haplotypes analysed earlier. All three markers indicate major change in genotypes in Nordic cattle from the Late Iron Age to the Medieval period followed by slower change through the historical periods until the present.

Parkinson\'s disease (PD, OMIM 168600) is a neurodegenerative disorder featured by degeneration of melanin-positive dopaminergic neurons. Epidemiologic studies have suggested that PD and malignant melanoma (MM) might share common genetic components. Recently, the p.R160W variant in the melanocortin 1 receptor gene (MC1R, OMIM 155555), a risk factor for MM, has been identified to be associated with PD in Spanish population. To explore whether the MC1R variants are associated with sporadic PD in Chinese population, we designed a case-control comparison study and studied three variants, including rs3212366 (p.F196L), rs33932559 (p.I120T) and rs34090186 (p.R67Q), in the MC1R gene in 512 Chinese Han patients with sporadic PD and 512 age, gender and ethnicity matched normal controls. For rs3212366, only the TT genotype was identified in both PD and control cohorts. For variants rs33932559 and rs34090186, we did not identify any statistically significant difference in either genotypic distribution or allelic distribution between the PD cohort and control cohort, and in addition, we did not identify any related haplotype that would either increase the risk for PD or play a protective role against PD. Our data suggest that none of the three variants of the MC1R gene and related haplotypes be associated with sporadic form of PD in Chinese Han population from Mainland China.