Genomic mapping identifies two genetic variants in the MC1R gene for coat colour variation in Chinese Tan sheep

Abstract

Coat colour is one of the most important economic traits of sheep and is mainly used for breed identification and characterization. This trait is determined by the biochemical function, availability and distribution of phaeomelanin and eumelanin pigments. In our study, we conducted a genome-wide association study to identify candidate genes and genetic variants associated with coat colour in 75 Chinese Tan sheep using the ovine 600K SNP BeadChip. Accordingly, we identified two significant SNPs (rs409651063 at 14.232 Mb and rs408511664 at 14.228 Mb) associated with coat colour in the MC1R gene on chromosome 14 with −log10(P) = 2.47E-14 and 1.00E-13, respectively. The consequence of rs409651063 was a missense variant (g.14231948 G>A) that caused an amino acid change (Asp105Asn); however, the second SNP (rs408511664) was a synonymous substitution and is an upstream variant (g.14228343G>A). Moreover, our PCR analysis revealed that the genotype of white sheep was exclusively homozygous (GG), whereas the genotypes of black-head sheep were mainly heterozygous (GA). Interestingly, allele-specific expression analysis (using the missense variant for the skin cDNA samples from black-head sheep) revealed that only the G allele was expressed in the skin covered with white hair, while both the G and A alleles were expressed in the skin covered with black hair. This finding indicated that the missense mutation that we identified is probably responsible for white coat colour in Tan sheep. Furthermore, qPCR analysis of MC1R mRNA level in the skin samples was significantly higher in black-head than white sheep and very significantly higher in GA than GG individuals. Taken together, these results help to elucidate the genetic mechanism underlying coat colour variation in Chinese indigenous sheep.

Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes

“…Moreover, a GWAS using the OvineSNP600K Beadchip was performed on 75 Chinese Tan sheep individuals (29 black-headed and 46 white-coated; see Additional file 1 : Fig. S4), which revealed two significant SNPs ( rs409651063 and rs408511664 ) in MC1R that were associated with coat color development [ 89 ]. Further information from previous studies on the sheep MC1R gene is shown in Additional file 2 : Table S9.…”

“…Table S9. Additional genetic studies on sheep coat color phenotype: The MC1R gene [89,302,[304][305][306][307][308][309]. Table S10.…”

The genomic architecture of a continuous color polymorphism in the European barn owl (Tyto alba)

“…For practical reasons, research on animal coloration has continued and flourished mainly on humans [3][4][5] and model systems (i.e. mice [6,7], or domestic animals [8,9]), and has been more recently extended to non-model species, with a handful of studies on birds [10,11], mammals [12,13], butterflies [14] and amphibians [15]. Moreover, many of these studies took advantage of color traits exhibiting relatively simple discrete variation and inheritance patterns thus often contrasting clearly distinctive (eco)morphs [11][12][13][14][15].…”

Thermoregulation in Sheep and Goats: A Review

“…Other genes associated with adaptability to temperature changes have been found in sheep and goats, including HSP70, which is a set of heat shock protein genes that defend the animals from overheating, and the ENOX2 gene, which has been found in goats susceptible to heat stress [10,11]. Other polymorphic genes, including MCIR, ASIP, and TYRP1, have been observed in different sheep species and are related to wool color, which controls the rate of heat absorption [12]. Accordingly, ruminants' capability to endure, develop, and produce in harsh climates is responsible for their adaptation to different climates.…”