Polymorphisms Of MC1R And ASIP Genes And Their Association With Coat Colours In Ten Chinese Indigenous Sheep Breeds

Variations in mammalian coat colour are due to the ratio of eumelanin andphaeomelanin synthesis within the melanocyte.MC1R and ASIP play an importantrole in regulation of eumelanin and phaeomelanin synthesis.In this paper,wesequenced the entire coding region of the MC1R gene and ASIP gene in ten Chineseindigenous sheep breeds with different coat colours. The results were showed asfollows:1．Five single nucleotide polymorphisms(SNPs)were detected in MC1R,three ofthe SNPs(c.429C>T,c.600T>G,c.735T>C) were silent mutations and the other two（c.218T>A,c.361G>A）were missense mutations caused a predicted amino acidsubstitution(p.M73K,p.D121N).Hardy-Weinberg balance is detected and all the locuswere in balance except c.218T>A and c.361G>A in Minxian black-fur sheep breedsand c.429C>T、c.600T>G and c.735C>T in Kazakh Fat-Rumped sheep breeds.Tensheep breeds performed higher genetic diversity(0.5621).2．The overall mean coefficient of gene differentiation among10populationswas0.2047, indicating that the variation existed mainly within differentpopulations.Molecular phylogenetic trees were made, the black or brown sheep(Minxian Black-fur and Kazakh Fat-Rumped) clustered together, while another whiteand white with black or brown face sheep (Big-tailed Han, Small-tailed Han, GansuAlpine Fine-wool, China Merino, Tibetan, Mongolian, Tan, Duolang) were dividedinto another group， and the results got here was identical with animal coatcolour,ecological types and breeding history.3．It only got three haplotypes through the5SNPs,and these showed that theywere close linkage with each other. The haplotype3of the all individual mutationswas observed only in the Minxian Black-fur sheep breed.This haplotype absent infour Chinese sheep breeds with white coat (Big-tailed Han, Small-tailed Han, GansuAlpine Fine-wool and China Merino) and was very low in other five Chineseindigenous breeds including Tibetan, Mongolian, Tan, Kazakh Fat-Rumped and Duolang.The results revealed that MC1R mutations determined black coat colour inChinese indigenous sheep breeds,but not correlated completely with other coatcolours.4．Five polymorphisms were indentified on ASIP gene,three SNPs（g.672G>A,g.1580G>A, g.1617G>A）on intron2.A9-bp deletion (c.10-18del) and5-bp deletion(c.100-105del),both of which were located in exon2. Two deletion mutations wereinvestigated in a larger sample of animals belonging to the ten breeds with differentcoat colors and patterns. All mutations were presented in10Chinese sheep breeds.Moreover, only two sheep have the D5D5genotype, one in Minxian black-fur sheepand one in Duolang sheep, no homozygosis D9D9was found in the437sheep.Although both of the deletions, based on the previous studies, affect the function ofthe ASIP, but from the genotype results suggested that these mutations are notassociated or not completely associated with coat color in the investigated sheepbreeds. These results indicated that the variation in the protein coding region of ASIPdid not explain the coat colour phenotypes variation of Chinese indigenous sheepbreeds. Together with previous studies on coat color,futher studies should be taken toreveal the relationship between gene and coat phenotypes.