The Study On Variations Of MC4R Genes In Different Sheep And Goat Populations

Based on the important regulatory function of MC4 R on brown adipose tissue thermogenesis activity,MC4 R gene could be one candidate gene that affects the adaptability to varied temperature conditions.Therefore,the single nucleotide polymorphisms of sheep MC4 R gene and the effects of the mutations were investigated.The influence of temperature on MC4 R gene variation was identified.In addition the genetic differentiation of MC4 R gene in a Chinese native goat breed,Yichang White goat,was investigated too.In this research,the samples included Ujimquin sheep(46),Sunit sheep(46),Guangling big tailed sheep(95),Small tailed Han sheep(40),Hu sheep(47),and Yichang White goat(53).Firstly,SNPs were detected through direct sequencing.Chi-square test was implemented to investigate the association between MC4 R alleles and ambient temperature.Expected heterozygosity,the effective number of alleles,Shannon’s Information index were calculated.The selection signatures between populations of sheep were detected.Phylogenetic tree of 142 species was constructed.In addition,the selection pressure was detected during the development of these species.The 3-dimensional structures and conservation of MC4 R proteins of both sheep and goat were constructed by silicon prediction to test the effects of the mutations detected in this research.The results are as follows:1.There were 3 synonymous mutations,C9 T,C12G and G93 A,2 nonsynonymous mutations,C519 G and G682 C,and a SNP at 3`UTR,G1016 A in MC4 R gene of sheep.C519 G and G682 C were two original SNPs found in sheep MC4 R gene.2.In the CDS region of goat MC4 R gene,9 SNPs were detected,including 3 synonymous SNPs,C144 T,T360C and T363 C,and 6 nonsynonymous SNPs,C26 T,C110A,G334 A,A359G,A612 G,and C906 A,respectively.3.In sheep allele frequency of C9 T,C12G,G93 A,C519G,G1016 A were identified to potentially significantly differ between high temperature populations and low temperature populations(P<0.0001).C9 T,C12G,G93 A,C519G,G1016 A associate with the temperature adaptability of sheep.4.Among the 5 sheep populations,Shannon’s information index(I)is from 0.5153 to 0.5831,where Hu sheep has the lowest I value,otherwise Ujimquin sheep has the highest I value.Average gene flow value(Nm)between populations is 2.9502.I value of Yichang White goat is 0.3037±0.1561,representing low genetic diversity.5.The result of Fst outlier detection showed that all the 6 SNPs detected in MC4 R gene of these 5 sheep populations were driven by neutral selection.Molecular evolution analysis based on MC4 R gene of 142 species indicated potential purifying selection on MC4 R gene.Above all,during the evolutionary history of species,MC4 R gene underwent potential purifying selection,maintaining the conservation of structure and function of MC4 R gene.C9 T,C12G,G93 A,C519G,G1016 A in sheep MC4 R gene associate with the temperature adaptive ability.Population genetic parameters calculated according to the 9 SNPs detected in MC4 R gene of Yichang White goat indicated low genetic diversity.