The Correlation Analysis Research Between COMT Gene Exon1polymorphism With Horse Heart Rate And Sport Performance

A total of 244 horses of three breeds of horses(Yili horses,Yanqi horses and Thoroughbred horses)were selected for this study.The COMT gene exon1 polymorphisms were analyzed by phenol-chloroform method and DNA sequencing method.Haplotype constructs were performed on each mutation site and analyze frequency differences in genotypes,alleles,and major haplotype combinations.The study Yili horses and Yanqi horses were divided into two groups,measured the heart rate and sport performance data to analysis the correlation between those data with genotype and haplotype combinations.The results are as follows:The amplification product sequencing result by direct sequencing shown that: there are 8 mutations were found in the COMT gene exon1,of which SNP3 was a nonsense mutation,SNP6 was a synonymous mutation,and all the others mutations were missense mutations.There have 3 genotypes were detected in all mutation sites in Ili horses: heterozygous AC genotypes weren’t detected in SNP1 of Yanqi horses,heterozygote genotype weren’t detected in SNP1,SNP2,SNP3,SNP4 and SNP6 of Thoroughbred horses.The chi-square test results of the COMT gene exon1 frequency and allele frequencies for the three horse breeds shown that: there was a significant difference in genotype frequencies between all mutation sites(P<0.01),the alleles frequencies of SNP2,SNP3,SNP4,and SNP8 mutation sites were significantly different(P<0.01),the allele frequencies of SNP6 mutations were significantly different(P<0.05)in Yili horses and Yanqi horses.The genotype frequencies and allele frequencies of SNP7 mutation sites in Yili horses and Thoroughbred horses were significantly different(P<0.05),the frequencies of genotypes and alleles at the others mutation sites were significantly different(P<0.01).There was a significant difference in genotype frequencies of SNP5 mutation sites between Yanqi and Thoroughbred horses(P<0.05),and allele frequencies were significantly different(P<0.01).It is suggested that the detected 8 mutation sites may be the mutation sites that affect the horses’ heart rate and sport performance.The result of linkage disequilibrium analysis and haplotype construction of three breed horses mutation sites shown that: The mutations of all three horse breeds have a strong linkage relationship,and some of them were completely linked.The 3 breeds horses construct 8 different haplotypes,all of the dominant haplotypes were H1.There did not appear H6,H7,and H8 haplotypes in Ili horses.The thoroughbred horses only appeared H1,H2,and H3 haplotypes.All of 8 haplotypes were detected in Yanqi horses.The analysis result of 3 breeds main haplotype combination(H1H1、H1H2、H1H3 and H1H4)frequency display,H1H2 haplotype combinations did not appear in Yanqi horses,H1H2 and H1H4 haplotype combinations did not appear in thoroughbred horses,and there was a significant difference in the combinations frequency of haplotypes between Yili horses with Yanqi horses and Thoroughbred horses(P<0.01).It’s meant that the 8 mutation sites may through the combined action to affect the horses’ heart rate and sport performanceThrough analysis the correlation between the Yili horses genotype with heart rate,the result display that: under mild stimulation conditions,the heart rate of AA genotypes at SNP3 and SNP5 mutation site is lower than anther homozygous genotypes,the heart rate of AA genotypes at SNP2,SNP6 and SNP8 mutation site,GG genotypes at SNP4 mutation site,TT genotypes at SNP7 are lower than anther homozygous genotypes when the horses subjected to intense stimulation conditions.Through analysis the correlation between the Yili horses genotype with sport performance,the result display that: the CC genotypes at SNP1 mutation site,AA genotypes at SNP2,SNP3,SNP5 and SNP8 mutation site,GG genotypes at SNP4 mutation site,TT genotypes at SNP7 mutation site didn’t appeared in short distance race.It indicates that the genotypes of the above mutation sites may be beneficial for long distance games.Haplotype analysis showed that the horse with H1H3 haplotype combination the heart rate lower under the intense stimulated.The horses with H1H3 haplotype combination were more suitable for long distance competition.The result which through analysis the correlation between the Yanqi horses genotype with heart rate indicate that: under mild stimulation conditions,the heart rate of AA genotypes at SNP2 and SNP6 mutation site is lower than another homozygous genotypes,the heart rate of AA genotypes at SNP2 and SNP5 mutation site,GG genotypes at SNP4 mutation site,TT genotypes at SNP7 are lower than another homozygous genotypes when the horses subjected to intense stimulation conditions.Through analysis the correlation between the Yanqi horses genotype with sport performance,the result display that: The genotypes of the SNP1,SNP3,SNP5,SNP6,and SNP8 mutation sites all had varying degrees of influence on the endurance performance of the endurance horses.It’s indicate that the Yanqi horses with each mutation site genotype of above are more suitable for long distance competition.Haplotype analysis showed that the horses with H1H3 haplotype combination have faster speed and more suitable for long distance competition.In conclusion,the horse COMT gene is associated with heart rate and sport performance in horses and suggesting that COMT gene exon1 may be an important functional gene that influences the temperament and sport performance of Yili horses.