Identification of genome regions and important variations associated with expression level of MYH genes and its correlation with meat quality traits in pigs

Meat quality is one of the most important economic traits in pig breeding. It has been reported that the composition of type II muscle fibers is correlated with meat quality in pigs. Type II muscle fibers contain three isoforms, IIa, IIb and IIx, which contain specific myofibrillar proteins MYH2, MYH4 and MYH1, respectively. In this study, the expression levels of MYH1, MYH2, and MYH4 genes in the Longissimus thoracis (LT) muscle were measured in 114 Yorkshire pigs. Further, the correlations between the expression level of MYH genes and the meat quality traits of intramuscular fat, drip loss, water-holding capacity and postmortem pH values were analyzed. The results showed that the expression level of MYH2 was positively correlated with the intramuscular fat (R= 0.20, P<0.05). The expression levels of MHY1 and MYH4 were negatively correlated with the pH at 24 h post mortem (pH_24h ; R= －0.28, P<0.01; R= －0.25, P<0.01, respectively). Besides, the 60K SNP chip was used for genotyping the individuals. Genome wide association analysis indicated that 15 SNPs were significantly associated with the expression levels of these three MYH genes. The results indicated the expression levels of MYH1, MYH2 and MYH4 genes could be useful markers for improvement of meat quality in pigs.