The effects of polymorphisms in porcine skeletal myosin heavy chain cluster on myosin heavy chain isoform composition and meat quality

Myosin heavy chain (MyHC) is one of the most important skeletal myofibrilar proteins. It is existed with different isoforms coded by different genes. The MyHC isoform composition is related to metabolic properties during the postmortem, and consequently to meat quality. In pigs,  three genes (Myosin heavy chain 2, 1 and 4) coding fast fiber-type MyHC isoforms (2a, 2x and 2b) were sited on skeletal myosin heavy chain cluster at chromosome 12. Six single nucleotide polymorphisms, including one SNP in 5’ regulatory region MYH2 and five SNPs in intergenic region, and one insertion/deletion in noncoding region between MYH2 and MYH1 were newly found in this study. Two SNPs (c.-2202T>C and *1085C>A) near MYH2 gene recognized by specific restriction enzymes (PstI and HpyCH4V, respectively) were evaluated for associations with MyHC isoform composition and production traits. Two hundred and thirty-one pigs were used in this study. The c.-2202T>C polymorphism in 5’ regulatory region of MYH2 was significantly associated with the percentage of MyHC slow isoform (P = 0.041) and muscle pH (P = 0.007), respectively. The *1085C>A polymorphism in 3’ downstream region of MYH2 was also significantly associated with the percentage of MyHC slow isoform (P = 0.037). Taken together, we suggest that c.-2202T>C polymorphism can be used as a meaningful genetic marker for MyHC isoform composition and meat quality.