A polymorphism in the porcine miR‐208b is associated with microRNA biogenesis and expressions of SOX‐6 and MYH7 with effects on muscle fibre characteristics and meat quality

Summary Micro RNA s (mi RNA s) encoded by the myosin heavy chain ( MHC ) genes are muscle‐specific mi RNA s (myomiRs) and regulate the expression of MHC isoforms in skeletal muscle. These mi RNA s have been implicated in muscle fibre types and their characteristics by affecting the heterogeneity of myosin. In pigs, miR‐208b and miR‐499 are embedded in introns of MYH 7 and MYH 7b respectively. Here, we identified a novel single nucleotide polymorphism ( SNP ) in intron 30 of MYH 7 by which porcine miR‐208b is encoded. Based on the association study using a total of 487 pigs including Berkshire ( n = 164), Landrace ( n = 121) and Yorkshire ( n = 202), the miR‐208b SNP (g.17104G>A) had significant effects on the proportions of types I and II b fibre numbers ( P < 0.010) among muscle fibre characteristics and on drip loss ( P = 0.012) in meat quality traits. Moreover, the SNP affected the processing of primary miR‐208b into precursor miR‐208b with a marginal trend towards significance ( P = 0.053), thereby leading to significant changes in the levels of mature miR‐208b ( P = 0.009). These SNP ‐dependent changes in mature miR‐208b levels were negatively correlated with the expression levels of its target gene, SOX ‐6 ( P = 0.038), and positively associated with the expression levels of its host gene, MYH 7 ( P = 0.046). Taken together, our data suggest that the porcine miR‐208b SNP differentially represses the expression of SOX ‐6 by regulating mi RNA biogenesis, thereby affecting the expression of MYH 7 and the traits of muscle fibre characteristics and meat quality.