Effects of polymorphisms in the porcine microRNA miR-1 locus on muscle fiber type composition and miR-1 expression

MicroRNAs (miRNAs) are a group of evolutionarily conserved small noncoding RNAs with regulatory functions. Increasing evidence suggests that polymorphisms in miRNA genes are associated with phenotypic variation by affecting miRNA expression and/or function. Here, we identified two single nucleotide polymorphisms (SNPs) in the porcine . miR-1 locus, both of which were linked and located downstream from the stem-loop miRNA precursor sequence within the primary miR-1 region. An association study on muscle fiber characteristics and meat quality traits was performed with a total of 451 pigs representing three pig breeds (Berkshire, . n=. 153; Landrace, . n=. 125; Yorkshire, . n=. 173). The . miR-1 SNPs were significantly associated with type I and type IIa muscle fibers in number and area compositions, respectively, but not with meat quality traits. Notably, these polymorphisms were also significantly associated with altered expression of the primary miR-1 transcript, ultimately leading to comparable changes in the levels of both precursor and mature miR-1. Furthermore, altered miR-1 levels were correlated with the variation in muscle fiber composition. Our data suggest that . miR-1 may be a candidate gene associated with muscle fiber type composition.