Effects of polymorphisms in the porcine microRNA MIR206 / MIR133B cluster on muscle fiber and meat quality traits.

MicroRNAs are a class of small non-coding RNA molecules that repress gene expression primarily at the post-transcriptional level. Genetic variations in microRNA genes may contribute to phenotypic differences by altering the expression of microRNAs and their targets. Here, we identified 12 single nucleotide polymorphisms (SNPs) in the genomic region of the porcine MIR206 / MIR133B cluster, 10 and 2 of which were associated with MIR206 and MIR133B respectively. All 12 SNPs were located within primary microRNAs. Allele frequency determination in different pig breeds (Berkshire, n = 153; Landrace, n = 125; Yorkshire, n = 173) and association studies of muscle fiber characteristics, lean meat production and meat quality traits were performed on the MIR206 and MIR133B SNPs. The MIR206 SNPs were associated with the percentage of type IIa and IIb fibers for muscle fiber area composition, meat quality traits including drip loss and lightness, and backfat thickness, a parameter of lean meat production. In addition, we found significant association of the MIR133B SNPs with total muscle fiber number, loin eye area, and muscle pH. Furthermore, these SNPs significantly affected the levels of mature MIR206 and MIR133B , respectively, primarily by regulating the processing of primary microRNAs into precursor microRNAs. Interestingly, altered MIR206 levels correlated with phenotypic variability among genotypes of the MIR206 SNP. Our data suggest that polymorphisms in the porcine MIR206 / MIR133B cluster are a genetic factor affecting muscle and meat quality traits.