Haplotypes within the regulatory region of MYL4 are associated with pig muscle fiber size

Our previous transcriptomic study identified MYL4 (myosin light chain 4) to be associated with muscle development and growth in pigs. In this study, we aimed to investigate the genetic variation of MYL4 and determine the effect of these variations in regulating MYL4 expression and muscle fiber size. After screening the regulatory region of MYL4 in Large White pigs, we identified nine completely linked single nucleotide polymorphisms within the MYL4 regulatory region, which showed two haplotypes (H1 and H2).And in MYL4 may affect the activity of the promoter region and regulate the traits of porcine muscle. The results of Western blotting and qRT-PCR showed that haplotype H2 significantly (p <0.01) increased the relative mRNA and protein expression of MYL4 gene in pig LD tissues, and tissue sections also showed the number of genotype H2H2 Significantly higher than genotype H1H1, in conclusion, our results suggest that MYL4 may promote muscle growth and development and can affect the transcriptional activity of MYL4 through haplotype H1 and haplotype H2.