A functional regulatory variant of MYH3 influences muscle fiber-type composition and intramuscular fat content in pigs

Abstract

Muscle development and lipid accumulation in muscle critically affect meat quality of livestock. However, the genetic factors underlying myofiber-type specification and intramuscular fat (IMF) accumulation remain to be elucidated. Using two independent intercrosses between Western commercial breeds and Korean native pigs (KNPs) and a joint linkage-linkage disequilibrium analysis, we identified a 488.1-kb region on porcine chromosome 12 that affects both reddish meat color (a*) and IMF. In this critical region, only the MYH3 gene, encoding myosin heavy chain 3, was found to be preferentially overexpressed in the skeletal muscle of KNPs. Subsequently, MYH3-transgenic mice demonstrated that this gene controls both myofiber-type specification and adipogenesis in skeletal muscle. We discovered a structural variant in the promotor/regulatory region of MYH3 for which Q allele carriers exhibited significantly higher values of a* and IMF than q allele carriers. Furthermore, chromatin immunoprecipitation and cotransfection assays showed that the structural variant in the 5′-flanking region of MYH3 abrogated the binding of the myogenic regulatory factors (MYF5, MYOD, MYOG, and MRF4). The allele distribution of MYH3 among pig populations worldwide indicated that the MYH3 Q allele is of Asian origin and likely predates domestication. In conclusion, we identified a functional regulatory sequence variant in porcine MYH3 that provides novel insights into the genetic basis of the regulation of myofiber type ratios and associated changes in IMF in pigs. The MYH3 variant can play an important role in improving pork quality in current breeding programs.

Comparison of Growth Performance and Meat Quality Traits of Commercial Cross-Bred Pigs versus the Large Black Pig Breed

“…However, the relationship between oxygen consumption and meat quality needs to be further evaluated to understand color variations between the two groups of pigs. A study of the muscle fiber type of Korean native pig reported a higher proportion of type I muscle fibers than that in commercial cross-bred pigs [ 32 ]. The type I slow twitch fiber has a higher mitochondria content for oxidative phosphorylation.…”

Targeted over-expression of PPARγ in pig skeletal muscle improves oxidative fiber formation and intramuscular fat deposition

“…The relationship between muscle fiber composition and IMF content is complex but high correlation was observed. Recent study showed that a functional regulatory sequence variant in porcine MYH3 led to large amount of slow myofibers in the muscles and excess accumulation of IMF (Cho et al, 2019). Slow muscle fiber contains higher lipid than fast muscle fiber.…”

Comparison of Growth Performance and Meat Quality Traits of Commercial Cross-bred Pig versus Large Black Pig Breeds

“…The oxygen consumption also represents the activation of mitochondrial metabolism. A study of the muscle fiber type of Korean native pig reported higher portion of type I muscle fibers than that of the commercial cross-bred pigs [27]. The type I slow twitch fiber has more content of mitochondria for oxidative phosphorylation.…”