N6-methyladenosine improves porcine longissimus dorsi muscle quality by regulating myofiber differentiation

The pivotal roles of post-transcriptional N6-methyladenosine (m⁶A) modification in animal muscle development regulation have been wildly reported previously. However, whether this epigenetic mechanism also takes part in the muscle fiber differentiation, which remarkedly affects the meat quality and production in livestock, remains unknown.

In this study, an eight-breeds crossbreed mosaic pig population consisted by 302 adult pigs was constructed to estimate the myofiber phenotypes. We found that despite the same genetic background, remarkable differences of longissimus dorsi muscle fiber types still existed between different subsets of this population. m⁶A abundance was evaluated subsequently in the subset samples with extremely low (Low group) or high (High group) proportions of type Ⅱb myofibers based on methylated RNA immunoprecipitation sequencing (MeRIP-seq) analysis. A total of 27,699 and 28,194 high-confidence m⁶A peaks were identified in Low and High group samples, respectively. Among them, 8128 differential peaks shared between two groups were screened out and were annotated into 189 differentially expressed genes (DEGs). Gene ontology analysis revealed that 22 of DEGs such as MYH7, TPM3, TNNT1, FHL1, CAMTA2 and MYL3, were involved in the skeletal muscle development regulations. Furthermore, 21 of these candidate genes were validated to regulate the myofiber differentiation in the mosaic pig population through quantitative trait transcript analysis.

The findings of this study demonstrated the critical roles of m⁶A modification in porcine longissimus dorsi muscle fiber differentiation regulation, and provide us with new clues in improving the animal growth rate and meat quality during the future husbandry production.