Identification and genetic effect of haplotypes in the promoter region of porcine myostatin gene

Myostatin plays a pivotal role in controlling skeletal muscle mass in mammals. Polymorphisms in its promoter region likely impact on transcription and production traits. In this study, haplotypes involving three polymorphic sites in the promoter region of the porcine myostatin gene, namely at sites 435, 447 and 879, were identified and their effect on production traits, gene expression as well as on skeletal muscle traits were analysed. Four haplotypes were revealed and the linkage disequilibrium and evolutionary relationship were assessed. The results revealed that haplotypes A, B and C are predominant in Yorkshire and Landrace, Duroc and two Chinese indigenous pig breeds (Laiwu and Dapulian) respectively. The genotypes are associated with body weight on day 21 (BW21), average daily gain from birth to day 21 (ADG1) and average daily gain from day 21 to day 70 (ADG2) (P < 0.05) in Duroc pigs. The activity of haplotype A (pGL3‐A) is significantly higher than other constructs in driving reporter gene transcription (P < 0.01). As compared with CC animals, the myostatin mRNA level in BC animals is relatively lower in both semimembranosus (SM) and semitendinosus (ST) skeletal muscles, and the difference was significant in the SM muscle (P < 0.01). Moreover, the mRNA levels of MyHCI, MyHCIIa, MyHCIIb and MyHCIIx and the muscle fibre diameter and density were also compared between BC and CC animals.