Haplotype and copy number variation analysis of the MSTN gene associated with body size traits in three Tibetan sheep breeds

Abstract

Under the constraints of ecological protection policies on the Qinghai-Tibet Plateau, the sheep industry must shift from quantitative expansion to meat yield improvement. Oula, Qiaoke, and Ganjia sheep are three Tibetan sheep breeds that exhibit significant differences in growth performance. The myostatin ( MSTN ) gene is a key negative regulator of muscle development. This study aimed to investigate variations in the MSTN gene—including single nucleotide polymorphisms (SNPs), insertions/deletions (InDels), and copy number variations (CNVs)—and analyze the associations of haplotypes and CNVs with body size traits. Thirty-six genetic variants (34 SNPs and 2 InDels) were identified, and six major haplotypes were constructed. The analysis revealed that individuals carrying the H1H3 haplotype combination exhibited a significantly larger cannon circumference. CNV analysis showed that Oula sheep, characterized by larger body size, had a higher frequency of MSTN deletions. Furthermore, individuals with the deletion type displayed significantly greater body weight, body slant length, chest girth, and cannon circumference compared to those with normal copy numbers. Specific MSTN gene variations, notably the H1H3 haplotype combination and the CNV deletion type, are potential genetic markers associated with superior body size traits in Tibetan sheep. These findings provide candidate molecular markers for marker-assisted selection to breed high-meat-performance sheep adapted to the ecological environment of the Qinghai-Tibet Plateau.