Genetic characterization of Mongolian native horses using the Myostatin (MSTN) gene variants

Approximately 5.1 million native horses are raised in Mongolia, representing a valuable genetic resource characterized by notable endurance, robustness, disease resistance, and adaptability.However, the distribution of genetic variants associated with racing performance and body conformation in Mongolian horses remains poorly understood.The myostatin gene (MSTN) negatively regulates skeletal muscle growth.In Thoroughbreds and Quarter Horses, an intronic SNP (SNP T>C) is in strong linkage disequilibrium with a 227-bp SINE insertion (Ins227bp) in the promoter region, which is associated with racing distance aptitude via effects on MSTN expression.In this study, we examined the frequency of the SNP T>C and the Ins227bp, and their associations with body conformation traits in Mongolian native horses.A total of 381 horses from seven breeds and strains of Mongolian native horses were genotyped.The SNP T>C was detected in all breeds, with a genotype distribution of 79.26% TT homozygotes, 18.90% TC heterozygotes, and 1.84% CC homozygotes, showing no significant differences among the breeds.The overall allelic frequencies of T and C were 0.89 and 0.11, respectively, with breed-specific frequencies of 0.90 and 0.10 in Darkhad; 0.87 and 0.13 in Tes; 0.85 and 0.15 in Myangad; 0.94 and 0.06 in Galshar; 0.89 and 0.11 in Ondorshil; 0.85 and 0.15 in Gobishankh; and 0.91 and 0.09 in Mongol.All populations except for Galshar were in Hardy-Weinberg equilibrium, and the widespread distribution of SNP T>C indicates that it is a common polymorphism in Mongolian native horses.In contrast, no Ins227bp was detected in the 381 horses genotyped in the present study, suggesting that Ins227bp does not exist in these Mongolian native horse breeds.Body conformation traits were assessed in 135 adult horses ( ≥ 6 years), and no significant associations were observed between the SNP T>C and seven body conformation traits, indicating that the SNP T>C does not affect body conformation in Mongolian native horses.The present findings indicate that SNP T>C is widely distributed in Mongolian native horses and, therefore, can be used as a linkage marker for evaluating the association of MSTN with horse traits.Also, the absence of Ins227bp in Mongolian native horse populations suggests that it can be used as a genetic marker for monitoring potential introgression from exotic breeds, including Thoroughbreds.