Interbreed Distribution of the Myostatin (MSTN) Gene 5′-Flanking Variants and Their Relationship With Horse Biometric Traits

To assess the involvement of the MSTN gene polymorphisms in the biometric traits interbreed variability, we have examined the distribution of the three known 5′-flanking variants (g.66495696T>C, g.66495826T>C, and 272 bp SINE insertion) within the group of 2,052 horses representing 12 breeds and compared the allele frequencies between breeds assigned to the different morphological types. Additionally, the association of particular genotypes with selected biometric traits intrabreed variability was studied in five horse breeds. Genotyping of the two SNPs (g.66495696T>C and g.66495826T>C) revealed significant (P < .01) differences of minor allele frequencies between horses representing various morphological types. The highest and the lowest minor allele frequency values were recorded for horses representing brachymorphic and dolichomorphic morphological types, respectively. The association study revealed significant (P < .05) differences in height at the withers (Silesian [SIL]) and cannon bone circumference (Polish Coldblood Horse) - the lowest trait means were recorded for horses carrying the CC genotype in the g.66495696T>C polymorphic site. The heterozygous genotype in g.66495826T>C SNP turned out to be associated (P < .05) with the lower chest circumference if compared to the TT genotype carriers in the Hucul horse breed. Similarly to other investigations, the SINE insertion was present predominantly in Thoroughbred and occurred sporadically in other warmblood horse breeds (Wielkopolski [WLKP], SIL). Our study has confirmed the impact of the MSTN gene polymorphisms on the interbreed and intrabreed variability of horse biometric traits.