Association of myostatin (MSTN) gene polymorphisms with morphological traits in the Italian Heavy Draft Horse breed

Abstract

The myostatin (MSTN) gene encodes a protein well known as a negative regulator of muscle mass in mammalian species. In a previous study, we identified single nucleotide polymorphisms (SNPs) in the equine MSTN gene that could be associated with variability of morphological traits in different horse breeds. In this study we carried out a first evaluation of the association of MSTN gene with morphological traits and body measurements obtained at adult age in the Italian Heavy Draft Horse (IHDH), an autochthonous cold-blooded breed currently selected for meat production and for heavy draught. We genotyped 202 horses for four SNPs of the MSTN gene: two located in the promoter (GQ193900:g.26T>C and GQ193900:g.156T>C) and two in the first intron (GQ193900:g.2077T>C and GQ193900:g.2115A>G). Minor allele frequencies of SNPs varied from 0.118 to 0.148. The haplotype [g.26T:g.156T:g.2077T:g.2115A] showed the greater frequency (0.596). Biometric measurements of three body measurements (height at withers, chest girth, and cannon bone circumference) and 14 linear type data related to general aspects (head size and expression, temperament/blood, frame size, fleshiness and bone incidence), trunk (thorax depth, fore diameter, rear diameter, upper line length, and upper line direction) and feet and legs (e.g. side and back view of rear legs, fore and rear feet) were used in the association study. Among the investigated SNPs, the GQ193900:g.26T>C polymorphism was the most interesting as it resulted associated with cannon bone circumference (P nominal=0.001) and side view of rear legs (P nominal=0.006) and suggestively associated with fleshiness (P nominal=0.027). In silico transcription factors binding sites (TFBSs) prediction located putative TFBSs involved in growth and differentiation of multiple cell types, including myoblasts and osteoblasts in the SNP positions, suggesting that the analyzed SNPs could play a functional role. Gene expression studies should be carried out to verify this hypothesis. Further association studies in the present and other heavy horse breeds are needed to confirm the effects of MSTN polymorphisms on morphological traits, and potentially apply these markers in breeding programs to improve selection efficiency for muscularity and strength in horses.