Comparative Neuromuscular Diseases Laboratory, Department of Veterinary Clinical Sciences, Royal Veterinary College, Royal College Street, London, UK.
Johnston Racing, Kingsley Park, Middleham, Leyburn, UK.
Sci Rep. 2021 Apr 12;11(1):7916. doi: 10.1038/s41598-021-86783-1.
Horse racing is a popular and financially important industry worldwide and researchers and horse owners are interested in genetic and training influences that maximise athletic performance. An association has been found between the presence of a short interspersed nuclear element (SINE) mutation in the myostatin (MSTN) gene promoter and optimal race distance in Thoroughbred horses. There is previous laboratory evidence that this mutation reduces MSTN expression in a cell culture model and influences skeletal muscle fibre type proportions in horses. Manipulating MSTN expression has been proposed for illicit gene doping in human and equine athletes and already, researchers have generated homozygous and heterozygous MSTN-null horse embryos following CRISPR/Cas9 editing at the equine MSTN locus and nuclear transfer, aiming artificially to enhance performance. To date however, the role of the naturally-occurring equine MSTN SINE mutation in vivo has remained unclear; here we hypothesised that it reduces, but does not ablate circulating myostatin expression. Following validation of an ELISA for detection of myostatin in equine serum and using residual whole blood and serum samples from 176 Thoroughbred racehorses under identical management, horses were genotyped for the SINE mutation by PCR and their serum myostatin concentrations measured. In our population, the proportions of SINE homozygotes, heterozygotes and normal horses were 27%, 46% and 27% respectively. Results indicated that horses that are homozygous for the SINE mutation have detectable, but significantly lower (p < 0.0001) serum myostatin concentrations (226.8 pg/ml; 69.3-895.4 pg/ml; median; minimum-maximum) than heterozygous (766 pg/ml; 64.6-1182 pg/ml) and normal horses (1099 pg/ml; 187.8-1743 pg/ml). Heterozygotes have significantly lower (p < 0.0001) myostatin concentrations than normal horses. Variation in serum myostatin concentrations across horses was not influenced by age or sex. This is the first study to reveal the direct functional effect of a highly prevalent mutation in the equine MSTN gene associated with exercise performance. Determining the reason for variation in expression of myostatin within SINE-genotyped groups might identify additional performance-associated environmental or genetic influences in Thoroughbreds. Understanding the mechanism by which altered myostatin expression influences skeletal muscle fibre type remains to be determined.
赛马是一项在全球范围内广受欢迎且具有重要经济意义的产业，研究人员和马主都对能够最大限度提高运动表现的遗传和训练因素感兴趣。在纯血马中，肌肉生长抑制素 (MSTN) 基因启动子中存在短散在核元件 (SINE) 突变与最佳比赛距离之间存在关联。之前的实验室证据表明，这种突变会降低细胞培养模型中的 MSTN 表达，并影响马的骨骼肌纤维类型比例。操纵 MSTN 的表达已被提议用于人类和赛马的非法基因兴奋剂，并且已经有研究人员通过 CRISPR/Cas9 在马 MSTN 基因座上进行编辑和核转移生成了纯合和杂合 MSTN 缺失的马胚胎，旨在人为地提高性能。然而，迄今为止，天然存在的马 MSTN SINE 突变在体内的作用仍不清楚；在这里，我们假设它降低了，但并没有消除循环 MSTN 的表达。在验证了用于检测马血清中 MSTN 的 ELISA 并使用 176 匹纯血赛马在相同管理下的剩余全血和血清样本后，通过 PCR 对 SINE 突变进行了基因分型，并测量了它们的血清 MSTN 浓度。在我们的人群中，SINE 纯合子、杂合子和正常马的比例分别为 27%、46%和 27%。结果表明，SINE 突变纯合子的马具有可检测但显著降低（p<0.0001）的血清 MSTN 浓度（226.8 pg/ml；69.3-895.4 pg/ml；中位数；最小值-最大值）比杂合子（766 pg/ml；64.6-1182 pg/ml）和正常马（1099 pg/ml；187.8-1743 pg/ml）。杂合子的 MSTN 浓度显著低于（p<0.0001）正常马。马的血清 MSTN 浓度的变化不受年龄或性别影响。这是第一项揭示与运动表现相关的高度流行的马 MSTN 基因突变的直接功能影响的研究。确定 SINE 基因分型组内 MSTN 表达变化的原因可能会确定纯种马中与性能相关的其他环境或遗传影响。了解改变的 MSTN 表达如何影响骨骼肌纤维类型的机制仍有待确定。
