Researchers have pinpointed the genetic basis that explains why some Thoroughbreds are better equipped to race over sprint distances and others over longer distances. The scientists from Trinity College Dublin and University College Dublin (UCD), both in Ireland, have discovered the inner workings of a known “speed gene” in Thoroughbred racehorses, which directly affects skeletal muscle growth and, in turn, race distance aptitude.
Thoroughbred horses are finely-tuned athletes with a high aerobic capacity relative to their skeletal muscle mass, which can be attributed to centuries of genetic selection for speed and stamina. Nongenetic factors, such as training schedule variations, can also influence how racehorse distance aptitudes and preferences develop. However, prior work by UCD professor Emmeline Hill, PhD, had demonstrated that different versions (polymorphisms) of the myostatin gene, a pronounced inhibitor of skeletal muscle growth, almost singularly account for gene-based race distance aptitude in racehorses.
This prior discovery earned the myostatin gene the speed gene moniker. Horses with CC copies tend to develop into sprinters, those with CT copies generally develop into middle-distance performers, and those with TT copies are typically best equipped for long distances.
However, until now, scientists didn’t know which element(s) of the gene held the secrets to understanding the all-important racing distance preference.
In their recently released study the researchers pinpointed the speed gene’s specific noncoding section. This is exclusively responsible for limiting myostatin protein production in Thoroughbreds which, in turn, affects skeletal muscle development and race distance aptitude.
“Our data provides the first mechanistic evidence as to the specific element of the speed gene that acts as the sole protagonist in dictating its expression in the Thoroughbred,” said senior author Richard Porter, PhD, FTCD, an associate professor in biochemistry at Trinity College Dublin. “As a result, this element is the key genetic factor in determining distance aptitude in Thoroughbred horses. This knowledge is extremely valuable to Thoroughbred breeders and trainers, in what is a multi-billion-dollar industry.”
Porter conducted this study with research scientist Mary Rooney, PhD, and associate professor Vincent Kelly, PhD, both from Trinity College, and Hill, from the UCD School of Agriculture and Food Science. The research was funded by a Science Foundation Ireland Principal Investigator grant (11/PI/1166) awarded to Hill and Porter.
The study, “The ‘speed gene’ effect of myostatin arises in Thoroughbred horses due to a promoter proximal SINE insertion,” was published in PLOS ONE.