Myostatin (Sprint vs. Endurance)

Thoroughbred races are held at a variety of distances, with individual racehorses usually displaying a preference for a range. There is some suggestion that sprint horses (which compete at distances less than 6 furlongs, or 2/3rds of a mile) are more compact and muscular than horses that run at longer distances. This insertion has been associated with racing distance for winning Thoroughbreds at the top level of competition, with C/C (Sprint/Sprint) horses excelling at distances of 8 furlongs or less and T/T (Endurance/Endurance) horses found more in races of 9 furlongs or more. Horses with one copy of each , C/T (Sprint/Endurance) allele won at all distances.

MSTN is a protein involved in the development of muscles. Mutations in several species are known to cause muscle hypertrophy (overgrowth), of which one of the most well-known examples is double muscling in Belgian Blue cattle. A variant in the whippet breed of dog has been positively associated with racing performance. This mutation is located within a non-coding portion of MSTN, however no variants with a stronger association have been found.

Publications

Guilotto E et al., "Genome-wide evolutionary and functional analysis of the Equine Repetitive Element 1: and insertion in the myostatin promoter affects gene expression." (2015) BMC Genet. Oct 26;16: 126

Binns MM et al., “Identification of the myostatin locus (MSTN) as having a major effect on optimum racing distance in the Thoroughbred horse in the USA.” (2010) Anim Genet. 41 Suppl 2: 154-8. PMID: 21070290

Hill EW et al., “A sequence polymorphism in MSTN predicts sprinting ability and racing stamina in thoroughbred horses.” (2010) PLoS One. 5: e8645. PMID: 20098749

Hill EW et al., “A genome-wide SNP-association study confirms a sequence variant (g.66493737C>T) in the equine myostatin (MSTN) gene as the most powerful predictor of optimum racing distance for Thoroughbred racehorses.” (2010) BMC Genomics. 11: 552. PMID: 20932346

Hill EW et al., “MSTN genotype (g.66493737C/T) association with speed indices in Thoroughbred racehorses.” (2012) J Appl Physiol (1985). 112: 86-90. PMID: 22016373

Bower MA et al., “The genetic origin and history of speed in the Thoroughbred racehorse.” (2012) Nat Commun. 3: 643. PMID: 22273681

McGivney BA et al., “MSTN genotypes in Thoroughbred horses influence skeletal muscle gene expression and racetrack performance.” (2012) Anim Genet. 43: 810-2. PMID: 22497477