• GWAS;
  • heritability;
  • horse;
  • racing performance;
  • Thoroughbred


Using 1400 microsatellites, a genome-wide association study (GWAS) was performed to identify genomic regions associated with lifetime earnings and performance ranks, as determined by the Japan Racing Association (JRA). The minimum heritability (h2) was estimated at 7–8% based on the quantitative trait model, suggesting that the racing performance is heritable. Following GWAS with microsatellites, fine mapping led to identification of three SNPs on ECA18, namely, g.65809482T>C (= 1.05E-18), g.65868604G>T (= 6.47E-17), and g.66539967A>G (= 3.35E-14) associated with these performance measures. The haplotype of these SNPs, together with a recently published nearby SNP, g.66493737C>T (= 9.06E-16) in strong linkage disequilibrium, also showed a very clear association with the performance (< 1E-05). The candidate genomic region contained eight genes annotated by ENSEMBL, including the myostatin gene (MSTN). These findings suggest the presence of a gene affecting the racing performance in Thoroughbred racehorses in this region on ECA18.