Targets of selection in the Thoroughbred genome contain exercise-relevant gene SNPs associated with elite racecourse performance.

The research focuses on identifying specific gene variations (single nucleotide polymorphisms, or SNPs) that may be associated with superior athletic performance in Thoroughbred horses. The key findings indicate that certain gene variations in the Thoroughbred genome were found to be significantly linked to top racecourse performance.

Research Context and Approach

• This study was predicated on the idea that athletic performance cannot be attributed to a solitary gene but instead relies on the complex interplay of multiple genes and their environment.
• The researchers selected a sample group comprising of elite (top performers) and non-elite (average performers) Thoroughbred horses and genotyped 68 single nucleotide polymorphisms (SNPs) in 17 probable exercise-relevant genes.
• These specific genes were chosen based on a genome scan for selection – a method of finding genes that have been targeted by natural or artificial selection.

Analysis and Findings

• A series of case-control and quantitative association tests were performed to establish relationships with racecourse performance.
• Thirteen SNPs in nine genes showed a significant association with performance phenotype (observable characteristics determined by genes).
• Five SNPs in four genes (ACSS1, ACN9, COX4I1, PDK4) were selected for validation in an independent sample set of elite and non-elite Thoroughbreds.
• Two SNPs in the PDK4 gene were validated for associations with elite racing performance. Specifically, the PDK4_38973231 SNP showed a strong correlation with superior racing ability.

Implications and Future Work

• Results revealed that individuals with the A:A and A:G genotypes (for the PDK4_38973231 SNP) had a clear advantage in racing performance over those with the G:G genotype.
• The study suggests that re-sequencing of the PDK4 gene and further genotyping would be required to identify the exact variant that influences the exercise-induced variation in expression of the gene.
• Nevertheless, the information gathered in this study can potentially serve as a primary reference marker for selecting racehorses with a genetically superior potential for racing performance.