Exclusion of linkage of the RYR1, CACNA1S, and ATP2A1 genes to recurrent exertional rhabdomyolysis in Thoroughbreds.

The research conducted attempts to find any genetic linkage between recurring exertional rhabdomyolysis (RER) — a muscle condition often spotted in racehorses — and genes known to control muscle contraction in horses. However, based on the analysis of data from certain gene markers, the study found no linkage, suggesting the cause of RER might be a gene not yet associated with such muscle disorders.

Objective of the Research

• The main objective of this research was to identify a possible genetic linkage between recurrent exertional rhabdomyolysis (RER), a muscle disorder in Thoroughbred horses, and genes associated with muscle control—specifically, the RYR1, CACNA1S, and ATP2A1 genes.

Research Methodology

• The study was carried out on a sample of 34 horses from the University of Minnesota RER resource herd and 62 Thoroughbreds from 3 other Thoroughbred families.
• All these horses had experienced two or more occurrences of exertional rhabdomyolysis (ER).
• The research team identified DNA markers from the RYR1, ATP2A1, and CACNA1S gene loci located on equine chromosomes 10, 13, and 30 respectively. They then obtained genotypes for all horses from the four RER-affected families to test these markers for potential linkage to the RER condition.

Research Findings

• The results of the analysis found no direct link between the genetic markers at the RYR1, CACNA1S, and ATP2A1 loci and recurrent exertional rhabdomyolysis.

Conclusions

• The absence of a link suggests that the heritable changes in muscle contractility causing RER could be driven by an unidentified gene.
• This unidentified gene possibly is not known yet to be involved in such muscle disease in other species.