Inheritance of recurrent exertional rhabdomyolysis in thoroughbreds.

The research explores the development of a diagnostic method for recurrent exertional rhabdomyolysis (RER) in Thoroughbred horses and delves into its inheritance pattern, suggesting a pattern consistent with an autosomal dominant trait.

Introduction to the Research

• The main objective of the study was to design a diagnostic protocol for recurrent exertional rhabdomyolysis (RER) in thoroughbred horses. RER is a muscle disorder, typically seen in high-performance horses.
• This diagnostic method would rely on the in vitro muscle contracture test involving biopsy specimens from horses.
• The study also aimed to elucidate the inheritance pattern of RER, hypothesizing that it might follow an autosomal dominant trait.

Methods Details

• The researchers conducted a clinical trial involving eight adult horses with RER and 16 control adult horses to develop the contracture test.
• For studying the inheritance, 23 foals were also included.
• The biopsy specimens from the adult horses’ external intercostal muscles were tested for contracture in response to halothane and caffeine, substances known to trigger muscular response.
• The researchers determined the criteria for a positive test result and applied the set parameters to the 23 foals to establish whether they had RER.
• To study inheritance patterns, simple segregation analysis was conducted to determine if the results align with a dominant inheritance pattern.

Findings of the Study

• The contracture test results were positive for nine out of 23 foals, suggesting the presence of RER.
• The researchers found patterns of inheritance consistent with an autosomal dominant trait, meaning the disease can be passed on even if only one parent carries the gene.
• They noticed that foals were produced with RER even when their sires with RER were the only affected parent. This discovery helped them conclude that RER is autosomal rather than X-linked (meaning the responsible gene is not located on the X-chromosome).
• Furthermore, an unaffected foal born to two affected parents negated the possibility of the disease being recessive.

Conclusion

• The study concluded that while different elements such as sex, diet, and temperament influence the expression of the RER trait, the muscle contracture test seems to establish it as a genetic trait with an autosomal dominant inheritance pattern.
• Therefore, the study not only informs the development of a potential diagnostic test for RER but also provides valuable insights into its genetic transmission model.