Estimated prevalence of the GYS-1 mutation in healthy Austrian Haflingers.
Authors: Schwarz B, Ertl R, Zimmer S, Netzmann Y, Klein D, Schwendenwein I, Hoven R V D
Journal: The Veterinary record
Summary
# Editorial Summary: GYS1 Mutation Prevalence in Austrian Haflingers Polysaccharide storage myopathy type 1 (PSSM1), caused by a mutation in the GYS1 gene encoding skeletal muscle glycogen synthase, represents a significant concern in certain equine breeds, yet its prevalence in Haflingers—a breed commonly used for driving and leisure work—remained undocumented. Researchers genotyped 50 Austrian Haflingers using a validated restriction fragment length polymorphism assay and compared resting and post-exercise muscle enzyme activities and blood glucose parameters between carriers and non-carriers of the mutation. The study identified nine heterozygous carriers (18% prevalence) with no homozygous affected horses, suggesting the mutation exists at a moderate frequency within this population. Heterozygous carriers demonstrated significantly elevated aspartate aminotransferase activity at rest and elevated creatine kinase and aspartate aminotransferase activity after exercise compared to non-carriers, indicating subclinical muscle stress even in clinically normal individuals. These findings underscore the importance of routine GYS1 screening in Haflingers and suggest that carriers may benefit from tailored management strategies—including modified exercise programmes and dietary adjustments—to mitigate muscle damage and potential clinical disease development.
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Practical Takeaways
- •Screen Haflingers for the GYS-1 mutation through RFLP genotyping, as approximately 1 in 5 healthy horses in this population carry the mutation without clinical signs
- •Carriers of the GYS-1 mutation demonstrate elevated muscle enzyme markers at rest and post-exercise, which may indicate subclinical muscle involvement even without overt PSSM type 1 symptoms
- •Use baseline muscle enzyme profiles to monitor carriers and adjust management strategies including diet and exercise protocols to reduce disease manifestation risk
Key Findings
- •18% of the 50 healthy Austrian Haflingers were heterozygous carriers (HR) of the GYS-1 mutation; none were homozygous
- •Horses with the GYS-1 mutation (HR) showed significantly higher resting aspartate aminotransferase (AST) activity compared to normal horses (RR)
- •Post-exercise creatine kinase and AST activities were significantly elevated in HR horses versus RR horses
- •No significant differences in glucose metabolism parameters were detected between mutant carriers and normal horses