Prevalence of the RAPGEF5 c.2624C>A and PLOD1 c.2032G>A variants associated with equine familial isolated hypoparathyroidism and fragile foal syndrome in the US Thoroughbred population (1988-2019).

Authors: Elcombe Megan E, Bellone Rebecca R, Magdesian K Gary, Finno Carrie J

Journal: Equine veterinary journal

DOI: 10.1111/evj.13883 PubMed: 36199159Log in to save

Summary

# Editorial Summary Two autosomal recessive conditions affecting Thoroughbred foals—equine familial isolated hypoparathyroidism (EFIH) and fragile foal syndrome (FFS)—have recently been linked to specific genetic variants, but their actual prevalence in the breed remained unknown until this investigation. Researchers genotyped over 3,000 Thoroughbred DNA samples collected between 1988 and 2019 from US populations to determine carrier frequencies for the RAPGEF5 c.2624C>A variant (causing EFIH) and the PLOD1 c.2032G>A variant (causing FFS). The findings revealed meaningful prevalence data for both variants across the historical population, enabling the authors to establish evidence-based recommendations for targeted genetic screening and breeding decisions. These results are particularly valuable for stud farms and veterinary practitioners involved in Thoroughbred breeding programmes, as they provide the statistical foundation necessary to assess risk at the population level and counsel breeders on carrier testing prior to mating. Given that both conditions are fatal in affected foals, understanding the proportion of carriers in the breed allows for informed management strategies to reduce the incidence of homozygous affected offspring.

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Practical Takeaways

•Breeders can use genetic testing for RAPGEF5 and PLOD1 variants to identify carrier horses and reduce incidence of fatal foal conditions in Thoroughbred breeding programs
•Understanding prevalence of these variants in the population enables informed breeding decisions and selective removal of carriers from reproduction
•Genetic screening should be considered standard practice for Thoroughbred breeding stock given the fatal nature of both EFIH and FFS in affected foals

Key Findings

•Prevalence assessment of RAPGEF5 c.2624C>A variant (causal for EFIH) conducted in US Thoroughbred population from 1988-2019
•Prevalence assessment of PLOD1 c.2032G>A variant (causal for FFS) conducted in US Thoroughbred population from 1988-2019
•Study provides evidence-based recommendations for genetic testing of these fatal recessive conditions in Thoroughbreds

Conditions Studied

equine familial isolated hypoparathyroidism (efih)fragile foal syndrome (ffs)

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Prevalence of the RAPGEF5 c.2624C&gt;A and PLOD1 c.2032G&gt;A variants associated with equine familial isolated hypoparathyroidism and fragile foal syndrome in the US Thoroughbred population (1988-2019).