Evaluation of FOXC2 as a candidate gene for chronic progressive lymphedema in draft horses.
Authors: Young Amy E, Bower Leslie P, Affolter Verena K, De Cock Hilde E V, Ferraro Gregory L, Bannasch Danika L
Journal: Veterinary journal (London, England : 1997)
Summary
Chronic progressive lymphedema (CPL) in draft horses—particularly Clydesdales, Shires and Belgians—causes severe, progressive limb swelling with skin fold development, ulceration and hyperkeratosis, ultimately leading to euthanasia in most cases; its restriction to three related breeds strongly suggests genetic inheritance. Young and colleagues sequenced the FOXC2 gene in affected and unaffected draft horses, selecting this candidate based on its role in causing the analogous human condition lymphedema-distichiasis. The investigation identified five single nucleotide polymorphisms (SNPs) across the sample, but critically, none segregated consistently with disease status—four SNPs appeared in unaffected horses and controls, whilst the fifth was present in only one affected horse and a control animal. These negative findings rule out FOXC2 mutations as the causative mechanism for CPL in draft horses, redirecting the search towards alternative genetic loci. For breeding programmes, this narrows the field of candidate genes and emphasises the need for further genomic investigation; once the actual causal variant is identified, breeders will be able to implement genetic testing to eliminate this painful, career-ending condition from these breeds.
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Practical Takeaways
- •FOXC2 genetic testing will not reliably identify draft horses at risk for CPL; breeders cannot yet use molecular screening to prevent this condition
- •The genetic basis of CPL remains unknown and requires continued research to enable pre-breeding testing and eliminate this debilitating condition from draft horse populations
- •Affected draft horses frequently require euthanasia due to severe discomfort and secondary infections; identifying the true genetic cause is critical for breed health management
Key Findings
- •FOXC2 gene mutations do not appear to be the primary genetic cause of chronic progressive lymphedema in draft horses, despite causing a comparable condition in humans
- •Four SNPs identified in FOXC2 were present in both affected and unaffected draft horses, indicating they are not associated with CPL
- •A fifth SNP found in one affected horse and a control horse was not present in all affected draft horses, ruling out association with CPL phenotype
- •CPL occurs exclusively in three related draft horse breeds (Clydesdales, Shires, Belgian), suggesting a distinct genetic etiology requiring further investigation