The candidate gene XIRP2 at a quantitative gene locus on equine chromosome 18 associated with osteochondrosis in fetlock and hock joints of South German Coldblood horses.

The study investigated how specific genetic variations in South German Coldblood horses may increase the risk for developing osteochondrosis in their fetlock and hock joints. Scientists found that mutations in the XIRP2 gene were significantly associated with this condition.

Introduction and Methods

• The research team conducted a whole-genome scan for skeletal abnormalities in fetlock and hock joints of South German Coldblood horses. This is a breed known for being robust and heavy, which can potentially put a strain on their joints, leading to the development of osteochondrosis.
• They used 250 microsatellite markers – genomic sequences associated with specific traits – to identify a quantitative trait locus (QTL) for this condition on Equus caballus chromosome (ECA) 18. A QTL is a DNA region associated with a particular phenotypic trait. Their goal was to find genetic mutations associated with osteochondrosis in these horses.

Results

• The researchers confirmed and isolated the QTL to an area between the GALNT13 and Xin actin-binding repeat containing 2 (XIRP2) genes.
• They then used 96 South German Coldblood horses to analyse correlations between single-nucleotide polymorphisms (SNPs) in the candidate genes for osteochondrosis found in this QTL region. SNPs are single base-pair differences in DNA sequence that occur in at least 1% of the population.
• The study found that SNPs in the XIRP2 gene were significantly associated with fetlock osteochondrosis, fetlock osteochondrosis dissecans, and hock osteochondrosis.
• The participant horses were grouped by their specific genetic variant and compared. The researchers found significant additive genetic effects of the intronic SNPs in the XIRP2 gene, pointing towards its involvement in the development of osteochondrosis.

Conclusion

• The study concluded that XIRP2 may play a vital role in the development of equine osteochondrosis in overweight horses, such as the South German Coldblood breed. Horses with variations in this gene were found to have a 1.3-2.4 times higher risk for fetlock and hock osteochondrosis.
• The findings provide useful information for selective breeding programs aimed at reducing the prevalence of osteochondrosis in affected horse breeds.