Abstract: Thoroughbred racehorses are subject to non-traumatic distal limb bone fractures that occur during racing and exercise. Susceptibility to fracture may be due to underlying disturbances in bone metabolism which have a genetic cause. Fracture risk has been shown to be heritable in several species but this study is the first genetic analysis of fracture risk in the horse. Results: Fracture cases (n = 269) were horses that sustained catastrophic distal limb fractures while racing on UK racecourses, necessitating euthanasia. Control horses (n = 253) were over 4 years of age, were racing during the same time period as the cases, and had no history of fracture at the time the study was carried out. The horses sampled were bred for both flat and National Hunt (NH) jump racing. 43,417 SNPs were employed to perform a genome-wide association analysis and to estimate the proportion of genetic variance attributable to the SNPs on each chromosome using restricted maximum likelihood (REML). Significant genetic variation associated with fracture risk was found on chromosomes 9, 18, 22 and 31. Three SNPs on chromosome 18 (62.05 Mb - 62.15 Mb) and one SNP on chromosome 1 (14.17 Mb) reached genome-wide significance (p < 0.05) in a genome-wide association study (GWAS). Two of the SNPs on ECA 18 were located in a haplotype block containing the gene zinc finger protein 804A (ZNF804A). One haplotype within this block has a protective effect (controls at 1.95 times less risk of fracture than cases, p = 1 × 10(-4)), while a second haplotype increases fracture risk (cases at 3.39 times higher risk of fracture than controls, p = 0.042). Conclusions: Fracture risk in the Thoroughbred horse is a complex condition with an underlying genetic basis. Multiple genomic regions contribute to susceptibility to fracture risk. This suggests there is the potential to develop SNP-based estimators for genetic risk of fracture in the Thoroughbred racehorse, using methods pioneered in livestock genetics such as genomic selection. This information would be useful to racehorse breeders and owners, enabling them to reduce the risk of injury in their horses.
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The research explores the genetic variance in Thoroughbred racehorses that make them susceptible to non-traumatic distal limb bone fractures. Key findings from the study highlight significant genetic variation linked with fracture risk on chromosomes 9, 18, 22, and 31.
Research Context
Thoroughbred racehorses are susceptible to non-traumatic distal limb bone fractures. These often occur during racing and exercise, presenting a notable risk to their health and careers.
Existing theories suggest that these fractures may result from disturbances in bone metabolism, which are potentially genetic.
Heritability of fracture risk has been previously demonstrated in multiple species. However, this study is the first to analyze fracture risk from a genetic standpoint in horses.
Study Design and Findings
The study examined fracture cases (n=269), consisting of horses that sustained catastrophic distal limb fractures during races and had to be euthanized.
The control group (n=253) comprised horses over 4 years old with no history of fractures. These horses were active during the same racing period as the cases.
Both the fracture cases and control group included horses bred for flat and National Hunt (NH) jump racing.
A genome-wide association analysis was performed using 43,417 SNPs (single nucleotide polymorphisms), which are variations in a single nucleotide that occur at specific positions in the genome.
The study discovered significant genetic variation associated with fracture risk on chromosomes 9, 18, 22, and 31.
Four SNPs reached genome-wide significance: three on chromosome 18 (62.05 Mb – 62.15 Mb) and one on chromosome 1 (14.17 Mb).
Two of the significant SNPs on chromosome 18 resided in a haplotype block containing the gene ZNF804A (zinc finger protein 804A). Different haplotypes within this block were found to either protect against, or increase fracture risk.
Research Conclusion and Implications
The researchers conclude that fracture risk in Thoroughbred horses is a complex condition with a genetic basis, and multiple genomic regions contribute to this susceptibility.
The findings suggest the potential to develop SNP-based estimators to predict the genetic risk of fractures in Thoroughbred racehorses. Such a development would leverage methods similar to those used in livestock genetics, such as genomic selection.
This information could be highly valuable to racehorse breeders and owners, as it could help them reduce risk of injury in their horses.
Cite This Article
APA
Blott SC, Swinburne JE, Sibbons C, Fox-Clipsham LY, Helwegen M, Hillyer L, Parkin TD, Newton JR, Vaudin M.
(2014).
A genome-wide association study demonstrates significant genetic variation for fracture risk in Thoroughbred racehorses.
BMC Genomics, 15, 147.
https://doi.org/10.1186/1471-2164-15-147
Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK. sarah.blott@aht.org.uk.
Swinburne, June E
Sibbons, Charlene
Fox-Clipsham, Laura Y
Helwegen, Maud
Hillyer, Lynn
Parkin, Tim D H
Newton, J Richard
Vaudin, Mark
MeSH Terms
Animals
Chromosomes, Mammalian
Fractures, Bone / genetics
Gene Frequency
Genetic Predisposition to Disease
Genetic Variation
Genome-Wide Association Study
Haplotypes
Horses / genetics
Linkage Disequilibrium
Male
Polymorphism, Single Nucleotide
Risk
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