Genetics of swayback in American Saddlebred horses.
Abstract: Extreme lordosis, also called swayback, lowback or softback, can occur as a congenital trait or as a degenerative trait associated with ageing. In this study, the hereditary aspect of congenital swayback was investigated using whole genome association studies of 20 affected and 20 unaffected American Saddlebred (ASB) Horses for 48,165 single-nucleotide polymorphisms (SNPs). A statistically significant association was identified on ECA20 (corrected P=0.017) for SNP BIEC2-532523. Of the 20 affected horses, 17 were homozygous for this SNP when compared to seven homozygotes among the unaffected horses, suggesting a major gene with a recessive mode of inheritance. The result was confirmed by testing an additional 13 affected horses and 166 unaffected horses using 35 SNPs in this region of ECA20 (corrected P=0.036). Combined results for 33 affected horses and 287 non-affected horses allowed identification of a region of homozygosity defined by four SNPs in the region. Based on the haplotype defined by these SNPs, 80% of the 33 affected horses were homozygous, 21% heterozygous and 9% did not possess the haplotype. Among the non-affected horses, 15% were homozygous, 47% heterozygous and 38% did not possess the haplotype. The differences between the two groups were highly significant (P<0.00001). The region defined by this haplotype includes 53 known and predicted genes. Exons from three candidate genes, TRERF1, RUNX2 and CNPY3 were sequenced without finding distinguishing SNPs. The mutation responsible for swayback may lie in other genes or in regulatory regions outside exons. This information can be used by breeders to reduce the occurrence of swayback among their livestock. This condition may serve as a model for investigation of congenital skeletal deformities in other species.
© 2010 The Authors, Journal compilation © 2010 Stichting International Foundation for Animal Genetics.
Publication Date: 2010-11-26 PubMed ID: 21070278DOI: 10.1111/j.1365-2052.2010.02108.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research highlights a study on the genetics of swayback (also known as extreme lordosis) in American Saddlebred horses, demonstrating the hereditary nature of swayback and identifying potential gene regions associated with this genetic disorder.
Introduction and Study Objectives
- The study focuses on the investigation of the congenital trait of swayback in American Saddlebred (ASB) horses, which is a hereditary condition manifesting as an unusually low or sagging back.
- Using whole genome association studies, the researchers aim to determine whether certain single-nucleotide polymorphisms (SNPs) are associated with the presence of swayback. SNP is a place in the genome where the DNA sequence varies by one nucleotide.
Methodology and Key Findings
- The study compared genetic sequences (genomes) of 20 horses with swayback and 20 unaffected horses, examining over 48,000 different SNPs.
- A significant association was found on a particular region (ECA20) of the horse genome for a SNP known as BIEC2-532523.
- Among the affected horses, 85% were homozygous for this SNP (having two identical alleles of the gene). This result lends support to the theory that a recessive gene may be causing the condition.
- Additional tests on a larger sample of horses confirmed this association, providing further evidence that a specific region (marked by four SNPs) on ECA20 is likely associated with the swayback condition.
- Despite sequencing exons (the region of a gene that codes for proteins) from three candidate genes in this region, the precise mutation causing swayback was not identified, suggesting it might be present in other genes or in regulatory regions outside exon sequences.
Implications and Conclusion
- This study provides breeders with valuable information to potentially reduce the occurrence of swayback in their horse populations through careful breeding strategies.
- The identified genome region could serve as a genetic marker for selecting horses for swayback-specific breeding programs.
- The findings of this study set the stage for further research and may serve as a model for investigating congenital skeletal deformities in other species.
- While the study did not identify the precise mutation causing swayback, it narrowed down potential genes candidates for further investigation.
Cite This Article
APA
Cook D, Gallagher PC, Bailey E.
(2010).
Genetics of swayback in American Saddlebred horses.
Anim Genet, 41 Suppl 2, 64-71.
https://doi.org/10.1111/j.1365-2052.2010.02108.x Publication
Researcher Affiliations
- Department of Veterinary Science, MH Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA.
MeSH Terms
- Animals
- Genes, Recessive
- Genetic Predisposition to Disease
- Haplotypes
- Horse Diseases / genetics
- Horses
- Lordosis / genetics
- Lordosis / veterinary
- Polymorphism, Single Nucleotide
Citations
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