Conformation Traits and Gaits in the Icelandic Horse are Associated with Genetic Variants in Myostatin (MSTN).

Many genes are known to have an influence on conformation and performance traits; however, the role of one gene, Myostatin (MSTN), has been highlighted in recent studies on horses. Myostatin acts as a repressor in the development and regulation of differentiation and proliferative growth of skeletal muscle. Several studies have examined the link between MSTN, conformation, and performance in racing breeds, but no studies have investigated the relationship in Icelandic horses. Icelandic horses, a highly unique breed, are known both for their robust and compact conformation as well as their additional gaits tölt and pace. Three SNPs (g.65868604G>T [PR8604], g.66493737C>T [PR3737], and g.66495826A>G [PR5826]) flanking or within equine MSTN were genotyped in 195 Icelandic horses. The SNPs and haplotypes were analyzed for association with official estimated breeding values (EBV) for conformation traits (n = 11) and gaits (n = 5). The EBV for neck, withers, and shoulders was significantly associated with both PR8604 and PR3737 (P < 0.05). PR8604 was also associated with EBV for total conformation (P = 0.05). These associations were all supported by the haplotype analysis. However, while SNP PR5826 showed a significant association with EBVs for leg stance and hooves (P < 0.05), haplotype analyses for these traits failed to fully support these associations. This study demonstrates the possible role of MSTN on both the form and function of horses from non-racing breeds. Further analysis of Icelandic horses as well as other non-racing breeds would be beneficial and likely help to completely understand the influence of MSTN on conformation and performance in horses.

Using an Inbred Horse Breed in a High Density Genome-Wide Scan for Genetic Risk Factors of Insect Bite Hypersensitivity (IBH).

While susceptibility to hypersensitive reactions is a common problem amongst humans and animals alike, the population structure of certain animal species and breeds provides a more advantageous route to better understanding the biology underpinning these conditions. The current study uses Exmoor ponies, a highly inbred breed of horse known to frequently suffer from insect bite hypersensitivity, to identify genomic regions associated with a type I and type IV hypersensitive reaction. A total of 110 cases and 170 controls were genotyped on the 670K Axiom Equine Genotyping Array. Quality control resulted in 452,457 SNPs and 268 individuals being tested for association. Genome-wide association analyses were performed using the GenABEL package in R and resulted in the identification of two regions of interest on Chromosome 8. The first region contained the most significant SNP identified, which was located in an intron of the DCC netrin 1 receptor gene. The second region identified contained multiple top SNPs and encompassed the PIGN, KIAA1468, TNFRSF11A, ZCCHC2, and PHLPP1 genes. Although additional studies will be needed to validate the importance of these regions in horses and the relevance of these regions in other species, the knowledge gained from the current study has the potential to be a step forward in unraveling the complex nature of hypersensitive reactions.