P568Genome Wide Association of Skeletal Size Variation in Tennessee Walking Horses
Genome Wide Association of Skeletal Size Variation in Tennessee Walking Horses
Date: Monday, January 13, 2014
Room: Grand Exhibit Hall
Conformation has long been a driving force in horse selection and breed identification, particularly as a predictor for performance and injury susceptibility. In any equine discipline there are certain conformations and body dimensions that are reported as desired and advantageous to performance. The Tennessee Walking Horse (TWH) ranges in size from 14.3 to 17 hands and is often used as a trail, show, and pleasure horse. To investigate the contribution of genetics to body size variation in TWH, we collected blood or hair samples, 35 body measurements, gait type, and horse use for 207 TWH. Principal Component Analysis (PCA) was conducted on 33 body measurements for the 161 horses that met inclusion criteria. Principal components 1, 2 and 3 comprised 25.1%, 12.7% and 7.0% proportions of the total variance, respectively. All factors (body measures) loaded positively for PC1, which therefore describes overall proportional body size. In an effort to identify genetic loci contributing to TWH body size, we genotyped DNA from 61 TWHs using the Equine SNP70k bead chip and used PC1 score as the phenotype. Allelic analysis using PLINK V1.07 (Purcell, 2007) revealed a single candidate locus on ECA9 (p=4.971E-7) that surpassed a Bonferroni cutoff of 6.05E-6 near the ZFAT gene. ZFAT is a zinc finger that plays a role during development in hematopoiesis, and prior studies have also reported an association with height in humans and other horse breeds. Ongoing work includes identification of polymorphisms and structural variants within this region from whole-genome sequences.