Genomic Regions Associated with Entropion in Domestic Sheep Using the Ovine High-Density BeadChip

Entropion is an inward rolling of the eyelid allowing direct contact between the eyelashes and cornea, causing abrasions which may lead to infections and blindness if not treated. In domestic sheep, entropion has a wide range of frequency (0-80%) worldwide, was found to be heritable (0.08-0.21) and appears to be recessive in inheritance. Currently producers must cull afflicted sheep and their parents to eliminate this condition from their flocks. Identification of genomic regions or genes associated with entropion could facilitate development of genetic markers to allow producers to make informed selection decisions to reduce entropion through selective breeding. Therefore, a genome-wide association scan was conducted with 473 Columbia, Polypay, and Rambouillet sheep genotyped using the Illumina OvineSNP600 BeadChip. Entropion status was recorded within 48 hours of birth and overall prevalence in this group of sheep was 6.1%. Data was analyzed using a mixed model in EMMAX that accounted for relatedness, breed, and SNP minor allele. Six genome-wide significant (P<1x10^-8) SNP were identified on chromosomes 2, 3, 15, and 20 as well as nine SNP that were genome-wide suggestive (P<1x10^-7) on chromosomes 2, 3, 7, 14, 15, and 22. Previously, locations on chromosome 2, 3, and 15 were found to be associated with entropion by Mousel et al., 2015 and/or Hadfield et al., 2016. We are evaluating these regions to identify underlying causal mutations.