Genetic Investigation of Sheep Families Demonstrating the Entropion Eye Condition

Lambs are sometimes born with a condition called entropion in which the lower eyelid is inverted, causing the bottom eyelashes to rub on the cornea which can lead to blindness if not treated.  Treatment is commonly done by unrolling the eyelid and surgically stapling it in correct alignment for a few weeks.  Previous reports on entropion have indicated that it is genetically controlled. In this study, samples from five paternal half-sibling families segregating for entropion were collected in 2014 and 2015.  Two of the five sires were born at the Utah State University sheep facility; one was from a flock with high incidence of entropion and born with the condition while the other sire, normal at birth, was from a flock with no recorded entropion births in the last 7 years.  The other three sires were purchased and their eye condition at birth is unknown.  Forty eight of the 159 lambs produced by these five rams were born with entropion. In an attempt to identify genetic regions involved with the entropion eye condition, genomic DNA was extracted from all lambs, sires and dams in the five families and the DNA samples genotyped with the Illumina HD SNP chip. Analysis of the SNP genotypes and entropion was done using SNP & Variation Suite v8. (Golden Helix, Inc.).  Preliminary results suggested associations between the entropion condition and SNP markers on ovine chromosomes 1 and 3.  Additional analyses are underway to localize the significant regions and identify underlying genes or genetic regulatory factors.