Identification of Equine Leukocyte Antigen Microsatellite Haplotypes in a Herd of Icelandic Horses

The Major Histocompatibility Complex (MHC) of the horse is located on chromosome 20 and called ELA (Equine Leukocyte Antigen). Using polymorphic microsatellites anchored within ELA, we characterized haplotypes from a herd of Icelandic horses that were imported to Cornell University.  The herd is composed of one stallion, fifteen dams, and three sets of foals from each dam.  We characterized a total of nine loci; two in the class I region, one in class III, and six in the class II region.  From the 32 chromosomes belonging to the founder stallion and mares, we identified 23 unique haplotypes.  In addition, we identified an F1 recombinant in the offspring.  The recombination event occurred between the class I and class II regions.  Finally, we examined ELA-DRB1 exon two sequences for a subset of the F1 individuals.  Overall, we found a large degree of diversity in our herd.  The Icelandic horse population originated from a small gene pool which experienced bottlenecking events throughout its history.  This would suggest that the population would show limited genetic diversity, however our results indicate otherwise.  This diversity may originate from the phenomenon of recombination within the MHC that has been seen in other isolated populations.