Diversity of equine major histocompatiblity complex class II DRA locus in Posavina and Croatian Coldblood horse: a new polymorphism detected

Domestic equidae display polymorphism within ELA-DRA locus which is not characteristic for other species. We characterised sequence polymorphism present at ELA-DRA locus exon 2 and estimated allele frequencies in two autochthonous breeds, Posavina and Croatian Coldblood. In 88 horses, four different alleles were found, one of them not reported before in horses. The new allele shows non-synonymous mutation at position 65 (T^A) causing amino acid change (Phe^Tyr) in antigen binding site and synonymous mutation at position 105 (C^T). Our findings emphasize the importance of DRA polymorphism among equids and some specific DRA frequency pattern potentially specific in draught horses.