Evidence for an additional cattle DQA locus, BoLA-DQA5.

Studying the genetic polymorphism of the major histocompatibility complex class II genes in cattle, we identified an allele (BNI13) which encodes a typical class II alpha chain. Its transcription was confirmed by RNA analysis. Sequence comparisons, Southern blot, and phylogenetic analyses indicate that (1) BNI13 represents a distinct DQA locus which we propose to designate BoLA-DQA5, (2) BoLA-DQA1 and BoLA-DQA5 separated after the divergence of BoLA-DQA1 and BoLA-DQA2, but prior to the separation of sheep DQA1 and cattle DQA1, and (3) DQA5 is distributed among various cattle breeds but is confined to certain haplotypes.