Nucleotide sequence and polymorphism of the caprine major histocompatibility complex class II DQA1 (Cahi-DQA1) gene

The major histocompatibility class II DQ molecules are dimeric glycoproteins involved in antigen presentation to CD4 + T cells. In the current work, we have performed the molecular analysis of the goat Cahi-DQA1 gene. Sequencing of the Cahi-DQA1 cDNA revealed a single 768 bp open reading frame. The alignment of this sequence with its bovine and ovine DQA1 counterparts revealed a remarkable degree of nucleotide identity (92-93% for the most similar bovine and ovine sequences). Moreover, we amplified a region including the 3′-end of intron 1, exon 2 and the 5′-end of intron 2. We identified seven Cahi-DQA1 alleles that likely correspond to four different allelic lineages. The alignment of these seven Cahi-DQA1 alleles revealed the existence of 23 amino acid polymorphic sites, seven of which (α 10, α 55, α 56, α 68, α 69, α 71 and α 76) are highly polymorphic with at least three amino acid substitutions. Ten of the 23 polymorphic amino acid sites were included in the peptide binding region and consequently they might play a crucial role in immunological processes modulating disease pathogenesis. © 2004 Elsevier Ltd. All rights reserved.