Molecular cloning and sequence characterization of two genes, DQA1 and DQA2, from the Chinese yakow (Bos grunniens x Bos taurus)

The major histocompatibility complex (MHC) plays a crucial role in the immune response to infectious diseases. The aim of the present study was to investigate the structural and functional characteristics and possible duplication of the MHC-DQA genes in the Chinese yakow, which is well adapted to the Qinghai-Tibetan Plateau. Two full-length cDNA sequences and partial 5'-and 3'-untranslated regions (UTRs) were retrieved and denoted as BogrxBoLA-DQA star 0101 (DQA1) and BogrxBoLA-DQA star 2001 (DQA2), respectively. The percentage of nucleotide and amino acid sequences homology between BogrxBoLA-DQA1 and BogrxBoLA-DQA2 showed that these two sequences have more identity to alleles of the corresponding DQA1 and DQA2 genes from other counterparts than to each other. Moreover, the BogrxBoLA-DQA1 and -DQA2 exhibited considerable variation with 99 nucleotide polymorphisms along the length of the coding regions, leading to 52 amino acid polymorphisms. The phylogenetic tree investigation also demonstrated that there is a larger genetic gap within these two identified genes than within orthologous genes from different animals, suggesting that these sequences belong to nonallelic and duplicated types in the Chinese yakow. This is the first report to isolate and identify the MHC-DQA1 and-DQA2 genes. This result will deepen our understanding of MHC diversity among different ruminant species based on comparative population genetics.