Molecular characteristics of the MHC-DRA genes from yak (Bos grunniens) and Chinese yakow (Bos grunniens × Bos taurus)

Cloning and characterization of MHC-DQA1 and MHC-DQA2 molecules from yak (<i>Bos grunniens</i>)

Abstract. The major histocompatibility complex (MHC) plays a crucial role in the processing and presentation of antigens and in discrimination between self and non-self. The aim of this investigation was to scrutinize the structural diversity and possible duplication of the MHC-DQA genes in yak (Bos grunniens). Two cDNA sequences were amplified and designated as Bogr-DQA1 (DQA*0101) and Bogr-DQA2 (DQA*2001) with GenBank accession numbers JQ864314 and JQ864315, respectively. The nucleotide and amino acid sequence alignment between Bogr-DQA1 and Bogr-DQA2 molecules showed that these two identified MHC-DQA gene sequences had more similarity to alleles of specific DQA1 and DQA2 genes from other Ruminantia species than to each other. The result from phylogenic investigation also revealed that there was a larger genetic distance between these two genes than between homologous genes from different species. The presence of different bovine DQA putative motifs and the large genetic distance between Bogr-DQA1 and Bogr-DQA2 suggest that these sequences are non-allelic. Further, these results indicate that DQA gene duplication occurs in ruminants. This study will be helpful in knowing MHC diversity in common ruminants and will deepen our understanding of the variation of immunological functions, evolutionary constraints, and selective forces that affect MHC variation within and between species.

Effect of Genetic Diversity in Swine Leukocyte Antigen-DRA Gene on Piglet Diarrhea

The swine leukocyte antigens (SLAs) are the multigene families related to immune responses. Little is known about the effect of the DRA gene on diarrheal disease. This study reported the genetic diversity of the DRA gene in exons 1, 3 and 4 in 290 Chinese Yantai black pigs. No variation was identified in exon 3. In exon 1, three genotypes and two alleles were identified, generated by two single nucleotide polymorphisms (SNPs). In exon 4, there were eight genotypes and five alleles containing seven SNPs were detected with four SNPs being novel SNPs. The low polymorphism found in swine DRA is consistent with the concept that the DRA gene is highly conserved among all mammalian species. Statistical analyses indicated that the genotypes of exon 1 were not significantly associated with piglet diarrhea (p > 0.05); however, genotypes C₄C₄ (1.80 ± 0.33) and A₄E₄ (1.66 ± 0.25) of exon 4 were significantly susceptible to diarrhea (p < 0.01). These indicate that the particular genotypes of the DRA gene are susceptible to diarrheal disease, which provides valuable information for disease-resistance breeding in swine.

Isolation and cDNA characteristics of MHC-DRA genes from gayal (Bos frontalis) and gaytle (Bos frontalis × Bos taurus)

The mammalian major histocompatibility complex (MHC) plays important roles in pathogen recognition and disease resistance. In the present study, the coding sequence and the 5′- and 3′-untranslated regions of MHC class II DR alpha chain (the DRA gene) from rare gayal and gaytle were cloned and analyzed to dissect structural and functional variations. The nucleotide and amino acid sequences for the DRA genes in gayal (Bofr-DRA) and gaytle (Bofr × BoLA-DRA) were almost identical to those for cattle and yak (99%). Compared to yak, two amino acids substitutions in the signal peptide (SP) domain for gayal were found within all Bos animals. Except for only one replacement in the amino acid within the α2 domain of the DRA protein in gayal, the additional residues were highly conserved across the species investigated. The 20 peptide-binding sites (PBS) of Bofr-DRA and Bofr × BoLA-DRA were essentially reserved in the α1 domain among all species investigated. The lesser degree of substitution in Bofr-DRA is concordant with the concept that the DRA gene is highly conserved among all mammals. The very high degree of conservativity of the DRA gene among ruminants, including gayal, suggests its recent evolutionary separation.