Polymorphic Analysis Of MHC-DPB1Gene Exon2in Tibetan Macaques (Macaca Thibetana)

Major histocompatibility complex (MHC) is a cluster of genes which coding the surface membrance glycoprotein. MHC molecules play an important role in the susceptibility and/or resistance to many diseases. MHC-DPB1gene is a member of the MHC class Ⅱ,the study found that the primate MHC-DPB1plays a fundamental and important role in the peptide-binging selectivity of the DP antigen and is a signigicant factor in the humoral response. To gain an insight into the diversity of MHC-DPBl gene of the Tibetan macaques (Macaca thibetana), and thereby facilitate their protection and application in biomedical research, the second exon of the MHC-DPB1genes from135Tibetan macaques were characterized by PCR, cloning, sequencing, and statistical analysis, these samples were from Sichuan, Yunnan, Guizhou, Gansu, Zhejiang, Fujian, Guangdong, Guangxi and Hunan Provinces. We analyzed the sequence features, positive detective rate of alleles, natural selective examination, alignment of the amino acid sequences and phylogenetic tree, et al, respectively.1、A total of58MHC-DPB1alleles were frist identified from Tibetan macaques, of which three (Math-DPB1*01:06N、Math-DPB1-New01*01、Math-DPB1-New01*13) was a pseudogene. Moreover,8Math-DPB1alleles exon2sequences were identical to rhesus macaques (Macaca mulatta) or cynomolgus macaques (Macaca fascicularis) orthologues, it demonstrated show the obvious Trans-species polymorphism between Tibetan macaques、rhesus macaque and cynomolgus macaques.2、Math-DPB1*01:03:01(37.78%) was the most frequent allele in the whole large population comprising all135Tibetan macaque samples (72.59%) and in Sichuan population (70.13%), in Guizhou population (50.00%), in Fujiang population (84.09%). Some Math-DPB1alleles can be detected in three Tibetan macaque populations, but some were detected only in one population.3、Selection analysis revealed all sites and antigen binding sites (ABS) of Math-DPB1gene exon2were subject to positive selection, Non-antigen binding sites (Non-ABS) wre subject to neutral selection. To detecte the balancing selection of Math-DPBl gene exon2, random sites models of PAML were used. The random sites models demonstrate extreme variability in selective pressure among sites and the presence of a number of sites under positive selection, balancing selection may play an important role in maintaining the polymorphism of Math-DPB1genes.4、The alignment of amino acids sequences showed that amino acids insertion or deletion was seen in Math-DPB1alleles, as well as pseudogenes phenomenon of Math-DPB1alleles due to the allele contain a termination codon. Besides, it also showed21variable sites were species-specific to Tibetan macaques.5、A phylogenetic tree constructed using DPB1alleles in different species demonstrated that the Math-DPB1alleles may share a same lineages with HLA-DPB1alleles, and the alleles for Math-DPB1, Mamu-DPB1and Mafa-DPB1tended to mix together, rather than cluster into a separate branch in a species-specific way, which showed apparent Trans-species polymorphism.