Polymorphism And Evolution Of New World Monkey MHC Ⅰ Molecules Composed

Major histocompatibility complex (MHC) is found in vertebrate, encoding immunoglobulin-like receptors, genes with highly polypeptide, which are directly involved in the resistance of invasion of pathogens and their stabilization process. For different MHC genotypesof individual animals, there is a large difference in the degree of tolerance of the disease.MHC molecules studies in primate establish the genotype of the typing method. It can not only improve the uniformity of primate experiment, but also can promote the study ofmolecular composition and the evolutionary characteristics of MHC. The experiment analyzed the allele in the New World monkey MHC class I molecules in composition and polymorphism. Functional parts of the gene are also conducted a preliminary analysis. This study provides important experimental basis in revealing the genetic characteristics of alleles in the New World monkey MHC class I molecules. Experimental study now is reported asfollows:ⅠThe results of the marmoset:8marmosets sequenced412clones, of which374clones are Caja-G gene and38clones are Caja gene, with a significant asymmetry. Found17Caja-G alleles, each marmoset has5-12Caja-G alleles; Found6Caja-B genes, each marmoset has1-3Caja-B genes.ⅡThe results of the brown-headed spider monkeys: Two brown-headed spider monkeysequenced a total of116clones.21new genes were identified, of which9Atfu-G and12Atfu-B genes. Each brown-headed spider monkey has3-4Atfu-G and4-8Atfu-B genes.Genes show relatively low expression levels and polymorphism in marmoset Caja-Bmolecules, which has similar characteristics to non-classical genes. Conducting a comparative analysis in their α2and α3structural domain of amino acid sequences, we found that B, binding to the polypeptide, and Fpockets presence certain polymorphism, which are different with non-classical MHC class I molecules.For Caja-B and Caja-G in vitro expression patterns were analyzed and found Caja-Bgene also express on cell surface. In vitro expression level shows no significant differences with Caja-G molecule. Further illustrates the Caja-B the same as the classical MHC I molecules. α2and α3structural domain of amino acid sequences of Brown-headed spidermonkeys’ Atfu-B and Atfu-B molecules results indicate that B and Fpocket are certain highly polymorphic. Both are described as classical MHC class I molecules. Based on amino acid sequence of4-8exons, we build the phylogenetic tree of these two animals of MHC-B and MHC-G. Caja-G and Atfu-G genes cluster into the same branch, and Caja-B and Atfu-B genes cluster into the same branch. It indicate that between these alleles are homologous. Two animals of the four PBR gene regions, non-PBR area of α1and α2structuraldomain and α3structural domain are conducted a natural selection pressure analysis.Wherein the Caja-G and Atfu-G gene analysis in line with expectations, but the difference was not significant in dN and dS in PBR area of Caja-B and Atfu-B, suggesting Atfu-B locus genetic exchange may exist.For α1and α2structural domain of Caja-G, Atfu-G and Atfu-B homology alignment of the amino acid sequence of results showed that α2structural domain of Caja-G exists a plurality of identical amino acid sequence, which is the same with α2domain structure of Atfu-B. Atfu-G has the same amino acid sequence is less.The gene phylogenetic tree also shows results that α2structural domain of Atfu-B gene is closer to Caja-G gene instead of Atfu-G gene sequences. There is a certain description of the phenomenon of gene exchange in the New World monkey Atfu-B genes during evolution. That is to say, the co-evolution played a role in the New World monkeys MNC formation of class I molecules. It also plays a role in the process of the formation ofrhesus-AG sites and ring-tailed lemur MHC class I molecules. So co-evolution and Birth-and-death evolution are both important way to the evolution of MHC I molecules.Based on amino acid sequence of4-8exons, we build MHC-B and MHC-G molecular phylogenetic tree of the New World monkey and the Old World monkey. The results show that MHC-B molecules of the New World monkey cluster with the MHC-B and MHC-A molecules of the Old World monkey. MHC-G molecules of the New World monkey cluster with MHC-G of the Old World monkey. Those fact indicates that MHC I moleculesof New World monkeys and Old World monkeys have homology.For amino acids of Intracellular tail on different molecules, the results show that MHC-B and MHC-G molecules of New World monkeys and Old World monkeys exist the same amino acid motif, which further indicating that they both are homology.