Polymorphism Of Major Histocompatibility Complex(MHC) Class Ⅰ Genes In Zootoca Vivipara And Their Effects On Maternal-fetal Immunity

As a representative of the Palaearctic realm lizard,Zootoca vivipara has a breeding model of viviparous.The distribution in China is limited to the three province of Heilongjiang,Inner Mongolia Autonomous Region and Xinjiang.Due to human disturbance,the habitat damage has caused Zootoca vivipara to be in a state of gradual danger.The major histocompatibility complex(MHC)gene is one of the highly polymorphic functional genes in the immune system,and its antigen binding region exists due to the need to recognize multiple pathogens and adapt to the environment,its antigen-binding region has high variability.For the first time,this study analyzed MHC class ? gene polymorphism and maternal fetal immunity of 74 individual Zootoca vivipara in 4 regions of the Greater Khingan Range and Lesser Khingan Range.The following four results were obtained:1.A total of 570 sequences were cloned from 19 individuals,of which the nucleotide length of α2 was 201~223 bp,the nucleotide length of α3 is 181~184 bp,and the amino acid length of α2 and α3 is 111~178 aa.A total of 47 alleles were obtained in the experiment,and at least 3 to 6 MHC class loci were speculated,which was consistent with the genetic "birth-and-death model of evolution",indicating that they experienced gene duplication or loss during evolution.2.The nucleotide polymorphism π of 4 populations was calculated from 0.305 to 0.659,and the nucleotide polymorphism of Yakeshi population was the highest,and Nenjiang population was the lowest,it was found to have a high level of nucleotide polymorphisms.3.The combined average amino acid distance is less than the average nucleotide distance,the non-synonymous mutation rate is greater than the synonymous mutation rate(ω>1),and 26 of the 37 selection sites predicted by MEME and MEGA are near the antigen binding site.The results suggest that the sequence at the antigen binding site has undergone a positive selection,associated with pathogen-mediated selection,and no detectable recombination.The existence of cross-species polymorphisms was found in the constructed phylogenetic tree.4.Through the study of the influence of MHC Ⅰ gene on maternal-fetal immunity,it was found that Zootoca vivipara was affected by the seasonality of the immune system and also related to the successful pregnancy.At the same time,the antigenic threat of different tissues and the synergistic effect of the tissue’s own functions led to modifies in the expression of MHC Ⅰ gene.In summary,MHC Ⅰ gene of Zootoca vivipara has undergone gene duplication in evolution,is highly polymorphic,and it is maintained by pathogen-mediated selection.In the immune regulation of maternal-fetal,it shows the phenomenon of reducing the relative expression of MHC Ⅰ gene,similar with the research of viviparous animals.This study gives a theoretical basis for species protection and maternal-fetal immunity studies of Zootoca vivipara.