Analysis Of The 14 Bp Insertion/deletion Polymorphism In Human Leukocyte Antigen-G Gene In Chinese Han, Bulang, Dai And Hani Ethnic Groups In Yunan Province

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule initially reported to be limitedly expressed in the extravillous cytotrophoblast. HLA-G plays maternal-fetol immunologic suppression and confers protection to fetus from maternal semi-allograft immune responses in the course of pregnancy through combined to its' specific inhibitory receptors such as ILT2 (LIR-1,CD85j),ILT4 (LIR-2, CD85d), and KIR2DL4 (CD158d) which expressed on NK cells, T lymphocyte and macrophage.A 14 bp insertion/deletion polymorphism(+14 bp/-14 bp) in exon 8 of HLA-G gene has been showed that this polymorphism locus was associated with HLA-G mRNA stability and could influence HLA-G protein expression. Pregnant woman sharing the 14-bp insertion has been documented with more sufferring from preeclampsia and recurrent miscarriages.Other studies indicated that-14 bp/-14 bp genotype could be a genetic marker for a series of diseases, such as systemic lupus erythematosusidiopathic, rheumatoid arthritis,dilated cardiomyopathy. The immportant function of HLA-G suggested that natural selection may exert a strong influence against the alleles containing the insertion, which could result in very low insertion frequencies, particularly in isolated populations. In the current study, a total of 103 Chinese Han,115 Chinese Bulang,122 Chinese Dai and 147 Chinese Hani ethnic minority populations had been genotyped for the 14 bp insertion (+14 bp) and deletion(-14 bp) polymorphism in the HLA-G gene. Data showed that the +14 bp frequencies of these populations are 40.87% for the Han,47.03% for the Bulang,32.94% for the Dai and 48.64% for the Hani respectively, significant difference was observed for this alle between Dai and Bulang, dai and hani groups. Similarly, the frequencies of +14 bp/+14 bp in the dai(8.20%) are lower than that of Han(17.48%), Bulang(20.34%), and Hani(25.17%),and significant difference was also showed for this genotype between Dai and Bulang, Dai and Hani groups.The frequencies of +14 bp/-14 bp in these four populations are very close,46.60% for the Han,53.39% for the Bulang,47.54% for the Dai and 46.94% for the Hani, and no significant difference was observed in any pairwise among of them. The Ewens-Watterson's neutrality test showed a obvious balancing selection operated on this locus between the Bulang(F=-1.9961,P=0.0196) and Hani(F=-2.0440,P=0.0077) populations. Strong LD was detected between the-14 bp and partial alle of HLA-A gene:1)absolute linkage was found between the-14 bp and the-A*0201,-A*0203 in four enthic groups; 2)the-14 bp and-A*0207 showed strong positive LD in the dai and hani groups; 3)in the Bulang groups, negative LD between the-14 bp and-A* 1101 was found; and 4)in the dai enthic groups, negative LD between the-14 bp and-A* 1102 and absolute linkage between the-14 bp and-A*3303 were detected.