[Study of the most often encountered allele of the HLA-B27 gene in Tuvinian and Russian inhabitants of Western Siberia]

HLA-B27 gene frequencies and allelic polymorphism were studied in two Siberian ethnic groups: Russians from Novosibirsk (western Siberia) and Tuvinians from Kyzyl (southern Siberia). The HLA-B27 frequencies were determined by means of serologic typing of HLA antigens in 198 Tuvinians and 288 Russians. Molecular typing was performed via hybridization of oligonucleotide probes with amplified DNAs obtained from 30 HLA-B27-positive Russians and 11 HLA-B27-positive Tuvinians. The HLA-B27 gene frequencies in Tuvinians and Russians were 5.5 and 10.4%, respectively. Molecular variants of the HLA-B27 gene were studied in Tuvinians for the first time. The proportions of the HLA-B2705 and HLA-B2704 alleles were found to be 64 and 36%, respectively, in the population studied. The presence of the HLA-B2704 allele indicates a Mongoloid origin of Tuvinians. In the Russian population of Novosibirsk, the HLA-B2704 allele was not found, whereas the proportions of the HLA-B2705 and HLA-B2702 alleles were 76.2 and 23.8%, respectively, which is characteristic of Caucasoid populations.

[Frequency of the HLA-DP genes and the antigens of the HLA-A, -B, -Cw, and -DR loci in Tuvinians]

The results of DNA typing of the HLA-DPB1 gene among Tuvinians are described. The allele 0201 was found to be the most frequent (26.66%); then, in order of decreasing frequency, followed the alleles 0401 (26.42%), 0402 (13.99%), 0301 (8.55%), 0501 (7.77%), 0901 (5.16%), and 1301 (2.07%). The frequency of the allele 0501 in Tuvinians was significantly lower than that in the published data on allele distributions characteristic of two other Mongoloid populations, the Manchu and Japanese. The results of the serological typing of the loci HLA-A, -B, and -Cw of class I in the Tuva population were compared to the corresponding published data on ten Mongoloid populations of Central and Eastern Asia: Uigurs, Kazakhs, Mongols, Manchu, Tibetans, the Chinese of the northern and southern regions of China, Thais (inhabitants of Northwestern Indochina), Koreans, and Japanese. In Tuvinians, the most frequent antigens were HLA-A2, -A9, -B0, -B35, -B17, -Cw4, and -DR5. In the inhabitants of Tuva, the frequency of the antigens HLA-A1, -A9, -B17, -Cw2, and -Cw4 was significantly higher than in other Mongoloids, while that of the antigens HLA-A26 and -B22 was lower. This difference was greatest in the case of antigen HLA-B40: it a frequency of 43.4% was detected in it, while in individuals of Mongolian origin, the frequency of this antigen did not exceed 22.5%. Indices of genetic similarity (IGSs), calculated from the gene frequencies of the loci HLA-A, -B, and -Cw, suggested that the Tuvinians were most closely related to Kazakhs (IGS = 0.73), and least related to the Japanese and Uigurs (IGS = 0.66). Our data suggest that Tuvinians significantly differ from the compared populations of Central and Eastern Asia.

[Polymorphism of the HLA-DRB1 04 gene in inhabitants of Tuva]

Data on the HLA-DRB1 04 gene typing among Tuvinians from Kyzyl are presented. Experiments were conducted by using the hybridization of allele-specific oligonucleotides with the amplified fragments of high molecular-weight DNA and reverse hybridization. The HLA-DRB1 0401 allele was most frequent among DR4-positive individuals. The HLA-DRB1 0405 and HLA-DRB1 0403 alleles were found at somewhat lower frequencies. In one individual, the rare HLA-DRB1 0410 subtype differing from HLA-DRB1 0405 subtype by the substitution of glycine for valine in codon 86 was detected.