Генетика чувашей.

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HLA genes in the Chuvashian population from European Russia: Admixture of central European and Mediterranean populations

Comments

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The origin of all other populations used for comparisons is detailed in Table 1

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Characteristic HLA Allele Frequencies of the Chuvashian Population Compared to Other Populations. The expected and observed allelic frequencies for HLA-A, -B, -DRB1, and -DQB1 loci do not differ significantly. There is no deviation from Hardy-Weinberg equilibrium. Table 2 shows the HLA allele frequencies found in the Chuvash population. Thirteen different HLA-A and 25 different HLA-B alleles were observed among the Chuvash. Six HLA-A alleles and four HLA-B alleles had frequencies higher than 5% (A*01, A*02, A*03, A*11, A*24, A*68, B*07, B*18, B*27, and B*15), and these are characteristic of Central European and Mediterranean populations (Imanishi et al. 1992c; Clayton and Lonjou 1997; Arnaiz-Villena et al. 1995, 1999). Alleles with frequencies higher than 3.5% may overlap the ones having a 5% frequency. With regard to HLA class II alleles, 18 different DRB1 alleles were found and only six had frequencies higher than 5%; DQ allele frequencies reflect the DRB1 locus allele distribution due to the strong linkage disequilibrium between

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Two types of analyses were carried out in order to compare Chuvashian HLA frequencies with other Central European, Mediterranean, Siberian, and NaDene population frequencies: (1) with DRB1-DQB1 data, which is probably a more informative and discriminating methodology; and (2) with generic (low-resolution) DR-DQ data. These two types of analyses were both performed because some of the populations used for comparison lacked HLA-DRB1 and -DQB1 high-resolution typing, and only generic HLA-DR and -DQ data were available (Portuguese, Turks, Iranians, Armenians, Egyptians, Bulgarians, Czech, Austrian, Belgians, Finns, Romanians, Hungarians, and Uralic [from the Caucasus]; see Table 1). These partially HLA-typed populations should have been ignored, but they could be analyzed conjointly taking into account DRB1 and DQB1 or generic DR and DQ frequencies (Tables 3 and 4; Figures 2, 3, 4, and 5) (Imanishi et al. 1992c). Finally, it should be pointed out that class I generic typing tends to homogenize the comparisons based on DRB1-DQB1 high

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On the other hand, low frequency haplotypes defined in this population (see footnote to Table 5) confirm the various contributions of central Europeans and Caucasians (Georgians) (A*24-B*35-DRB1*1101-DQB1*0301), Euroasiatics (A*30-B*13-DRB1*0701-DQB1*02), and Mediterraneans (A*02-B*18-DRB1*0301-DQB1*02, A*23-B*44-DRB1*1104-DQB1*0301). These haplotype results are concordant with those obtained by the allele frequency analyses (genetic distances, neighbor-joining trees, and correspondence analysis; see above). Otherwise, a migration from Chuvashian area to central Europe and the Mediterranean area cannot be discarded

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Figures 2, 3, 4, and 5 show that Siberians are outside the Oriental cluster and do not indicate any close genetic affinities to the Chuvash. All Siberian populations cluster together and also cluster with the Na-Dene speakers (Athabascans and Tlingit) and Eskimos, both in the dendrograms and in the correspondence analyses (see also Martinez-Laso et al. 2001; Arnaiz-Villena et al. 2000). These results are confirmed with the DA genetic distances data (Tables 3 and 4), where the Chuvash-Siberians distance is 30%-50%.

However, some Uralic haplotypes have been found in the Chuvashian population: (1) a part of A*02-B*27-DRB1*0801-DQB1*0402 and (T) A*03-B*07-DRB1*01Ol-DQB1*0501 in low frequency (see Table 5 and footnote), reflecting a certain influence of the populations living in the region close to the Chuvash.