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 resolution typing (Gomez-Casado et al. 2000); one class I allele obtained by generic DNA typing may contain several class I alleles, and many populations lacked HLA-A and -B data (see references from Table 1).
Figure 2 depicts an HLA class II (DRB1-DQB1) neighbor-joining tree. Populations are grouped into two main branches. The first includes Siberians and Na-Dene Native Americans, and the second groups Asians and Caucasoids. The latter group is subdivided into three groups comprised of central Europeans (including Russians, Danish, and Chuvash), western Mediterraneans (Spaniards and North Africans), and eastern Mediterraneans (including Macedonians, Cretans, Jews, and Lebanese). This distribution is also confirmed in the correspondence analysis (Figure 3): the three groups are clearly delimited and an east-to-west Mediterranean and central European gradient is evident. The Chuvash population shows the closest genetic distance with the French followed by Russians, Spaniards, Germans, and Danes (Table 3). These results are confirmed using DR and DQ generic typings (see Figures 4 and 5), which were used in order to include other central and southern Europeans (Finns, Austrians, Belgians, Czech, Hungarians, and Romanians) and other Mediterranean populations (Portuguese, Iranians, Armenians, Egyptians, and Turks; see Table 1). A DR-DQ neighbor-joining tree (Figure 4) maintains the central European and the east-to-west Mediterranean distribution.
Figure 2 depicts an HLA class II (DRB1-DQB1) neighbor-joining tree. Populations are grouped into two main branches. The first includes Siberians and Na-Dene Native Americans, and the second groups Asians and Caucasoids. The latter group is subdivided into three groups comprised of central Europeans (including Russians, Danish, and Chuvash), western Mediterraneans (Spaniards and North Africans), and eastern Mediterraneans (including Macedonians, Cretans, Jews, and Lebanese). This distribution is also confirmed in the correspondence analysis (Figure 3): the three groups are clearly delimited and an east-to-west Mediterranean and central European gradient is evident. The Chuvash population shows the closest genetic distance with the French followed by Russians, Spaniards, Germans, and Danes (Table 3). These results are confirmed using DR and DQ generic typings (see Figures 4 and 5), which were used in order to include other central and southern Europeans (Finns, Austrians, Belgians, Czech, Hungarians, and Romanians) and other Mediterranean populations (Portuguese, Iranians, Armenians, Egyptians, and Turks; see Table 1). A DR-DQ neighbor-joining tree (Figure 4) maintains the central European and the east-to-west Mediterranean distribution.
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