Diversity at eight polymorphic Alu insertion loci in Chinese populations shows evidence for European admixture in an ethnic minority population from Northwest China

Human Biology, Aug 2002 by Xiao, Feng-Xia, Yang, Jun-Fang, Cassiman, Jean-Jacques, Decorte, Ronny

Materials and Methods

Population Samples. China consists of a Han majority (93.3%) and 55 official minorities (6.7%). In this study, 323 unrelated individuals from four populations of China belonging to three ethnic groups were analyzed. The geographic locations of the four populations are illustrated in Figure 1. The samples of 98 Hans from Shanghai (East China) and 80 Hans from Guangzhou (Southeast China) were previously described (Xiao et al. 1998). Bloodstain samples of 85 Uyghurs and single-hair samples of 60 Sibos were collected from Yining in the Xinjiang autonomous region (Northwest China). The Uyghurs, living in a region of Central Asia along the Silk Road in ancient China, represent the second largest minority in China. The Sibos, currently residing in Yining, are descendants of approximately 3000 Sibos (1000 Sibo warriors and their families), who migrated from Shenyang (Northeast China) to Yining in 1764 during the Qing dynasty. The Han populations speak different dialects of a Sino-Tibetan language (Chinese), whereas Uyghurs are Turkic speakers and Sibos are Tungusic speakers. Both of the latter two languages belong to the Altaic language family.

DNA from bloodstain samples was extracted by using the QIAamp Tissue kit (Qiagen, Hilden). DNA extraction from hair samples was done according to published protocols (Higuchi et al. 1988). To overcome an inhibitory effect of a high salt concentration in the polymerase chain reaction (PCR), buccal samples from the Shanghai population were desalted on a Microcon100 filter (Amicon, Beverly, MA). All samples were obtained anonymously through local physicians and with consent of the participants.

Analysis of Alu Insertion Polymorphisms. Eight human-specific nuclear polymorphic Alu insertions, TPA25, PV92, APO, ACE, FXIIIB, DI, A25, and B65, were analyzed in the four population samples. Primer sequences for all loci have been described previously (Arcot et al. 1995a; Arcot et al. 1995b; Batzer et al. 1996). The loci TPA25, PV92, DI, and FXIIIB were, respectively, amplified in a single locus PCR reaction as published by Batzer et al. (1996).

Results

Genetic Variation within and between Populations. A total of 323 individuals from four Chinese populations were typed for the eight Alu insertion polymorphic loci. For each locus, the frequency of the Alu element in each population was recorded (Table 1). All loci were polymorphic in all populations, with the lowest level of polymorphism at A25. Exact tests showed that all loci in each population met HWE expectations except for FXIIIB in the Shanghai (p = 0.036) and DI in the Guangzhou populations (p = 0.023). In addition, exact tests also showed that there were significant genotype associations in the Uyghurs in 4 out of 28 locus pairs (TPA25 / APO, p = 0.025; PV92 / ACE, p = 0.003; ACE / B65, p = 0.018, and DI / B65, p = 0.018). However, when a Bonferroni correction for multiple testing was applied, all the tests for HWE expectations and genotype associations were not statistically significant.