Alpha-globin gene cluster haplotypes and D1S80, D17S5, and TPO VNTR polymorphisms among four ethnic populations from lower northeastern Thailand

Laos, Khmer, Kui, and Yer ethnic populations had a high prevalence of α⁺-thalassemia, but the genetic background remains poorly understood. This study examined genetic variation at the α-globin gene cluster and three VNTR loci (D1S80, D17S5, and TPO) in these ethnic populations. For α-globin haplotype analysis, 110 subjects with normal α-globin and 232 subjects with α⁺-thalassemia were selected to analyze six polymorphic sites using the PCR-RFLP technique. For VNTR loci analysis, 447 subjects were examined for D1S80, D17S5, and TPO allele frequencies using a PCR-based method. The results of this study revealed that the most frequent haplotypes found in Laos, including (framework 1; + M - + - 0) linked to (-α^3.7) and (framework 3; - S - + + -) related to (α^CSα) were different from those found in Khmer and Kui [(framework 2; + S - + - 0) linked to (-α^3.7) and (framework 1; + M - + + -) related to (α^CSα)]. For the (α^PSα) gene, the haplotype (+ S - + - -) of framework 2 was found in all ethnic groups, and the haplotype (- M - + + -) of framework 1 in the Yer only. The distribution of allele frequencies for the D1S80, D17S5, and TPO VNTR loci showed extensive genetic variation in the ethnic population studied. The number of alleles is higher than that of the previously reported populations. Based on D17S5 analysis, the phylogenetic tree suggested that Khmer and Kui ethnic groups had a close relationship but were distant from Laos. In addition, ethnic relationships were observed in the Yer and Kui populations. In contrast, consistent results were not obtained based on D1S80 and TPO analysis. The findings indicate genetic variation in these ethnic populations, but the conclusion remains tentative. However, this study provides useful information to better understand genetic origins and ethnic relationships in the region.