Genetic variability of 23 autosomal STRs in Austroasiatic-speaking populations from Thailand.

Austroasiatic (AA) speakers constitute around 4% of the population of Thailand, while the majority (89.4%) speak Kra-Dai (KD) languages. Previous forensic and population genetic studies in various Thai populations have employed a limited number of short tandem repeats (STRs). This study aims to expand the investigation of the genetic makeup of AA populations in Thailand and their relationship to KD populations using a larger number of autosomal STRs with the VeriFiler™ Plus PCR Amplification Kit. We generated 593 new genotypes from AA-speaking groups and combined them with previously reported data from AA and KD groups. A total of 1,129 genotypes across 23 STR loci were used to construct the largest allelic frequency profile for Thai and Lao populations. However, several loci deviated from Hardy-Weinberg equilibrium, likely due to the reduced genetic diversity in some highland populations, which should be considered in forensic investigations. Beyond forensic applications, our findings reveal genetic differences between AA-speaking groups in Northern and Northeastern Thailand. The AA groups from Northeastern Thailand exhibit greater genetic homogeneity and diversity, likely due to population interactions. In contrast, reduced diversity and increased heterogeneity in AA groups from Northern Thailand are possibly driven by genetic drift and cultural and geographic isolation. In conclusion, we emphasize the usefulness of increasing the number of autosomal STRs in forensic and anthropological genetic studies. Additional Y-STR and X-STR data from various AA-speaking groups in Thailand would further enhance and strengthen forensic STR databases in the region.

Forensic efficiency and genetic polymorphisms of 12 X-chromosomal STR loci in Northeastern Thai populations.

Northeastern Thailand comprises one-third of the country and is home to various populations, with Lao Isan constituting the majority, while others are considered minority groups. Previous studies on forensic short tandem repeats (STRs) in Thailand predominantly focused on autosomal STRs but there was a paucity of X-STRs, exclusively reported from the North and Central regions of the country. In this study, we have newly established a 12 X-STRs from a total of 896 samples from Northeastern Thailand, encompassing Lao Isan as the major group in the region, alongside nine minor populations (Khmer, Mon, Nyahkur, Bru, Kuy, Phutai, Kalueang, Nyaw, and Saek). Across all ten populations, the combined powers of discrimination in both genders were high and the combined mean exclusion chance (MEC) indices calculated for deficiency, normal trio and duo cases were also high (> 0.99999). DXS10148 emerged as the most informative marker, while DXS7423 was identified as the least informative. Genetic comparison based on X-STRs frequency supported genetic distinction of cerain minor groups such as Kuy, Saek and Nyahkur from other northeastern Thai groups as well as genetic differences according to the geographic region of Thai groups (Northeast, North and Central). In sum, the overall results on population genetics are in agreement with earlier reports on other genetic systems, indicating the informativeness of X-STRs for use in anthropological genetics studies. From a forensic perspective, despite the limitations of small sample sizes for minority groups, the present results contribute to filling the gap in the reference X-STRs database of the major group Lao Isan, providing valuable frequency data for forensic applications in Thailand and neighboring countries.

Autosomal Microsatellite Investigation Reveals Multiple Genetic Components of the Highlanders from Thailand.

The hill tribes of northern Thailand comprise nine officially recognized groups: the Austroasiatic-speaking (AA) Khmu, Htin and Lawa; the Hmong-Mien-speaking (HM) IuMien and Hmong; and the Sino-Tibetan-speaking (ST) Akha, Karen, Lahu and Lisu. Except the Lawa, the rest of the hill tribes migrated into their present habitats only very recently. The Thai hill tribes were of much interest to research groups focusing on study of cultural and genetic variation because of their unique languages and cultures. So far, there have been several genetic studies of the Thai hill tribes. However, complete forensic microsatellite database of the Thai hill tribes is still lacking. To construct such database, we newly generated 654 genotypes of 15 microsatellites commonly used in forensic investigation that belong to all the nine hill tribes and also non-hill tribe highlanders from northern Thailand. We also combined 329 genotypes from previous studies of northern Thai populations bringing to a total of 983 genotypes, which were then subjected to genetic structure and population relationships analyses. Our overall results indicated homogenous genetic structure within the HM- and Tai-Kadai (TK)-speaking groups, large genetic divergence of the HM-speaking Hmong but not IuMien from the other Thai groups, and genetic heterogeneity within the ST- and AA-speaking groups, reflecting different population interactions and admixtures. In addition to establishing genetic relationships within and among these populations, our finding, which provides a more complete picture of the forensic microsatellite database of the multiple Thai highland dwellers, would not only serve to expand and strengthen forensic investigation in Thailand, but would also benefit its neighboring countries of Laos and Myanmar, from which many of the Thai hill tribes originated and where large populations of these ethnic groups still reside.