Tai-Kadai-speaking Gelao population: Forensic features,genetic diversity and population structure

Genetic analyses of geographically and ethno-linguistically different populations are essential for understanding population stratification and genomic structure in medical Genome-Wide Association Studies (GWAS) and genetic variation and diversity related to forensic and population genetics studies. Here, we genotyped 30 autosomal insertion/deletion (Indel) markers from 502 Tai-Kadai-speaking Gelao individuals residing in the rugged topographical area in Southeastern China. In addition, two comprehensive population genetic comparisons of 15,327 individuals from 95 worldwide populations and of 6122 individuals from Asia and adjoining populations were conducted based on allele frequency data and raw genotype data, respectively. All studied markers were found to be in Hardy-Weinberg equilibrium. The combined power of discrimination in the Gelao minority group was 0.999999999975, and the combined probability of exclusion was 0.9879. Our results from the forensic statistical parameters indicated that this Indel panel can be independently used as a powerful tool in forensic individual identification but can only be used as a complementary tool in paternity cases involving East Asians. We also found significant allele frequency differences between the Gelao and other continental populations with respect to the markers grouped in clusters ∼Ⅳ, suggesting that these can be used as forensic ancestry informative Indel markers to distinguish the Gelao from other continental populations. Genetic ancestry analyses demonstrated that Tai-Kadai-speaking Gelao share a dominant ancestry component with Hmong-Mien-speaking Miao. Our population genetic results from multidimensional scaling plots, principal component analysis, neighboring-joining tree construction and hierarchical clustering also suggested that the Zunyi Gelao are genetically closer to their linguistically or geographically close populations, such as the Han Chinese, Guizhou Bouyei and the Hubei Tujia, than to Turkic and Tibeto-Burman speakers.     

Forensic features and genetic structure of 23 autosomal STRs in Artux Turkic-speaking population residing in southwestern Xinjiang Uyghur Autonomous Region

Autosomal short tandem repeats (STRs) are viewed as the gold standard in forensic individual identification and parentage testing. The Huaxia Platinum System contains 23 autosomal markers along with rs2032678 (Yindel) and amelogenin. Here, we genotyped 23-STRs in the southwestern Xinjiang Uyghur residing in the Artux Region and assessed the allele frequency and forensic statistical parameters. All investigated STRs are in conformity with the Hardy-Weinberg equilibrium with an effective combined power of discrimination (0.99999999999999999999999999992) and cumulative probability of exclusion (0.9999999997) in the Artux Uyghur population. Population comparisons among 54 worldwide populations via PCA and MDS indicate that the Artux Uyghur population has a close genetic relationship with geographically distinct Uyghurs and Kazakh groups than other East Asians or Eurasians. Genetic ancestry component dissection among 2198 individuals from Sinitic, Turkic, and Tibeto-Burman language groups further demonstrates the genetic homogeneity within the Turkic language family and apparent genetic heterogeneity among other language groups.

     

MATP polymorphisms in Germans and Japanese: the L374F mutation as a population marker for Caucasoids

Inference of the population and ancestry to which an individual belongs is important in forensic individualization and personal identification. In this study, five polymorphisms of the membrane-associated transporter protein (MATP) gene were investigated in German and Japanese populations. The L374F mutation was present at an allele frequency as high as 0.96 in the German population, whereas it was completely absent in the Japanese population. This extreme difference in allele frequency suggests that the L374F mutation is valuable as a population and ancestry informative marker for Caucasoids.     

Application of machine learning for ancestry inference using multi-InDel markers

Ancestry inference through population stratification plays an important role in forensic applications. Specifically, ancestry information inferred from forensic DNA evidence can provide vital clues for criminal investigations. Current advances in ancestry inference mostly focus on ancestry informative markers. Hereinto, multi-InDel was proposed as one of the compound markers performing well in complex ancestral classification in the subpopulation of Asia. However, research on analytical methods necessary to make reliable predictions is lacking. The newly proposed compound markers could be assessed with alternative methods. In this study, promising discriminant methods were explored using multi-InDel markers for forensic ancestry inference. As a prerequisite, the adopted multi-InDel markers were assessed by classical methods for population genetics, such as F_ST analysis, MDS and STRUCTURE. In addition, dimensionality reduction methods and serial reduction strategies were applied for data visualization. Subsequently, machine learning methods, including logistic regression (LR), support vector machine (SVM), k-nearest neighbors (KNN) and extreme gradient boosting (XGBoost), were evaluated by diverse approaches. As the result of multifarious analyses through comparisons and estimations, XGBoost with one-hot encoding was shown to be more effective in population stratification and ancestry inference for challenging cases with admixed populations.     

Completion of a worldwide reference panel of samples for an ancestry informative Indel assay

The use of ancestry informative markers (AIMs) in forensic analysis is of considerable utility since ancestry inference can progress an investigation when no identification has been made of DNA from the crime-scene. Short-amplicon markers, including insertion deletion polymorphisms, are particularly useful in forensic analysis due to their mutational stability, capacity to amplify degraded samples and straightforward amplification technique. In this study we report the completion of H952 HGDP–CEPH panel genotyping with a set of 46 AIM-Indels. The study adds Central South Asian and Middle Eastern population data, allowing a comparison of patterns of variation in Eurasia for these markers, in order to enhance their use in forensic analyses, particularly when combined with sets of ancestry informative SNPs. Ancestry analysis using principal component analysis and Bayesian methods indicates that a proportion of classification error occurs with European–Middle East population comparisons, but the 46 AIM-Indels have the capability to differentiate six major population groups when European–Central South Asian comparisons are made. These findings have relevance for forensic ancestry analyses in countries where South Asians form much of the demographic profile, including the UK, USA and South Africa. A novel third allele detected in MID-548 was characterized – despite a low frequency in the HGDP–CEPH panel samples, it appears confined to Central South Asian populations, increasing the ability to differentiate this population group. The H952 data set was implemented in a new open access SPSmart frequency browser – forInDel: Forensic Indel browser.     

Genetic analysis of 20 autosomal STR loci in the Miao ethnic group from Yunnan Province,Southwest China

The genetic polymorphisms of 20 autosomal short tandem repeat (STR) loci included in the PowerPlex^® 21 kit were evaluated from 748 unrelated healthy individuals of the Miao ethnic minority living in the Yunnan province in southwestern China. All of the loci reached Hardy–Weinberg equilibrium. These loci were examined to determine allele frequencies and forensic statistical parameters. The genetic relationship between the Miao population and other Chinese populations were also estimated. The combined discrimination power and probability of excluding paternity of the 20 STR loci were 0.999 999 999 999 999 999 999 991 26 and 0.999 999 975, respectively. The results suggested that the 20 STR loci were highly polymorphic, which makes them suitable for forensic personal identification and paternity testing.     

EASplex: A panel of 308 AISNPs for East Asian ancestry inference using next generation sequencing

Ancestry inference is useful in many scientific fields, such as forensic genetics, medical genetics, and molecular archaeology. Various ancestry inferring methods have been released for major continental populations. However, few reports refer to sub-populations within the East Asian population using hundreds of ancestry informative SNPs (AISNPs). In this study, we developed a 308-AISNP panel (EASplex NGS DNA panel) using multiplex PCR and next generation sequencing (NGS). This panel included 56 SNPs relevant for the continent-level ancestry inference and 252 Japanese-, Korean-, and/or Han Chinese-specific AISNPs to address the ancestry inference of global populations and regional populations among Japanese (JPT), Korean minority (CHK), and Han Chinese (CHH). A total of 87 CHK and 59 CHH samples were used to check the performance of the EASplex NGS DNA panel. By analyzing 146 profiles of samples with JPT and CHH data from Beijing and South China in 1000 genomes project, the following results were obtained: (1) the 146 tested samples were correctly assigned to the East Asian group; (2) the paired population assignment rate was 99.73% for JPT and CHH, 95% for JPT and CHK, and 90.11% for CHK and CHH; and (3) the whole population assignment was 92.14% for the JPT, CHK, and CHH data. Overall, the EASplex NGS DNA panel displayed informativeness for continental ancestry inference and regional ancestry inference among JPT, CHH, and CHK and has the potential for use in forensic and genetic population studies.     

Population data of 19 autosomal STR loci in the Li population from Hainan Province in southernmost China

In the present study, population data of 19 autosomal STR loci included in the Goldeneye™ DNA ID System 20A in 653 Li individuals was obtained and population genetic relationships among 13 populations were investigated. MDS and phylogenetic analysis suggested that the Hainan Li population kept a close genetic relationship with the Chinese Han populations, especially for Southern Han populations (Guangdong Han, Sichuan Han, and Hunan Han). Our results indicated that the 19 autosomal STRs are highly discriminative and polymorphic in the Hainan Li population suitable for personal forensic identification and paternity testing.

     

AIM-SNPtag: A computationally efficient approach for developing ancestry-informative SNP panels

Inferring an individual's ancestry or group membership using a small set of highly informative genetic markers is very useful in forensic and medical genetics. However, given the huge amount of SNP data available from a diverse of populations, it is challenging to develop informative panels by exhaustively searching for all possible SNP combinations. In this study, we formulate it as an algorithm problem of selecting an optimal set of SNPs that maximizes the inference accuracy while minimizes the set size. Built on this conception, we develop a computational approach that is capable of constructing ancestry informative panels from multi-population genome-wide SNP data efficiently. We evaluated the performance of the method by comparing the panel size and membership inference accuracy of the constructed SNP panels to panels selected through empirical procedures in previous studies. For the membership inference of population groups including Asian, European, African, East Asian and Southeast Asian, a 36-SNP panel developed by our approach has an overall accuracy of 99.07%, and a 21-SNP subset of the panel has an overall accuracy of 95.36%. In comparison, an existing panel requires 74 SNPs to achieve an accuracy of 94.14% on the same set of population groups. We further apply the method to four subpopulations within Europe (Finnish, British, Spanish and Italian); a 175-SNP panel can discriminate individuals of those European subpopulations with an accuracy of 99.36%, of which a 68-SNP subset can achieve an accuracy of 95.07%. We expect our method to be a useful tool for constructing ancestry informative markers in forensic genetics.     

Population data and forensic efficiency of 21 autosomal STR loci included in AGCU EX22 amplification system in the Wanzhou Han population

Autosomal short tandem repeats (STRs), widely distributed in the whole human genome, play an important role in personal identification and parentage testing. In this study, the allele frequencies and forensic efficiency parameters of 21 autosomal STR loci included in the AGCU EX22 kit were obtained from 433 Chinese Han individuals residing in the Wanzhou District in the north of Chongqing Municipality, Southwest China. No deviation from Hardy-Weinberg equilibrium was observed in all of the 21 STR loci. A total of 241 alleles were observed with allele frequencies ranging from 0.0011 to 0.5418. The cumulative power of discrimination and the cumulative probability of exclusion were 0.9999999999999999999999999 and 0.999999996, respectively. The results of genetic distance, neighbor-joining tree, principal component plots, and multidimensional scaling analysis revealed that the Wanzhou Han had more genetic differences when compared with Kazakh and Uyghur populations from Xinjiang than other included reference populations. In summary, the results in forensic characteristic analyses indicated that the 21 STRs are highly polymorphic and can be served as a useful tool in forensic routine practices. The population comparison indicated that close geographic or ethnic origin groups had a strong genetic affinity with each other.

     

Analysis of ancestry informative markers in three main ethnic groups from Ecuador supports a trihybrid origin of Ecuadorians

Ancestry inference is traditionally done using autosomal SNPs that present great allele frequency differences among populations from different geographic regions. These ancestry informative markers (AIMs) are useful for determining the most likely biogeographic ancestry or population of origin of an individual. Due to the growing interest in AIMs and their applicability in different fields, commercial companies have started to develop AIM multiplexes targeted for Massive Parallel Sequencing platforms.This project focused on the study of three main ethnic groups from Ecuador (Kichwa, Mestizo, and Afro-Ecuadorian) using the Precision ID Ancestry panel (Thermo Fisher Scientific). In total, 162 Ecuadorian individuals were investigated. The Afro-Ecuadorian and Mestizo showed higher average genetic diversities compared to the Kichwa. These results are consistent with the highly admixed nature of the first two groups. The Kichwa showed the highest proportion of Native Amerindian (NAM) ancestry relative to the other two groups. The Mestizo had an admixed ancestry of NAM and European with a larger European component, whereas the Afro-Ecuadorian were highly admixed presenting proportions of African, Native Amerindian, and European ancestries. The comparison of our results with previous studies based on uniparental markers (i.e. Y chromosome and mtDNA) highlighted the sex-biased admixture process in the Ecuadorian Mestizo.Overall, the data generated in this work represent one important step to assess the application of ancestry inference in admixed populations in a forensic context.     

A comprehensive exploration of the genetic legacy and forensic features of Afghanistan and Pakistan Mongolian-descent Hazara

Afghanistan and Pakistan are rich with a complex landscape of culture, linguistics, ethnicity and genetic legacy at the crossroads between Indian-Subcontinent and Central Asia. Hazara people have historically been suggested to be Mongolian decedents but seldom been genetically studied. To dissect the genetic structure and explore the forensic characteristics of Hazara people, we first genotyped 30 Insertion/deletion (Indel) markers in 468 samples from 2 aboriginal Hazara populations from Afghanistan and Pakistan, and 100 East Asian comparative Bouyei samples using the Investigator® DIPplex kit. Subsequently, we carried out a comprehensive population genetic analysis from four different datasets: 8895 30-Indel genotype data from 51 populations, 15,895 30-Indel allele frequency data from 98 populations, 1048 genotypes of 993 STRs and Indels from 53 HGDP populations and 2068 whole-genomes (621,799 single nucleotide polymorphisms) from 165 worldwide Human origin reference populations, to further unravel the genetic complexity between Hazara and worldwide human populations using various statistical analysis. We find that 30 Indels are in accordance with HWE, and informative and polymorphic in both Central Asians Hazara and East Asian Bouyei populations. The forensic combined probability of exclusion is larger than 0.9943 and the cumulative power of discrimination is larger than 0.99999999999936. These forensic parameters show the high level of diversity, which makes the Indel amplification system suitable for forensic routine work and may be used as a supplementary assay for routine forensic investigation. The results from pairwise genetic distances, MDS, PCA, and phylogenetic relationship reconstruction demonstrate that present-day Hazaras are genetically closer to the Turkic-speaking populations (Uyghur, Kazakh, and Kyrgyz) residing in northwest China than with other Central/South Asian populations and Mongolian. Outgroup and admixture f_3, f₄, f₄-ratio, qpWave, and qpAdm results further demonstrate that Hazara shares more alleles with East Asians than with other Central Asians and carries 57.8% Mongolian-related ancestry. Overall, our findings suggest that Hazaras have experienced genetic admixture with the local or neighboring populations and formed the current East-West Eurasian admixed genetic profile after their separation from the Mongolians.     

Population genetics,diversity, forensic characteristics of four Chinese populations inferred from X-chromosomal short tandem repeats

We genotyped 19 X-STRs included in the AGCU X19 kit in 712 unrelated Chinese individuals from four populations (Li, Hui, Tibetan, and Han) and then merged with 4156 previously genotyped subjects from 19 populations to investigate genetic relationships and population structure, as well as the association between the genetic affinity and language classification. The combined mean paternity exclusion chances and the combined probabilities of discrimination based on single allele frequencies of 19-X-STRs and haplotype frequencies of seven linkage groups were high, indicating that this set of markers was very polymorphic in the four populations studied. Therefore, this panel can complement autosomal or uniparental markers in kinship analysis and complex deficient paternity testing. Subsequently, population differentiation analyses among 23 populations based on 19 STRs and 15 populations based on over 62 million single nucleotide polymorphisms consistently demonstrated that genetic stratifications exist between the different language-speaking populations, especially Tibeto-Burman-speaking, Tungusic and Turkic-speaking populations. Our newly studied populations are genetically close to ethnolinguistically adjacent populations. Our datasets can and should be used as an allele and haplotype frequencies reference database to facilitate the use of 19-X-STRs panel in routine forensic practice.     

Phylogenetic analysis among 27 Chinese populations and genetic polymorphisms of 20 autosomal STR loci in a Chinese Uyghur ethnic minority group

Allele frequency data and forensic statistical parameters were determined for 20 autosomal short tandem repeat (STR) loci of the PowerPlex 21 System in 214 unrelated healthy individuals of a Uyghur ethnic minority group living in Xinjiang province, northwest China. A total of 232 alleles were observed with the corresponding allele frequencies ranging from 0.0023 to 0.5304. All loci were consistent with Hardy–Weinberg equilibrium (HWE) after the Bonferroni correction (p > 0.0025). The combined probability of exclusion, power of discrimination, probability of matching value were 0.999999999, 0.9999999999999999999999995, and 4.78246 × 10^?25, respectively. Our results revealed that the 20 STRs were highly polymorphic and informative, and could be suitable for forensic application, especially parentage test and personal identification. The further population comparison between the Uyghur and other 26 reference populations revealed that the loci of D13S317, TH01 and D6S1043 showed high ethnical specificity. Phylogenetic analysis based on 19 shared loci demonstrated that the Uyghur had a close genetic relationship with the Kazakh, but a distinct genetic distance with other Chinese populations from different ethnicity and regions.     

Evaluation of 12 Multi-InDel markers for forensic ancestry prediction in Asian populations

Various types of genetic markers have been applied to forensic ancestry inference. Biallelic markers, such as SNPs and InDels, have proven to be optimal choices except for the low information content provided by a single locus. Multi-InDel marker is defined as a specific DNA fragment with several InDel markers located tightly in the physical position. Previous research indicates that multi-InDel markers perform well in population analysis and ancestry inference because of higher degree of polymorphism and remarkable population differences. In this study, a panel consisting of 12 multi-InDel markers was employed to evaluate the general performance in forensic practice and the discrimination power for population analysis. Sample types encountered in routine forensic practice were genotyped to validate the feasibility of regular use. A population study was performed on a total of five Asian populations to verify the discrimination power. Moreover, a double-blind test for ancestry prediction was conducted to assess the predictive capability. In conclusion, these results revealed the significance of multi-InDel markers for population structure stratification. The present panel showed the potential as a valid complementary tool in forensic applications.     

Phylogenic analysis and forensic genetic characterization of Guizhou Miao tribes from 58 microareas via autosomal STR

Genetic polymorphism of 17 autosomal short tandem repeat (STR) loci, included in the PowerPlex®18D amplification kit, were analyzed in Miao tribes from 58 different sampling microareas (N = 5255) of Guizhou as well as two cities (N = 151) of Hunan, China. Allele frequencies and forensic efficiency parameters were calculated. Moreover, comprehensive population genetic comparisons among 91 nationwide populations and 174 Asian populations were conducted based on raw genotype data and allele frequency data, respectively. Our results of forensic efficiency parameters showed that the panel was a robust tool in forensic individual identification and paternity cases for this population. Genetic affinities were observed among most of the Miao tribes revealed by multidimensional scaling plot, principal component analysis, and neighboring-joining tree. The genetic distance between Miao tribes and Han nationalities were varies by different geographical positions. Some of the Miao tribes were genetically closer to the Hmong-Mien populations living in southeastern contiguous regions and even the Indochina. The result coincided with the migration or reverse migration routes for Miao nationality in modern history. This study of the Miao tribes from plenty of microareas in Guizhou would be useful in reconstructing the population history and establishing a more comprehensive forensic reference database.     

A single nucleotide polymorphism panel for individual identification and ancestry assignment in Caucasians and four East and Southeast Asian populations using a machine learning classifier

Single nucleotide polymorphism (SNP) profiling is an effective means of individual identification and ancestry inferences in forensic genetics. This study established a SNP panel for the simultaneous individual identification and ancestry assignment of Caucasian and four East and Southeast Asian populations. We analyzed 220 SNPs (125 autosomal, 17 X-chromosomal, 30 Y-chromosomal, and 48 mitochondrial SNPs) of the DNA samples from 563 unrelated individuals of five populations (89 Caucasian, 234 Taiwanese Han, 90 Filipino, 79 Indonesian and 71 Vietnamese) and 18 degraded DNA samples. Informativeness for assignment (In) was used to select ancestry informative SNPs (AISNPs). A machine learning classifier, support vector machine (SVM), was used for ancestry assignment. Of the 220 SNPs, 62 were individual identification SNPs (IISNPs) (51 autosomal and 11 X-chromosomal SNPs) and 191 were AISNPs (100 autosomal, 13 X-chromosomal, 30 Y-chromosomal, and 48 mitochondrial SNPs). The 51 autosomal IISNPs offered cumulative random match probabilities (cRMPs) ranging from 1.56 × 10−21 to 3.16 × 10−22 among these five populations. Using AISNPs with the SVM, the overall accuracy rate of ancestry inference achieved in the testing dataset between Caucasian, Taiwanese Han, and Filipino populations was 88.9%, whereas it was 70.0% between Caucasians and each of the four East and Southeast Asian populations. For the 18 degraded DNA samples with incomplete profiling, the accuracy rate of ancestry assignment was 94.4%. We have developed a 220-SNP panel for simultaneous individual identification and ethnic origin differentiation between Caucasian and the four East and Southeast Asian populations. This SNP panel may assist with DNA analysis of forensic casework.     

Using forensic microsatellites to decipher the genetic structure of linguistic and geographic isolates: A survey in the eastern Italian Alps

The study of geographically and/or linguistically isolated populations could represent a potential area of interaction between population and forensic genetics. These investigations may be useful to evaluate the suitability of loci which have been selected using forensic criteria for bio-anthropological studies. At the same time, they give us an opportunity to evaluate the efficiency of forensic tools for parentage testing in groups with peculiar allele frequency profiles. Within the frame of a long-term project concerning Italian linguistic isolates, we studied 15 microsatellite loci (Identifiler kit) comprising the CODIS panel in 11 populations from the north-eastern Italian Alps (Veneto, Trentino and Friuli Venezia Giulia regions). All our analyses of inter-population differentiation highlight the genetic distinctiveness of most Alpine populations comparing them either to each other or with large and non-isolated Italian populations. Interestingly, we brought to light some aspects of population genetic structure which cannot be detected using unilinear polymorphisms. In fact, the analysis of genotypic disequilibrium between loci detected signals of population substructure when all the individuals of Alpine populations are pooled in a single group. Furthermore, despite the relatively low number of loci analyzed, genetic differentiation among Alpine populations was detected at individual level using a Bayesian method to cluster multilocus genotypes. Among the various populations studied, the four linguistic minorities (Fassa Valley, Luserna, Sappada and Sauris) showed the most pronounced diversity and signatures of a peculiar genetic ancestry. Finally, we show that database replacement may affect estimates of probability of paternity even when the local database is replaced by another based on populations which share a common genetic background but which differ in their demographic history. These findings point to the importance of considering the demographic and cultural profile of populations in forensic applications, even in a context of substantial genetic homogeneity such as that of European populations.     

Forensic genetic analyses in isolated populations with examples of central European Valachs and Roma

Isolated populations present a constant threat to the correctness of forensic genetic casework. In this review article we present several examples of how analyzing samples from isolated populations can bias the results of the forensic statistics and analyses. We select our examples from isolated populations from central and southeastern Europe, namely the Valachs and the European Roma. We also provide the reader with general strategies and principles to improve the laboratory practice (best practice) and reporting of samples from supposedly isolated populations. These include reporting the precise population data used for computing the forensic statistics, using the appropriate θ correction factor for calculating allele frequencies, typing ancestry informative markers in samples of unknown or uncertain ethnicity and establishing ethnic-specific forensic databases.     

Genetic diversity and haplotype analysis of Guizhou Miao identified with 19 X-chromosomal short tandem repeats

We analyzed Chinese Miao population samples (n = 268) from Guizhou province, Southwest China, with 19 X-chromosomal short tandem repeats (STRs) included in the AGCU X19 amplification kit. The combined PE is 0.999999922 and the combined PDs in males and females are 0.9999999999999999999994 and 0.9999999999998, respectively. The mean paternity exclusion change values are larger than 0.99999996. The HDs in seven linkage groups vary from 0.9324 to 0.9968. Subsequently, comparison among different Chinese populations shows that the substructures of Chinese were significantly influenced by ethno-linguistic rather than geographical boundaries, including most prominently Turkic-speaking and Tibeto-Burman-speaking populations.