Defining mtDNA origins and population stratification in Rio de Janeiro

Maternal ancestry and lineages diversity of the Santander population from Colombia

Santander, located in the Andean region of Colombia, is one of the 32 departments of the country. Its population was shaped by intercontinental admixture between autochthonous native Americans, European settlers, and African slaves. To establish forensic databases of haplotype frequencies, the evaluation of population substructure is crucial to capture the genetic diversity in admixed populations. Total control region mitochondrial deoxyribonucleic acid haplotypes were determined for 204 individuals born in the seven provinces across the department. The maternal native heritage is highly preserved in Santander genetic background, with 90% of the haplotypes belonging to haplogroups inside A2, B4, C1, and D. Most native lineages are found broadly across the American continent, while some sub-branches are concentrated in Central America and north South America. Subtle European (6%) and African (4%) input was detected. In pairwise comparisons between provinces, relatively high FST values were found in some cases, although not statistically significant. Nonetheless, when provinces were grouped according to the principal component analysis results, significant differences were detected between groups. The database on mitochondrial deoxyribonucleic acid control region haplotype frequencies established here can be further used for populational and forensic purposes.

Population analysis of complete mitogenomes for 334 samples from El Salvador

The use of mitochondrial DNA (mtDNA) in the field of forensic genetics is widely spread mainly due to its advantages when identifying highly degraded samples. In this sense, massive parallel sequencing has made the analysis of the whole mitogenome more accessible, noticeably increasing the informativeness of mtDNA haplotypes. The civil war (1980-1992) in El Salvador caused many deaths and disappearances (including children) all across the country and the economic and social instability after the war forced many people to emigration. For this reason, different organizations have collected DNA samples from relatives with the aim of identifying missing people. Thus, we present a dataset containing 334 complete mitogenomes from the Salvadoran general population. To the best of our knowledge, this is the first publication of a nationwide forensic-quality complete mitogenome database of any Latin American country. We found 293 different haplotypes, with a random match probability of 0.0041 and 26.6 mean pairwise differences, which is similar to other Latin American populations, and which represent a marked improvement from the values obtained with just control region sequences. These haplotypes belong to 54 different haplogroups, being 91% of them of Native American origin. Over a third (35.9%) of the individuals carried at least a heteroplasmic site (excluding length heteroplasmies). Ultimately, the present database aims to represent mtDNA haplotype diversity in the general Salvadoran populations as a basis for the identification of people that disappeared during or after the civil war.

Whole mitochondrial genome analysis of Tai-Kadai-speaking populations in Southwest China

As a single matrilineal gene, human mitochondrial DNA plays a very important role in the study of population genetics. The whole mitogenome sequences of 287 individuals of the Tai-Kadai-speaking population in Guizhou were obtained. It was discovered that there were 82, 104, and 94 haplotypes in 83 Bouyei individuals, 107 Dong individuals, and 97 Sui individuals, respectively; and the haplotype diversity in Bouyei, Dong, and Sui groups was 1.000 ± 0.02, 0.9993 ± 0.0015, and 0.999 ± 0.002, respectively. The result of neutrality tests of the Tai-Kadai-speaking population in Guizhou showed significant negative values, and the analysis of mismatch distribution showed an obvious unimodal distribution. The results implied that Guizhou Tai-Kadai-speaking populations had high genetic diversities and may have experienced recent population expansion. In addition, the primary haplogroups of studied populations were M*, F, B, D, and R*, implying that they may origin from Southern China. The matrilineal genetic structure of the Tai-Kadai-speaking populations in Guizhou was analyzed by merging the mitogenome data of 79 worldwide populations as reference data. The results showed that there were close relationships between studied populations and other Tai-Kadai as well as some Austronesian populations in East and Southeast Asia. Overall, the mitogenome data generated in this study will provide important data for the study of genetic structure of Tai-Kadai speaking populations.

The Ancestry of Eastern Paraguay: A Typical South American Profile with a Unique Pattern of Admixture

Immigrants from diverse origins have arrived in Paraguay and produced important demographic changes in a territory initially inhabited by indigenous Guarani. Few studies have been performed to estimate the proportion of Native ancestry that is still preserved in Paraguay and the role of females and males in admixture processes. Therefore, 548 individuals from eastern Paraguay were genotyped for three marker sets: mtDNA, Y-SNPs and autosomal AIM-InDels. A genetic homogeneity was found between departments for each set of markers, supported by the demographic data collected, which showed that only 43% of the individuals have the same birthplace as their parents. The results show a sex-biased intermarriage, with higher maternal than paternal Native American ancestry. Within the native mtDNA lineages in Paraguay (87.2% of the total), most haplogroups have a broad distribution across the subcontinent, and only few are concentrated around the Paraná River basin. The frequency distribution of the European paternal lineages in Paraguay (92.2% of the total) showed a major contribution from the Iberian region. In addition to the remaining legacy of the colonial period, the joint analysis of the different types of markers included in this study revealed the impact of post-war migrations on the current genetic background of Paraguay.

Uniparental Lineages from the Oldest Indigenous Population of Ecuador: The Tsachilas

Together with Cayapas, the Tsachilas constitute the oldest population in the country of Ecuador and, according to some historians, they are the last descendants of the ancient Yumbos. Several anthropological issues underlie the interest towards this peculiar population: the uncertainty of their origin, their belonging to the Barbacoan linguistic family, which is still at the center of an intense linguistic debate, and the relations of their Yumbo ancestors with the Inca invaders who occupied their ancient territory. Our contribution to the knowledge of their complex past was the reconstruction of their genetic maternal and paternal inheritance through the sequencing of 70 entire mitochondrial genomes and the characterization of the non-recombinant region of the Y chromosome in 26 males. For both markers, we built comprehensive datasets of various populations from the surrounding geographical area, northwestern South America, NW, with a known linguistic affiliation, and we could then compare our sample against the overall variability to infer relationships with other Barbacoan people and with other NW natives. We found contrasting patterns of genetic diversity for the two markers, but generally, our results indicated a possible common origin between the Tsachilas, the Chachi, and other Ecuadorian and Colombian Barbacoans and are suggestive of an interesting ancient linkage to the Inca invaders in Yumbo country.

Polymorphisms and haplotypes in the Interleukin 17 Alfa gene: potential effect of smoking habits in the association with periodontitis and type 2 diabetes mellitus

Few studies evaluate interrelationships between periodontitis (P) and Type 2 Diabetes Mellitus (T2DM). The aim of this study is to investigate the genetic susceptibility to periodontitis alone, or concomitant with T2DM (as comorbidities), analyzing single nucleotide polymorphisms (SNPs) in the Interleukin 17 alpha (IL17A) gene, considering the biochemical profile and smoking habits on the subjects' periodontal status. We investigated 879 individuals divided into: T2DM subjects also affected by severe or moderate periodontitis (T2DM-P, n = 199); non-diabetics with severe or moderate periodontitis (PERIODONTITIS, n = 342); and healthy subjects (HEALTHY, n = 338). Subjects underwent complete periodontal examination, history of smoking habits, glycemic and lipid biochemical evaluation. DNA from buccal cells was utilized to genotype the SNPs rs2275913, rs3819024 and rs10484879. The impact of the subjects' biochemical profile was analyzed in their periodontal status. Each SNP was analyzed independently, and as haplotypes, by multiple logistic regressions, adjusted for covariates, and also stratifying the groups by age, sex and smoking habits. Independently of the periodontitis degree, poorly-controlled T2DM subjects showed worse glycemic and lipid profile. Multiple logistic regressions demonstrated that smokers and former-smokers carrying the GG genotype of rs3819024 seemed to have higher risk for T2DM-Periodontitis (OR = 6.33; 95% CI = 1.26-31.77, p = 0.02), and mainly for T2DM alone (OR = 5.11; 95% CI = 1.37-19.06, p = 0.01), than never smokers. We found the potential effect of smoking habits in the association of IL17A-rs3819024-GG with diseased phenotypes. Because the observed wide confidence intervals, further studies enrolling larger populations, and SNPs' functional evaluations are needed to better understand our findings.

Searching for the roots of the first free African American community

San Basilio de Palenque is an Afro-descendant community near Cartagena, Colombia, founded in the sixteenth century. The recognition of the historical and cultural importance of Palenque has promoted several studies, namely concerning the African roots of its first inhabitants. To deepen the knowledge of the origin and diversity of the Palenque parental lineages, we analysed a sample of 81 individuals for the entire mtDNA Control Region as well as 92 individuals for 27 Y-STRs and 95 for 51 Y-SNPs. The results confirmed the strong isolation of the Palenque, with some degree of influx of Native American maternal lineages, and a European admixture exclusively mediated by men. Due to the high genetic drift observed, a pairwise F_ST analysis with available data on African populations proved to be inadequate for determining population affinities. In contrast, when a phylogenetic approach was used, it was possible to infer the phylogeographic origin of some lineages in Palenque. Contradicting previous studies indicating a single African origin, our results evidence parental genetic contributions from widely different African regions.

Evaluation of the Precision of Ancestry Inferences in South American Admixed Populations

Ancestry informative markers (AIMs) are used in forensic genetics to infer biogeographical ancestry (BGA) of individuals and may also have a prominent role in future police and identification investigations. In the last few years, many studies have been published reporting new AIM sets. These sets include markers (usually around 100 or less) selected with different purposes and different population resolutions. Regardless of the ability of these sets to separate populations from different continents or regions, the uncertainty associated with the estimates provided by these panels and their capacity to accurately report the different ancestral contributions in individuals of admixed populations has rarely been investigated. This issue is addressed in this study by evaluating different AIM sets. Ancestry inference was carried out in admixed South American populations, both at population and individual levels. The results of ancestry inferences using AIM sets with different numbers of markers among admixed reference populations were compared. To evaluate the performance of the different ancestry panels at the individual level, expected and observed estimates among families and their offspring were compared, considering that (1) the apportionment of ancestry in the offspring should be closer to the average ancestry of the parents, and (2) full siblings should present similar ancestry values. The results obtained illustrate the importance of having a good balance/compromise between not only the number of markers and their ability to differentiate ancestral populations, but also a balanced differentiation among reference groups, to obtain more precise values of genetic ancestry. This work also highlights the importance of estimating errors associated with the use of a limited number of markers. We demonstrate that although these errors have a moderate effect at the population level, they may have an important impact at the individual level. Considering that many AIM-sets are being described for inferences at the individual level and not at the population level, e.g., in association studies or the determination of a suspect's BGA, the results of this work point to the need of a more careful evaluation of the uncertainty associated with the ancestry estimates in admixed populations, when small AIM-sets are used.

Mutational data and population profiling of 23 Y-STRs in three Brazilian populations

Y-chromosomal STRs are important markers in forensic genetics, due to some peculiar characteristics. The absence of recombination makes them a useful tool to infer kinship in complex cases involving distant paternal relatives, or to infer paternal bio-geographic ancestry. The presence of a single copy, being transmitted from father to son, allow tracing mutational events in Y-STRs without ambiguity. For the statistical interpretation of forensic evidences based on Y-STR profiles, it is necessary to have estimates on both mutation rates and haplotype frequencies. In this work, 407 father-son duos from São Paulo and Rio de Janeiro states and 204 unrelated individuals from Manaus were analyzed. Haplotype frequencies and mutation rates for the Y-STRs from the PowerPlex Y23 commercial kit were estimated. Thirty-six mutations were observed in 15 of the 22 Y-STRs analyzed, for an average mutation rate of 3.84 × 10^-3 (95 % CI 2.69 × 10^-3 to 5.32 × 10^-3). All mutations in GAAA repeats occurred in alleles with 13 or more uninterrupted units. Mutations in GATA repeats were observed in alleles with 9-17 uninterrupted units. An analysis carried out in different father's age groups showed an increase of 2.48 times the mutation rate in the age group of 40-50 years, when compared to the 20-30 age group, in agreement with the described for autosomal STRs. A high haplotype diversity was found in the three Brazilian populations. Pairwise genetic distance analysis (F_ST) showed no significant differences between the three populations in this study, which were also close to populations with strong European influence. The highest distances among the Brazilian populations were with São Gabriel da Cachoeira, which has a high Native American ancestry.

Massively parallel sequencing of mitogenome sequences reveals the forensic features and maternal diversity of tai-kadai-speaking hlai islanders

As a single maternally inherited locus, human mitochondrial DNA (mtDNA) is geographically arranged and plays a key role in forensic applications. Hlai population has been evidenced as the most typical and unmixed representative of the Tai-Kadai-speaking populations via genome-wide analyses. However, forensic features and maternal diversity of the complete mitogenomes in this Tai-Kadai ancestrally related population are scarce. Thus, we sequenced the complete mitogenomes in 127 Hainan Hlais and found 109 distinct haplotypes belonging to 43 terminal haplogroups resulting in the haplotype diversity of 0.9970. Our results of comprehensive population comparisons showed that Hlai islanders had a close genetic affinity with Tai-Kadai-speaking populations from Southeast Asia, which is consistent with the back-migration of Chinese Neolithic farmers into this region via the inland route. Besides, maternally genetic evidence further revealed a close genetic relationship between Tai-Kadai-speaking and Austronesian-speaking populations when only East Asian dataset was considered, which is consistent with the common origin from Yangtze rice farmers and then spread southward along the inland and coastal routes, respectively. In the reconstructed phylogenetic tree and median-joining networks, the vast majority of Hlais were clustered in exclusive clades, which demonstrated that Hlai people probably had undergone founder effect or genetic bottleneck in their history, and remained genetically isolated for a long time. Collectively, Hainan Hlai did not exhibit detectable maternal gene flow from surrounding or incoming populations. Mitogenome information generated in this study is a contribution in mitigating the underrepresentation of Chinese data in forensic mitogenetics and will assist geography-, metapopulation-, as well as phylogeny-based queries.

Whole mitochondrial genome analysis of highland Tibetan ethnicity using massively parallel sequencing

Mitochondrial DNA (mtDNA) is a key player in numerous multifaceted and intricate biological processes and plays a pivotal role in dissecting the peopling of different populations, due to its maternally inherited property and comparatively high mutation rate. In this study, 119 Tibetan individuals from the Muli Tibetan Autonomous County of China (average altitude above 3,000 m) were employed in mitochondrial genome (mitogenome) sequencing by massively parallel sequencing (MPS) techniques using the Precision ID mtDNA Whole Genome Panel on an Ion S5XL system. The dataset presented 88 distinct haplotypes, resulting in the haplotype diversity of 0.9909. The majority of haplotypes were assigned to East Asian lineages and the distribution of haplogroups of Muli Tibetan significantly differed from reference Tibetan populations. The maximum parsimony phylogeny reconstructed by 119 newly generated mitogenomes revealed 12 major Muli Tibetan lineages. Intriguingly, a Sherpa-specific sub-haplogroup A15c1 with the lack of mutations at 4216 and 15,924 was discerned in our dataset, which suggested that the maternal gene pool of Sherpas may derive from Tibetan populations. The shared haplogroups between Muli Tibetan and lowland Han Chinese hinted that these lineages may derive from non-Tibetans and have already differentiated before their arrival on the Tibetan Plateau. Furthermore, extensive pairwise population comparisons displayed that Muli Tibetan had a closer genetic relationship with ethnically or linguistically close Nyingtri Tibetan, Nyingtri Lhoba and Chamdo Tibetan populations. Genetic affinity was also observed between the Muli Tibetan and North Han Chinese. Collectively, the results generated in this study enriched the existing forensic mtDNA database and raised additional interest in the application of whole mitogenome sequencing in forensic investigations.

Mitochondrial DNA control region haplotypes and haplogroup diversity in a sample from Brasília, Federal District, Brazil

Brazilians form one of the most heterogeneous populations in the world, as the result of five centuries of miscegenation between its native populations with migrants from Europe, Africa and Asia. The present study intended to characterize the frequencies of mtDNA haplotypes in a dataset of 306 individuals from Brasília, Federal District of Brazil. Brasília was built from scratch in the late 1950s and its construction attracted migrants from different regions of Brazil, mostly from Central-West, Northeast and Southeast regions. Due to its formation, its population is admixed. The goal of this study was to collect mtDNA population data and contribute to databases for a better use of mtDNA for forensic purposes. The haplotypes are available at EMPOP website under accession number EMP00695.