Publications by authors named "Ajai K Pathak"

8 Publications

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Unraveling a fine-scale high genetic heterogeneity and recent continental connections of an Arabian Peninsula population.

Eur J Hum Genet 2021 Mar 22. Epub 2021 Mar 22.

Department of Genetics and Bioinformatics, Dasman Diabetes Institute, Dasman, Kuwait.

Recent studies have showed the diverse genetic architecture of the highly consanguineous populations inhabiting the Arabian Peninsula. Consanguinity coupled with heterogeneity is complex and makes it difficult to understand the bases of population-specific genetic diseases in the region. Therefore, comprehensive genetic characterization of the populations at the finest scale is warranted. Here, we revisit the genetic structure of the Kuwait population by analyzing genome-wide single nucleotide polymorphisms data from 583 Kuwaiti individuals sorted into three subgroups. We envisage a diverse demographic genetic history among the three subgroups based on drift and allelic sharing with modern and ancient individuals. Furthermore, our comprehensive haplotype-based analyses disclose a high genetic heterogeneity among the Kuwaiti populations. We infer the major sources of ancestry within the newly defined groups; one with an obvious predominance of sub-Saharan/Western Africa mostly comprising Kuwait-B individuals, and other with West Eurasia including Kuwait-P and Kuwait-S individuals. Overall, our results recapitulate the historical population movements and reaffirm the genetic imprints of the legacy of continental trading in the region. Such deciphering of fine-scale population structure and their regional genetic heterogeneity would provide clues to the uncharted areas of disease-gene discovery and related associations in populations inhabiting the Arabian Peninsula.
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http://dx.doi.org/10.1038/s41431-021-00861-6DOI Listing
March 2021

Historic migration to South Asia in the last two millennia: A case of Jewish and Parsi populations.

J Biosci 2019 Jul;44(3)

Estonian Biocentre, Institute of Genomics, University of Tartu, Riia 23b, Tartu 51010, Estonia.

The South Asian populations have a mosaic of ancestries likely due to the interactions of long-term populations of the landmass and those of East andWest Eurasia. Apart from prehistoric dispersals, there are some known population movements to India. In this study,we focussed on the migration of Jewish and Parsi populations on temporal and spatial scales. The existence of Jewish and Parsi communities in India are recorded since ancient times. However, due to the lack of high-resolution genetic data, their origin and affiliation with other Indian and non-Indian populations remains shrouded in legends. Earlier genetic studies on populations of Indian Jews have found evidence for a minor shared ancestry of Indian Jews with Middle Eastern (Jews) populations, whereas for Parsis, the Iranian link was proposed. Recently, in our high-resolution study, we were able to quantify the admixture dynamics of these groups, which has suggested a male-biased admixture. Here, we added the newly available ancient samples and revisited the interplay of genes and cultures. Thus, in this study we reconstructed a broad genetic profile of Indian Jews and Parsis to paint a fine-grained picture of these ethnic groups.
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July 2019

Shifts in the Genetic Landscape of the Western Eurasian Steppe Associated with the Beginning and End of the Scythian Dominance.

Curr Biol 2019 07 11;29(14):2430-2441.e10. Epub 2019 Jul 11.

A. Kh. Margulan Institute of Archaeology, 44 Dostyk Avenue, Almaty 480100, Kazakhstan.

The Early Iron Age nomadic Scythians have been described as a confederation of tribes of different origins, based on ancient DNA evidence [1-3]. It is still unclear how much of the Scythian dominance in the Eurasian Steppe was due to movements of people and how much reflected cultural diffusion and elite dominance. We present new whole-genome sequences of 31 ancient Western and Eastern Steppe individuals, including Scythians as well as samples pre- and postdating them, allowing us to set the Scythians in a temporal context (in the Western, i.e., Ponto-Caspian Steppe). We detect an increase of eastern (Altaian) affinity along with a decrease in eastern hunter-gatherer (EHG) ancestry in the Early Iron Age Ponto-Caspian gene pool at the start of the Scythian dominance. On the other hand, samples of the Chernyakhiv culture postdating the Scythians in Ukraine have a significantly higher proportion of Near Eastern ancestry than other samples of this study. Our results agree with the Gothic source of the Chernyakhiv culture and support the hypothesis that the Scythian dominance did involve a demic component.
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http://dx.doi.org/10.1016/j.cub.2019.06.019DOI Listing
July 2019

Author Correction: The genetic legacy of continental scale admixture in Indian Austroasiatic speakers.

Sci Rep 2019 Apr 10;9(1):6104. Epub 2019 Apr 10.

Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu, 51010, Estonia.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-019-42195-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6456613PMC
April 2019

Ancestry-Specific Analyses Reveal Differential Demographic Histories and Opposite Selective Pressures in Modern South Asian Populations.

Mol Biol Evol 2019 08;36(8):1628-1642

Institute of Genomics, University of Tartu, Tartu, Estonia.

Genetic variation in contemporary South Asian populations follows a northwest to southeast decreasing cline of shared West Eurasian ancestry. A growing body of ancient DNA evidence is being used to build increasingly more realistic models of demographic changes in the last few thousand years. Through high-quality modern genomes, these models can be tested for gene and genome level deviations. Using local ancestry deconvolution and masking, we reconstructed population-specific surrogates of the two main ancestral components for more than 500 samples from 25 South Asian populations and showed our approach to be robust via coalescent simulations. Our f3 and f4 statistics-based estimates reveal that the reconstructed haplotypes are good proxies for the source populations that admixed in the area and point to complex interpopulation relationships within the West Eurasian component, compatible with multiple waves of arrival, as opposed to a simpler one wave scenario. Our approach also provides reliable local haplotypes for future downstream analyses. As one such example, the local ancestry deconvolution in South Asians reveals opposite selective pressures on two pigmentation genes (SLC45A2 and SLC24A5) that are common or fixed in West Eurasians, suggesting post-admixture purifying and positive selection signals, respectively.
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http://dx.doi.org/10.1093/molbev/msz037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6657728PMC
August 2019

The genetic legacy of continental scale admixture in Indian Austroasiatic speakers.

Sci Rep 2019 03 7;9(1):3818. Epub 2019 Mar 7.

Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu, 51010, Estonia.

Surrounded by speakers of Indo-European, Dravidian and Tibeto-Burman languages, around 11 million Munda (a branch of Austroasiatic language family) speakers live in the densely populated and genetically diverse South Asia. Their genetic makeup holds components characteristic of South Asians as well as Southeast Asians. The admixture time between these components has been previously estimated on the basis of archaeology, linguistics and uniparental markers. Using genome-wide genotype data of 102 Munda speakers and contextual data from South and Southeast Asia, we retrieved admixture dates between 2000-3800 years ago for different populations of Munda. The best modern proxies for the source populations for the admixture with proportions 0.29/0.71 are Lao people from Laos and Dravidian speakers from Kerala in India. The South Asian population(s), with whom the incoming Southeast Asians intermixed, had a smaller proportion of West Eurasian genetic component than contemporary proxies. Somewhat surprisingly Malaysian Peninsular tribes rather than the geographically closer Austroasiatic languages speakers like Vietnamese and Cambodians show highest sharing of IBD segments with the Munda. In addition, we affirmed that the grouping of the Munda speakers into North and South Munda based on linguistics is in concordance with genome-wide data.
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http://dx.doi.org/10.1038/s41598-019-40399-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6405872PMC
March 2019

The Genetic Ancestry of Modern Indus Valley Populations from Northwest India.

Am J Hum Genet 2018 12;103(6):918-929

Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia.

The Indus Valley has been the backdrop for several historic and prehistoric population movements between South Asia and West Eurasia. However, the genetic structure of present-day populations from Northwest India is poorly characterized. Here we report new genome-wide genotype data for 45 modern individuals from four Northwest Indian populations, including the Ror, whose long-term occupation of the region can be traced back to the early Vedic scriptures. Our results suggest that although the genetic architecture of most Northwest Indian populations fits well on the broader North-South Indian genetic cline, culturally distinct groups such as the Ror stand out by being genetically more akin to populations living west of India; such populations include prehistorical and early historical ancient individuals from the Swat Valley near the Indus Valley. We argue that this affinity is more likely a result of genetic continuity since the Bronze Age migrations from the Steppe Belt than a result of recent admixture. The observed patterns of genetic relationships both with modern and ancient West Eurasians suggest that the Ror can be used as a proxy for a population descended from the Ancestral North Indian (ANI) population. Collectively, our results show that the Indus Valley populations are characterized by considerable genetic heterogeneity that has persisted over thousands of years.
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http://dx.doi.org/10.1016/j.ajhg.2018.10.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288199PMC
December 2018