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Post by Admin on Apr 30, 2022 18:32:36 GMT
Estimating the date of European admixture in Roma We applied ROLLOFF from the ADMIXTURE Software Package to infer the date of gene flow between Roma and West Eurasians. We used CEU and TSI as the source of West Eurasian ancestry of Roma. Onge represented the South Asian source of Roma ancestry. ROLLOFF analysis, which is based on the exponential decay rate of admixture LD (Fig. 5), estimated that the date of the beginning of gene flow between West Eurasians and Roma occurred 29.883 +/− 2.353 generations ago, which means that Roma admixture with West Eurasians began approximately 800–935 years ago, taken into account that one generation equals 29 years [25]. According to the calculated weighted LD values (Fig. 6), analysis with ALDER gave similar results, ALDER dates this event to 28.45 +/−2.66 generations, 750–900 years ago. Fig. 5 ROLLOFF analysis results. Estimating the date of admixture of Roma with Europeans Fig. 6 ALDER analysis results. Weighted LD values computed in two separate 2-reference runs (Onge-CEU and Onge-TSI)
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Post by Admin on Apr 30, 2022 21:15:44 GMT
The source of European and South Asian Ancestry of Roma Previous tests were able to refer only to the West Eurasian ancestry of Roma, which includes also their admixture with West Eurasians before their exodus and during their migration period (populations of the Caucasus region, from the Middle East and also Central Asia) besides their admixture with Europeans. Using identity-by-descent segment analysis, we investigated the relationship of Europeans and the Roma. In order to find the South Asian origin of Romani people, we also investigated the IBD sharing between South Asians (Indian and Pakistani populations) and the Roma population. IBD analysis showed that Roma are closer related to European populations (Fig. 7a). Central European populations show a significantly higher share in the European ancestry of Roma than other regions of Europe. Average shared IBD segment length of Roma with Central European populations was 0.355 Mb. Eastern nations of Europe also show higher IBD sharing with Roma. The average length of shared IBD segments was 0.058 Mb. These findings are consistent with the demographic data of Roma and the suggested migration route the Roma took during their migration from South Asia into Europe. Fig. 7 Population relationships based on identity-by-descent sharing estimation. We computed the genome-wide pairwise average shared IBD length between certain groups. a Average shared IBD length between Roma and Europeans. b Average shared IBD length between Roma and South Asians Analyzing the source of South Asian ancestry of Roma revealed that Roma shows the highest relatedness to Northwest Indian groups throughout India with an average shared IBD segment length value of 0.132 Mb. However, Pakistani groups show also high relatedness to Roma compared to other regions of India with an average share of 0.087 Mb (Fig. 7b). The extent of IBD share between Roma and Pakistani populations was only approached by the IBD share of Roma with Central Indian groups, which was 0.066 Mb. Estimated homozygozity by descent in Roma As previous genome-wide SNP data based studies suggested, Roma population has descended from a small number of ancestors due to one or more founder events before reaching Europe. To estimate the extent of HBD segments in Roma using our extended Roma dataset, we applied also Refined IBD. We compared Roma to other worldwide populations using the HGDP data. We separated the HGDP dataset to regional groups as Europe, Africa, Americas (Native American groups), Western Asia, Eastern Asia and Central and Southern Asia. We found that Roma have the highest individual genome-wide HBD compared to worldwide populations, and also observed that individuals in our extended Roma dataset shows an even more high HBD than results of previous studies suggested. Native American and Western Asian individuals from the HGDP data showed a slightly similar extent of HBD (Fig. 8). Fig. 8 Individual genome-wide HBD estimation in Roma and HGDP populations. Grouping of HGDP populations are based on their regional location. Each point represents one individual. Color coding of Roma and HGDP groups are described in the figure legend
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Post by Admin on May 1, 2022 0:06:32 GMT
Discussion Population structure and ancestry estimation analyses using PCA and model-based clustering methods placed Roma between Europeans and South Asians. These analyses anticipated that European (or more precisely West Eurasian) ancestry in Roma is significant and its proportion is higher than the proportion of the Indian ancestry. Our results showed that Northwest and likely Central Indians are the closest to Roma from Indian groups and Pakistani groups might also play an important role in the South Asian ancestry of Roma.
We confirmed with formal test of admixture that Roma are a mixture of West Eurasians and South Asians as ancestry analyses suggested and proportion of West Eurasian Ancestry in Roma compared to Onge (as accurate surrogate for a South Asian ancestral group) was also estimated. The proportion of West Eurasian ancestry in Roma was approximately 81.08%, which value corresponded to the previously reported results.
We estimated the date of the West Eurasian admixture of Roma, which corresponds to the date of previous reports based on genome-wide marker data and also to historical data, which state that Romani arrived to the Balkans in the 11th and 12th centuries [2]. Admixture of Roma with West Eurasian populations occurred 750–900 years ago.
Using our extended datasets of Roma and Indian samples and involving also Pakistani samples in our tests, we performed IBD analysis. Our results suggest that the source of South Asian ancestry of Roma could expand to the Pakistani area. Our results showed an even greater involvement of Northwest Indian populations in the South Asian ancestry of the Romani people.
We also measured the individual genome-wide HBD in Roma compared to worldwide populations. Using significantly higher number of Roma individuals, which gives us a more representative sample size of Romani people, individual genome-wide HBD showed an even more degree than the results of previous studies suggested.
Using genome-wide SNP array data of extended number of Roma individuals and Indian groups confirmed that the South Asian source of Roma ancestry originates likely from the Northwest region of India, with a less significant involvement of Central India. Investigated Northwest and Central Indian ethnic groups were the Meghawal, Gujarati, Bhil, Jain, Gond, Kharia and Satnami. However, the area of origin might also extend to the region of Pakistan, the neighboring country of India, since Pakistani populations Balochi, Brahui, Burusho, Kalash, Makrani, Pashtun and Sindhi showed a significant relatedness to Romani people according to our analyses. We estimated that the West Eurasian ancestry of Roma originates mainly from East and Central European populations, represented here with Bosnians, Croatians, Czechs, Hungarians, Polish, Romanians, Serbians, Slovakians, Russian and Ukrainian. These data corresponds to the demographic data of European Roma.
Conclusion Using a uniquely high number of Roma samples and Indian groups allowed us to further investigate the ancestry of Romani people. This study aimed to refine the findings of previous studies that investigated the history of Roma based on genome-wide SNP array data.
In conclusion, the results of our study suggest that the West Eurasian ancestry of Roma originates likely from Central and East Europe, and Northwest India plays an even more important role in the South Asian ancestry of Roma than previous studies suggested. Our results also suggest that besides Northwest Indian populations, Pakistani populations play also an important role of the source of South Asian ancestry of Romani people. These new findings extend the South Asian origin of the Romani people making the Pakistani region a similarly important source of ancestry for the Romani people as the Indian subcontinent.
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