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Post by Admin on Jul 25, 2024 20:42:04 GMT
Council of Europe estimates: approximately 1.85 million Roma live in Romania (8.32% of the population). National strategy for Roma integration. Ancestry of Roma people from Romania. (A) Principal component analysis of Roma (ROM) from Romania in the context of other worldwide populations. The graph shows the two principal components and the variance explained by them. Roma fall in a cline between Indian and European populations. (B) Proportion of shared genetic drift between Roma and extant worldwide populations measured using outgroup f3 statistic in the form f3(Roma; X, YRI). (C) Clustering analysis showing K = 3 and K = 4. Roma show their own component in K = 4 (best supported model). Roma share more drift with Europeans than with South East Asian populations. See Supplementary Notes for the description of the population abbreviations; some coordinates were slightly displaced to avoid overlap.  The shaping of immunological responses through natural selection after the Roma Diaspora |
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Post by Admin on Jul 25, 2024 20:46:40 GMT
Origins, admixture and founder lineages in European Roma European Journal of Human Genetics volume 24, pages937–943 (2016) The Roma, also known as ‘Gypsies’, represent the largest and the most widespread ethnic minority of Europe. There is increasing evidence, based on linguistic, anthropological and genetic data, to suggest that they originated from the Indian subcontinent, with subsequent bottlenecks and undetermined gene flow from/to hosting populations during their diaspora. Further support comes from the presence of Indian uniparentally inherited lineages, such as mitochondrial DNA M and Y-chromosome H haplogroups, in a significant number of Roma individuals. However, the limited resolution of most genetic studies so far, together with the restriction of the samples used, have prevented the detection of other non-Indian founder lineages that might have been present in the proto-Roma population. We performed a high-resolution study of the uniparental genomes of 753 Roma and 984 non-Roma hosting European individuals. Roma groups show lower genetic diversity and high heterogeneity compared with non-Roma samples as a result of lower effective population size and extensive drift, consistent with a series of bottlenecks during their diaspora. We found a set of founder lineages, present in the Roma and virtually absent in the non-Roma, for the maternal (H7, J1b3, J1c1, M18, M35b, M5a1, U3, and X2d) and paternal (I-P259, J-M92, and J-M67) genomes. This lineage classification allows us to identify extensive gene flow from non-Roma to Roma groups, whereas the opposite pattern, although not negligible, is substantially lower (up to 6.3%). Finally, the exact haplotype matching analysis of both uniparental lineages consistently points to a Northwestern origin of the proto-Roma population within the Indian subcontinent. www.nature.com/articles/ejhg2015201 |
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Post by Admin on Jul 27, 2024 20:56:52 GMT
The Roma constitute one of the less documented human diaspora phenomena and an excellent model to evaluate the consequences of recent, multiple, and widespread dispersals and founder events. Social and political factors preclude the collection of precise census on the Roma, but they are acknowledged as the largest ethnic minority of Europe, with a population of up to 10 million people spread across the continent and mostly concentrated in Central and South-Eastern Europe.1, 2
Based on linguistic, cultural, anthropological, and genetic evidence, the proto-Roma population is thought to have originated on the Indian subcontinent.1, 3, 4, 5, 6, 7, 8, 9 Their migration routes probably encompassed Persia, Armenia, and the Balkans, with a large consensus on their arrival in Eastern Europe around a thousand years ago. Within a period of about two centuries, most Roma became sedentary in the Balkan Peninsula (Balkan Roma), in the relatively ethnically tolerant surroundings of the newly established Ottoman Empire.10 Some groups instead initiated a rapid migration that, by the end of the fifteenth century, had spread all across the European continent.1 Some, whose descendants are now known as Vlax Roma, moved across the Danube into the Danubian Principalities (nowadays Romania, Moldova, and parts of Hungary) where they were forced into slavery and divided into small groups. Another migration group out of the Balkan Peninsula, known as the Romungro, spread within the Austro-Hungarian Empire, where they were subject to attempts at assimilation.11 Other Roma groups continued moving in small groups into Central and Western Europe, where they were persecuted during Medieval times.1, 2 The abolition of Roma slavery in the Danubian Principalities Walachia and Moldova in the nineteenth century was followed by a mass migration, spreading the Vlax Roma into nearby countries and worldwide; most kept their endogamous rules and nomadic lifestyle.1, 3, 12 Recent Roma movements include migrations during the twentieth century triggered by the economic and political transformation of Eastern Europe.13
From a medical perspective, the genetic drift due to multiple founder events and endogamy in the Roma have increased the prevalence of Mendelian disorders caused by variants that are rare in other populations.14, 15 This complex demographic pattern might have also caused an increase of slightly deleterious variants in Roma groups as a result of a lower efficiency of purifying selection in purging deleterious alleles.16
The east-to-west genetic gradient observed in Roma populations is compatible with the postulated waves of migration within Europe.4, 7, 17, 18 All European Roma appear to descend from a low number of founders, and to have diverged into socially distinct endogamous groups after their arrival in Europe.14, 17, 18 The Indian component of the proto-Roma ancestry was supported by the identification of disease-causing mutations described in affected subjects in India and Pakistan.9, 15, 19, 20 Furthermore, the Roma show high frequencies of the H-M69 Y-chromosome4, 17, 21, 22 and mitochondrial DNA (mtDNA) M5, M18, M25, and M35 haplogroups4, 7, 17, 23, 24, 25 reported to have an Indian origin.25, 26, 27 Accordingly, studies of autosomal markers identified the Northwest of India as the most probable homeland of the European Roma.6
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Post by Admin on Aug 30, 2024 20:05:32 GMT
Despite these previous genetic studies, the Roma demographic history remains poorly understood. Y-chromosome and mtDNA lineages other than H and the M major haplogroups, respectively, have been attributed to genetic influences from populations along the proto-Roma migration way7, 21 without a more specific definition of their geographic origins. Furthermore, the small numbers and different sets of Y-STRs used in some studies, the insufficient and variable phylogenetic resolution, and the local character of the studies have prevented the reconstruction of a clear general picture.4, 22, 28, 29, 30 Moreover, studies that used a large number of markers were forced to reduce the phylogenetic resolution in order to compare with previous data.21 In addition to these limitations, the information of the Roma volunteers has been restricted to their geography tracks (ie, country of the sampling) ignoring the Roma group affiliation, which might have masked their complex population history.
To overcome these limitations, we analyzed uniparental lineages at high resolution in ~750 European Roma and ~980 non-Roma, in order to: (1) test whether there is a paternal and a maternal signature of the spread of Roma throughout Europe from the Balkan Peninsula; (2) revisit the potential role of geography and migration routes in the genetic structure of Roma; (3) determine the degree of gene flow from hosting populations to Roma and vice versa, and whether this gene flow is sex-biased; and (4) investigate the origins of the Roma ancestors within the Indian subcontinent.
Y-chromosome data
One thousand seven hundred and thirty-two unrelated individuals from Roma (N=748) and host populations (N=984) were genotyped for 131 SNPs. A group of 121 SNPs were typed as in Martinez-Cruz et al,32 six SNPs were genotyped in a single multiplex (Multiplex-2),33 and four SNPs were typed with individual TaqMan assays (L48, M458, L2, and L20). Nomenclature of the haplogroups is in accordance with the Y-Chromosome Consortium.34 All individuals were typed for a set of 19 STRs: 17 using the Yfiler kit (Applied Biosystems, Foster City, CA, USA) and two STRs included in Multiplex-2 (Martinez-Cruz et al33 and Supplementary Table S2). Some individuals from previous studies using lower number of markers17, 22 were genotyped to the same resolution level. All individuals with complete genotypes were submitted to the Y-HRD database (accession numbers YA004094–YA004107). As the Yfiler kit amplifies DYS385a/b simultaneously, avoiding the determination of each of the two alleles (a or b), DYS385a/b were excluded from all analyses performed.
mtDNA data
One thousand three hundred and forty-one samples from Roma (N=736) and host (N=605) populations were sequenced for both hypervariable segments (HVS) I and II of the control region (positions 16 001–573; Supplementary Table S3). In addition, 22 coding region SNPs were genotyped using the multiplex GenoCoRe22.35 For 12 samples (8 Spanish and 1 Slovakian Roma, and 3 Romanian non-Roma) only HVS-I could be sequenced. All complete sequences were submitted to EMPOP data base (under the accession number EMP00671). Mitochondrial haplogroup H was subtyped with a specific multiplex.33 Based on HVS and coding SNP data, individuals were assigned to mtDNA haplogroups using Haplogrep36 and the PhyloTree build 15.37 Owing to their phylogenetic uncertainty, indels at nucleotide positions 309, 315, and 16 193 were not taken into account.
Statistical analyses
Haplogroup and haplotype diversities, mean number of pairwise differences, and haplotype frequencies were calculated with Arlequin 3.4.38 The potential role of geography and migration routes was tested through analyses of molecular variance (AMOVAs) by pooling populations into country or migration route (see Supplementary Table S4). Greek and some Hungarian Roma were not included in the AMOVA, owing to the lack of detailed information about their migrational group, and Ukrainian Roma were also excluded because of their low sample size. We used FST distances for the Y-STRs and number of pairwise differences for mtDNA sequence data.
We defined founder lineages as lineages that the Roma most probably incorporated before their spread across Europe.7 Besides those already defined in Mendizabal et al,7 we include as founder lineages those haplogroups common in Roma (with frequencies over 5%) and not present or rare (<2%) in other Europeans. This definition of founder lineages is conservative and the founder nature of the lineages was further explored by studying their internal diversity. Namely, WIMP values (weighted intralineage mean pairwise differences)39 were estimated for the Roma founding lineages. Given the lower resolution of the Y-chromosome compared with the mtDNA in the definition of founders, we also built phylogenetic networks that were computed through sequential reduced median and median joining using the NETWORK v.4610 software package40 and were weighted for intra-haplogroup variance. The STR DYS389II was excluded from network analyses, as indicated by the Network software authors.40 In order to quantify admixture, we counted the exact matches of lineages classified as Roma or non-Roma in origin (ie, founder versus non-founder), assuming that exact matches represent the minimum gene flow between populations.
Under a simple stepping stone model in which sub-populations diverge from the neighboring sub-population, one expects genetic drift to accumulate (intra-population diversity decreased and genetic distances increased) with time. We tested correlations between internal diversity through WIMP (and genetic distances through FST) and geography, taking as a proxy a geographical point related to the Roma migration routes (Plovdiv in Bulgaria for Balkan Roma, Sibiu in Romania for Vlax Roma, Mezökövesd in Hungary for Central Roma, and Zaragoza in Spain for Western Roma) and independently for founder and non-founder lineages.
We constructed a Bayesian skyline plot (BSP) for M mtDNA lineages using BEAST.41 MCMC samples were based on a run of 300 000 000 generations, sampled every 30 000, discarding the first 30 000 000 generations as burn-in. We used a constant linear function of population size change, the HKY substitution model with a gamma site heterogeneity model, and a strict clock with a mean substitution rate of 9.883E−8 substitutions/site/year.42 Results reported were based on three independent runs showing identical results, with values of effective sample sizes higher than 200 for the parameters of interest, and after the visual evaluation of the convergence of the chains in stationary distributions by using the software Tracer v.1.6.43
Indian geographic areas were tested as putative origins for Roma lineages. We used a database with a total of 641 Indian Y-chromosomes from five regions,44 excluding the Northeastern populations, of Tibeto-Burman origin, and searched for identical matches of H-M52 Roma haplotypes. Identical matches for the mtDNA M lineages were assessed by comparison with the Indian database45 as in Medizabal et al.46 The weighted proportion of Roma lineages was used to infer the probabilities of origin.
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