The phylogeography of Y-chromosome haplogroup H1a1a-M82 reveals the likely Indian origin of the European Romani populations

<div><p>Linguistic and genetic studies on Roma populations inhabited in Europe have unequivocally traced these populations to the Indian subcontinent. However, the exact parental population group and time of the out-of-India dispersal have remained disputed. In the absence of archaeological records and with only scanty historical documentation of the Roma, comparative linguistic studies were the first to identify their Indian origin. Recently, molecular studies on the basis of disease-causing mutations and haploid DNA markers (i.e. mtDNA and Y-chromosome) supported the linguistic view. The presence of Indian-specific Y-chromosome haplogroup H1a1a-M82 and mtDNA haplogroups M5a1, M18 and M35b among Roma has corroborated that their South Asian origins and later admixture with Near Eastern and European populations. However, previous studies have left unanswered questions about the exact parental population groups in South Asia. Here we present a detailed phylogeographical study of Y-chromosomal haplogroup H1a1a-M82 in a data set of more than 10,000 global samples to discern a more precise ancestral source of European Romani populations. The phylogeographical patterns and diversity estimates indicate an early origin of this haplogroup in the Indian subcontinent and its further expansion to other regions. Tellingly, the short tandem repeat (STR) based network of H1a1a-M82 lineages displayed the closest connection of Romani haplotypes with the traditional scheduled caste and scheduled tribe population groups of northwestern India.</p> </div

The Phylogeography of Y-Chromosome Haplogroup H1a1a-M82 Reveals the Likely Indian Origin of the European Romani Populations

Linguistic and genetic studies on Roma populations inhabited in Europe have unequivocally traced these populations to the Indian subcontinent. However, the exact parental population group and time of the out-of-India dispersal have remained disputed. In the absence of archaeological records and with only scanty historical documentation of the Roma, comparative linguistic studies were the first to identify their Indian origin. Recently, molecular studies on the basis of disease-causing mutations and haploid DNA markers (i.e. mtDNA and Y-chromosome) supported the linguistic view. The presence of Indianspecific Y-chromosome haplogroup H1a1a-M82 and mtDNA haplogroups M5a1, M18 and M35b among Roma has corroborated that their South Asian origins and later admixture with Near Eastern and European populations. However, previous studies have left unanswered questions about the exact parental population groups in South Asia. Here we present a detailed phylogeographical study of Y-chromosomal haplogroup H1a1a-M82 in a data set of more than 10,000 global samples to discern a more precise ancestral source of European Romani populations. The phylogeographical patterns and diversity estimates indicate an early origin of this haplogroup in the Indian subcontinent and its further expansion to other regions. Tellingly, the short tandem repeat (STR) based network of H1a1a-M82 lineages displayed the closest connection of Romani haplotypes with the traditional scheduled caste and scheduled tribe population groups of northwestern India

Phylogenetic network relating Y-STR haplotypes within haplogroup H1a1a -M82- of Roma with northwest Indian populations.

<p>The network was constructed using a median joining with MP (maximum parsimony) algorithm as implemented in the Network 4.6 program. The size of the circles is proportional to the number of samples. SC = Scheduled Caste and ST = Scheduled Tribe.</p

Y-chromosomal haplogroup H1a1a-M82 founder analysis for Roma.

<p>Different founders were identified based on the Network analysis (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048477#pone.0048477.s001" target="_blank">Text S1</a>). The age was estimated from the ρ statistic (the mean number of mutations from the assumed root of each and every founder), using a 25-year generation time and the TD statistic, assuming a mutation rate of 6.9×10⁻⁴<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048477#pone.0048477-Zhivotovsky1" target="_blank">[11]</a>, based on variation at 15 common Y-STR loci.</p

Analysis of Molecular Variance (AMOVA) using Y-STRs between groups of populations categorized on the basis of geography.

<p>Analysis of Molecular Variance (AMOVA) using Y-STRs between groups of populations categorized on the basis of geography.</p

Measure of Genetic Diversity and expansion ages of haplogroup H1a1a-M82 among different population groups.

<p><i>n</i> = number of samples; <i>h</i> = number of haplotypes; HD = haplotype diversity; MPD = mean pairwise difference; AMD = average mutational distance from Roma modal haplotype.</p

Phylogenetic network relating Y-STR haplotypes within haplogroup H1a1a -M82.

<p>The network was constructed using a median joining with MP (maximum parsimony) algorithm as implemented in the Network 4.6 program. The size of the circles is proportional to the number of samples. The data used for comparison have been taken from the literature (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048477#pone.0048477.s001" target="_blank">Text S1</a>).</p

The average number of pairwise differences are shown within (PiX along diagonal) and between (PiXY above diagonal) populations; pairwise (δμ)2 genetic distance values are depicted below the diagonal.

<p>The average number of pairwise differences are shown within (PiX along diagonal) and between (PiXY above diagonal) populations; pairwise (δμ)2 genetic distance values are depicted below the diagonal.</p

The most parsimonious route of prehistoric expansion of Y-chromosomal haplogroup H1a1a-M82 and the recent out-of -India migration of European Roma ancestors.

<p>The most parsimonious route of prehistoric expansion of Y-chromosomal haplogroup H1a1a-M82 and the recent out-of -India migration of European Roma ancestors.</p