Genetic heterogeneity of Berber peoples as a result of differential migration and admixture patterns

Trabajo presentado en la Annual Meeting of the Society for Molecular Biology and Evolution (SMBE 2015), celebrada en Viena del 12 al 16 de julio de 2015.The genome-wide structure of North African populations has been describe d as an amalgam of autochthonous, Middle Eastern, European and Sub-Saharan ancestries. The indigenous North African genetic ancestry has been estimated to be derived from a "back to Africa" migration dated in pre-Holocean times, and suggested to be in high est frequency in Berber populations, which are considered the autochthonous populations of North Africa.The lack of genetic knowledge on Berber populations in the current datasets prevents the understanding of the complex population processes occurred in North Africa. We have genotyped ~900,000 genome-wide SNPs in four different Berber groups and compared the results with other North African and neighboring groups. Our research reflects the complex structure of North African populations due to multiple admixture processes. Berber groups are very heterogeneous, showing different patterns of admixture and demographic histories, such as relevant endogamy levels within groups. The analysis of haplotype structure and the ancestral relationship between individuals has allowed us to estimate historical dates for some migrations coming from the Middle East and Sub-Saharan Africa into North Africa, affecting in an heterogeneous way the populations of the region. In addition, the comparison of autosomal and sexual chromosomes has shown a sexual bias in the admixture between North African populations and their surrounding neighbors, being the North African autochthonous component mainly derived from males and the European admixture driven by women. This study brings light to the origin of Berbers and the complex admixture processes in the population of North Africa.N

Genetic heterogeneity in Algerian human populations

The demographic history of human populations in North Africa has been characterized by complex processes of admixture and isolation that have modeled its current gene pool. Diverse genetic ancestral components with different origins (autochthonous, European, Middle Eastern, and sub-Saharan) and genetic heterogeneity in the region have been described. In this complex genetic landscape, Algeria, the largest country in Africa, has been poorly covered, with most of the studies using a single Algerian sample. In order to evaluate the genetic heterogeneity of Algeria, Y-chromosome, mtDNA and autosomal genome-wide makers have been analyzed in several Berber- and Arab-speaking groups. Our results show that the genetic heterogeneity found in Algeria is not correlated with geography or linguistics, challenging the idea of Berber groups being genetically isolated and Arab groups open to gene flow. In addition, we have found that external sources of gene flow into North Africa have been carried more often by females than males, while the North African autochthonous component is more frequent in paternally transmitted genome regions. Our results highlight the different demographic history revealed by different markers and urge to be cautious when deriving general conclusions from partial genomic information or from single samples as representatives of the total population of a region.This study was supported by the Ministerio de Economía y Competitividad grant CGL2013-44351-P and by Direcció General de Recerca, Generalitat de Catalunya grant 2014SGR866

Bidimensional plots based on uniparental genomes.

<p>PC analyses based on haplogroup data for Y-chromosome and mtDNA; and MDS analyses based on Y-STR haplotype data and on mtDNA sequence data. Abbreviations: ALG/ALG1: Algiers (this study), ALG2: Algiers (Y-chromosome; [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138453#pone.0138453.ref010" target="_blank">10</a>]), ORN1: Oran (present study), ORN2: Oran (Y-chromosome, [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138453#pone.0138453.ref021" target="_blank">21</a>]; mtDNA, [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138453#pone.0138453.ref017" target="_blank">17</a>]), RGB: Reguibate, ZNT: Zenata, MZB: Mozabite, TZO: Tizi Ouzou</p

Correlation plots of the ancestry proportions at k = 4 in the ADMIXTURE analysis comparing autosomes and X-chromosome SNPs.

<p>North African, sub-Saharan, Middle Eastern, and European ancestry proportions are shown in different plots. Solid black lines represent linear correlations between autosomal and X-chromosome components.</p

Y chromosome Analyses of Molecular Variance (AMOVA) in the Algerian samples.

<p>*** P<0.0001</p><p>* P<0.05; ns: not significant</p><p>North = Algiers, Oran, Tizi Ouzou</p><p>South = Mozabite, Reguibate, Zenata</p><p>Arabs = Reguibate, Algiers, Oran</p><p>Berbers = Zenata, Mozabite, Tizi Ouzou</p><p>^# Arabs without the Reguibate</p><p>Y chromosome Analyses of Molecular Variance (AMOVA) in the Algerian samples.</p

mtDNA Analyses of Molecular Variance (AMOVA) in the Algerian samples.

<p>*** P<0.0001; ns: not significant</p><p>North = Algiers, Oran (both)</p><p>South = Mozabite, Reguibate, Zenata</p><p>Arabs = Reguibate, Algiers, Oran1, Oran2</p><p>Berbers = Zenata, Mozabite</p><p>^# Arabs without the Reguibate</p><p>mtDNA Analyses of Molecular Variance (AMOVA) in the Algerian samples.</p

Geographic location of the Algerian samples genotyped in the present study (in red) and the samples obtained from the literature (in yellow).

<p>Geographic location of the Algerian samples genotyped in the present study (in red) and the samples obtained from the literature (in yellow).</p

Completing the genetic landscape of Nort Africa: Genomic chatracterization of berber peoples

Trabajo presentado en la 4th Meeting of the Spanish Society of the Evolutionary Biology (SESBE 2013) celebrada en Barcelona del 27 al 29 de noviembre de 2013.N

Plots for the analysis of genome-wide SNPs.

<p>PC analysis (upper figures) based on autosomal data, and X-chromosome SNPs. ADMIXTURE proportions (bottom figures) at k = 2,3, and 4 based on autosomal data and X-chromosome SNPs. Algeria, stands for general Algerian sample [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138453#pone.0138453.ref003" target="_blank">3</a>]; Mozabite, stands for the Algerian Berber Mozabites [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138453#pone.0138453.ref032" target="_blank">32</a>]; and Zenata, stands for Algerian Berber Zenata (present study).</p

Introducing the Algerian Mitochondrial DNA and Y-Chromosome Profiles into the North African Landscape

<div><p>North Africa is considered a distinct geographic and ethnic entity within Africa. Although modern humans originated in this Continent, studies of mitochondrial DNA (mtDNA) and Y-chromosome genealogical markers provide evidence that the North African gene pool has been shaped by the back-migration of several Eurasian lineages in Paleolithic and Neolithic times. More recent influences from sub-Saharan Africa and Mediterranean Europe are also evident. The presence of East-West and North-South haplogroup frequency gradients strongly reinforces the genetic complexity of this region. However, this genetic scenario is beset with a notable gap, which is the lack of consistent information for Algeria, the largest country in the Maghreb. To fill this gap, we analyzed a sample of 240 unrelated subjects from a northwest Algeria cosmopolitan population using mtDNA sequences and Y-chromosome biallelic polymorphisms, focusing on the fine dissection of haplogroups E and R, which are the most prevalent in North Africa and Europe respectively. The Eurasian component in Algeria reached 80% for mtDNA and 90% for Y-chromosome. However, within them, the North African genetic component for mtDNA (U6 and M1; 20%) is significantly smaller than the paternal (E-M81 and E-V65; 70%). The unexpected presence of the European-derived Y-chromosome lineages R-M412, R-S116, R-U152 and R-M529 in Algeria and the rest of the Maghreb could be the counterparts of the mtDNA H1, H3 and V subgroups, pointing to direct maritime contacts between the European and North African sides of the western Mediterranean. Female influx of sub-Saharan Africans into Algeria (20%) is also significantly greater than the male (10%). In spite of these sexual asymmetries, the Algerian uniparental profiles faithfully correlate between each other and with the geography.</p> </div