The Mediterranean Sea as a barrier to gene flow: evidence from variation in and around the F7 and F12 genomic regions

<p>Abstract</p> <p>Background</p> <p>The Mediterranean has a long history of interactions among different peoples. In this study, we investigate the genetic relationships among thirteen population samples from the broader Mediterranean region together with three other groups from the Ivory Coast and Bolivia with a particular focus on the genetic structure between North Africa and South Europe. Analyses were carried out on a diverse set of neutral and functional polymorphisms located in and around the coagulation factor VII and XII genomic regions (F7 and F12).</p> <p>Results</p> <p>Principal component analysis revealed a significant clustering of the Mediterranean samples into North African and South European groups consistent with the results from the hierarchical AMOVA, which showed a low but significant differentiation between groups from the two shores. For the same range of geographic distances, populations from each side of the Mediterranean were found to differ genetically more than populations within the same side. To further investigate this differentiation, we carried out haplotype analyses, which provided partial evidence that sub-Saharan gene flow was higher towards North Africa than South Europe.</p> <p>Conclusions</p> <p>As there is no consensus between the two genomic regions regarding gene flow through the Sahara, it is hard to reach a solid conclusion about its role in the differentiation between the two Mediterranean shores and more data are necessary to reach a definite conclusion. However our data suggest that the Mediterranean Sea was at least partially a barrier to gene flow between the two shores.</p

Population genetic dynamics in the French Guiana region

International audienceThree sets of genetic markers (blood group plus protein polymorphisms, mitochondrial DNA and Y-chromosome) were compared in four French Guiana and one Brazilian Amerindian populations. Spearman's rank correlation coefficient between five gene diversity statistics and historical or present-day population sizes showed significant values, indicating loss of diversity due to population bottlenecks. The three sets of markers furnished distinct admixture estimates, and the blood group plus protein polymorphisms could have overestimated the European contribution to their gene pool. Correspondence analysis distinguished the coastal from the interior populations, possibly reflecting past migration events

Molecular Variation in Endothelial Nitric Oxide Synthase Gene (eNOS) in Western Mediterranean Populations

Endothelial nitric oxide synthase (eNOS or NOS3) is the main responsible for nitric oxide (NO) production in vascular system and different polymorphisms have been identified in epidemiological studies. Trying to test the eNOS genetic variation in general populations we studied the 27-bp VNTR in intron 4 and G894T substitution in exon 7 markers in 6 Western Mediterranean populations (3 from Iberian Peninsula, 1 from North Africa, and 2 from Sardinia) and a sample from Ivory Coast. The VNTR frequencies in Western Mediterranean and Ivory Coast fit well into the ranges previously described for Europeans and Sub-Saharans respectively, and a typical African allele has been detected in polymorphic frequencies in the Berber sample. The G894T substitution presents the highest frequencies described for the T allele in the North Mediterranean populations. Linkage disequilibrium is present between both markers in all populations except in the Ivory Coast sample. The variation found for these polymorphisms indicates that they may be a useful tool for population studies even at microgeographical level

The imprint of the Slave Trade in an African American population: mitochondrial DNA, Y chromosome and HTLV-1 analysis in the Noir Marron of French Guiana

<p>Abstract</p> <p>Background</p> <p>Retracing the genetic histories of the descendant populations of the Slave Trade (16^th-19^thcenturies) is particularly challenging due to the diversity of African ethnic groups involved and the different hybridisation processes with Europeans and Amerindians, which have blurred their original genetic inheritances. The Noir Marron in French Guiana are the direct descendants of maroons who escaped from Dutch plantations in the current day Surinam. They represent an original ethnic group with a highly blended culture. Uniparental markers (mtDNA and NRY) coupled with HTLV-1 sequences (<it>env </it>and LTR) were studied to establish the genetic relationships linking them to African American and African populations.</p> <p>Results</p> <p>All genetic systems presented a high conservation of the African gene pool (African ancestry: mtDNA = 99.3%; NRY = 97.6%; HTLV-1 e<it>nv </it>= 20/23; HTLV-1 LTR = 6/8). Neither founder effect nor genetic drift was detected and the genetic diversity is within a range commonly observed in Africa. Higher genetic similarities were observed with the populations inhabiting the Bight of Benin (from Ivory Coast to Benin). Other ancestries were identified but they presented an interesting sex-bias. Whilst male origins spread throughout the north of the bight (from Benin to Senegal), female origins were spread throughout the south (from the Ivory Coast to Angola).</p> <p>Conclusions</p> <p>The Noir Marron are unique in having conserved their African genetic ancestry, despite major cultural exchanges with Amerindians and Europeans through inhabiting the same region for four centuries. Their maroon identity and the important number of slaves deported in this region have maintained the original African diversity. All these characteristics permit to identify a major origin located in the former region of the Gold Coast and the Bight of Benin; regions highly impacted by slavery, from which goes a sex-biased longitudinal gradient of ancestry.</p

Diversité génétique de l’allèle O dans des populations berbères

Nous avons analysé le polymorphisme de l’allèle O chez 33 individus non apparentés de phénotype O d’une population berbère de l’oasis de Siwa en Égypte. Malgré le faible nombre d’individus étudiés, les résultats montrent un polymorphisme important de l’allèle O. Cette population a probablement eu des contacts avec d’autres populations malgré son isolement géographique. Siwa fut une étape importante pour les caravanes parcourant le désert ; elle fut soumise à de nombreux raids et conflits. Les fréquences des allèles O01 et O02 sont similaires à celles retrouvées dans une population berbère de l’Atlas marocain (Amizmiz). Trois nouveaux allèles ont été mis en évidence dans la population de Siwa. Ces résultats confirment tout l’intérêt d’étudier le polymorphisme moléculaire de l’allèle O pour mieux comprendre l’histoire génétique des populations.We analysed the O allele polymorphism in a sample of 33 Berbers from the Siwa population, all of them of phenotype O and unrelated to one another. The results show an important genetic diversity considering the limited number of individuals under study. The population must have been in contact with other people in spite of the geographical and cultural isolation. Siwa was an important stopping place for caravans in the desert: it was subjected to many raids and armed conflicts. The frequencies of the O01 and O02 alleles are similar to those in the Amizmiz Berbers in Morocco. Three new alleles were discovered in the Siwa population. These results confirm the importance of studying the molecular polymorphism of the O allele to better understand the genetic history of populations

French Guiana Amerindian demographic history as revealed by autosomal and Y-chromosome STRs.

International audienc

Uniparental (mtDNA, Y-chromosome) Polymorphisms in French Guiana and Two Related Populations - Implications for the Region's Colonization

International audienceBlood samples collected in four Amerindian French Guiana populations (Palikur, Emerillon, Wayampi and Kali'na) in the early 1980s were screened for selected mtDNA and Y-chromosome length polymorphisms, and sequenced for the mtDNA hypervariable segment I (HVS-I). In addition, two other Amerindian populations (Apalaí and Matsiguenga) were examined for the same markers to establish the genetic relationships in the area. Strong dissimilarities were observed in the distribution of the founding Amerindian haplogroups, and significant p-values were obtained from F(ST) genetic distances. Interpopulation similarities occurred mainly due to geography. The Palikur did not show obvious genetic similarity to the Matsiguenga, who speak the same language and live in a region from where they could have migrated to French Guiana. The African-origin admixture observed in the Kali'na probably derives from historical contacts they had with the Bushinengue (Noir Marron), a group of escaped slaves who now lead independent lives in a nearby region. This analysis has identified significant clues about the Amerindian peopling of the North-East Amazonian region

Human Genomic Diversity Where the Mediterranean Joins the Atlantic

Throughout the past few years, a lively debate emerged about the timing and magnitude of the human migrations between the Iberian Peninsula and the Maghreb. Several pieces of evidence, including archaeological, anthropological, historical, and genetic data, have pointed to a complex and intermingled evolutionary history in the western Mediterranean area. To study to what extent connections across the Strait of Gibraltar and surrounding areas have shaped the present-day genomic diversity of its populations, we have performed a screening of 2.5 million single-nucleotide polymorphisms in 142 samples from southern Spain, southern Portugal, and Morocco. We built comprehensive data sets of the studied area and we implemented multistep bioinformatic approaches to assess population structure, demographic histories, and admixture dynamics. Both local and global ancestry inference showed an internal substructure in the Iberian Peninsula, mainly linked to a differential African ancestry. Western Iberia, from southern Portugal to Galicia, constituted an independent cluster within Iberia characterized by an enriched African genomic input. Migration time modeling showed recent historic dates for the admixture events occurring both in Iberia and in the North of Africa. However, an integrative vision of both paleogenomic and modern DNA data allowed us to detect chronological transitions and population turnovers that could be the result of transcontinental migrations dating back from Neolithic times. The present contribution aimed to fill the gaps in the modern human genomic record of a key geographic area, where the Mediterranean and the Atlantic come together

Rapidly mutating Y-STRs in rapidly expanding populations: Discrimination power of the Yfiler Plus multiplex in northern Africa

The male-specific northern African genetic pool is characterised by a high frequency of the E-M81 haplogroup, which expanded in very recent times (2-3 kiloyears ago). As a consequence of their recent coalescence, E-M81 chromosomes often cannot be completely distinguished on the basis of their Y-STR profiles, unless rapidly-mutating Y-STRs (RM Y-STRs) are analysed. In this study, we used the Yfiler® Plus kit, which includes 7 RM Y-STRs and 20 standard Y-STR, to analyse 477 unrelated males coming from 11 northern African populations sampled from Morocco, Algeria, Libya and Egypt. The Y chromosomes were assigned to monophyletic lineages after the analysis of 72 stable biallelic polymorphisms and, as expected, we found a high proportion of E-M81 subjects (about 46%), with frequencies decreasing from west to east. We found low intra-population diversity indexes, in particular in the populations that experienced long-term isolation. The AMOVA analysis showed significant differences between the countries and between most of the 11 populations, with a rough differentiation between northwestern Africa and northeastern Africa, where the Egyptians Berbers from Siwa represented an outlier population. The comparison between the Yfiler® and the Yfiler® Plus network of the E-M81 Y chromosomes confirmed the high power of discrimination of the latter kit, thanks to higher variability of the RM Y-STRs: indeed, the number of chromosomes sharing the same haplotype was drastically reduced from 201 to 81 and limited, in the latter case, to subjects from the same population

Aporte aborigen y africano de diferentes regiones de la Argentina en Buenos Aires

En trabajos anteriores realizados en muestras poblacionales de la Región Metropolitana de Buenos Aires (RMBA) hemos observado un 15,2 % de aporte indígena (AI) y un 3,8% de africano (AA). En el presente estudio se analizó una muestra de 169 individuos provenientes de las regiones del noroeste (NOA), del nordeste (NEA) y del centro del país (CP, se excluye la RMBA) que fueron donantes en el Banco de Sangre de la Provincia de Buenos Aires. Esta muestra se adicionó a las previamente obtenidas de las mismas regiones en los hospitales de Clínicas e Italiano. El objetivo fue evaluar si existe una distribución diferencial del AI y el AA según la región de origen de los dadores. Para ello se determinaron los sistemas ABO, Rh, MNS, Diego, Duffy, Gm y Km. Las frecuencias génicas y haplotípicas fueron calculadas mediante métodos de máxima verosimilitud y la mezcla génica se calculó aplicando el programa ADMIX. La región con mayor AI fue NOA (49,5%) seguida por NEA (28,4%) y CP (17,2%), mientras que el AA fue similar en las tres regiones (NOA 3,2%, NEA 3,5% y CP 3,8).Asociación de Antropología Biológica de la República Argentina (AABRA