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

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

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 YSTRs (RM Y-STRs) are analysed. In this study, we used the Yfiler® Plus kit, which includes 7 RM Y-STRs, 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 intrapopulation 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 EM81 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