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.

Genetic variation patterns of ß-thalassemia in Western Andalusia (Spain) reveal a structure of specific mutations within the Iberian Peninsula.

BACKGROUND: Analyses of the genomic variation in the western Mediterranean population are being used to reveal its evolutionary history and to understand the molecular basis of particular diseases. AIM: To observe the ß-thalassemia mutational spectrum in western Andalusia, Spain, in the context of the Mediterranean. In addition, associations between disease and neutral gene variants within the ß-globin gene (HBB) were also evaluated. SUBJECTS AND METHODS: This study included 63 unrelated individuals diagnosed with ß-thalassemia. In addition, 97 unrelated, healthy subjects of the same territory were also analysed as proxies of the normal genetic background. Allele associations and population genetic structure analyses were performed using different methodologies. RESULTS: Data have revealed a rather restricted spectrum of ß-thalassemia mutations in the analysed sample. Although the detected variants fit well with the Mediterranean pattern, certain singularities support a structure of some specific ß-thalassemia alleles. The IVSI-1 (G > A) shows a strong regionalisation. The spatial correlogram revealed a typically narrow wave structure, presumably linked to genetic isolation and genetic drift. CONCLUSIONS: The long history of endemic malaria in the study territory, the rather high consanguinity rates among its autochthonous population, and other demographic features have been used here to understand the western Andalusian ß-thalassemia molecular portrait.

Paternal lineages in southern Iberia provide time frames for gene flow from mainland Europe and the Mediterranean world.

BACKGROUND: The geography of southern Iberia and an abundant archaeological record of human occupation are ideal conditions for a full understanding of scenarios of genetic history in the area. Recent advances in the phylogeography of Y-chromosome lineages offer the opportunity to set upper bounds for the appearance of different genetic components. AIM: To provide a global knowledge on the Y haplogroups observed in Andalusia with their Y microsatellite variation. Preferential attention is given to the vehement debate about the age, origin and expansion of R1b-M269 clade and sub-lineages. SUBJECT AND METHODS: Four hundred and fourteen male DNA samples from western and eastern autochthonous Andalusians were genotyped for a set of Y-SNPs and Y-STRs. Gene diversity, potential population genetic structures and coalescent times were assessed. RESULTS: Most of the analysed samples belong to the European haplogroup R1b1a1a2-M269, whereas haplogroups E, J, I, G and T show lower frequencies. A phylogenetic dissection of the R1b-M269 was performed and younger time frames than those previously reported in the literature were obtained for its sub-lineages. CONCLUSION: The particular Andalusian R1b-M269 assemblage confirms the shallow topology of the clade. Moreover, the sharing of lineages with the rest of Europe indicates the impact in Iberia of an amount of pre-existing diversity, with the possible exception of R1b-DF27. Lineages such as J2-M172 and G-M201 highlight the importance of maritime travels of early farmers who reached the Iberian Peninsula.