Search

Sicily, due to its strategic geographical position, located in the heart of Mediterranean Basin, has received the passage of various human groups both in pre-historical and historical times, acting as a bridge in different major migratory events. In addition to the Upper Paleolithic and Mesolithic cultures, several migrations have affected the genetic composition of the island after the Neolithic transition (Greeks, Phoenicians, Romans, Arabs and Normans), thus contributing to complicate the genetic landscape of the largest Mediterranean island. Made up of different superimposed historical genetic layers, Sicily offers a unique opportunity to test hypotheses connected with the peopling of Mediterranean shores. Both the presence (Romano et al. 2003, Di Gaetano et al. 2008) and absence (Rickards et al. 1998) of an internal genetic differentiation along the east-west axis has been previously described in Sicily, and several hypotheses, connected with the aforementioned dynamics of peopling, have been proposed to explain the heterogeneity observed. Nevertheless the extent of each independent historical contributions to the current genetic composition of Sicilian population is still highly debated. The present study aims to contribute to this debate using new samples and deeper analyzing the Y chromosome genetic markers. More precisely, a total of 24 Y-SNPs and 17 Y-STRs have been typed in more than 300 individuals from 8 different provinces, 5 in Sicily (Agrigento, Catania, Ragusa-Siracusa, Enna, Trapani) and 3 in Southern Italy (Matera, Lecce, Cosenza). Y-chromosome preliminary results reveal a substantial lack of genetic structure within the island, coupled with high levels of within-population genetic variability. These findings well agree with Sicily's historic role as major migration crossroads. Comparing our results with other Mediterranean populations (Southern Europe, Northern Africa and the Levant) we observe a marked geography-related global structure within the Mediterranean Basin. Two well separated clusters have been identified, suggesting a shared genetic background between north-western Mediterranean populations (Iberian Peninsula and Northern Italy) on one side, and south-eastern ones (Sicily and Southern Italy, Balkan Peninsula, North Africa and Levant) on the other side. The completion of Y-chromosome analysis, as well as the future study of mtDNA variation, will consent to explore more in detail specific issues related to the peopling of Sicily and to clarify its role in Mediterranean genetic context.

Two Amerindian populations from the Peruvian Amazon (Yanesha) and from rural lowlands of the Argentinean Gran Chaco (Wichi) were analyzed. They represent two case study of the South American genetic variability. The Yanesha represent a model of population isolated for long-time in the Amazon rainforest, characterized by environmental and altitudinal stratifications. The Wichi represent a model of population living in an area recently colonized by European populations (the Criollos are the population of the admixed descendents), whose aim is to depict the native ancestral gene pool and the degree of admixture, in relation to the very high prevalence of Chagas disease. The methods used for the genotyping are common, concerning the Y chromosome markers (male lineage) and the mitochondrial markers (maternal lineage). The determination of the phylogeographic diagnostic polymorphisms was carried out by the classical techniques of PCR, restriction enzymes, sequencing and specific mini-sequencing. New method for the detection of the protozoa Trypanosoma cruzi was developed by means of the nested PCR. The main results show patterns of genetic stratification in Yanesha forest communities, referable to different migrations at different times, estimated by Bayesian analyses. In particular Yanesha were considered as a population of transition between the Amazon basin and the Andean Cordillera, evaluating the potential migration routes and the separation of clusters of community in relation to different genetic bio-ancestry. As the Wichi, the gene pool analyzed appears clearly differentiated by the admixed sympatric Criollos, due to strict social practices (deeply analyzed with the support of cultural anthropological tools) that have preserved the native identity at a diachronic level. A pattern of distribution of the seropositivity in relation to the different phylogenetic lineages (the adaptation in evolutionary terms) does not appear, neither Amerindian nor European, but in relation to environmental and living conditions of the two distinct subpopulations.

OBJECTIVES: Behçet's disease is a multifactorial vasculitis that shows its highest prevalence in geographical areas historically involved in the Silk Road, suggesting that it might have originated somewhere along these ancient trade routes. This study aims to provide a first clue towards genetic evidence for this hypothesis by testing it via an anthropological evolutionary genetics approach. METHODS: Behçet's disease variation at ancestry informative mitochondrial DNA control region and haplogroup diagnostic sites was characterised in 185 disease subjects of Italian descent and set into the Eurasian mitochondrial landscape by comparison with nearly 9,000 sequences representative of diversity observable in Italy and along the main Silk Road routes. RESULTS: Dissection of the actual genetic ancestry of disease individuals by means of population structure, spatial autocorrelation and haplogroup analyses revealed their closer relationships with some Middle Eastern and Central Asian groups settled along the Silk Road than with healthy Italians. CONCLUSIONS: These findings support the hypothesis that the Behçet's disease genetic risk has migrated to western Eurasia in parallel with ancestry components typical of Silk Road-related groups. This provided new insights that are useful to improve the understanding of disease origins and diffusion, as well as to inform future association studies aimed at properly accounting for the actual genetic ancestry of the examined Behçet's disease samples in order to minimise the detection of spurious associations and to improve the identification of genetic variants with actual clinical relevance.