Giuseppe Vona

Tracing European Founder Lineages in the Near Eastern mtDNA Pool

Founder analysis is a method for analysis of nonrecombining DNA sequence data, with the aim of identification and dating of migrations into new territory. The method picks out founder sequence types in potential source populations and dates lineage clusters deriving from them in the settlement zone of interest. Here, using mtDNA, we apply the approach to the colonization of Europe, to estimate the proportion of modern lineages whose ancestors arrived during each major phase of settlement. To estimate the Palaeolithic and Neolithic contributions to European mtDNA diversity more accurately than was previously achievable, we have now extended the Near Eastern, European, and northern-Caucasus databases to 1,234, 2, 804, and 208 samples, respectively. Both back-migration into the source population and recurrent mutation in the source and derived populations represent major obstacles to this approach. We have developed phylogenetic criteria to take account of both these factors, and we suggest a way to account for multiple dispersals of common sequence types. We conclude that (i) there has been substantial back-migration into the Near East, (ii) the majority of extant mtDNA lineages entered Europe in several waves during the Upper Palaeolithic, (iii) there was a founder effect or bottleneck associated with the Last Glacial Maximum, 20,000 years ago, from which derives the largest fraction of surviving lineages, and (iv) the immigrant Neolithic component is likely to comprise less than one-quarter of the mtDNA pool of modern Europeans.

Phylogeographic analysis of haplogroup E3b (E-M215) y chromosomes reveals multiple migratory events within and out of Africa.

We explored the phylogeography of human Y-chromosomal haplogroup E3b by analyzing 3401 individuals from five continents. Our data refine the phylogeny of the entire haplogroup, which appears as a collection of lineages with very different evolutionary histories, and reveal signatures of several distinct processes of migrations and/or recurrent gene flow that occurred in Africa and western Eurasia over the past 25000 years. In Europe, the overall frequency pattern of haplogroup E-M78 does not support the hypothesis of a uniform spread of people from a single parental Near Eastern population. The distribution of E-M81 chromosomes in Africa closely matches the present area of distribution of Berber-speaking populations on the continent, suggesting a close haplogroup-ethnic group parallelism. E-M34 chromosomes were more likely introduced in Ethiopia from the Near East. In conclusion, the present study shows that earlier work based on fewer Y-chromosome markers led to rather simple historical interpretations and highlights the fact that many population-genetic analyses are not robust to a poorly resolved phylogeny.

Genetic analysis of Sardinia: I. Data on 12 polymorphisms in 21 linguistic domains

(1) The microgeographic structure of Sardinia, well documented from a historical and linguistic point of view, further supported by archaeological evidence, can also be dissected at the genetic level: gene frequencies show heterogeneities which are statistically significant.

Human Y-chromosome variation in the western mediterranean area: Implications for the peopling of the region

Y-chromosome variation was analyzed in a sample of 1127 males from the Western Mediterranean area by surveying 16 biallelic and 4 multiallelic sites. Some populations from Northeastern Europe and the Middle East were also studied for comparison. All Y-chromosome haplotypes were included in a parsimonious genealogic tree consisting of 17 haplogroups, several of which displayed distinct geographic specificities. One of the haplogroups, HG9.2, has some features that are compatible with a spread into Europe from the Near East during the Neolithic period. However, the current distribution of this haplogroup would suggest that the Neolithic gene pool had a major impact in the eastern and central part of the Mediterranean basin, but very limited consequences in Iberia and Northwestern Europe. Two other haplogroups, HG25.2 and HG2.2, were found to have much more restricted geographic distributions. The first most likely originated in the Berbers within the last few thousand years, and allows the detection of gene flow to Iberia and Southern Europe. The latter haplogroup is common only in Sardinia, which confirms the genetic peculiarity and isolation of the Sardinians. Overall, this study demonstrates that the dissection of Y-chromosome variation into haplogroups with a more restricted geographic distribution can reveal important differences even between populations that live at short distances, and provides new clues to their past interactions.

The peopling of Europe and the cautionary tale of Y chromosome lineage R-M269

Recently, the debate on the origins of the major European Y chromosome haplogroup R1b1b2-M269 has reignited, and opinion has moved away from Palaeolithic origins to the notion of a younger Neolithic spread of these chromosomes from the Near East. Here, we address this debate by investigating frequency patterns and diversity in the largest collection of R1b1b2-M269 chromosomes yet assembled. Our analysis reveals no geographical trends in diversity, in contradiction to expectation under the Neolithic hypothesis, and suggests an alternative explanation for the apparent cline in diversity recently described. We further investigate the young, STR-based time to the most recent common ancestor estimates proposed so far for R-M269-related lineages and find evidence for an appreciable effect of microsatellite choice on age estimates. As a consequence, the existing data and tools are insufficient to make credible estimates for the age of this haplogroup, and conclusions about the timing of its origin and dispersal should be viewed with a large degree of caution.

Differential structuring of human populations for homologous X and Y microsatellite loci.

The global pattern of variation at the homologous microsatellite loci DYS413 (Yq11) and DXS8174 and DXS8175 (Xp22) was analyzed by examination of 30 world populations from four continents, accounting for more than 1,100 chromosomes per locus. The data showed discordant patterns of among- and within-population gene diversity for the Y-linked and the X-linked microsatellites. For the Y-linked polymorphism, all groups of populations displayed high FST values (the correlation between random haplotypes within subpopulations, relative to haplotypes of the total population) and showed a general trend for the haplotypes to cluster in a population-specific way. This was especially true for sub-Saharan African populations. The data also indicated that a large fraction of the variation among populations was due to the accumulation of new variants associated with the radiation process. Europeans exhibited the highest level of within-population haplotype diversity, whereas sub-Saharan Africans showed the lowest. In contrast, data for the two X-linked polymorphisms were concordant in showing lower FST values, as compared with those for DYS413, but higher within-population variances, for African versus non-African populations. Whereas the results for the X-linked loci agreed with a model of greater antiquity for the African populations, those for DYS413 showed a confounding pattern that is apparently at odds with such a model. Possible factors involved in this differential structuring for homologous X and Y microsatellite polymorphisms are discussed.

Realidad social de los pacientes con isquemia crítica de miembros inferiores

Realidad social de los pacientes con isquemia critica de miembros inferiores Resumen. Objetivo. Realizar una aproximacion a la realidad social de los pacientes que alcanzan los estadios mas avanzados de isquemia cronica de miembros inferiores (MMII) (isquemia critica). Pacientes y metodos. Se registran mediante entrevista a paciente y familiar, datos relacionados con la vivienda habitual, entorno sociofamiliar, recursos economicos y nivel de instruccion de 50 pacientes ingresados en nuestro servicio con el diagnostico de isquemia critica de MMII, entre el 1 de octubre y el 31 de diciembre de 2005. Se realiza una comparacion posterior con los mismos datos de la Encuesta de condiciones de vida del Instituto Nacional de Estadistica (INE) correspondiente a la zona estudiada y al mismo grupo de edad. Resultados. La media de edad de los pacientes es de 69,1 anos, siendo el 84% hombres y el 16% mujeres. Se constata una tasa de pobreza relativa del 50% en los pacientes con isquemia critica frente al 24,8% en la poblacion local correspondiente a la edad. El 26% de los pacientes estudiados son analfabetos, frente al 11,5% de la poblacion general. Con respecto a la vivienda, el 32% de los pacientes viven en un piso alto sin ascensor, y este porcentaje se mantiene en pacientes a los que se les somete a una amputacion mayor. Conclusiones. Constatamos una tendencia a la exclusion social en los pacientes con isquemia grave de las extremidades. Dicha realidad social debe ser conocida por el cirujano vascular a la hora de tratar a estos pacientes, imponiendose un abordaje multidisciplinar junto con trabajadores sociales, medicos de familia y personal de enfermeria y asistencia domiciliaria. [ANGIOLOGIA 2008; 60: 241–5]

Patterns of male‐specific inter‐population divergence in Europe, West Asia and North Africa

We typed 1801 males from 55 locations for the Y‐specific binary markers YAP, DYZ3, SRY10831 and the (CA)n microsatellites YCAII and DYS413. Phylogenetic relationships of chromosomes with the same binary haplotype were condensed in seven large one‐step networks, which accounted for 95% of all chromosomes. Their coalescence ages were estimated based on microsatellite diversity. The three largest and oldest networks undergo sharp frequency changes in three areas. The more recent network 3.1A clearly discriminates between Western and Eastern European populations. Pairwise Fst showed an overall increment with increasing geographic distance but with a slope greatly reduced when compared to previous reports. By sectioning the entire data set according to geographic and linguistic criteria, we found higher Fst‐on‐distance slopes within Europe than in West Asia or across the two continents.

Strong intra- and inter-continental differentiation revealed by Y chromosome SNPs M269, U106 and U152

More than 2700 unrelated individuals from Europe, northern Africa and western Asia were analyzed for the marker M269, which defines the Y chromosome haplogroup R1b1b2. A total of 593 subjects belonging to this haplogroup were identified and further analyzed for two SNPs, U106 and U152, which define haplogroups R1b1b2g and R1b1b2h, respectively. These haplogroups showed quite different frequency distribution patterns within Europe, with frequency peaks in northern Europe (R1b1b2g) and northern Italy/France (R1b1b2h).

Mitochondrial control–region sequence variation in the Corsican population, France

The mtDNA sequence variation of the hypervariable segment I of the control region was studied in 47 unrelated individuals of Corsican origin from Corte (Corsica, France). Thirty‐one different sequences were identified by 40 variable sites, of which five involve transversions. The nucleotide diversity among the sequences was estimated as 1.03%. The pairwise difference agreed with the model proposed by Rogers and Harpending ([1992] Mol Biol Evol 9:552–569) and appeared bell‐shaped, with only one peak at 3.71, indicating the occurrence of a single episode of demographic expansion roughly 14,443 to 41,584 years ago. From our results it seems that the ancestral Corsican population expanded more recently than all other studied European populations. Compared to other populations by genetic distances and a neighbor‐joining tree, Corsicans appear most closely linked to the Basques and Sardinians than to other populations. Although the results substantiate an east‐to‐west migration, some problems are evident: 1) the estimates of demographic expansion are not in agreement with paleontological data; 2) the expansion occurred later than the expansion of the Sardinian population; and 3) the genetic affinity between Corsicans, Basques, and Sardinians. Answers will need to come from archaeological, paleontological, genetic, geological, and climatological observations. Finally, the study of mtDNA confirms what had already been shown with classic genetic markers. Am. J. Hum. Biol. 12:339–351, 2000.