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Due to its numerous environmental extremes, the Tibetan Plateau--the world's highest plateau--is one of the most challenging areas of modern human settlement. Archaeological evidence dates the earliest settlement on the plateau to the Late Paleolithic, while previous genetic studies have traced the colonization event(s) to no earlier than the Neolithic. To explore whether the genetic continuity on the plateau has an exclusively Neolithic time depth, we studied mitochondrial DNA (mtDNA) genome variation within 6 regional Tibetan populations sampled from Tibet and neighboring areas. Our results confirm that the vast majority of Tibetan matrilineal components can trace their ancestry to Epipaleolithic and Neolithic immigrants from northern China during the mid-Holocene. Significantly, we also identified an infrequent novel haplogroup, M16, that branched off directly from the Eurasian M founder type. Its nearly exclusive distribution in Tibetan populations and ancient age (>21 kya) suggest that M16 may represent the genetic relics of the Late Paleolithic inhabitants on the plateau. This partial genetic continuity between the Paleolithic inhabitants and the contemporary Tibetan populations bridges the results and inferences from archaeology, history, and genetics. mtDNA | origin doi/10.1073/pnas.0907844106

The distribution and extent of variation of Sardinian Y chromosome halogroup in European population and the importance of Franco-Cantabrian refugium is discussed

Several studies are conducted to determine the causes, pathogenesis and treatments that can be used for leber hereditary optic neuropathy (LHON), an extensively studied mitochondrial disease. The results show that the clinical expression of LHON in Chinese families with the m.1178G-> A mutation is highly affected by the mitochondrial DNA haplogroups M7b1'2 and M8a.

A possible ancient link between Europe/Western Asia and North America in mtDNA haplogroup X is discussed with information on investigation of the origins, continental relationships and diversity of the haplogroup. Investigation was carried out with mtDNA high-resolution RFLP and complete control region sequence analysis of 14 putative European haplogroup X and 22 putative Native American haplogroup X mtDNAs and identified a consensus haplogroup X motif characterizing Native American and European samples, so some Native American founders may have had Caucasian ancestry.

mtDNA analysis shows that a significant population expansion from southwestern Europe into northeastern Europe took place during the Late Paleolithic, about 10,000-15,000 years ago. Haplogroup V acts as an mtDNA marker of the expansion, while haplogroup H also was spread. Other genetic evidence supports the expansion. Nine Eurasian populations, a total of 419 individuals, were studied for the mtDNA analysis.

THE 13 MAY ISSUE CONTAINED THREE PAPERS ('Single, rapid coastal settlement of Asia revealed by analysis of complete mitochondrial genomes,' V. Macaulay et al., Reports, p. 1034; 'Reconstructing the origin [...]

A recent dispersal of modern humans out of Africa is now widely accepted, but the routes taken across Eurasia are still disputed. We show that mitochondrial DNA variation in isolated 'relict' populations in southeast Asia supports the view that there was only a single dispersal from Africa, most likely via a southern coastal route, through India and onward into southeast Asia and Australasia. There was an early offshoot, leading ultimately to the settlement of the Near East and Europe, but the main dispersal from India to Australia ~65,000 years ago was rapid, most likely taking only a few thousand years., The traditional 'out of Africa' model for modern human origins posits an ancestry in sub-Saharan Africa, followed by a dispersal via the Levant ~45,000 years ago (1, 2). However, the [...]

The shortest-path metric d of a graph G = (V, E) is called δ-hyperbolic if for any four vertices u, v, w, x ∈ X the two larger of the three sums d(u, v) + d(w, x), d(u, w) + d(v, x), d(u, x) + d(v, w) differ by at most δ. In this paper, we characterize the graphs with 1-hyperbolic metrics in terms of a convexity condition and forbidden isometric subgraphs. [ABSTRACT FROM AUTHOR]

Mitochondrial HVS-I sequences from 10,365 subjects belonging to 56 populations/geographical regions of western Eurasia and northern Africa were first surveyed for the presence of the T C transition at nucleotide position 16298, a mutation which has previously been shown to characterize haplogroup V mtDNAs. All mtDNAs with this mutation were then screened for a number of diagnostic RFLP sites, revealing two major subsets of mtDNAs. One is haplogroup V proper, and the other has been termed "preV." since it predates V phylogenetically. The rather uncommon pre*V tends to be scattered throughout Europe (and northwestern Africa), whereas V attains two peaks of frequency: one situated in southwestern Europe and one in the Saami of northern Scandinavia. Geographical distributions and ages support the scenario that pre*V originated in Europe before the Last Glacial Maximum (LGM), whereas the more recently derived haplogroup V arose in a southwestern European refugium soon after the LGM. The arrival of V in eastern/central Europe, however, occurred much later, possibly with (post-)Neolithic contacts. The distribution of haplogroup V mtDNAs in modern European populations would thus, at least in part, reflect the pattern of postglacial human recolonization from that refugium, affecting even the Saami. Overall, the present study shows that the dissection of mtDNA variation into small and well-defined evolutionary units is an essential step in the identification of spatial frequency patterns. Mass screening of a few markers identified using complete mtDNA sequences promises to be an efficient strategy for inferring features of human prehistory. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article on a study on the mtDNA genome diversity in worldwide human population.

Leber hereditary optic neuropathy (LHON) is the most extensively studied mitochondrial disease, with the majority of the cases being caused by one of three primary mitochondrial DNA (mtDNA) mutations. Incomplete disease penetrance and gender bias are two features of LHON and indicate involvement of additional genetic or environmental factors in the pathogenesis of the disorder. Haplogroups J, K, and H have been shown to influence the clinical expression of LHON in subjects harboring primary mutations in European families. However, whether mtDNA haplogroups would affect the penetrance of LHON in East Asian families has not been evaluated yet. By studying the penetrance of LHON in 1859 individuals from 182 Chinese families (including one from Cambodia) with the m.11778G→A mutation, we found that haplogroup M7b1'2 significantly increases the risk of visual loss, whereas M8a has a protective effect. Analyses of the complete mtDNA sequences from LHON families with m.11778G →A narrow the association of disease expression tom. 12811T→C (Y159H) in the NADHdehydrogenase 5 gene (MT-NDS) in haplogroup M7b1'2 and suggest that the specific combination of amino acid changes (A20T-T531) in the ATP synthase 6 protein (MT-ATP6) caused by m.8584G→A and m.8684C→T might account for the beneficial background effect of M8a. Protein secondary-structure prediction for the MT-ATP6 with the two M8a-specific amino acid changes further supported our inferences. These findings will assist in further understanding the pathogenesis of LHON and guide future genetic counseling in East Asian patients with m.11778G→A. [ABSTRACT FROM AUTHOR]

A response by Anna Olivieri and colleagues to a letter to the editor about their article "The mtDNA Legacy of the Levantine Early Upper Paleolithic in Africa" in the December 15, 2006 issue is presented.

Presents several letters to the editor on genetics. Analysis on the population frequencies of mtDNA haplogroups; Clarifications on the haplogroup classification; Examination on the autocorrelation patterns in different loci.

The origin of the Etruscan people has been a source of major controversy for the past 2,500 years, and several hypotheses have been proposed to explain their language and sophisticated culture, including an Aegean/Anatolian origin. To address this issue, we analyzed the mitochondrial DNA (mtDNA) of 322 subjects from three well-defined areas of Tuscany and compared their sequence variation with that of 55 western Eurasian populations. Interpopulation comparisons reveal that the modern population of Murlo, a small town of Etruscan origin, is characterized by an unusually high frequency (17.5%) of Near Eastern mtDNA haplogroups. Each of these haplogroups is represented by different haplotypes, thus dismissing the possibility that the genetic allocation of the Murlo people is due to drift. Other Tuscan populations do not show the same striking feature; however, overall, ~5% of mtDNA haplotypes in Tuscany are shared exclusively between Tuscans and Near Easterners and occupy terminal positions in the phylogeny. These findings support a direct and rather recent genetic input from the Near East--a scenario in agreement with the Lydian origin of Etruscans. Such a genetic contribution has been extensively diluted by admixture, but it appears that there are still locations in Tuscany, such as Murlo, where traces of its arrival are easily detectable.