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      Eurasian and African mitochondrial DNA influences in the Saudi Arabian population

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          Abstract

          Background

          Genetic studies of the Arabian Peninsula are scarce even though the region was the center of ancient trade routes and empires and may have been the southern corridor for the earliest human migration from Africa to Asia. A total of 120 mtDNA Saudi Arab lineages were analyzed for HVSI/II sequences and for haplogroup confirmatory coding diagnostic positions. A phylogeny of the most abundant haplogroup (preHV)1 (R0a) was constructed based on 13 whole mtDNA genomes.

          Results

          The Saudi Arabian group showed greatest similarity to other Arabian Peninsula populations (Bedouin from the Negev desert and Yemeni) and to Levantine populations. Nearly all the main western Asia haplogroups were detected in the Saudi sample, including the rare U9 clade. Saudi Arabs had only a minority sub-Saharan Africa component (7%), similar to the specific North-African contribution (5%). In addition, a small Indian influence (3%) was also detected.

          Conclusion

          The majority of the Saudi-Arab mitochondrial DNA lineages (85%) have a western Asia provenance. Although the still large confidence intervals, the coalescence and phylogeography of (preHV)1 haplogroup (accounting for 18 % of Saudi Arabian lineages) matches a Neolithic expansion in Saudi Arabia.

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          Most cited references 50

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          Natural selection shaped regional mtDNA variation in humans.

          Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have enriched for certain mtDNA lineages as people migrated north into colder climates. To test this hypothesis we analyzed 104 complete mtDNA sequences from all global regions and lineages. African mtDNA variation did not significantly deviate from the standard neutral model, but European, Asian, and Siberian plus Native American variations did. Analysis of amino acid substitution mutations (nonsynonymous, Ka) versus neutral mutations (synonymous, Ks) (kaks) for all 13 mtDNA protein-coding genes revealed that the ATP6 gene had the highest amino acid sequence variation of any human mtDNA gene, even though ATP6 is one of the more conserved mtDNA proteins. Comparison of the kaks ratios for each mtDNA gene from the tropical, temperate, and arctic zones revealed that ATP6 was highly variable in the mtDNAs from the arctic zone, cytochrome b was particularly variable in the temperate zone, and cytochrome oxidase I was notably more variable in the tropics. Moreover, multiple amino acid changes found in ATP6, cytochrome b, and cytochrome oxidase I appeared to be functionally significant. From these analyses we conclude that selection may have played a role in shaping human regional mtDNA variation and that one of the selective influences was climate.
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            Molecular Evolutionary Genetics

             M Nei,  M. NEI,  N. Masatoshi (1987)
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              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.
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                Author and article information

                Journal
                BMC Evol Biol
                BMC Evolutionary Biology
                BioMed Central (London )
                1471-2148
                2007
                1 March 2007
                : 7
                : 32
                Affiliations
                [1 ]Mitochondrial Research Laboratory, Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
                [2 ]Department of Genetics, Faculty of Biology, University of La Laguna, Tenerife, Canary Islands, Spain
                [3 ]Neurology Division, Cooper University Hospital, Camden, NJ, USA
                Article
                1471-2148-7-32
                10.1186/1471-2148-7-32
                1810519
                17331239
                Copyright © 2007 Abu-Amero et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Research Article

                Evolutionary Biology

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