圖片說明：Novembre小組在研究中得到的遺傳地圖,，根據(jù)1387個(gè)樣本的基因組信息確定出他們在圖中的坐標(biāo)位置,。不同字母縮寫代表研究對象自稱的出生國家。從中可以看出,，遺傳地圖與地理地圖的相似度,。（圖片來源：Nature）
歐洲的歷史上充滿著戰(zhàn)爭、入侵和移民,，這些因素似乎可以徹底地將不同人種混合在一起,。然而，美國和荷蘭科學(xué)家獨(dú)立進(jìn)行的兩項(xiàng)最新研究表明,，一個(gè)歐洲人的基因組信息足以表明他的地理起源,，歐洲人的基因地圖和地理地圖間存在著一種映射關(guān)系。相關(guān)論文分別發(fā)表在《自然》和《當(dāng)代生物學(xué)》雜志上,。
領(lǐng)導(dǎo)其中一項(xiàng)研究的是美國加州大學(xué)洛杉磯分校的人類群體遺傳學(xué)家John Novembre，他說,，“這一結(jié)果說明地理位置確實(shí)有影響,。”不論語言、移民和通婚,，歐洲人的遺傳差異幾乎完全與出生地相關(guān),。不過，這并不意味著歐洲各個(gè)民族和國家間的遺傳差異性很大,。領(lǐng)導(dǎo)另一項(xiàng)研究的荷蘭鹿特丹大學(xué)的Manfred Kayser表示,，“歐洲的遺傳多樣性真的不多。”
盡管是兩項(xiàng)獨(dú)立研究工作,，但它們所用的方法基本相同,，都是通過分析數(shù)千位歐洲人基因組中的微小差異——單核苷酸多態(tài)性（SNPs）,。同時(shí)，這兩項(xiàng)研究中的一些DNA樣本也是相同的,，它們由GlaxoSmithKline制藥公司搜集,，用于調(diào)查與藥物副作用相關(guān)的基因。
對每份個(gè)體基因組而言,，研究人員都破譯了數(shù)十萬個(gè)SNP,。利用新一代基因芯片，可以一次測定基因組中的50萬個(gè)堿基組成,。然而,，為了對兩套基因組的差異進(jìn)行全面的評估，他們利用一種數(shù)學(xué)手段,，將數(shù)十萬計(jì)的SNP轉(zhuǎn)化成兩個(gè)坐標(biāo),，每個(gè)人的基因組就用一個(gè)點(diǎn)來代表。兩個(gè)點(diǎn)間的距離越大,，表明他們基因組的差異也越大,。
當(dāng)兩支研究小組在單一圖表上標(biāo)出代表數(shù)千個(gè)個(gè)體基因組的點(diǎn)后，一張明顯的歐洲地圖出現(xiàn)了,。西班牙和葡萄牙人的基因組“點(diǎn)”聚集在法國人的西南面,，而代表意大利人基因組的“點(diǎn)”則在瑞士人的東南部尤為突出。
這張地圖的精確性令人驚訝,。當(dāng)Novembre小組將一張地理政治學(xué)地圖放在遺傳地圖上后,，半數(shù)的基因組“點(diǎn)”落在研究對象自稱的出生地192公里的范圍內(nèi)，而落在434公里范圍內(nèi)的達(dá)到了90%（父母來自不同國家的個(gè)體不包括在此分析內(nèi)）,。
兩組研究人員同時(shí)發(fā)現(xiàn),，南部歐洲的遺傳多樣性比北歐、英國和愛爾蘭更為豐富,。Kayser認(rèn)為,，這與3.5萬年前、2萬年前和1萬年前幾次較大規(guī)模的遷入歐洲事件十分吻合,。每次都是南方的人群向北入侵,。美國密歇根大學(xué)的遺傳學(xué)家Noah Rosenberg表示，“基因反映地理學(xué)的模式本質(zhì)上可以從人們緩慢移動(dòng)和主要與近鄰聯(lián)姻上預(yù)期出來,。”
由于目前的基因芯片只探測常見基因變異可能發(fā)生的位點(diǎn),，因此，Novembre認(rèn)為,，隨著基因鑒定技術(shù)的不斷發(fā)展,，將有像單個(gè)村莊中才有的基因變異被整合入芯片中，而科學(xué)家也有可能得到精確得多的歐洲人地理起源。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature,，doi:10.1038/nature07331,，John Novembre, Carlos D. Bustamante
Genes mirror geography within Europe
John Novembre1,2, Toby Johnson4,5,6, Katarzyna Bryc7, Zoltán Kutalik4,6, Adam R. Boyko7, Adam Auton7, Amit Indap7, Karen S. King8, Sven Bergmann4,6, Matthew R. Nelson8, Matthew Stephens2,3 & Carlos D. Bustamante7
Understanding the genetic structure of human populations is of fundamental interest to medical, forensic and anthropological sciences. Advances in high-throughput genotyping technology have markedly improved our understanding of global patterns of human genetic variation and suggest the potential to use large samples to uncover variation among closely spaced populations1, 2, 3, 4, 5. Here we characterize genetic variation in a sample of 3,000 European individuals genotyped at over half a million variable DNA sites in the human genome. Despite low average levels of genetic differentiation among Europeans, we find a close correspondence between genetic and geographic distances; indeed, a geographical map of Europe arises naturally as an efficient two-dimensional summary of genetic variation in Europeans. The results emphasize that when mapping the genetic basis of a disease phenotype, spurious associations can arise if genetic structure is not properly accounted for. In addition, the results are relevant to the prospects of genetic ancestry testing6; an individual's DNA can be used to infer their geographic origin with surprising accuracy—often to within a few hundred kilometres.
Current Biology，Vol 18, 1241-1248, 26 August 2008,，Oscar Lao, Manfred Kayser
Correlation between Genetic and Geographic Structure in Europe
Oscar Lao,1,22 Timothy T. Lu,2,22 Michael Nothnagel,2 Olaf Junge,2 Sandra Freitag-Wolf,2 Amke Caliebe,2 Miroslava Balascakova,3 Jaume Bertranpetit,4 Laurence A. Bindoff,5 David Comas,4 Gunilla Holmlund,6 Anastasia Kouvatsi,7 Milan Macek,3 Isabelle Mollet,8 Walther Parson,9 Jukka Palo,10 Rafal Ploski,11 Antti Sajantila,10 Adriano Tagliabracci,12 Ulrik Gether,13 Thomas Werge,14 Fernando Rivadeneira,15,16 Albert Hofman,16 André G. Uitterlinden,15,16 Christian Gieger,17,18 Heinz-Erich Wichmann,17,18 Andreas Rüther,19 Stefan Schreiber,19 Christian Becker,20 Peter Nürnberg,20 Matthew R. Nelson,21 Michael Krawczak,2,23 and Manfred Kayser1,23
Understanding the genetic structure of the European population is important, not only from a historical perspective, but also for the appropriate design and interpretation of genetic epidemiological studies. Previous population genetic analyses with autosomal markers in Europe either had a wide geographic but narrow genomic coverage [1, 2], or vice versa [3, 4, 5, 6]. We therefore investigated Affymetrix GeneChip 500K genotype data from 2,514 individuals belonging to 23 different subpopulations, widely spread over Europe. Although we found only a low level of genetic differentiation between subpopulations, the existing differences were characterized by a strong continent-wide correlation between geographic and genetic distance. Furthermore, mean heterozygosity was larger, and mean linkage disequilibrium smaller, in southern as compared to northern Europe. Both parameters clearly showed a clinal distribution that provided evidence for a spatial continuity of genetic diversity in Europe. Our comprehensive genetic data are thus compatible with expectations based upon European population history, including the hypotheses of a south-north expansion and/or a larger effective population size in southern than in northern Europe. By including the widely used CEPH from Utah (CEU) samples into our analysis, we could show that these individuals represent northern and western Europeans reasonably well, thereby confirming their assumed regional ancestry.
