“珠峰上班族”夏尔巴人和藏族高原适应机制研究

The Tibetan Plateau, known as "the roof of the world" and with an average elevation of over 4,500 meters, is the highest plateau in the world. There are more than twenty populations living there including Tibetan, Sherpa, Menba, Luoba and Deng. .It is almost certain that biological adaptability has contributed to the success of the ethnic groups, such as Sherpas and Tibetans，occupying the plateau as traditional technology could not buffer them against the unavoidable and severe environmental stress of lifelong high-altitude hypoxia. Compared with other indigenous highlanders living in Andean Altiplano and Ethiopian Highlands, Qinghai-Tibet plateau residents, located at higher altitude, developed distinctly different physiological characteristics for survival in the environment of oxygen-thin air, and it seems that Sherpa have stronger high-altitude adaptation than other populations living in Tibet. .Efforts based on candidate gene approaches so far have not been successful in identifying specific genetic loci contributing to high-altitude adaptation (HAA). Population genomics offers a potential solution to the limitations of candidate gene studies, in which the genome can be surveyed without any priori assumptions which genes are under selection, and population demographic history and natural selection can be distinguished. A genome-wide (GW) study by sampling a large number of loci throughout the genome and searching "outliers" in the extreme tail of the empirical distribution, which is the most commonly used population genomics approach, may provide new insights into the understanding of biological mechanism underlying HAA of Tibetans. .This study focuses on the genetic basis of Sherpa in high altitude adaptation. Firstly, we used Affymetrix Genome-Wide Human SNP Array 6.0 probes, which encompassed the entire genome and conducted a genome-wide allelic differentiation scan (GWADS), to detect the signals of HAAs in genomes of indigenous Sherpa living in the Tibetan Plateau, and compared them with closely related Tibetan and lowland Han. As a result, a genome-wide significant divergence between Sherpa and Tibetan was revealed; Secondly, we select candidate genes by GWADS and genes studied previously associated with high altitude adaptation, and detected SNP polymorphism of Sherpa and other populations living in different sea levels of Tibet by Taqman and SNPshot technique for researching the relation and genetic mechanism between key genes and Tibetan HAAs. As the combination of population genetics and candidate gene strategy, this project, taking advantage of Chinese high-altitude population genetic resources, will help to clarify the genetic basis and molecular mechanism of Tibetan, and also has vital meanings to the development of the western regions.

平均海拔4500米以上、被称为"世界屋脊"的青藏高原居住着20多个群体。与其他高原人群如安第斯和埃塞俄比亚的原著民相比，青藏高原居民所处海拔更高且在长期进化过程中对高原缺氧环境的适应有不同的生物学机制，其中夏尔巴可能具有更强的高原适应性。但传统候选基因策略很难系统揭示人群适应高原背后的遗传学基础, 群体基因组学研究可弥补这一缺憾。本研究着重研究夏尔巴人对高原适应的遗传学基础，首先利用基因芯片对夏尔巴进行全基因组扫描，在基因组水平比较两者在高原适应上有何差异; 然后采用Taqman或SNaPshots技术,选择全基因组研究得到的候选基因及前人研究认为可能与高原适应相关的基因, 对西藏人群进行大规模基因变异检测并深入研究。将群体基因组学和候选基因策略结合，充分利用我国高原人群遗传资源优势，研究结果有助于阐明西藏人群高原适应的遗传学基础和分子机理; 本项目的开展对西部大开发也具有重要的现实意义。

青藏高原居住着夏尔巴、门巴、珞巴、僜人和藏族等五个世居民族。其中夏尔巴具有更强于其他民族的高原适应性。为了更好的了解其在长期进化过程中对高原缺氧环境适应的生物学机制，我们对西藏民族的mtDNA进行全测，用基因芯片对夏尔巴进行全基因组扫描，在基因组水平比较藏族和夏尔巴在高原适应上有何差异; 然后采用SNaPshots技术,选择全基因组研究得到的候选基因及前人研究认为可能与高原适应相关的基因, 对西藏人群进行大规模基因变异检测并深入研究。.采集样本2000份，采取Affymetrix 6.0 chip对60例夏尔巴样本进行全基因组SNP和CNV分型；500份样本mtDNA序列全测，10例夏尔巴人进行全基因组检测。对于藏族和夏尔巴人中Fst》0.3的22个SNPs，在西藏不同海拔1500份样本中进行显著性位点验证。结果发现：（1）线粒体DNA多样性与高原适应密切相关：夏尔巴mtDNA haplogroup组成和藏族接近；夏尔巴群体的三个主要单倍群：9a1a1c1b1(14.47%), C4a3b1 (14.47%)and A4e3a(18.42%)与高原适应有关；（2）全序列和microarray 数据分析发现：①90%高原人群EPAS1基因附近有一段3.4kb的CNV缺失突变，西藏人群的特异性缺失定位于chr2，在EPAS1下游80 kb。并且与DEPA1呈强烈的连锁不平衡（LD：r2=0.8），而EPAS1 的变异与血红蛋白的浓度相关。②西藏人的古代祖先成分显著高于汉族和其他东亚人群，并且与海拔相关。显著的是在一个-300kb区域，临近8个基因包括EPAS1和TMEM247等；③评估人类基因组高Fst值的组织功能区域，GenoSkyline注释了7个功能区。FST 大于0.2的SNPs分别为：脑、肺脏、心脏、肌肉和上皮组织。有趣的是肺脏的Fst值强于其他组织,可能建议肺脏特异性功能区SNPs在藏族和夏尔巴之间呈现强列的正选择。也可能部分解释夏尔巴人具有“高原第三肺”的说法。.受项目资助在《Molecule Biology Evolution》等刊物发表论文16篇；分别在国际高原医学会议、美洲人类遗传学会等展示成果；培养研究生6名、年轻教师4名；其成果获得西藏自治区科技进步奖二等奖.研究阐明西藏人高原适应的遗传基础和分子机理，对高原病的防治有重要意义。