藏族人群中低氧通路基因的进化模式及其对高原低氧适应的遗传贡献

Tibetan Plateau represents one of the most extremes of human settlement environment due to its high-altitude hypoxic stress. Currently there are over 5 million indigenous Tibetans residing on the Plateau. Our latest genetic evidence suggested that the ancestors of modern Tibetan populations have successfully settled on the Plateau as early as 30,000 years ago during the Upper Paleolithic rather than the Neolithic. Therefore, today's superior adaptation to high-altitude hypoxia in modern Tibetans was acquired by the continuous adaptive selection of biological functions of key organs sensitive to hypoxia since their ancestor population first settled on the Plateau 30,000 years ago, however, the genetic mechanism that how this superior adaptation to hypoxia in Tibetans was developed through fine regulation of functions of key organs sensitive to hypoxia at genome level remains unclear. Several research groups have identified 18 genes showing significant genetic differentiation between Tibetans and Han ethnic groups by using genome-wide SNP array and exon sequencing analyses. These genes involve in the hypoxic pathway and therefore probably play important biological roles in genetic adaptation to high-altitude hypoxia in Tibetans. Due to the low coverage of SNPs in the current commercial array or sequencing difficulty for GC-rich regions for next-generation sequencing methods, these array and exon capturing based analysis may miss important SNPs. For example, we identified a potential causal SNP (D4E) in EGLN1 gene, a negative regulator of hypoxic inducible factor 2α (HIF2α), by re-sequencing the whole gene sequence for 50 representative Tibetan individuals, while this important SNP was unable to identify in the previous analysis because it is located at GC-rich region of the first exon of the gene. For the same technical reasons, the previous methods may also miss some important SNPs in other candidate genes. To identify potential causal SNPs in candidate genes identified in the previous genome-wide studies, we plan to sequence the whole length of candidate genes involving in hypoxic pathway for 50 representative Tibetan individuals, and identify all SNPs by comparing the resulted sequences with the counterpart in 1000 human genomes database. This is the continuity of a just completed pre-973 project supported by the Ministry of Science and Technology (MOST), within which we have identified the potential causal SNPs for EPAS1 and its negative regulator EGLN1. The objective of this project is to identify potential causal SNPs in the remaining 16 candidate genes by using the same re-sequencing strategy with Ion ProtonTM platform and association analysis between SNPs or haplotypes and physiological characters such as blood hemoglobin concentration (Hb), pulmonary hypertension (PH) and lung function that important for transportation, exchange and utilization of oxygen at high altitude hypoxic environment.

青藏高原是人类居住的最极端环境之一，目前有500多万藏族居民世代生活在青藏高原。现代藏族人群的祖先早在3万多年前就已成功定居于青藏高原，然后经过对低氧敏感器官的连续的适应性选择形成了对高原低氧的最佳生理适应性。但是，适应性选择是如何通过基因组水平的精细调控来实现对关键低氧敏感器官的功能适应这一遗传机制仍然不清楚。本项目利用PCR产物的二代测序技术，对前期全基因组学分析发现的可能与低氧适应相关的16个低氧通路基因的全长序列进行测序，并利用基因序列变异与氧运输、氧交换等关键生理性状之间的遗传相关性来鉴定在高原低氧敏感器官的功能适应过程中发挥重要作用的潜在关键基因及其功能性位点。旨在为揭示"人类是如何通过基因组水平的精细调控来实现对关键低氧敏感器官的功能适应"这一核心科学问题作出贡献。研究成果不仅为解密高原适应这一复杂性状提供基础数据，还将为平原人到高原地区短期旅游与长期工作提供健康指导与预警。

青藏高原是人类居住的最极端环境之一，目前有500多万藏族居民世代生活在青藏高原。现代藏族人群的祖先早在3万多年前就已成功定居于青藏高原，然后经过对低氧敏感器官的连续的适应性选择形成了对高原低氧的最佳生理适应性。但是，适应性选择是如何通过基因组水平的精细调控来实现对关键低氧敏感器官的功能适应这一遗传机制仍然不清楚。本项目对低氧通路基因的全长序列进行测序，并利用基因序列变异与氧运输、氧交换等关键生理性状之间的遗传相关性来鉴定在高原低氧敏感器官的功能适应过程中发挥重要作用的潜在关键基因及其功能性位点。旨在为揭示“人类是如何通过基因组水平的精细调控来实现对关键低氧敏感器官的功能适应”这一核心科学问题作出贡献。研究成果不仅为解密高原适应这一复杂性状提供基础数据，还将为平原人到高原地区短期旅游与长期工作提供健康指导与预警。.通过本课题的实施，在藏族人群对高原低氧环境适应的调控机制研究中取得了阶段性的成果，建立了低、中、高海拔藏族人群的完整的生理指标与生物样本资源库；提出了一氧化氮在藏族人群对高原低氧环境适应过程中的“钝化调控机制”、利用大样本数据提出海拔4500米可能是藏族人群对高原低氧环境最佳适应的临界海拔理论，初步回答了藏族人群究竟能适应多高海拔低氧环境这一科学问题；系统解析了低氧通路关键基因EPAS1、HMOX2、GCH1、EP300等关键基因对藏族人群在高原低氧环境适应的调控机制及其功能位点，为最终揭示藏族人群对高原低氧环境适应背后的分子机制做出了新的贡献。共在SCI收录的学术期刊发表研究论文7篇，综述论文1篇。其中在National Science Review, Molecular Biology and Evolution等影响因子大于10的SCI学术期刊发表高质量研究论文2篇，在影响因子大于4的期刊发表论文4篇。培养博士毕业生1人，硕士毕业生2人。