广东客家人G6PD基因位点优势选择的研究
【外文题名】Positive Selection of Glucose-6-phosphate Dehydrogenase Gene From Guangdong Hakka Population
【作者】 丁峰
【关键词】 葡萄糖 6 磷酸脱氢酶 单核苷酸多态性 LD Block 客家 优势选择
【外文关键词】 Glucose 6 Phosphate Dehydrogenase SNPs Haplotype block Hakka positive selection
【导师姓名】蒋玮莹
【学位名称】硕士
【学位年度】2009
【学位授予单位】暂无
【所属分类】Q532,Q343.1,Q524,B845,I236.65,O613.62,Q554,Q346
【录入时间】2009-01-01
【摘要】PH。G6PD具有显著的遗传多样性，研究显示不同种族人群G6PD基因突变类型和发生频率不同。中国人群主要以G6PD Kaiping，c.1388 G>A、G6PD Canton，c.1376 G>T、G6PD Gaohe，c.95 A>G为主。G6PD缺乏症是一组常见的人类酶缺陷病，全球范围内约有四亿人受累。患者酶活性变异范围很大。可引起新生儿黄疸、急性溶血和重症慢性非球型细胞溶血性贫血等。高发地区为非洲、地中海部分地区、东南亚和拉丁美洲。 疟疾被认为是已知的近期人类基因组受到的最强的进化选择因素之一。G6PD在保护红细胞免受氧化性应激上发挥着重要作用。群体中G6PD缺乏症等位基因的高频率是对抗疟疾的保护作用。关于非洲G6PDA–基因位点的进化研究也显示出了局部和近期的优势选择作用，这一过程可能起始于距今2500—3800年。这些都与非洲疟疾的流行病学调查是吻合的。 客家是一个具有显著特征的汉族分支族群，也是汉族在世界上分布范围广阔、影响深远的民系之一。从西晋永嘉之乱开始，中原汉族居民大举南迁，抵达粤赣闽等地，与当地土著居民杂处，互通婚姻，经过千年演化最终形成相对稳定的客家民系。关于客家渊源的看法主要有两种：（1）纯粹由北方南迁汉人发展演变而来；（2）北方南迁汉人融合南方土著发展演变而来。更早的史料记载的关于秦朝军事活动相关的移民也有可能是更早的南迁汉民。这些移民加速了民族融合和这一地区经济文化的发展。本课题组使用X染色体LD Block分析的方法，寻找G6PD等位基因受到优势选择的证据，并为追溯客家人的起源和迁徙历史提供遗传学证据。 本研究应用聚合酶链反应（polymerase chain reaction，PCR），变性高效液相色谱（denaturing high performance liquid chromatography，DHPLC）和DNA测序技术等方法对104例广东客家男性进行了G6PD基因分型，共发现10种SNPs，其中有9种在数据库中已报道，在第5内含子发现的g.14359 C>A为首报SNP。 在本课题组以往研究的基础上，本研究扩大样本量，分析比较广东客家G6PD缺陷男性患者和广东客家G6PD正常男性对照的G6PD和L1CAM的SNPs分布、LD Block和单体型结构。研究结果发现客家G6PD缺乏症男性患者在G6PD基因和L1CAM基因之间形成了一个由12个SNPs构成的、长639kb的LD Block，显示出长的LD，其中中国人常见的G6PD Kaiping c.1388 G>A、G6PD Canton c.1376 G>T、G6PD Gaohe c.95 A > G等致病性突变频率升高，其它位点的频率显现出渐次降低的趋势，表现出明显的hitchhiking effect和Selective Sweep。说明G6PD Kaiping c.1388 G>A、G6PD Canton c.1376 G>T、G6PD Gaohe c.95 A > G受到了优势选择。 本课题组以往的研究结果显示了河南人群和山东人群的LD Block和单体型结构一致，由相同的7个SNPs位点构成。本研究的广东客家G6PD正常对照组构成的LD Block较小，分为两个仅由3个和4个SNPs构成的小LD Block，与构成河南和山东人群LD Block的7个SNPs有6个是相同的。这样的结构反映了始祖单体型的部分遗迹及混合人群的特点。...
【外文摘要】Glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49; MIM# 305900) is a key enzyme in the pentose phosphate pathway. This protein is a cytosolic enzyme encoded by a housekeeping X-linked gene，and it consists of 13 exons and 12 introns, spanning 20114bp. Its main function is to produce NADPH, a key electron donor in the defense against oxidizing agents and in reductive biosynthetic reactions. G6PD is remarkable for its genetic diversity. The Molecular analysis of G6PD deficiency has revealed that different ethnic groups have different gene variants. The mainly pathogenic mutations in Chinese are G6PD c.1376 G>T、c.1388 G>A、c.95 A > G and c.871 G>A. Hereditary deficiency in human Glucose-6-phosphate dehydrogenase (G6PD) is estimated to affect about 400 million worldwide. It has been described with wide ranging levels of enzyme activity and associated clinical symptoms. G6PD deficiency may cause neonatal jaundice, acute hemolysis, or severe chronic non-spherocytic hemolytic anemia. The highest prevalence rates are found in Africa, Mediterranean Europe, South-East Asia, and Latin America.. Malaria is considered to be one of the strongest known forces of evolutionary selection in the recent history of the human genome. Plasmodium falciparum and Plasmodium vivax seem to have exerted strong selective pressure on the cellular phenotype of human erythrocytes, causing increased prevalence of hemoglobinopathies and other inherited blood disorders. Glucose-6-phosphate dehydrogenase (G6PD) plays a key role in protecting cells from oxidative stress and is particularly important in red blood cells. G6PD deficiency is associated with several clinical disorders. The high overall frequency of G6PD-deficient alleles in the population is thought to result from their protective effect against malaria. Evolutionary studies of the G6PD locus suggest that local and recent positive selection has targeted the G6PD-deficient allele G6PDA– in Africa and that this process started 2500 to 3800 years before present. These observations are consistent with signs of recent expansion of P. falciparum in Africa. Hakka, with salient features, is a branch of the Han ethnic group. It is widespread and far-reaching. From the Yongjia dynasty of the West Jin, Han population migrated to southern China and arrived in Guangdong, Jiangxi and Fujian. Then, they married with local indigenous populations, finally formed the relative stability of the Hakka. There are two main views of Hakka origin. One is solely evolution of northern Han Chinese. The other is integration of northern Han Chinese and indigenous populations. Historical records related to military activities on the Qin Dynasty showed that Qin's army might be the earlier Han immigration. These immigrants accelerate national integration and economic and cultural development in the region. By X chromosome haplotype block analysis, we are trying to search for the evidence of positive selection on G6PD gene and reveal Hakka origin and migratory history. With informed consent, a total of 104 individuals from Xingning Hakka were analyzed for genotyping with PCR, DHPLC and DNA direct sequencing. We found 7 G6PD deficiency patients with variable alleles in G6PD gene. We also found 10 SNPs. 9 of SNPs have been reported in GeneBank and HapMap database, whereas 1 of them is novel, g.14359 C>A, which is located in intro V. We also screened 5 exons of the L1CAM gene in 104 Hakka samples and none was found. We analyzed the distribution of SNPs, haplotype and haplotype block in 5 male groups (Hakka G6PD deficiency, Shandong, Henan, Hakka male control and Dai). The result showed the SNPs of the G6PD deficient patients from Guangdong Hakka population have formed a very long haplotype block, which is 639kb in length and consists of 12 SNPs. It has initially displayed high LD, illustrated the most popular pathogenic mutations in China including G6PD c.1376 G>T、c.1388 G>A、c.95 A > G and c.871 G>A. have been influenced by positive selection. The result also showed that the LD blocks from Henan and Shandong populations are the same, which are composed of 7 identical SNPs, whereas the one acting as the control from Guangdong Hakka population is different from them .The LD blocks from Hakka who are G6PD normality was formed by 3 and 4 SNPs, 6 of them are included in the 7 SNPs mentioned above....