特定基因拷贝数的不同造就人类的特殊性
生物谷：人类为何如此特殊？美国科学家近日对比研究了人类和其它灵长类动物的基因组，发现这可能是因为人类某些基因的拷贝数与其它动物有很大不同。这一发现将有助于人们对疾病、寿命等展开更深入的研究。相关论文在线发表于7月31日的《基因组研究》（Genome Research）上。
美国科罗拉多大学的James Sikela等人比较了24000多种人类及黑猩猩、大猩猩等8种灵长类动物基因中的DNA。应用比较基因组杂交（CGH）技术，他们总共发现了4000多种表现了种系特异性变化的基因拷贝，而且这个数量还随着进化不断增长。比较起来，人类比其它灵长动物的这种基因要少得多——人类只有84种这种基因，而狐猴则有1180种。
这些具有多个拷贝的基因往往具有很特殊的作用。比如其中一个名为aquaporin 7的基因，人类具有它的五个拷贝，而其它灵长类动物只有两个。研究人员推测，这个基因可能与人类特有的运动性出汗及耐力跑有关。
研究人员还确定了染色体中一些基因复制和基因损失特别活跃的区域。Sikela表示，这些复制和损失是一把双刃剑，它能为进化提供多种可供选择的变异，但也很容易导致疾病，比如能够扩大大猩猩食谱的基因会使人类患上易导致心脏病的DiGeorge综合症。
美国加州大学圣地亚哥分校的Ajit Varki表示，此次的研究使我们认识到，人类和其它灵长动物基因组之间的差别比我们想象得要复杂的多。此次的研究只是个开始，更明确的结果则有待于更深入的研究。（科学网 梅进/编译）
原始出处:
Published online before print July 31, 2007
Genome Research, DOI: 10.1101/gr.6557307
Gene copy number variation spanning 60 million years of human and primate evolution
Laura Dumas1, Young H. Kim2, Anis Karimpour-Fard3, Michael Cox1,4,5, Janet Hopkins1,4,5, Jonathan R. Pollack2, and James M. Sikela1,4,5,6
1 Human Medical Genetics Program, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA; 2 Department of Pathology, Stanford University, Stanford, California 94305, USA; 3 Department of Preventative Medicine and Biometrics, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA; 4 Neuroscience Program, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA; 5 Department of Pharmacology, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA
Given the evolutionary importance of gene duplication to the emergence of species-specific traits, we have extended the application of cDNA array-based comparative genomic hybridization (aCGH) to survey gene duplications and losses genome-wide across 10 primate species, including human. Using human cDNA arrays that contained 41,126 cDNAs, corresponding to 24,473 unique human genes, we identified 4159 genes that likely represent most of the major lineage-specific gene copy number gains and losses that have occurred in these species over the past 60 million years. We analyzed 1,233,780 gene-to-gene data points and found that gene gains typically outnumbered losses (ratio of gains/losses = 2.34) and these frequently cluster in complex and dynamic genomic regions that are likely to serve as gene nurseries. Almost one-third of all human genes (6696) exhibit an aCGH- predicted change in copy number in one or more of these species, and within-species gene amplification is also evident. Many of the genes identified here are likely to be important to lineage-specific traits including, for example, human-specific duplications of the AQP7 gene, which represent intriguing candidates to underlie the key physiological adaptations in thermoregulation and energy utilization that permitted human endurance running.
6 Corresponding author.
E-mail james.sikela@uchsc.edu ; fax: (303) 724-3663.
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