Origin and evolution of new exons in rodents
Origin and evolution of new exons in rodents
复制标题
啮齿动物新外显子的起源和进化
DOI：
10.1101/gr.3929705
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发表时间：
2005-09-01
期刊：
影响因子：
7
通讯作者：
Wang, J
中科院分区：
文献类型：
--
作者：
Wang, W;Zheng, HK;Wang, J
生物体之间的基因数量差异表明新基因的起源是进化中的基本生物过程。外显子改组在新基因的形成中被普遍观察到。目前尚待了解的是新外显子产生和进化的方式，以及新外显子出现的频率。为了解决这些问题，我们使用 743,856 个猪 EST 作为外群，通过比较人和小鼠之间 12,419 个直系同源基因的表达序列，鉴定了小鼠和大鼠中的 2695 个新进化的外显子。新的外显子起源率约为每百万年每个基因 2.71 x 10(-3)。这些新的外显子显着加快了非同义替换和插入/删除 (indel) 的速度。与人类和小鼠共有的旧外显子相比，Kappa(a)/Kappa(s) 比率 > 1（其中 K-a 是非同义替换率，K-s 是同义替换率）的新外显子比例要高得多，这意味着正选择在快速进化中发挥着作用。这些新外显子中的大多数具有基因组中独特的序列，这表明大多数新外显子可能源自内含子序列的“外显子化”。大多数新外显子似乎是低水平表达的替代外显子。
Gene number difference among organisms demonstrates that new gene origination is a fundamental biological process in evolution. Exon shuffling has been universally observed in the formation of new genes. Yet to be learned are the ways new exons originate and evolve, and how often new exons appear. To address these questions, we identified 2695 newly evolved exons in the mouse and rat by comparing the expressed sequences of 12,419 orthologous genes between human and mouse, using 743,856 pig ESTs as the outgroup. The new exon origination rate is about 2.71 x 10(-3) per gene per million years. These new exons have markedly accelerated rates both of nonsynonymous substitutions and of insertions/ deletions (indels). A much higher proportion of new exons have Kappa(a)/Kappa(s) ratios > 1 (where K-a is the nonsynonymous substitution rate and K-s is the synonymous substitution rate) than K do the old exons shared by human and mouse, implying a role of positive selection in the rapid evolution. The majority of these new exons have sequences unique in the genome, suggesting that most new exons might originate through "exonization" of intronic sequences. Most of the new exons appear to be alternative exons that are expressed at low levels.