中科院昆明动物所宿兵研究小组最近通过对灵长类代表物种的研究，发现了一个快速进化的microRNA家族。这个家族位于X染色体上，并在睾丸中优势表达。在灵长类的进化过程中，这个家族不断通过基因重复产生新的拷贝，且拷贝数在灵长类物种间存在差异。同时，这个家族的microRNA序列变异的速度明显高于基因组中已知microRNA基因的平均水平，从而导致一些物种特异的microRNA基因的产生。以前的很多研究表明，在灵长类的进化中，与雄性生殖相关的蛋白编码基因由于受到很强的选择，进化速度很快。宿兵研究员实验室的研究结果证实，除蛋白编码基因以外，microRNA基因也会受到达尔文正选择的影响，发生快速的进化。这一研究结果将为我们更为全面地了解非蛋白编码基因的进化模式及其在功能进化中的作用提供崭新的视角。研究结果发表于基因组学国际知名刊物——Genome Research上(http://www.genome.org/papbyrecent.shtml
microRNA是近年发现的在基因组中广泛存在的一类小的、非编码基因。它通过与mRNA中特定的互补位点结合来调节蛋白编码基因的表达和翻译，从而参与发育的精细调控等一系列重要的生命过程。目前，绝大多数已知的microRNA在序列上都很保守，表明其承担着重要的生物学功能。然而，基因组中也可能存在快速进化的microRNA, 并在新的表型和功能的产生中发挥作用。
部分英文原文：
Published online before print April 6, 2007
Genome Research, DOI: 10.1101/gr.6146507
Letter
Rapid evolution of an X-linked microRNA cluster in primates
Rui Zhang1,2,3, Yi Peng1,2, Wen Wang1, and Bing Su1,2,4
1 Key Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China; 2 Kunming Primate Research Center, Chinese Academy of Sciences, Kunming 650223, China; 3 Graduate School of Chinese Academy Sciences, Beijing 100039, China
MicroRNAs (miRNAs) are a growing class of small RNAs (about 22 nt) that play crucial regulatory roles in the genome by targeting mRNAs for cleavage or translational repression. Most of the identified miRNAs are highly conserved among species, indicating strong functional constraint on miRNA evolution. However, nonconserved miRNAs may contribute to functional novelties during evolution. Recently, an X-linked miRNA cluster was reported with multiple copies in primates but not in rodents or dog. Here we sequenced and compared this miRNA cluster in major primate lineages including human, great ape, lesser ape, Old World monkey, and New World monkey. Our data indicate rapid evolution of this cluster in primates including frequent tandem duplications and nucleotide substitutions. In addition, lineage-specific substitutions were observed in human and chimpanzee, leading to the emergence of potential novel mature miRNAs. The expression analysis in rhesus monkeys revealed a strong correlation between miRNA expression changes and male sexual maturation, suggesting regulatory roles of this miRNA cluster in testis development and spermatogenesis. We propose that, like protein-coding genes, miRNA genes involved in male reproduction are subject to rapid adaptive changes that may contribute to functional novelties during evolution.
4 Corresponding author.
E-mail sub@mail.kiz.ac.cn ; fax 86-871-5193137.
