中科院昆明动物所发现由重复序列介导的灵长类microRNA家族
昆明动物所宿兵研究员的实验室(博士研究生张锐)最近通过对灵长类代表物种的研究，发现了一个由Alu介导产生并快速复制的microRNA家族。这个家族位于人类19号染色体上，在胎盘和胎儿大脑中优势表达。在灵长类的进化过程中，这个家族在Alu的介导下，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很大差异(8－85个拷贝)。序列比较表明，物种内和物种间microRNA的序列分歧相似；同时，在各个灵长类分支中均存在基因拷贝的获得和丢失，也存在基因的假基因化。由此表明，这个miroRNA家族在灵长类中经历了典型的“生－死”(Birth and Death)进化历程。它暗示这个家族的microRNA基因在灵长类的进化中其功能可能发生了多样化，以适应不同灵长类物种在发育过程中的需要。microRNA是近年发现的在基因组中广泛存在的一类小的、非蛋白编码基因。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。另外，在灵长类基因组中存在一类中等重复序列－Alu。它是灵长类特有的重复序列，对灵长类基因组的演化具有深远的影响。
这一研究结果将为科研人员更好地了解Alu对灵长类基因组进化的影响以及非蛋白编码基因的进化模式提供崭新的视角。
研究结果已发表于分子进化领域国际知名刊物《Molecular Biology and Evolution》。http://mbe.oxfordjournals.org/cgi/content/abstract/msn094?ijkey=nSaqAXfjxSCTbd0&keytype=ref
Molecular evolution of a primate-specific microRNA family
Rui Zhang*,,, Yin-Qiu Wang*, and Bing Su*,
* State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
Kunming Primate Research Center, Chinese Academy of Sciences, Kunming 650223, China
Graduate School of Chinese Academy Sciences, Beijing 100039, China
Corresponding author: E-mail: sub@mail.kiz.ac.cn; Tel: 86-871-5120212; Fax: 86-871-5193137
Received for publication March 7, 2008. Revision received April 9, 2008. Accepted for publication April 10, 2008.
Lineage-specific microRNA (miRNA) families may contribute to developmental novelties during evolution. However, little is known about the origin and evolution of new miRNA families. We report evidence of an Alu-mediated rapid expansion of miRNA genes in a previously-identified primate-specific miRNA family, drawn from sequencing and comparative analysis of nine diverse primate species. Evolutionary analysis reveals similar divergence among miRNA copies whether they are within or between species, lineage-specific gain and loss of miRNAs, and gene pseudolization in multiple species. These observations support a birth-and-death process of miRNA genes in this family, implicating functional diversification during primate evolution. In addition, both secondary structure conservation and reduced SNP density attest to functional constraint of this family in primates. Finally, we observed preferential expression of miRNAs in human placenta and fetal brain, suggesting a functional importance of this family for primate development.
Key Words: MicroRNA • Birth-and-death evolution • Alu • Primates
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