微RNA（MicroRNAs）是1993年在線蟲中發(fā)現的抑制性小RNA分子,，廣泛分布在復雜動物中,。人們普遍假設，它們是當動物形成雙側對稱性（即動物身體結構復雜到有前部和后部以及上部和下部）時作為微調基因表達的一種方式而出現的,。
新的研究工作（這項工作是基于對三種“基底后生動物門”的代表動物（一種扁盤動物,、一種海綿和一種海葵）及一種單細胞“領鞭毛蟲”的總RNA內容所做測序進行的）表明,，微RNA出現的時間要比人們以前所想的長得多,。調控性微RNA通道似乎是在后生動物演化過程中非常早的時候出現的——是當多細胞生命方式出現時出現的，盡管這種機制后來在一些生命分支中丟失了,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 455, 1193-1197 (30 October 2008) | doi:10.1038/nature07415
Early origins and evolution of microRNAs and Piwi-interacting RNAs in animals
Andrew Grimson1,2, Mansi Srivastava4, Bryony Fahey3, Ben J. Woodcroft3, H. Rosaria Chiang1,2, Nicole King4, Bernard M. Degnan3, Daniel S. Rokhsar4,5 & David P. Bartel1,2
1 Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA
2 Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
3 School of Integrative Biology, University of Queensland, Brisbane 4072, Australia
4 Department of Molecular and Cell Biology and Center for Integrative Genomics, University of California at Berkeley, Berkeley, California 94720, USA
5 Department of Energy, Joint Genome Institute, Walnut Creek, California 94598, USA
In bilaterian animals, such as humans, flies and worms, hundreds of microRNAs (miRNAs), some conserved throughout bilaterian evolution, collectively regulate a substantial fraction of the transcriptome. In addition to miRNAs, other bilaterian small RNAs, known as Piwi-interacting RNAs (piRNAs), protect the genome from transposons. Here we identify small RNAs from animal phyla that diverged before the emergence of the Bilateria. The cnidarian Nematostella vectensis (starlet sea anemone), a close relative to the Bilateria, possesses an extensive repertoire of miRNA genes, two classes of piRNAs and a complement of proteins specific to small-RNA biology comparable to that of humans. The poriferan Amphimedon queenslandica (sponge), one of the simplest animals and a distant relative of the Bilateria, also possesses miRNAs, both classes of piRNAs and a full complement of the small-RNA machinery. Animal miRNA evolution seems to have been relatively dynamic, with precursor sizes and mature miRNA sequences differing greatly between poriferans, cnidarians and bilaterians. Nonetheless, miRNAs and piRNAs have been available as classes of riboregulators to shape gene expression throughout the evolution and radiation of animal phyla.
