Wed, 20 Aug 2008 21:19:57 BST CiteULike: megraw's Shen http://www.citeulike.org/user/megraw/author/Shen CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/megraw/article/2410420 <i>Nat Genet (17 February 2008)</i><br /><br />MicroRNAs (miRNAs) are small, endogenously expressed RNAs that regulate mRNAs post-transcriptionally. The class of miRNA genes, like other gene classes, should experience birth, death and persistence of its members. We carried out deep sequencing of miRNAs from three species of Drosophila, and obtained 107,000 sequences that map to no fewer than 300 loci that were not previously known. We observe a large class of miRNA genes that are evolutionarily young, with a rate of birth of 12 new genes per million years (Myr). Most of these new miRNAs originated from non-miRNA sequences. Among the new genes, we estimate that 96% disappeared quickly in the course of evolution; only 4% of new miRNA genes were retained by natural selection. Furthermore, only 60% of these retained genes became integrated into the transcriptome in the long run (60 Myr). This small fraction (2.5%) of surviving miRNAs may later on become moderately or highly expressed. Our results suggest that there is a high birth rate of new miRNA genes, accompanied by a comparably high death rate. The estimated net gain of long-lived miRNA genes, which is not strongly affected by either the depth or the breadth (number of tissues) of sequencing, is 0.3 genes per Myr in Drosophila. The birth and death of microRNA genes in Drosophila. Jian Lu Yang Shen Qingfa Wu Supriya Kumar Bin He Suhua Shi Richard W Carthew San Ming Wang Chung-I Wu doi:10.1038/ng.73 Nat Genet (17 February 2008) 2008-02-22T08:12:45-00:00 2008 Nat Genet 1546-1718 no-tag