title: Early origins and evolution of microRNAs and Piwi-interacting RNAs in animals.
abstract: 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.
authors.affiliation: Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Grimson
authors.forename: Mansi
authors.initials: M
authors.lastname: Srivastava
authors.forename: Bryony
authors.initials: B
authors.lastname: Fahey
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Woodcroft
authors.forename: H Rosaria
authors.initials: HR
authors.lastname: Chiang
authors.forename: Nicole
authors.initials: N
authors.lastname: King
authors.forename: Bernard M
authors.initials: BM
authors.lastname: Degnan
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Rokhsar
authors.forename: David P
authors.initials: DP
authors.lastname: Bartel
mesh_terms: D000818:Animals; D001483:Base Sequence; D005057:Eukaryotic Cells / Q000378:metabolism; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D010802:Phylogeny; D034741:RNA, Small Interfering / Q000235:genetics*; D012615:Sea Anemones / Q000235:genetics*; D017421:Sequence Analysis
chemical_list: D035683:MicroRNAs; D034741:RNA, Small Interfering