title: Characterization of the compact bicistronic microRNA precursor, miR-1/miR-133, expressed specifically in Ciona muscle tissues.
abstract: Muscle-specific miR-1/206 and miR-133 families have been suggested to play fundamental roles in skeletal and cardiac myogenesis in vertebrates. To gain insights into the relationships between the divergence of these miRs and muscular tissue types, we investigated the expression patterns of miR-1 and miR-133 in two ascidian Ciona species and compared their genomic structures with those of other chordates. We found that Ciona intestinalis and Ciona savignyi each possess a single copy of the miR-1/miR-133 cluster, which is only 350 nucleotide long. During embryogenesis, Ciona miR-1 and miR-133 are generated as a single continuous primary transcript accumulated in the nuclei of the tail muscle cells, starting at the gastrula stage. In adults, mature miR-133 and miR-1 are differentially expressed in the heart and body wall muscle. Expression of the reporter gene linked to the 850-bp upstream region of the predicted transcription start site confirmed that this region drives the muscle-specific expression of the primary transcript of miR-1/miR-133. In many deuterostome lineages, including that of Ciona, the miR-1/133 cluster is located in the same intron of the mind bomb (mib) gene in reverse orientation. Our results suggest that the origin of genomic organization and muscle-specific regulation of miR-1/133 can be traced back to the ancestor of chordates. Duplication of this miR cluster might have led to the remarkable elaboration in the morphology and function of skeletal muscles in the vertebrate lineage.
authors.affiliation: Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodaicho, Kobe 657-8501, Japan. riek@ruby.kobe-u.ac.jp
authors.forename: Rie
authors.initials: R
authors.lastname: Kusakabe
authors.forename: Saori
authors.initials: S
authors.lastname: Tani
authors.forename: Koki
authors.initials: K
authors.lastname: Nishitsuji
authors.forename: Miyuki
authors.initials: M
authors.lastname: Shindo
authors.forename: Kohji
authors.initials: K
authors.lastname: Okamura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Kenta
authors.initials: K
authors.lastname: Nakai
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Takehiro G
authors.initials: TG
authors.lastname: Kusakabe
authors.forename: Kunio
authors.initials: K
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001483:Base Sequence; D002938:Ciona intestinalis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D035683:MicroRNAs / Q000378:metabolism*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*; D009928:Organ Specificity; D010802:Phylogeny; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D035683:MicroRNAs; D012322:RNA Precursors