title: Genomic organization and embryonic expression of miR-430 in medaka (Oryzias latipes): insights into the post-transcriptional gene regulation in early development.
abstract: MicroRNAs (miRNAs, miRs) are short noncoding RNA molecules that negatively control the target mRNAs by binding to the 3' untranslated region (UTR). Previous studies have demonstrated that miR-430 is encoded by a clustered multigene family and is abundantly expressed in early development. In zebrafish, miR-430 is needed to suppress primordial germ cell (PGC)-specific genes, such as nanos1, in somatic cells. However, the molecular characteristics of the miR-430 family in other teleost species have not been reported, and it is unclear whether such a function of miR-430 in PGC specification is a conserved feature of animals or not. In medaka (Oryzias latipes), a distantly related teleost, it has been suggested that PGC might be established in a different mode of specification from that of zebrafish. We characterized 16 miR-430 precursors in the medaka genomic sequence. These miR-430 genes form clusters on chromosome 4, which might share its evolutionary origin with that of the very large miR-430 clusters in zebrafish chromosome 4. However, none of the medaka miR-430 genes are identical to the zebrafish miR-430 paralogs. Medaka miR-430 expression starts during epiboly and decreases after axis formation. Functional analysis using reporter gene constructs showed that miR-430 repressed protein expression by binding to the 3'UTR of zebrafish TDRD7. Consistently, the 3'UTR of medaka TDRD7 contains at least two significant candidates for the putative miR-430 binding site. The ubiquitous and early expression of medaka miR-430 and its ability to downregulate GFP:TDRD7 reporter mRNA imply that miR-430 has a conserved role in early embryogenesis. Smaller copy numbers of miR-430 genes and relatively brief expression in medaka might represent the characteristics of this miRNA family in the common ancestor of teleosts. Changes in the relationships between miR-430 and the target mRNA might be related to differences in the localization patterns of PGC-related genes in medaka and zebrafish.
authors.affiliation: Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodaicho, Nadaku, Kobe 657-8501, Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Tani
authors.forename: Rie
authors.initials: R
authors.lastname: Kusakabe
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Naruse
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Kunio
authors.initials: K
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002874:Chromosome Mapping; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D017403:In Situ Hybridization; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009990:Oryzias / Q000196:embryology* / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional; D022661:RNA, Untranslated / Q000737:chemistry / Q000235:genetics
chemical_list: D035683:MicroRNAs; D022661:RNA, Untranslated