title: Identification and differential expression of microRNAs during metamorphosis of the Japanese flounder (Paralichthys olivaceus).
abstract: BACKGROUND
  MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs of 20-25 nucleotides that play a key role in diverse biological processes. Japanese flounder undergo dramatic metamorphosis in their early development. The metamorphosis is characterized by morphological transformation from a bilaterally symmetrical to an asymmetrical body shape concomitant with extensive morphological and physiological remodeling of organs. So far, only a few miRNAs have been identified in fish and there are very few reports about the Japanese flounder miRNA.
  
  
  RESULTS
  Solexa sequencing technology was used to perform high throughput sequencing of the small RNA library from the metamorphic period of Japanese flounder. Subsequently, aligning these sequencing data with metazoan known miRNAs, we characterized 140 conserved miRNAs and 57 miRNA: miRNA* pairs from the small RNA library. Among these 57 miRNA: miRNA* pairs, twenty flounder miRNA precursors were amplified from genomic DNA. We also demonstrated evolutionary conservation of Japanese flounder miRNAs and miRNA* in the animal evolution process. Using miRNA microarrays, we identified 66 differentially expressed miRNAs at two metamorphic stages (17 and 29 days post hatching) of Japanese flounder. The results show that miRNAs might play a key role in regulating gene expression during Japanese flounder metamorphosis.
  
  
  CONCLUSIONS
  We identified a large number of miRNAs during flounder metamorphosis, some of which are differentially expressed at two different metamorphic stages. The study provides an opportunity for further understanding of miRNA function in the regulation of flounder metamorphosis and gives us clues for further studies of the mechanisms of metamorphosis in Japanese flounder.
authors.affiliation: Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Shanghai Ocean University, Ministry of Education, Shanghai, People's Republic of China.
authors.forename: Yuanshuai
authors.initials: Y
authors.lastname: Fu
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Shi
authors.forename: Minglin
authors.initials: M
authors.lastname: Wu
authors.forename: Junling
authors.initials: J
authors.lastname: Zhang
authors.forename: Liang
authors.initials: L
authors.lastname: Jia
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D005432:Flounder / Q000235:genetics* / Q000254:growth & development*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D007564:Japan; D008675:Metamorphosis, Biological / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D017422:Sequence Analysis, DNA
chemical_list: D035683:MicroRNAs