title: miR-148a plays a pivotal role in the liver by promoting the hepatospecific phenotype and suppressing the invasiveness of transformed cells.
abstract: MicroRNAs (miRNAs) are evolutionary conserved small RNAs that post-transcriptionally regulate the expression of target genes. To date, the role of miRNAs in liver development is not fully understood. By using an experimental model that allows the induced and controlled differentiation of mouse fetal hepatoblasts (MFHs) into mature hepatocytes, we identified miR-148a as a hepatospecific miRNA highly expressed in adult liver. The main finding of this study revealed that miR-148a was critical for hepatic differentiation through the direct targeting of DNA methyltransferase (DNMT) 1, a major enzyme responsible for epigenetic silencing, thereby allowing the promotion of the "adult liver" phenotype. It was also confirmed that the reduction of DNMT1 by RNA interference significantly promoted the expression of the major hepatic biomarkers. In addition to the essential role of miR-148a in hepatocyte maturation, we identified its beneficial effect through the repression of hepatocellular carcinoma (HCC) cell malignancy. miR-148a expression was frequently down-regulated in biopsies of HCC patients as well as in mouse and human HCC cell lines. Overexpressing miR-148a led to an enhancement of albumin production and a drastic inhibition of the invasive properties of HCC cells, whereas miR-148a silencing had the opposite consequences. Finally, we showed that miR-148a exerted its tumor-suppressive effect by regulating the c-Met oncogene, regardless of the DNMT1 expression level.
  
  
  CONCLUSIONS
  miR-148a is essential for the physiology of the liver because it promotes the hepatospecific phenotype and acts as a tumor suppressor. Most important, this report is the first to demonstrate a functional role for a specific miRNA in liver development through regulation of the DNMT1 enzyme.
authors.affiliation: Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Luc
authors.initials: L
authors.lastname: Gailhouste
authors.forename: Laura
authors.initials: L
authors.lastname: Gomez-Santos
authors.forename: Keitaro
authors.initials: K
authors.lastname: Hagiwara
authors.forename: Izuho
authors.initials: I
authors.lastname: Hatada
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kitagawa
authors.forename: Kazushi
authors.initials: K
authors.lastname: Kawaharada
authors.forename: Muriel
authors.initials: M
authors.lastname: Thirion
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Kosaka
authors.forename: Ryou-U
authors.initials: RU
authors.lastname: Takahashi
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Shibata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyajima
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ochiya
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology; D022781:Hepatocytes / Q000473:pathology*; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D035683:MicroRNAs / Q000502:physiology*; D009361:Neoplasm Invasiveness / Q000473:pathology; D010641:Phenotype
chemical_list: D000418:Albumins; C550570:MIRN148 microRNA, human; D035683:MicroRNAs; C554644:Mirn148 microRNA, mouse; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse