title: The Hippo pathway effector YAP controls mouse hepatic stellate cell activation.
abstract: OBJECTIVE
  Hepatic stellate cell activation is a wound-healing response to liver injury. However, continued activation of stellate cells during chronic liver damage causes excessive matrix deposition and the formation of pathological scar tissue leading to fibrosis and ultimately cirrhosis. The importance of sustained stellate cell activation for this pathological process is well recognized, and several signalling pathways that can promote stellate cell activation have been identified, such as the TGFβ-, PDGF-, and LPS-dependent pathways. However, the mechanisms that trigger and drive the early steps in activation are not well understood.
  
  
  RESULTS
  We identified the Hippo pathway and its effector YAP as a key pathway that controls stellate cell activation. YAP is a transcriptional co-activator and we found that it drives the earliest changes in gene expression during stellate cell activation. Activation of stellate cells in vivo by CCl4 administration to mice or activation in vitro caused rapid activation of YAP as revealed by its nuclear translocation and by the induction of YAP target genes. YAP was also activated in stellate cells of human fibrotic livers as evidenced by its nuclear localization. Importantly, knockdown of YAP expression or pharmacological inhibition of YAP prevented hepatic stellate cell activation in vitro and pharmacological inhibition of YAP impeded fibrogenesis in mice.
  
  
  CONCLUSIONS
  YAP activation is a critical driver of hepatic stellate cell activation and inhibition of YAP presents a novel approach for the treatment of liver fibrosis.
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Inge
authors.initials: I
authors.lastname: Mannaerts
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Sofia Batista
authors.initials: SB
authors.lastname: Leite
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: Verhulst
authors.affiliation: VIB Center for the Biology of Disease, and KU Leuven Center for Human Genetics, University of Leuven, 3000 Leuven, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Claerhout
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Eysackers
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Lien F R
authors.initials: LF
authors.lastname: Thoen
authors.affiliation: Department of Pathology, Universitair Ziekenhuis Brussel, Brussels, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Hoorens
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Reynaert
authors.affiliation: VIB Center for the Biology of Disease, and KU Leuven Center for Human Genetics, University of Leuven, 3000 Leuven, Belgium.
authors.forename: Georg
authors.initials: G
authors.lastname: Halder
authors.affiliation: Liver Cell Biology Lab, Vrije Universiteit Brussel, 1090 Brussel, Belgium. Electronic address: leo.van.grunsven@vub.ac.be.
authors.forename: Leo A
authors.initials: LA
authors.lastname: van Grunsven
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D018797:Cell Cycle Proteins; D055166:Hepatic Stellate Cells / Q000502:physiology*; D000090683:Hippo Signaling Pathway; D006801:Humans; D008103:Liver Cirrhosis / Q000517:prevention & control; D051379:Mice; D008807:Mice, Inbred BALB C; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human; C486223:Yap1 protein, mouse; D017346:Protein Serine-Threonine Kinases
keywords: Ankrd1; Ctgf; Fibrosis; Gene expression profiling; Hepatic stellate cell; Liver; Spheroid; YAP