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Loss of c-Met disrupts gene expression program required for G2/M progression during liver regeneration in mice.

ABSTRACT: Previous work has established that HGF/c-Met signaling plays a pivotal role in regulating the onset of S phase following partial hepatectomy (PH). In this study, we used Met(fl/fl);Alb-Cre(+/-) conditional knockout mice to determine the effects of c-Met dysfunction in hepatocytes on kinetics of liver regeneration.The priming events appeared to be intact in Met(fl/fl);Alb-Cre(+/-) livers. Up-regulation of stress response (MAFK, IKBZ, SOCS3) and early growth response (c-Myc, c-Jun, c-Fos, DUSP1 and 6) genes as assessed by RT-qPCR and/or microarray profiling was unchanged. This was consistent with an early induction of MAPK/Erk and STAT3. However, after a successful completion of the first round of DNA replication, c-Met deficient hepatocytes were blocked in early/mid G2 phase as shown by staining with phosphorylated form of histone H3. Furthermore, loss of c-Met in hepatocytes diminished the subsequent G1/S progression and delayed liver recovery after partial hepatectomy. Upstream signaling pathways involved in the blockage of G2/M transition included lack of persistent Erk1/2 activation and inability to up-regulate the levels of Cdk1, Plk1, Aurora A and B, and Mad2 along with a defective histone 3 phosphorylation and lack of chromatin condensation. Continuous supplementation with EGF in vitro increased proliferation of Met(fl/fl);Alb-Cre(+/-) primary hepatocytes and partially restored expression levels of mitotic cell cycle regulators albeit to a lesser degree as compared to control cultures.In conclusion, our results assign a novel non-redundant function for HGF/c-Met signaling in regulation of G2/M gene expression program via maintaining a persistent Erk1/2 activation throughout liver regeneration.

SUBMITTER: Factor VM

PROVIDER: S-EPMC2940888 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Loss of c-Met disrupts gene expression program required for G2/M progression during liver regeneration in mice.

Factor Valentina M VM Seo Daekwan D Ishikawa Tsuyoshi T Kaposi-Novak Pal P Marquardt Jens U JU Andersen Jesper B JB Conner Elizabeth A EA Thorgeirsson Snorri S SS

PloS one 20100916 9

<h4>Background</h4>Previous work has established that HGF/c-Met signaling plays a pivotal role in regulating the onset of S phase following partial hepatectomy (PH). In this study, we used Met(fl/fl);Alb-Cre(+/-) conditional knockout mice to determine the effects of c-Met dysfunction in hepatocytes on kinetics of liver regeneration.<h4>Methodology/principal finding</h4>The priming events appeared to be intact in Met(fl/fl);Alb-Cre(+/-) livers. Up-regulation of stress response (MAFK, IKBZ, SOCS3) ...[more]

PMID: 20862286

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Project description:UnlabelledHepatocyte growth factor (HGF)/c-Met supports a pleiotrophic signal transduction pathway that controls stem cell homeostasis. Here, we directly addressed the role of c-Met in stem-cell-mediated liver regeneration by utilizing mice harboring c-met floxed alleles and Alb-Cre or Mx1-Cre transgenes. To activate oval cells, the hepatic stem cell (HSC) progeny, we used a model of liver injury induced by diet containing the porphyrinogenic agent, 3,5-diethocarbonyl-1,4-dihydrocollidine (DDC). Deletion of c-met in oval cells was confirmed in both models by polymerase chain reaction analysis of fluorescence-activated cell-sorted epithelial cell adhesion molecule (EpCam)-positive cells. Loss of c-Met receptor decreased the sphere-forming capacity of oval cells in vitro as well as reduced oval cell pool, impaired migration, and decreased hepatocytic differentiation in vivo, as demonstrated by double immunofluorescence using oval- (A6 and EpCam) and hepatocyte-specific (i.e. hepatocyte nuclear factor 4-alpha) antibodies. Furthermore, lack of c-Met had a profound effect on tissue remodeling and overall composition of HSC niche, which was associated with greatly reduced matrix metalloproteinase (MMP)9 activity and decreased expression of stromal-cell-derived factor 1. Using a combination of double immunofluorescence of cell-type-specific markers with MMP9 and gelatin zymography on the isolated cell populations, we identified macrophages as a major source of MMP9 in DDC-treated livers. The Mx1-Cre-driven c-met deletion caused the greatest phenotypic impact on HSCs response, as compared to the selective inactivation in the epithelial cell lineages achieved in c-Met(fl/fl); Alb-Cre(+/-) mice. However, in both models, genetic loss of c-met triggered a similar cascade of events, leading to the failure of HSC mobilization and death of the mice.ConclusionThese results establish a direct contribution of c-Met in the regulation of HSC response and support a unique role for HGF/c-Met as an essential growth-factor-signaling pathway for regeneration of diseased liver.

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Loss of c-Met disrupts gene expression program required for G2/M progression during liver regeneration in mice.

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Loss of c-Met disrupts gene expression program required for G2/M progression during liver regeneration in mice.

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