title: Loss of c-Met disrupts gene expression program required for G2/M progression during liver regeneration in mice.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Valentina M
authors.initials: VM
authors.lastname: Factor
authors.forename: Daekwan
authors.initials: D
authors.lastname: Seo
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Pal
authors.initials: P
authors.lastname: Kaposi-Novak
authors.forename: Jens U
authors.initials: JU
authors.lastname: Marquardt
authors.forename: Jesper B
authors.initials: JB
authors.lastname: Andersen
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Conner
authors.forename: Snorri S
authors.initials: SS
authors.lastname: Thorgeirsson
mesh_terms: D000818:Animals; D002455:Cell Division; D005260:Female; D016195:G2 Phase; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D008115:Liver Regeneration; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D019859:Proto-Oncogene Proteins c-met / Q000172:deficiency* / Q000235:genetics; D015854:Up-Regulation
chemical_list: D019859:Proto-Oncogene Proteins c-met