title: The 4 Notch receptors play distinct and antagonistic roles in the proliferation and hepatocytic differentiation of liver progenitors.
abstract: The Notch signaling pathway is involved in liver development and regeneration. Here, we investigate the role of the 4 mammalian Notch paralogs in the regulation of hepatoblast proliferation and hepatocytic differentiation. Our model is based on bipotential mouse embryonic liver (BMEL) progenitors that can differentiate into hepatocytes or cholangiocytes in vitro and in vivo. BMEL cells were subjected to Notch antagonists or agonists. Blocking Notch activation with a γ-secretase inhibitor, at 50 μM for 48 h, reduced cell growth by 50%. S-phase entry was impaired, but no apoptosis was induced. A systematic paralog-specific strategy was set using lentiviral transduction with constitutively active forms of each Notch receptor along with inhibition of endogenous Notch signaling. This assay demonstrates that proliferation of BMEL cells requires Notch2 and Notch4 activity, resulting in significant down-regulation of p27(Kip1) and p57(Kip2) cyclin-dependent kinase inhibitors. Conversely, Notch3-expressing cells proliferate less and express 3-fold higher levels of p57(Kip2). The Notch3 cells present a hepatocyte-like morphology, enhanced multinucleation, and a ploidy shift. Moreover, Notch3 activity is conducive to hepatocytic differentiation in vitro, while its paralogs impede this fate. Our study provides the first evidence of a functional diversity among the mammalian Notch homologues in the proliferation and hepatocytic-lineage commitment of liver progenitors.
authors.affiliation: 1Unité de Signalisation Moléculaire et Activation Cellulaire, URA 2582 CNRS, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France. neetu.gupta@pasteur.fr.
authors.forename: Sara
authors.initials: S
authors.lastname: Ortica
authors.forename: Nadine
authors.initials: N
authors.lastname: Tarantino
authors.forename: Nathalie
authors.initials: N
authors.lastname: Aulner
authors.forename: Alain
authors.initials: A
authors.lastname: Israël
authors.forename: Neetu
authors.initials: N
authors.lastname: Gupta-Rossi
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation; D005455:Fluorescent Antibody Technique; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism*; D008099:Liver / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D060888:Real-Time Polymerase Chain Reaction; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*
chemical_list: D051880:Receptors, Notch
keywords: CDK inhibitors; bipotential stem cells; hepatoblasts; paralogs; polyploidy