Transcriptional profiling implicates TGFβ/BMP and Notch signaling pathways in ductular differentiation of fetal murine hepatoblasts

Abstract

Bile duct morphogenesis involves sequential induction of biliary specific gene expression, bilayer generation, cell proliferation, remodeling and apoptosis. HBC-3 cells are a model system to study differentiation of hepatoblasts along the hepatocytic or bile ductular lineage in vitro and in vivo. We used microarray to define molecular pathways during ductular differentiation in response to Matrigel. The temporal pattern of expression of marker genes induced was similar to that observed during bile duct formation in vivo. Notch, HNF1beta, Polycystic kidney disease 2, Bicaudal C 1 and beta-catenin were up regulated during the time course. Functional clustering analysis revealed significant up regulation of clusters of genes involved in extracellular matrix remodeling, ion transport, vacuoles, lytic vacuoles, pro-apoptotic and anti-apoptotic genes, transcription factors and negative regulators of the cell proliferation, while genes involved in the cell cycle were significantly down regulated. Notch signaling pathway was activated by treatment with Matrigel. In addition, TGFbeta/BMP signaling pathway members including the type I TGFbeta receptor and Smads 3, 4 and 5 were significantly up regulated, as were several TGFbeta/BMP responsive genes including Hey 1, a regulator of Notch pathway signaling. SMADS 3, 4 and 5 were present in the nuclear fraction of HBC-3 cells during ductular differentiation in vitro, but not during hepatocyte differentiation. SMAD 5 was preferentially expressed in hepatoblasts undergoing bile duct morphogenesis in the fetal liver, while the TGFbeta/BMP signaling antagonist chordin, was expressed throughout the liver suggesting a mechanism by which TGFbeta/BMP signaling is limited to hepatoblasts that contact portal mesenchyme in vivo.

Stabilization of β-catenin affects mouse embryonic liver growth and hepatoblast fate

“…The two main pathways identified and validated by in vivo experiments are the transforming growth factor ␤ (TGF␤) and Notch pathways. 16,[29][30][31] Furthermore, ␤-catenin signaling may be the missing link accounting for the extinction of hepatocyte differentiation in biliary cells. Indeed, in compound mice invalidated for both Onecut transcription factors, Hnf6 and Oc2, TGF␤ signaling is no longer restricted to the ductal plate and is instead observed throughout the lobule.…”

WNT/β-catenin signaling in liver health and disease

“…This is of further interest, especially because its role in biliary development is beginning to be understood. 18,53 ␤-Catenin: A Potential Therapeutic Target in HCC?…”

FGF signaling segregates biliary cell‐lineage from chick hepatoblasts cooperatively with BMP4 and ECM components in vitro

“…In addition, the expression of Smad5, an intracellular mediator of BMP signaling, is strongest in the ductal plate area (Ader et al 2006). This pattern of expression is consistent with our observation that BMP4 enhances biliary differentiation in cooperation with bFGF, whose receptors FGFR1 and FGFR2 are expressed in the ductal plate.…”