The stable repression of mesenchymal program is required for hepatocyte identity: A novel role for hepatocyte nuclear factor 4α

Authors

  • Laura Santangelo,

    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    Search for more papers by this author
  • Alessandra Marchetti,

    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    Search for more papers by this author
  • Carla Cicchini,

    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    Search for more papers by this author
  • Alice Conigliaro,

    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    Search for more papers by this author
  • Beatrice Conti,

    1. National Institute for Infectious Diseases L. Spallanzani, Institute of Research and Cure of Scientific Character, Rome, Italy
    Search for more papers by this author
  • Carmine Mancone,

    1. National Institute for Infectious Diseases L. Spallanzani, Institute of Research and Cure of Scientific Character, Rome, Italy
    Search for more papers by this author
  • Jessica A. Bonzo,

    1. Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
    Search for more papers by this author
  • Frank J. Gonzalez,

    1. Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
    Search for more papers by this author
  • Tonino Alonzi,

    1. National Institute for Infectious Diseases L. Spallanzani, Institute of Research and Cure of Scientific Character, Rome, Italy
    Search for more papers by this author
  • Laura Amicone,

    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    Search for more papers by this author
  • Marco Tripodi

    Corresponding author
    1. Department of Cellular Biotechnologies and Hematology, Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
    2. National Institute for Infectious Diseases L. Spallanzani, Institute of Research and Cure of Scientific Character, Rome, Italy
    • Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica, Molecolare, Sapienza University of Rome, Viale Regina Elena 324, 00161 Rome, Italy
    Search for more papers by this author
    • fax: (39)-06-4462891


  • Supported by Cancer Research Italian Foundation (FIRC), Ministry of Health, MIUR Ministry of University and Scientific Research, and Waldensian Church. L. S. is recipient of a “Giorgio Ferraresi” FIRC 2010-2012 Fellowship for Cancer Research.

Abstract

The concept that cellular terminal differentiation is stably maintained once development is complete has been questioned by numerous observations showing that differentiated epithelium may undergo an epithelial-to-mesenchymal transition (EMT) program. EMT and the reverse process, mesenchymal-to-epithelial transition (MET), are typical events of development, tissue repair, and tumor progression. In this study, we aimed to clarify the molecular mechanisms underlying these phenotypic conversions in hepatocytes. Hepatocyte nuclear factor 4α (HNF4α) was overexpressed in different hepatocyte cell lines and the resulting gene expression profile was determined by real-time quantitative polymerase chain reaction. HNF4α recruitment on promoters of both mesenchymal and EMT regulator genes was determined by way of electrophoretic mobility shift assay and chromatin immunoprecipitation. The effect of HNF4α depletion was assessed in silenced cells and in the context of the whole liver of HNF4 knockout animals. Our results identified key EMT regulators and mesenchymal genes as new targets of HNF4α. HNF4α, in cooperation with its target HNF1α, directly inhibits transcription of the EMT master regulatory genes Snail, Slug, and HMGA2 and of several mesenchymal markers. HNF4α-mediated repression of EMT genes induces MET in hepatomas, and its silencing triggers the mesenchymal program in differentiated hepatocytes both in cell culture and in the whole liver. Conclusion: The pivotal role of HNF4α in the induction and maintenance of hepatocyte differentiation should also be ascribed to its capacity to continuously repress the mesenchymal program; thus, both HNF4α activator and repressor functions are necessary for the identity of hepatocytes. (HEPATOLOGY 2011;)

Ancillary