Polycomb group protein Ezh2 regulates hepatic progenitor cell proliferation and differentiation in murine embryonic liver

PLoS One. 2014 Aug 25;9(8):e104776. doi: 10.1371/journal.pone.0104776. eCollection 2014.

Abstract

In embryonic liver, hepatic progenitor cells are actively proliferating and generate a fundamental cellular pool for establishing parenchymal components. However, the molecular basis for the expansion of the progenitors maintaining their immature state remains elusive. Polycomb group proteins regulate gene expression throughout the genome by modulating of chromatin structure and play crucial roles in development. Enhancer of zeste homolog 2 (Ezh2), a key component of polycomb group proteins, catalyzes tri-methylation of lysine 27 of histone H3 (H3K27me3), which trigger the gene suppression. In the present study, we investigated a role of Ezh2 in the regulation of the expanding hepatic progenitor population in vivo. We found that Ezh2 is highly expressed in the actively proliferating cells at the early developmental stage. Using a conditional knockout mouse model, we show that the deletion of the SET domain of Ezh2, which is responsible for catalytic induction of H3K27me3, results in significant reduction of the total liver size, absolute number of liver parenchymal cells, and hepatic progenitor cell population in size. A clonal colony assay in the hepatic progenitor cells directly isolated from in vivo fetal livers revealed that the bi-potent clonogenicity was significantly attenuated by the Ezh2 loss of function. Moreover, a marker expression based analysis and a global gene expression analysis showed that the knockout of Ezh2 inhibited differentiation to hepatocyte with reduced expression of a number of liver-function related genes. Taken together, our results indicate that Ezh2 is required for the hepatic progenitor expansion in vivo, which is essential for the functional maturation of embryonic liver, through its activity for catalyzing H3K27me3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Differentiation*
  • Cell Proliferation*
  • Enhancer of Zeste Homolog 2 Protein
  • Gene Expression Regulation
  • Hepatocytes / cytology
  • Hepatocytes / metabolism
  • Liver / cytology
  • Liver / embryology
  • Liver / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Polycomb Repressive Complex 2 / genetics
  • Polycomb Repressive Complex 2 / metabolism
  • Polycomb Repressive Complex 2 / physiology*
  • Protein Structure, Tertiary

Substances

  • Enhancer of Zeste Homolog 2 Protein
  • Ezh2 protein, mouse
  • Polycomb Repressive Complex 2

Grants and funding

This work was supported by grants from the Special Coordination Funds for Promoting Science (11800122), grants from Stategic Promotion of Innovative Research and Development (S-innovation, 62890004), the Grant-in-Aid for Scientific Research on Innovative Areas, and the Japan Health Sciences Foundation of the Japan Science and Technology Agency (JST). This work was also supported by the Grants-in-Aid No. 20591532, 21249071, 22390260, 23791490, 23791491, 24106510, 24689052, 25253079, and 25461956 of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan; by the Specified Research Grant from Takeda Science Foundation; by a grant from Yokohama Foundation for Advanced Medical Science; and by a grant from Japan Insulin Dependent Diabetes Mellitus (IDDM) network. This work was partially supported by funding from Creation of Innovation Centers for Advanced Interdisciplinary Research Areas Program in the Project for Developing Innovation Systems from the MEXT, by funding from Centers for Clinical Application Research on Specific Disease/Organ of the MEXT, and by the Grants-in-Aid for Pancreas Research 2013 from Pancreas Research Foundation of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.