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A High-content In Vitro Pancreatic Islet β-cell Replication Discovery Platform
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A High-content In Vitro Pancreatic Islet β-cell Replication Discovery Platform

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Polycomb protein Ezh2 regulates pancreatic beta-cell Ink4a/Arf expression and regeneration in diabetes mellitus

Hainan Chen1, Xueying Gu, I-hsin Su

  • 1Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.

Genes & Development
|April 25, 2009
PubMed

Insights

Enhancer of zeste homolog 2 (Ezh2) represses Ink4a/Arf in pancreatic islet beta cells. Declining Ezh2 in aging cells impairs beta-cell regeneration and contributes to diabetes pathogenesis.

Area of Science:

  • Endocrinology
  • Epigenetics
  • Cell Biology

Background:

  • Pancreatic islet beta cell proliferation is crucial for self-renewal and adaptive expansion.
  • The Ink4a/Arf locus, encoding p16(INK4a) and p19(Arf), limits beta-cell regeneration in aging mice.
  • Regulation of beta-cell Ink4a/Arf is poorly understood.

Purpose of the Study:

  • To investigate the role of Enhancer of zeste homolog 2 (Ezh2) in regulating Ink4a/Arf expression in pancreatic islet beta cells.
  • To elucidate the mechanisms underlying beta-cell regenerative failure in aging and diabetes.

Main Methods:

  • Utilized conditional Ezh2 deletion in beta cells of juvenile mice.
  • Assessed histone H3 trimethylation at the Ink4a/Arf locus.
  • Quantified levels of p16(INK4a), p19(Arf), beta-cell proliferation, and mass.
  • Induced beta-cell destruction using streptozotocin in control and mutant mice.

Main Results:

  • Ezh2 represses Ink4a/Arf in islet beta cells.
  • Ezh2 levels decline in aging beta cells, correlating with reduced histone methylation and increased p16(INK4a)/p19(Arf).
  • Conditional beta-cell Ezh2 deletion caused precocious Ink4a/Arf induction, reduced beta-cell mass, hypoinsulinemia, and mild diabetes, phenotypes rescued by Ink4a/Arf deletion.
  • In response to injury, control mice showed increased Ezh2 and beta-cell regeneration, while mutant mice failed to regenerate, leading to lethal diabetes.

Conclusions:

  • Ezh2 is a key epigenetic regulator of beta-cell proliferation and regeneration.
  • Ezh2-dependent regulation of Ink4a/Arf is critical for maintaining beta-cell mass and function.
  • Dysregulation of Ezh2 contributes to age-related beta-cell regenerative failure and diabetes pathogenesis.

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