Overexpression of Hepatocyte Nuclear factor-4α Initiates Cell Cycle Entry, but Is Not Sufficient to Promote β-cell Expansion in Human Islets

Mol Endocrinol. 2012 Sep;26(9):1590-602. doi: 10.1210/me.2012-1019. Epub 2012 Jul 13.

Abstract

The transcription factor HNF4α (hepatocyte nuclear factor-4α) is required for increased β-cell proliferation during metabolic stress in vivo. We hypothesized that HNF4α could induce proliferation of human β-cells. We employed adenoviral-mediated overexpression of an isoform of HNF4α (HNF4α8) alone, or in combination with cyclin-dependent kinase (Cdk)6 and Cyclin D3, in human islets. Heightened HNF4α8 expression led to a 300-fold increase in the number of β-cells in early S-phase. When we overexpressed HNF4α8 together with Cdk6 and Cyclin D3, β-cell cycle entry was increased even further. However, the punctate manner of bromodeoxyuridine incorporation into HNF4α(High) β-cells indicated an uncoupling of the mechanisms that control the concise timing and execution of each cell cycle phase. Indeed, in HNF4α8-induced bromodeoxyuridine(+,punctate) β-cells we observed signs of dysregulated DNA synthesis, cell cycle arrest, and activation of a double stranded DNA damage-associated cell cycle checkpoint mechanism, leading to the initiation of loss of β-cell lineage fidelity. However, a substantial proportion of β-cells stimulated to enter the cell cycle by Cdk6 and Cyclin D3 alone also exhibited a DNA damage response. HNF4α8 is a mitogenic signal in the human β-cell but is not sufficient for completion of the cell cycle. The DNA damage response is a barrier to efficient β-cell proliferation in vitro, and we suggest its evaluation in all attempts to stimulate β-cell replication as an approach to diabetes treatment.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle
  • Cell Division
  • Cells, Cultured
  • Fluorescent Antibody Technique
  • Glucose / pharmacology
  • Hepatocyte Nuclear Factor 4 / genetics
  • Hepatocyte Nuclear Factor 4 / metabolism*
  • Humans
  • In Situ Nick-End Labeling
  • Insulin / metabolism
  • Insulin-Secreting Cells / cytology*
  • Insulin-Secreting Cells / drug effects
  • Insulin-Secreting Cells / metabolism*
  • Islets of Langerhans / cytology*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Hepatocyte Nuclear Factor 4
  • Insulin
  • Glucose