Overexpression of hepatocyte nuclear factor-4α initiates cell cycle entry, but is not sufficient to promote β-cell expansion in human islets.
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.
Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, 12-126 Translational Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-5156, USA.
Sebastian
S
Rieck
Jia
J
Zhang
Zhaoyu
Z
Li
Chengyang
C
Liu
Ali
A
Naji
Karen K
KK
Takane
Nathalie M
NM
Fiaschi-Taesch
Andrew F
AF
Stewart
Jake A
JA
Kushner
Klaus H
KH
Kaestner
D002453:Cell Cycle; D002455:Cell Division; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000494:pharmacology; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D051557:Hepatocyte Nuclear Factor 4; D007328:Insulin; D005947:Glucose