Δ40 Isoform of p53 Controls β-Cell Proliferation and Glucose Homeostasis in Mice

Abstract

Objective: Investigating the dynamics of pancreatic β-cell mass is critical for developing strategies to treat both type 1 and type 2 diabetes. p53, a key regulator of the cell cycle and apoptosis, has mostly been a focus of investigation as a tumor suppressor. Although p53 alternative transcripts can modulate p53 activity, their functions are not fully understood. We hypothesized that β-cell proliferation and glucose homeostasis were controlled by Δ40p53, a p53 isoform lacking the transactivation domain of the full-length protein that modulates total p53 activity and regulates organ size and life span in mice. Research design and methods: We phenotyped metabolic parameters in Δ40p53 transgenic (p44tg) mice and used quantitative RT-PCR, Western blotting, and immunohistochemistry to examine β-cell proliferation. Results: Transgenic mice with an ectopic p53 gene encoding Δ40p53 developed hypoinsulinemia and glucose intolerance by 3 months of age, which worsened in older mice and led to overt diabetes and premature death from ∼14 months of age. Consistent with a dramatic decrease in β-cell mass and reduced β-cell proliferation, lower expression of cyclin D2 and pancreatic duodenal homeobox-1, two key regulators of proliferation, was observed, whereas expression of the cell cycle inhibitor p21, a p53 target gene, was increased. Conclusions: These data indicate a significant and novel role for Δ40p53 in β-cell proliferation with implications for the development of age-dependent diabetes.