Related Experiment Video
Updated: Jun 17, 2026
A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging
Published on: July 14, 2016
Hypophosphorylated pRb knock-in mice exhibit hallmarks of aging and vitamin C-preventable diabetes
Zhe Jiang1, Huiqin Li1, Stephanie A Schroer1
1Max Bell Research Centre, Toronto General Research Institute, University Health Network, Toronto, ON, Canada.
Abstract:
Despite extensive analysis of pRB phosphorylation in vitro, how this modification influences development and homeostasis in vivo is unclear. Here, we show that homozygous Rb∆K4 and Rb∆K7 knock-in mice, in which either four or all seven phosphorylation sites in the C-terminal region of pRb, respectively, have been abolished by Ser/Thr-to-Ala substitutions, undergo normal embryogenesis and early development, notwithstanding suppressed phosphorylation of additional upstream sites. Whereas Rb∆K4 mice exhibit telomere attrition but no other abnormalities, Rb∆K7 mice are smaller and display additional hallmarks of premature aging including infertility, kyphosis, and diabetes, indicating an accumulative effect of blocking pRb phosphorylation. Diabetes in Rb∆K7 mice is insulin-sensitive and associated with failure of quiescent pancreatic β-cells to re-enter the cell cycle in response to mitogens, resulting in induction of DNA damage response (DDR), senescence-associated secretory phenotype (SASP), and reduced pancreatic islet mass and circulating insulin level. Pre-treatment with the epigenetic regulator vitamin C reduces DDR, increases cell cycle re-entry, improves islet morphology, and attenuates diabetes. These results have direct implications for cell cycle regulation, CDK-inhibitor therapeutics, diabetes, and longevity.
Insights
Blocking pRB phosphorylation sites in mice causes premature aging and diabetes. Vitamin C treatment improved cell cycle re-entry and attenuated diabetes in Rb∆K7 mice.
Area of Science:
- Molecular Biology
- Cell Biology
- Aging Research
Background:
- The in vivo role of pRB phosphorylation in development and homeostasis remains poorly understood.
- Previous studies focused on in vitro analysis of pRB phosphorylation.
Purpose of the Study:
- To investigate the in vivo effects of abolishing pRB phosphorylation sites on mouse development and aging.
- To explore the mechanisms underlying premature aging phenotypes and diabetes in mice with altered pRB phosphorylation.
Main Methods:
- Generation of homozygous Rb∆K4 and Rb∆K7 knock-in mouse models with specific phosphorylation sites abolished.
- Analysis of developmental, aging, and metabolic phenotypes in these mouse models.
- Investigation of pancreatic beta-cell function, DNA damage response (DDR), and senescence-associated secretory phenotype (SASP).
Main Results:
- Rb∆K7 mice, unlike Rb∆K4 mice, exhibited smaller size, infertility, kyphosis, and diabetes, indicating an accumulative effect of blocking pRB phosphorylation.
- Diabetes in Rb∆K7 mice was linked to impaired pancreatic beta-cell proliferation, DDR, SASP, and reduced insulin levels.
- Vitamin C pre-treatment mitigated DDR, enhanced beta-cell cycle re-entry, improved islet morphology, and attenuated diabetes.
Conclusions:
- Abolishing multiple pRB phosphorylation sites in vivo leads to premature aging and insulin-sensitive diabetes.
- Impaired pancreatic beta-cell regeneration contributes to diabetes in Rb∆K7 mice.
- Vitamin C shows potential therapeutic benefits for age-related diabetes by modulating DDR and cell cycle re-entry.
