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Hypophosphorylated pRb knock-in mice exhibit hallmarks of aging and vitamin C-preventable diabetes

ABSTRACT: Despite extensive in vitro analyses of retinoblastoma protein (pRB) phosphorylation, it is still unclear how this modification influences development and homeostasis in vivo. 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 a cumulative effect of blocking multiple pRb phosphorylation events. Diabetes in Rb∆K7 mice is insulin-sensitive and associated with failure of quiescent pancreatic -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 reductions in pancreatic islet mass and circulating insulin levels. Pre-treatment with the epigenetic regulator vitamin C reduces the 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.

SUBMITTER: Zhe Jiang

PROVIDER: S-SCDT-EMBOJ-2020-106825P | biostudies-other |

REPOSITORIES: biostudies-other

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Hypophosphorylated pRb knock-in mice exhibit hallmarks of aging and vitamin C-preventable diabetes.

Project description: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.

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