DNA repair protein RAD50 is involved in the streptozotocin-induced diabetes susceptibility of mice

Streptozotocin (STZ) is widely used as a pancreatic beta-cell toxin to induce experimental diabetes in rodents. Strain-dependent variations in STZ-induced diabetes susceptibility have been reported in mice. Differences in STZ-induced diabetes susceptibility are putatively related to pancreatic beta-cell fragility via DNA damage response. In this study, we identified two STZ-induced diabetes susceptibility regions in chromosome 11 (Chr11) of Nagoya-Shibata-Yasuda (NSY) mice via congenic mapping using the C3H-11^NSY consomic strains, in which the entire Chr11 of STZ-resistant C3H/He (C3H) mice was replaced with that of NSY mice, and named them STZ susceptibility region for NSY (Ssnsy)-1 and -2, respectively. Screening for variants in the Ssnsy1 region revealed that NSY mice exhibited a characteristic missense c.599G>T (p.G200V) variant in a highly conserved region within the DNA repair gene, RAD50 double-strand break repair protein (Rad50). Subsequently, we generated R2B1-Rad50 knock-in mice, in which c.599T in Rad50 of STZ-susceptible C3H.NSY-R2B1 subcongenic mice was replaced with c.599G via genome editing. Compared with C3H.NSY-R2B1 mice, and R2B1-Rad50 knock-in mice showed suppressed hyperglycemia, incidence of diabetes, and decrease in plasma insulin levels following single high-dose and multiple low-dose injections of STZ. Our results suggest Rad50 as a susceptibility gene for STZ-induced diabetes that is involved in pancreatic beta-cell fragility. Forward genetic approaches using inbred mouse strains with STZ susceptibility as a phenotypic indicator will further elucidate the molecular mechanisms of pancreatic beta-cell destruction via DNA damage response.