375-OR: Epigenetic Control of Beta-Cell Stress Response and Senescence

Both type 1 and type 2 diabetes (T1D and T2D) result from chronic insulin insufficiency due to progressive dysfunction and loss of beta cells, driven by cellular stress. Beta cell failure in both forms of diabetes involves defective stress-response and the onset of premature senescence, an irreversible form of cell-cycle arrest induced by chronic stress. However, the mechanisms by which cellular stress triggers beta cell senescence are not clear. We now show that CTCF, a stress-sensitive epigenetic regulator, controls the beta cell stress-response and senescence programs during beta cell maturation process along with the cohesin Smc3. Chromatin immunoprecipitation data suggest that CTCF and Smc3 differentially occupy genes associated with stress and DNA damage responses, functional maturation, and senescence in neonatal versus adult beta cells. Our data show that CTCF and cohesin Smc3 dependent control protects replicating beta cells from DNA damage, and is especially critical during the neonatal growth phase marked by high rates of replication. Beta cell specific loss of CTCF triggers a p53/p21 dependent senescence program, followed by beta cell dysfunction and eventual beta cell failure with advancing age. We further demonstrate that reduced CTCF levels in beta cells lead to adaptive failure in response to a high fat diet challenge, and recapitulate a neonatal beta cell like epigenetic landscape. Notably, CTCF levels are reduced in beta cells in T1D and T2D in mice and humans, and lead to reduced occupancy of CTCF and Smc3 at genes involved in senescence, DNA damage response, and beta cell function. Our data show that CTCF and cohesin collectively protect against senescence and govern beta cell function and fitness through a program established in the neonatal maturation phase. Disclosure S.S.Varghese: None. N.Parveen: None. J.K.Wang: Employee; Pfizer Inc., Johnson & Johnson. A.G.Hernandez-de la pena: None. S.Dhawan: None. Funding National Institutes of Health (R01DK120253)