Adaptation to chronic ER stress enforces pancreatic β-cell plasticity

Pancreatic {beta}-cells undergo high levels of endoplasmic reticulum (ER) stress due to their role in insulin secretion. Hence, they require sustainable and efficient adaptive stress responses to cope with the stress. Whether duration and episodes of chronic ER stress directly compromises {beta}-cell identity is largely unknown. We show that under reversible, chronic ER stress, {beta}-cells undergo a distinct transcriptional and translational reprogramming. During reprogramming, expression of master regulators of {beta}-cell function and identity and proinsulin processing is impaired. Upon recovery from stress, {beta}-cells regain their identity, highlighting a high-degree of adaptive {beta}-cell plasticity. Remarkably, when stress episodes exceed a certain threshold, {beta}-cell identity is gradually lost. Single cell RNA-seq analysis of islets from type 1 diabetes (T1D) patients, identifies the severe deregulation of the chronic stress-adaptation program, and reveals novel biomarkers for progression of T1D. Our results suggest {beta}-cell adaptive exhaustion ({beta}EAR) is a significant component of the pathogenesis of T1D.