β-cell-specific XBP1 mutant mice caused hyperglycemia and glucose intolerance due to decreased insulin secretion from β-cells due to hyperactivated IRE1α which degraded a subset of mRNAs encoding proinsulin-processing enzymes and insulin mRNA through RIDD, contributing to the reduction of proinsulin biosynthesis and further β-cell death [205]. The gene discussed is ERN1; the disease is Hyperglycemia.