With regard to IRE1α the functional analysis of this molecule in adult KO mice has been lagging because the KO mice suffer embryonic lethality; however, we could show here using the conditional KO method that IRE1α-deficient mice exhibit mild hypoinsulinemia, hyperglycemia, and a low-weight trend, and that IRE1α disruption causes histological abnormality of the pancreatic acinar and salivary serous tissues and decrease of serum level of immunoglobulin produced in the plasma cells. This evidence concerns the gene ERN1 and Hypoinsulinemia.