All of the dysfunctions in WRS are mirrored in mice deficient for PERK [4,5], and detailed genetic studies in mice have shown that the diabetes is caused by the loss of expression of PERK in the insulin secreting beta cells [6], whereas the exocrine pancreas deficiency is caused by the absence of PERK in the pancreatic acinar cells [7]. Here, EIF2AK3 is linked to diabetes mellitus.