Glucose tolerance tests (GTTs) confirmed that both male and female heterozygous Neurod1Cre/+; Isl1f/+ mice were comparable to controls (Additional file 1: Fig. S2c), but we were unable to perform GTTs by intraperitoneal injection of glucose (2 g/kg body weight) in Isl1CKO. Although we selected Isl1CKO mice with low hyperglycemia, the mutants died after administration of exogenous glucose, indicating a severe inability to maintain an insulin secretion response when challenged with glucose. The gene discussed is INS; the disease is Hyperglycemia.