PDX1 and Hypoglycemia: To identify pancreatic cell type(s) responsible for the observed perinatal lethality and hypoglycemia in Pdx-1-Creearly;VhlhLoxP/LoxP mice, Vhlh was specifically inactivated in the endocrine lineage using the Ngn3-Cre mouse strain, as Ngn3 marks all endocrine progenitors during embryogenesis [8].