Insulin response of a hybrid amylase/CAT gene in transgenic mice

Expression of an amylase/CAT hybrid gene was analyzed in transgenic mice. The amylase promoter was derived from a pancreatic amylase gene whose expression is repressed in diabetic animals. Pancreas-specific expression of the amylase/chloramphenicol acetyl-transferase (CAT) construct was observed in two independent transgenic lines. Correct initiation of transcription was demonstrated by protection of an anti-sense riboprobe. To evaluate the insulin dependence of the hybrid gene, diabetes was induced by treatment with streptozotocin. As a result of this treatment, pancreatic CAT activity was reduced to undetectable levels. Subsequent administration of insulin restored CAT activity to normal levels. The abundance of CAT transcripts was also greatly reduced in diabetic pancreas. These studies localize the determinants of pancreas specificity and insulin dependence to the region between -208 and +19 of the mouse pancreatic Amy-2.2 gene. The results are consistent with an effect of insulin on amylase transcription, rather than post-transcriptional regulation of mRNA processing or stability.