Description
ABSTRACT: The human growth hormone (hGH) minigene is frequently used in the derivation of transgenic mouse lines to enhance transgene expression. Although this minigene is present in the transgenes as a secondcistron, and thus not thought to be expressed, we found that three commonly used lines, Pdx1-CreLate, RIP-Cre, and MIP-GFP, each expressed significant amounts of hGH in pancreatic islets. Locally secreted hGH binds to prolactin receptors on cells, activates STAT5 signaling, and induces pregnancy-like changes in gene expression, thereby augmenting pancreatic cell mass and insulin content. In addition, islets of Pdx1-CreLate mice have lower GLUT2 expression and reduced glucose-induced insulin release and are protected against the cell toxin streptozotocin. These findings may be important when interpreting results obtained when these and other hGH minigene-containing transgenic mice are used.