From Jackson Labs: Cre expression in these mice is observed in islets of the adult pancreas, small intestine enteroendocrine cells, endocrine portions of the stomach, all pancreatic endocrine cells, and in some non-endocrine intestinal cells. When bred with a mouse containing a loxP site-flanked sequence of interest, Cre-mediated recombination results in deletion of the flanked gene in the tissues that normally express neurogenin 3.