Transgenic mice with green fluorescent protein-labeled pancreatic β-cells

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Abstract
We have generated transgenic mice that express green fluorescent protein (GFP) under the control of the mouse insulin I gene promoter (MIP). The MIP-GFP mice develop normally and are indistinguishable from control animals with respect to glucose tolerance and pancreatic insulin content. Histological studies showed that the MIP-GFP mice had normal islet architecture with coexpression of insulin and GFP in the β-cells of all islets. We observed GFP expression in islets from embryonic day E13.5 through adulthood. Studies of β-cell function revealed no difference in glucose-induced intracellular calcium mobilization between islets from transgenic and control animals. We prepared single-cell suspensions from both isolated islets and whole pancreas from MIP-GFP-transgenic mice and sorted the β-cells by fluorescence-activated cell sorting based on their green fluorescence. These studies showed that 2.4 ± 0.2% (n = 6) of the cells in the pancreas of newborn (P1) and 0.9 ± 0.1% (n = 5) of 8-wk-old mice were β-cells. The MIP-GFP-transgenic mouse may be a useful tool for studying β-cell biology in normal and diabetic animals.