AAV GCG-EGFP, a new tool to identify glucagon-secreting α-cells

The study of primary glucagon-secreting alpha-cells is hampered by their low abundance and scattered distribution in rodent pancreatic islets. We have designed a double-stranded adeno-associated virus containing a rat proglucagon promoter (700 bp) driving enhanced green fluorescent protein (AAV GCG-EGFP), to specifically identify alpha-cells. The administration of AAV GCG-EGFP by intraperitoneal or intraductal injection led to EGFP expression selectively in the alpha-cell population. AAV GCG-EGFP delivery to mice followed by islet isolation, dispersion and separation by FACS for EGFP resulted in an 86% pure population of alpha-cells. Furthermore, the administration of AAV GCG-EGFP at various doses to adult wild type mice did not significantly alter body weight, blood glucose, plasma insulin or glucagon levels, glucose tolerance or arginine tolerance. In vitro experiments in transgene positive alpha-cells demonstrated that EGFP expression did not alter the intracellular Ca2+ pattern in response to glucose or adrenaline. This approach may be useful for studying purified primary alpha-cells and for the in vivo delivery of other genes selectively to alpha-cells to further probe their function or to manipulate them for therapeutic purposes.