Targeting of a phogrin-green fluorescent protein chimaera to insulin secretory granules of pancreatic beta-cells in transgenic mice.

We have generated a transgenic mouse expressing a chimaeric phogrin-enhanced green fluorescent protein (EGFP) targeted to pancreatic beta-cells by the rat insulin II promoter. The transgenic animals appear healthy, have normal weight gain and normal glucose tolerance. Morphological analyses of adult transgenic mice revealed that the fluorescent reporter molecule was specifically expressed in beta-cells of the pancreatic islet and not in extra-pancreatic tissues. The distribution of phogrin-EGFP in beta-cells, however, was heterogeneous with three distinct populations distinguishable by FACS analysis and immunofluorescence microscopy. Superficially-localized islets in the whole pancreas were readily visualized in the animals as was the developing endocrine pancreas in undissected 15.5 day old mouse embryos. We envisage that the animal will be an important resource for future investigations of islet development, regeneration and the molecular cell biology of insulin secretion.