Insulin production by the pancreatic islet is tightly coupled to the concentration of blood
glucose. The mechanism by which glucose controls proinsulin biosynthesis in β cells is
poorly understood. Analysis of insulin gene expression in individual cells within whole, living
islets using adenovirus gene transfer and direct observation of insulin promoter-directed
green fluorescent protein activity indicates that β cells are functionally heterogeneous. An
increase in glucose concentration not only stimulates expression within individual β cells …