The proximal islet-specific glucose-6-phosphatase catalytic subunit-related protein autoantigen promoter is sufficient to initiate but not maintain transgene expression in mouse islets in vivo

We have previously reported the discovery of an islet-specific glucose-6-phosphatase catalytic subunit–related protein (IGRP) that is predominantly expressed in islet -cells. IGRP has recently been identified as a major autoantigen in a mouse model of type 1 diabetes. The analysis of IGRP–chloramphenicol acetyltransferase (CAT) fusion gene expression in transiently trans-fected islet-derived hamster insulinoma tumor and TC-3 cells revealed that the promoter region located between 306 and 3 confers high-level reporter gene expression. To determine whether this same promoter region is sufficient to confer islet -cell–specific gene expression in vivo, it was ligated to a -galactosidase reporter gene, and transgenic mice expressing the re-sulting fusion gene were generated. In two independen