The pancreatic islet ?-cell-enriched transcription factor Pdx-1 regulates Slc30a8 gene transcription through an intronic enhancer.

ABSTRACT: The SLC30A8 gene encodes the zinc transporter ZnT-8, which provides zinc for insulin-hexamer formation. Genome-wide association studies have shown that a polymorphic variant in SLC30A8 is associated with altered susceptibility to Type 2 diabetes and we recently reported that glucose-stimulated insulin secretion is decreased in islets isolated from Slc30a8-knockout mice. The present study examines the molecular basis for the islet-specific expression of Slc30a8. VISTA analyses identified two conserved regions in Slc30a8 introns 2 and 3, designated enhancers A and B respectively. Transfection experiments demonstrated that enhancer B confers elevated fusion gene expression in both ?TC-3 cells and ?TC-6 cells. In contrast, enhancer A confers elevated fusion gene expression selectively in ?TC-3 and not ?TC-6 cells. These data suggest that enhancer A is an islet ?-cell-specific enhancer and that the mechanisms controlling Slc30a8 expression in ?- and ?-cells are overlapping, but distinct. Gel retardation and ChIP (chromatin immunoprecipitation) assays revealed that the islet-enriched transcription factor Pdx-1 binds enhancer A in vitro and in situ respectively. Mutation of two Pdx-1-binding sites in enhancer A markedly reduces fusion gene expression suggesting that this factor contributes to Slc30a8 expression in ?-cells, a conclusion consistent with developmental studies showing that restriction of Pdx-1 to pancreatic islet ?-cells correlates with the induction of Slc30a8 gene expression and ZnT-8 protein expression in vivo.

SUBMITTER: Pound LD 

PROVIDER: S-EPMC4130494 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature