Expression of a novel zinc-finger cDNA, IA-1, is associated with rat AR42J cells differentiation into insulin-positive cells

Introduction: IA-1, an insulinoma-associated cDNA-1, encodes a zinc-finger DNA-binding protein originally isolated from a human insulinoma subtraction library. Aim: To demonstrate the restriction of IA-1 gene expression in human fetal pancreata of different gestational stages and to determine whether the expression of IA-1 gene is associated with rat AR42J cell differentiation into insulin-positive cells. Methodology: To examine whether the IA-1 gene is associated with pancreatic endocrine cell differentiation, we used a rat pancreatic amphicrine cell line, AR42J, to investigate whether the expression of the IA-1 gene coincides with AR42J cells converting into either endocrine or exocrine lineage. We also examined a set of islet transcription factors that regulate key differentiation steps involved in activating the genes that confer the specialized functions of terminally differentiated pancreatic islet cells. Results: When the AR42J cells were converted into insulin-positive cells induced by GLP-1, insulinoma conditioned-medium, or both, we observed a significant elevated expression of mRNA for IA-1 and islet-specific transcription factors such as Pdx-1, NeuroD/beta2, and Nkx6. L In contrast, dramatically decreased expression of mRNA for IA-1 and islet-specific transcription factors was displayed when AR42J cells were converted into the acinar-like phenotype by dexamethasone. Conclusions: IA-1 gene was shown to be developmentally regulated in fetal pancreatic cells, and its expression pattern is consistent with parallel changes in islet-specific transcription factors during the endocrine differentiation of AR42J cells.