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The pancreatic β- and α-cells are developmentally related to each other but reveal diverse gene expression patterns. Among the two important transcription factors for insulin gene expression, IEF1 is present both in α- and β-cells, but PDX-1/IPF1/STF-1/IDX-1, a homeodomain-containing transcription factor, is present in β-cells but not in α-cells. To elucidate the function of PDX-1 in the expression of β-cell-specific genes, we established stable αTC1 clone 6 (αTC1.6)-derived transfectants expressing PDX-1 and examined the changes in the gene expression patterns in them. The exogenous expression of PDX-1 in αTC1.6 cells alone could induce islet amyloid polypeptide (IAPP) mRNA expression in the cells but not the expression of insulin, glucokinase, or GLUT2 gene. However, when βcellulin was added to the medium, the PDX-1-expressing αTC1.6 cells, but not the control αTC1.6 cells, came to express insulin …