title: Activin A decreases glucagon and arx gene expression in alpha-cell lines.
abstract: Activin A is a potent growth and differentiation factor involved in development, differentiation, and physiological functions of the endocrine pancreas; it increases insulin and pax4 gene expression in beta-cells and can induce transdifferentiation of the exocrine acinar cell line AR42J into insulin-producing cells. We show here that Activin A decreases glucagon gene expression in the alpha-cell lines InR1G9 and alphaTC1 in a dose- and time-dependent manner and that the effect is blocked by Follistatin. This effect is also observed in adult human islets. Glucagon gene expression is inhibited at the transcriptional level by the Smad signaling pathway through the G3 DNA control element. Furthermore, Activin A decreases cell proliferation of InR1G9 and alphaTC1 cells as well as cyclin D2 and arx gene expression, whose protein product Arx has been shown to be critical for alpha-cell differentiation. Overexpression of Arx in Activin A-treated InR1G9 cells does not prevent the decrease in glucagon gene expression but corrects the inhibition of cell proliferation, indicating that Arx mediates the Activin A effects on the cell cycle. We conclude that Activin A has opposite effects on alpha-cells compared with beta-cells, a finding that may have relevance during pancreatic endocrine lineage specification and physiological function of the adult islets.
authors.affiliation: Diabetes Unit, Division of Endocrinology, Diabetes and Nutrition, University Hospital Geneva, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland. aline.mamin@medecine.unige.ch
authors.forename: Aline
authors.initials: A
authors.lastname: Mamin
authors.forename: Jacques
authors.initials: J
authors.lastname: Philippe
mesh_terms: D028341:Activins / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D006224:Cricetinae; D038681:Follistatin / Q000494:pharmacology; D005786:Gene Expression Regulation; D005934:Glucagon / Q000096:biosynthesis*; D050416:Glucagon-Secreting Cells / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism; D051379:Mice; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis*
chemical_list: C469264:ARX protein, human; C469265:ARX protein, mouse; D038681:Follistatin; D018398:Homeodomain Proteins; D007328:Insulin; D051785:Smad Proteins; D014157:Transcription Factors; C422405:activin A; D028341:Activins; D005934:Glucagon