title: Conditional expression of hepatocyte nuclear factor-1beta, the maturity-onset diabetes of the young-5 gene product, influences the viability and functional competence of pancreatic beta-cells.
abstract: Mutations in the gene encoding hepatocyte nuclear factor (HNF)1beta result in maturity-onset diabetes of the young-(MODY)5, by impairing insulin secretory responses and, possibly, by reducing beta-cell mass. The functional role of HNF1beta in normal beta-cells is poorly understood; therefore, in the present study, wild-type (WT) HNF1beta, or one of two naturally occurring MODY5 mutations (an activating mutation, P328L329del, or a dominant-negative form, A263insGG) were conditionally expressed in the pancreatic beta-cell line, insulin-1 (INS-1), and the functional consequences examined. Surprisingly, overexpression of the dominant-negative mutant did not modify any of the functional properties of the cells studied (including insulin secretion, cell growth and viability). By contrast, expression of WT HNF1beta was associated with a time- and dose-dependent inhibition of INS-1 cell proliferation and a marked increase in apoptosis. Induction of WT HNF1beta also inhibited the insulin secretory response to nutrient stimuli, membrane depolarisation or activation of protein kinases A and C and this correlated with a significant decrease in pancrease-duodenum homeobox-1 protein levels. The attenuation of insulin secretion was, however, dissociated from the inhibition of proliferation and loss of viability, since expression of the P328L329del mutant led to a reduced rate of cell proliferation, but failed to induce apoptosis or to alter insulin secretion. Taken together, the present results suggest that mature rodent beta-cells are sensitive to increased expression of WT HNF1beta and they imply that the levels of this protein are tightly regulated to maintain secretory competence and cell viability.
authors.affiliation: Institute of Biomedical and Clinical Science, Peninsula Medical School, Universities of Exeter and Plymouth, Research Way, Plymouth, Devon PL6 8BU, UK.
authors.forename: Hannah J
authors.initials: HJ
authors.lastname: Welters
authors.forename: Sabine
authors.initials: S
authors.lastname: Senkel
authors.forename: Ludger
authors.initials: L
authors.lastname: Klein-Hitpass
authors.forename: Silke
authors.initials: S
authors.lastname: Erdmann
authors.forename: Heike
authors.initials: H
authors.lastname: Thomas
authors.forename: Lorna W
authors.initials: LW
authors.lastname: Harries
authors.forename: Ewan R
authors.initials: ER
authors.lastname: Pearson
authors.forename: Coralie
authors.initials: C
authors.lastname: Bingham
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hattersley
authors.forename: Gerhart U
authors.initials: GU
authors.lastname: Ryffel
authors.forename: Noel G
authors.initials: NG
authors.lastname: Morgan
mesh_terms: D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western / Q000379:methods; D002460:Cell Line; D049109:Cell Proliferation; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D051539:Hepatocyte Nuclear Factor 1-beta / Q000235:genetics* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; D007328:Insulin; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D051539:Hepatocyte Nuclear Factor 1-beta