title: A novel function of Onecut1 protein as a negative regulator of MafA gene expression.
abstract: The transcription factor MafA is a key regulator of insulin gene expression and maturation of islet β cells. Despite its importance, the regulatory mechanism of MafA gene expression is still unclear. To identify the transcriptional regulators of MafA, we examined various transcription factors, which are potentially involved in β cell differentiation. An adenovirus-mediated overexpression study clearly demonstrated that Onecut1 suppresses the promoter activity of MafA through the Foxa2-binding cis-element on the MafA enhancer region (named area A). However, ChIP analysis showed that Foxa2 but not Onecut1 could directly bind to area A. Furthermore, overexpression of Onecut1 inhibited the binding of Foxa2 onto area A upon ChIP analysis. Importantly, insertion of a mutation in the Foxa2-binding site of area A significantly decreased the promoter activity of MafA. These findings suggest that Onecut1 suppresses MafA gene expression through the Foxa2-binding site. In the mouse pancreas, MafA expression was first detected at the latest stage of β cell differentiation and was scarcely observed in Onecut1-positive cells during pancreas development. In addition, Onecut1 expression was significantly increased in the islets of diabetic db/db mice, whereas MafA expression was markedly decreased. The improved glucose levels of db/db mice with insulin injections significantly reduced Onecut1 expression and rescued the reduction of MafA expression. These in vivo experiments also suggest that Onecut1 is a negative regulator of MafA gene expression. This study implicates the novel role of Onecut1 in the control of normal β cell differentiation and its involvement in β cell dysfunction under diabetic conditions by suppressing MafA gene expression.
authors.affiliation: Department of Metabolic Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, 565-0871 Suita, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Taka-aki
authors.initials: TA
authors.lastname: Matsuoka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kawashima
authors.forename: Satomi
authors.initials: S
authors.lastname: Takebe
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Kubo
authors.forename: Noriyo
authors.initials: N
authors.lastname: Kubo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Miyatsuka
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kaneto
authors.forename: Iichiro
authors.initials: I
authors.lastname: Shimomura
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics; D045744:Cell Line, Tumor; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D051542:Hepatocyte Nuclear Factor 3-beta / Q000235:genetics / Q000378:metabolism; D051559:Hepatocyte Nuclear Factor 6 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000473:pathology; D051473:Maf Transcription Factors, Large / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008957:Models, Genetic; D010179:Pancreas / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C496503:Foxa2 protein, mouse; D051559:Hepatocyte Nuclear Factor 6; D051473:Maf Transcription Factors, Large; C485160:Mafa protein, mouse; C496606:Onecut1 protein, mouse; D051542:Hepatocyte Nuclear Factor 3-beta
keywords: Cell Biology; Diabetes; Insulin Synthesis; Islet; Transcription Factors