title: Survival of pancreatic beta cells is partly controlled by a TCF7L2-p53-p53INP1-dependent pathway.
abstract: The transcription factor T-cell factor 7-like 2 (TCF7L2) confers type 2 diabetes risk mainly through impaired insulin secretion, perturbed incretin effect and reduced beta-cell survival. The aim of this study was to identify the molecular mechanism through which TCF7L2 influences beta-cell survival. TCF7L2 target genes in INS-1 cells were identified using Chromatin Immunoprecipitation. Validation of targets was obtained by: siRNA silencing, real-time quantitative polymerase chain reaction, electrophoretic mobility shift assay, luciferase reporter assays and western blot. Apoptosis rate was measured by DNA degradation and caspase-3 content. Islet viability was estimated by measuring metabolic rate. TCF7L2 binds to 3646 gene promoters in INS-1 cells in high or low glucose, including Tp53, Pten, Uggt1, Adamts9 and Fto. SiRNA-mediated reduction in TCF7L2 activity resulted in increased apoptosis and increased expression of Tp53, which resulted in elevated p53 protein activity and an increased expression of the p53 target gene Tp53inp1 (encoding p53-induced-nuclear-protein 1). Reversing the increase in p53INP1 protein expression, seen after Tcf7l2 silencing, protected INS-1 cells from Tcf7l2 depletion-induced apoptosis. This result was replicated in primary rat islets. The risk T-allele of rs7903146 is associated with increased TCF7L2 mRNA expression and transcriptional activity. On the other hand, in vitro silencing of TCF7L2 lead to increased apoptosis. One possibility is that the risk T-allele increases expression of an inhibitory TCF7L2 isoform with lower transcriptional activity. These results identify the p53-p53INP1 pathway as a molecular mechanism through which TCF7L2 may affect beta-cell survival and established a molecular link between Tcf7l2 and two type 2 diabetes-associated genes, Tp53inp1 and Adamts9.
authors.affiliation: Department of Clinical Sciences, CRC, Lund University, Malmö 20502, Sweden. yuedan.zhou@med.lu.se
authors.forename: Yuedan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Enming
authors.initials: E
authors.lastname: Zhang
authors.forename: Christine
authors.initials: C
authors.lastname: Berggreen
authors.forename: Xingjun
authors.initials: X
authors.lastname: Jing
authors.forename: Peter
authors.initials: P
authors.lastname: Osmark
authors.forename: Stefan
authors.initials: S
authors.lastname: Lang
authors.forename: Corrado M
authors.initials: CM
authors.lastname: Cilio
authors.forename: Olga
authors.initials: O
authors.lastname: Göransson
authors.forename: Leif
authors.initials: L
authors.lastname: Groop
authors.forename: Erik
authors.initials: E
authors.lastname: Renström
authors.forename: Ola
authors.initials: O
authors.lastname: Hansson
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000378:metabolism; D009687:Nuclear Proteins; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D058118:Transcription Factor 7-Like 2 Protein / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D009687:Nuclear Proteins; C498966:Tp53INP1 protein, rat; D058118:Transcription Factor 7-Like 2 Protein; D016159:Tumor Suppressor Protein p53