title: MDA5 and PTPN2, two candidate genes for type 1 diabetes, modify pancreatic beta-cell responses to the viral by-product double-stranded RNA.
abstract: beta-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a 'dialog' between beta-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects beta-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic beta-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat beta-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic-polycitidilic acid-PIC). Real-time RT-PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary beta-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify beta-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate beta-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic beta-cell level.
authors.affiliation: Laboratory of Experimental Medicine, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Maikel L
authors.initials: ML
authors.lastname: Colli
authors.forename: Fabrice
authors.initials: F
authors.lastname: Moore
authors.forename: Esteban N
authors.initials: EN
authors.lastname: Gurzov
authors.forename: Fernanda
authors.initials: F
authors.lastname: Ortis
authors.forename: Decio L
authors.initials: DL
authors.lastname: Eizirik
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D018925:Chemokines / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology* / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D050417:Insulin-Secreting Cells / Q000201:enzymology / Q000473:pathology*; D016899:Interferon-beta / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000378:metabolism*; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014780:Viruses / Q000378:metabolism*
chemical_list: D018925:Chemokines; D016328:NF-kappa B; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D016899:Interferon-beta; D048031:JNK Mitogen-Activated Protein Kinases; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; C516654:Ptpn2 protein, rat; D053487:DEAD-box RNA Helicases; D011070:Poly I-C