title: Epigenome analysis reveals TBX5 as a novel transcription factor involved in the activation of rheumatoid arthritis synovial fibroblasts.
abstract: In this study, we analyzed the methylation status of human promoters in rheumatoid arthritis synovial fibroblasts (RASF). Differentially methylated genes between RASF and osteoarthritis synovial fibroblasts (OASF) were identified by methylated DNA immunoprecipitation and hybridization to human promoter tiling arrays. The methylation status was confirmed by pyrosequencing. Gene and protein expression of differentially methylated genes was evaluated with real-time PCR, Western blot, and immunohistochemistry. Chromatin immunoprecipitation was used to measure the gene promoter-associated acetylation and methylation of histones. Transcription factor-specific targets were identified with microarray and luciferase assays. We found that the transcription factor T-box transcription factor 5 (TBX5) was less methylated in rheumatoid arthritis (RA) synovium and RASF than in osteoarthritis (OA) samples. Demethylation of the TBX5 promoter in RASF and RA synovium was accompanied by higher TBX5 expression than in OASF and OA synovium. In RA synovium, TBX5 expression was primarily localized to the synovial lining. In addition, the TBX5 locus was enriched in activating chromatin marks, such as histone 4 lysine 4 trimethylation and histone acetylation, in RASF. In our functional studies, we observed that 790 genes were differentially expressed by 2-6-fold after overexpression of TBX5 in OASF. Bioinformatic analysis of these genes revealed that the chemokines IL-8, CXCL12, and CCL20 were common targets of TBX5 in OASF. Taken together, our data show that TBX5 is a novel inducer of important chemokines in RASF. Thus, we conclude that RASF contribute to the inflammatory processes operating in the pathogenesis of RA via epigenetic control of TBX5.
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland emmanuel.karouzakis@usz.ch.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Karouzakis
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland.
authors.forename: Michelle
authors.initials: M
authors.lastname: Trenkmann
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland.
authors.forename: Renate E
authors.initials: RE
authors.lastname: Gay
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland.
authors.forename: Beat A
authors.initials: BA
authors.lastname: Michel
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, CH-8952 Schlieren, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Neidhart
mesh_terms: D000107:Acetylation; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D054418:Chemokine CCL20 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D054377:Chemokine CXCL12 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002843:Chromatin / Q000276:immunology / Q000378:metabolism; D019295:Computational Biology; D044127:Epigenesis, Genetic; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008745:Methylation; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D013583:Synovial Membrane / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D020825:T-Box Domain Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C108355:CCL20 protein, human; C515255:CXCL12 protein, human; D054418:Chemokine CCL20; D054377:Chemokine CXCL12; D002843:Chromatin; D016209:Interleukin-8; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5