Background In genetically susceptible individuals, we suspect that other environmental factors, which are yet to be determined, induce epigenetic changes that result in the development of rheumatoid arthritis (RA). However, to our knowledge, a genome-wide profile of DNA methylation changes in RA is not yet available.

Objectives To investigate the possible epigenomic biomarker of RA pathogenesis, the CpG methylation profiles of peripheral whole blood were analyzed using microarray profiling. using methylated DNA isolation assay (MeDIA)-CpG promoter microarray, and compared it with peripheral whole blood of healthy controls.

Methods Human peripheral whole blood samples were obtained from 16 RA and from 16 age, sex-matched healthy vontrols. Total genomic DNA extracted using the QIAamp DNA mini and blood kit protocol (Qiagen, Hilden, Germany). To discover novel hypermethylated genes in RA by genome-wide search, we introduce a MeDIA-coupled CpG microarray method for directly identifying differentially methylated regions of the genomes in each pooled whole blood between RA patients and healthy controls. A minimized methyl-DNA binding domain (MBD) tagged by histidine (MBD2bt) of human MBD2b was used, which provides high binding sensitivity to methylated DNA. Four independent CpG microarray analyses with human 244K CpG island microarrays (Agilent, Santa Clara, CA) were done for screening of candidate gene.

Results In four CpG microarray, 16 genes were screened as 2 fold hypermethylated targets among 267 porbes. Through stepwise subtraction processes, we finally selected four candidate targets. Among of these targets, four genes, LBX2, HOXA5, HUS1B, INPP5A gene in the promoter region have shown so far a significant increase in the methylation frequency in RA when compared with healthy controls (see figure 1). The methylation status of promising candidates will be validated by quantitative pyrosequencing assay in each samples.

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Figure 1. Candidate genes selection-screening.

Conclusions LBX2, HOXA5, HUS1B, INPP5A gene in peripheral blood of RA patients can possibliy be a epigenomic biomarker. Pathophysiologic correlation and their role as a diagnostic or prognostic marker should be investigated by quantitative pyrosequencing in a larger number of patients group hereafter.

1. Costenbader KH, Gay S, Riquelme ME, Iaccarino L, Doria A. Genes, epigenetic regulation and environmental factors: Which is the most relevant in developing autoimmune diseases? Autoimmun Rev 2011: epub

2. Ballestar E. Epigenetic alterations in autoimmune rheumatic diseases. Nat Rev Rheumatol 2011:7:263-71.

3. van Baarsen LG, Bos CL, van der Pouw Kraan TC, Verweij CL. Transcription profiling of rheumatic diseases. Arthritis Res Ther 2009;11:207.

Disclosure of Interest S.-H. Park Grant/Research support from: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2011-0007659)., S.-K. Kim: None Declared, J.-Y. Choe: None Declared, J. H. Kim: None Declared, H.-J. Lee: None Declared, J. N. Chae: None Declared, W.-T. Chung: None Declared