THU0080 The Role of C5ORF30 in Rheumatoid Arthritis Pathogenesis
Authors: H. Davies, M. Muthana, S. Khetan, G. Adeleke, S. Hawtree, F. Morrow, B. Ciani, A. G. Wilson
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> A recent genome wide association study identified the variant rs26232 in the first exon of an uncharacterized gene <i>C5orf30</i> as a rheumatoid arthritis susceptibility variant<sup>1</sup>. In addition, it has been associated with severity of radiological joint damage suggesting a role in tissue breakdown<sup>2</sup>. To date there is no function assigned for <i>C5orf30</i> and neither the gene or protein coded show homology to any known functional sequences. However, <i>C5orf30</i> is highly conserved in chimpanzee, dog, cow, mouse, chicken, and zebrafish (orthologs). <h3>Objectives</h3> The aim of this study is to determine the biological roles of <i>C5orf30</i> in rheumatoid arthritis. <h3>Methods</h3> Real time PCR and western blotting were used to examine <i>C5orf30</i> transcript and protein levels in fibroblast-like synovial cells (FLS stimulated with TNF &amp; hypoxia) and peripheral blood leukocytes isolated from RA patients and healthy individuals. Immunohistochemistry on synovial samples was used to determine expression of <i>C5orf30</i> including co-localisation using antibodies to macrophages (CD68), fibroblasts (5B5), T (CD3) &amp; B (CD19) cells. To investigate gene function siRNA was used to knockdown <i>C5orf30</i> in synovial FLS <i>in vitro.</i> <h3>Results</h3> Expression of <i>C5orf30</i> was detected at lower levels in peripheral blood leukocytes of RA patients compared to healthy controls (117 patients vs. 102 controls, <i>p</i>=0.00052). <i>C5orf30</i> was expressed in FLS and was found to be up-regulated by hypoxia (8-fold) and down-regulated by TNF (0.5-fold). Confocal microscopy revealed <i>C5orf30</i> to be strongly expressed in both the nuclear and cytoplasmic compartment of synovial lining cells including macrophages and fibroblasts, but not T &amp; B cells. <i>C5orf30</i> was undetectable in arthroscopy sections obtained from osteoarthritis or control synovium. Approximately 80% <i>C5orf30</i> knockdown has been achieved by siRNA, and preliminary studies have shown <i>C5orf30</i> knockdown increased FLS invasion into matrigel. <h3>Conclusions</h3> <i>C5orf30</i> is expressed in synovial cells but not in circulating peripheral blood leukocytes obtained from RA patients, implying that <i>C5orf30</i> is expressed in a tissue-specific manner. <i>C5orf30</i> knockdown increased FLS migration into matrigel suggesting <i>C5orf30</i> is negatively regulating cellular invasion. Together this points to an anti-inflammatory role for <i>C5orf30</i> in RA and this may be a promising target for novel therapeutic strategies. <h3>References</h3> Stahl EA, Raychaudhuri S, Remmers EF, et al. Genome-wide association study meta-analysis identifies seven new rheumatoid arthritis risk loci. Nat Genet 2010;42:508-14. Wilson AG, Teare M, van der Helm-van AH, Moore D, Knevel R, Kleszcz A, Huizinga T (2011). Identification and validation of a novel marker for radiological severity in RA. Abstract N° OP0229. EULAR <h3>Disclosure of Interest</h3> None Declared