SAT0234 RNA SEQUENCING IDENTIFIES AN IGA VASCULITIS ASSOCIATED SERUM MICRORNA SIGNATURE, DISCRIMINATING PATIENTS WITH IGA VASCULITIS FROM AGE- AND SEX-MATCHED HEALTHY SUBJECTS
Authors: Alojzija Hocevar, Katja Lakota, Thomas Grentzinger, Alexis Sarazin, Neža Brezovec, Tadeja Kuret, Oliver Distler, Sasa Cucnik, Olivier Voinnet, Snežna Sodin-Šemrl, Matija Tomšič, Mojca Frank-Bertoncelj
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Immunoglobulin A vasculitis (IgAV) is a small vessel vasculitis with IgA deposits in the vessel wall, manifesting with skin purpura, arthralgia/arthritis, gastrointestinal (GI) and renal complications. Altered serum miRNA signatures can reflect disease-specific pathology, which makes serum miRNAs promising disease biomarkers. We have recently reported that miRNA expression is changed in the affected skin of IgAV patients. The profile of serum miRNAs in IgAV, however, remains unknown. <h3>Objectives:</h3> To determine the serum miRNA signatures in adult patients with IgAV as compared with healthy controls (HC) and explore <i>in silico</i> their gene targets and pathways. <h3>Methods:</h3> Small RNA were isolated from sera of IgAV patients with high disease activity (sera collected at the time of diagnosis) and from the age- and sex-matched HC (n=6 each). Small RNA libraries were sequenced with Illumina technology and reads were mapped onto human genome (GRCh38). One IgAV sample was omitted from analysis due to too low number of recovered miRNA reads. Unsupervised clustering was based on the expression of 150 miRNAs with the highest variance across samples. The miRror platform was used to predict gene targets of differentially expressed (DE) miRNAs with log2 fold change ≥ │1│and p<sub>adj</sub> &lt; 0.01. The STRING protein networks platform was used for pathway enrichment analysis of these genes. <h3>Results:</h3> Unsupervised clustering of serum miRNA reads clearly distinguished between IgAV patients and HC (Figure 1). Among 1918 annotated miRNA (miRBase), 446 miRNAs were detected in serum samples and 88 miRNAs were identified as DE between IgAV patients and HC (log2 fold change ≥ │1│, p<sub>adj</sub> &lt; 0.05). Specifically, 28 miRNAs were elevated in the serum of IgAV patients (e.g. miRNA-22, -146a, -185, -320a/b/c, -378a, -423, -3184; p<sub>adj</sub> &lt; 10<sup>-10</sup>), whereas 60 miRNAs were decreased (e.g. miRNA-128, -937, -30c, -328, -26a, p<sub>adj</sub> &lt; 0.005), thereby representing the IgAV-associated serum miRNA signature. The miRror platform identified 426 protein-coding genes as targets of the 54 DE miRNAs (log2 fold change ≥ │1│, p<sub>adj</sub> &lt;0.01). As analyzed by STRING, these miRNA target genes were enriched in distinct molecular networks and biological pathways, including "Phosphoproteins (FDR 7.4*10<sup>-5</sup>), "Alternative splicing" (FDR 2.8*10<sup>-4</sup>), "Regulation of actin cytoskeleton" (FDR 0.008), "Proteoglycans in cancer" (FDR 0.009) and "Fcgamma receptor dependent phagocytosis" (FDR 0.01) (Figure 2). Additionally, miRNA gene targets formed three distinct molecular clusters, specifically "Chemokines and their receptors", "Ubiquitination process" and "Vesicle, endocytosis, lysosomes and their trafficking" (Figure 2). This suggests that the altered miRNAs in IgAV regulate diverse cellular functions, reflecting or contributing to the key aspects of disease pathogenesis. <h3>Conclusion:</h3> Here we report for the first time an IgAV-associated serum miRNA signature. The altered miRNAs clearly discriminate IgAV patients from HC, and might play a key role in the pathogenesis of IgAV. Our study sets the basis for the identification of novel, serum-based disease biomarkers in vasculitis. <h3>Disclosure of Interests:</h3> ALOJZIJA HOCEVAR: None declared, Katja Lakota: None declared, Thomas Grentzinger: None declared, Alexis Sarazin: None declared, Neža Brezovec: None declared, Tadeja Kuret: None declared, Oliver Distler Grant/research support from: Prof. Distler received research funding from Actelion, Bayer, Boehringer Ingelheim and Mitsubishi Tanabe to investigate potential treatments of scleroderma and its complications, Consultant for: Prof. Distler has/had consultancy relationship within the last 3 years with Actelion, AnaMar, Bayer, Boehringer Ingelheim, ChemomAb, espeRare foundation, Genentech/Roche, GSK, Inventiva, Italfarmaco, iQvia, Lilly, medac, MedImmune, Mitsubishi Tanabe Pharma, Pharmacyclics, Novartis, Pfizer, Sanofi, Serodapharm and UCB in the area of potential treatments of scleroderma and its complications. In addition, he had/has consultancy relationship within the last 3 years with A. Menarini, Amgen, Abbvie, GSK, Mepha, MSD, Pfizer and UCB in the field of arthritides and related disorders, Sasa Cucnik: None declared, Olivier Voinnet: None declared, Snežna Sodin-Šemrl: None declared, Matija Tomšič: None declared, Mojca Frank-Bertoncelj : None declared