172. RNA sequencing of leukocytes reveals unique differences among groups of adult patients with IgA vasculitis
Creators: name: Matija Bajželj1, 3
name: Matjaž Hladnik2
name: Toluay2, Tanya Deniz
name: Snežna  Sodin-Šemrl1, 2
name: Alojzija Hočevar1, 3
name: Katja  Lakota1, 2
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background: I</strong>mmunoglobulin A vasculitis (IgAV) is a small vessel leukocytoclastic vasculitis, characterized by vascular IgA deposits. Renal involvement, found in up to 84% of patients, is associated with an increased risk of progression to chronic kidney failure. An invasive procedure of skin biopsy is still the golden standard for diagnosis. Omics data from NCBI-GEO and Array Express databanks is lacking from IgAV samples of adult patients. Thus, our aim was to perform RNA sequencing and identify differentially expressed genes and dysregulated molecular pathways in leukocytes of IgAV patients with renal involvement, patients with skin-limited IgAV and healthy controls (HC). <strong>Methods: </strong>Peripheral blood leukocytes were collected from treatment-naive IgAV patients at time of diagnosis with: 1) renal complications (n=3), 2) skin-limited disease (n=3), and age-/sex-matched HC (n=3), in the University Medical Center Ljubljana. RNA was isolated from leukocytes and 100 bp paired-end sequenced using the Illumina HiSeq 4000 platform (25.9 to 30.8 million reads). Reads were mapped with Salmon tool onto the human transcriptome (Ensemble Release 104). Differentially expressed genes (log2 fold change ≥ │1│, padj &lt; 0.05) were computed using the R package DeSEQ2. Data were clustered using principal component analysis (PCA), KEGG pathway over-representation analysis (ORA) was performed with R package clusterProfiler and protein-protein interaction analyses were done using STRING analysis. <strong>Results: </strong>PCA distinguished between IgAV (renal and skin-limited) and healthy controls, suggesting specific transcriptome signatures in IgAV. 300 genes were differentially expressed (220 up- and 80 down-regulated) in leukocytes between IgAV patients with renal involvement and healthy controls (HC), thereby representing renal-associated IgAV pathology and an associated leukocyte mRNA signature. 198 genes were identified as differentially expressed (144 up- and 54 down-regulated) between skin-limited IgAV and HC. 67 overlapping genes were differentially expressed in both groups of patients in comparison to controls. 48 genes were differentially expressed between patients with renal involvement, as compared to those with skin involvement only. Differentially expressed genes in patients with renal involvement exhibited enriched KEGG Pathways involved in the Antigen processing and presentation (padj 0.0000043), Platelet activation (padj 0.0000010), the Natural killer cell-mediated cytotoxicity (padj 0.0070636), as analysed by ORA approach. Genes, differentially expressed in patients with skin-limited disease were enriched in the Antigen processing and presentation (padj 0.0000000), NOD-like receptor signaling (padj 0.0000226) and Platelet activation (padj 0.0459034) KEGG Pathways. Interestingly, using STRING analysis, an Interferon signaling Reactome pathway (FDR 3.01e -11) emerged in patients with skin-limited disease. <strong>Conclusions: </strong>Here, we report an IgAV-associated leukocyte mRNA signature in adults. We showed, that it is possible to discriminate between patients with different organ involvement and healthy controls based on differentially expressed genes that regulate various innate immunity responses. Deregulated molecular pathways in patients with IgA vasculitis could serve as the basis for further investigations for potential clinically-relevant biomarkers and functional <em>in-vitro</em> studies deciphering organ-specific pathology in IgAV patients. <strong>Disclosures: </strong>None