Rare and Novel RELA Variants Contribute to Systemic Autoimmunity.

Abstract

Phenotypic diversity of autoimmune diseases presents an ongoing diagnostic and therapeutic challenge. The discovery of mutations in RELA (encoding RELA/p65) in patients with diverse disease phenotypes suggests heterogeneous pathophysiologic mechanisms are at play, which may explain the observed phenotypic diversity. We identified seven novel/rare RELA variants in patients with autoimmune diseases and examined the functional consequences on immune signaling. Whole-exome sequencing analysis revealed seven novel/rare RELA variants. Following ectopic expression of wild type (WT) and mutant RELA proteins in HEK293 cells, NF-κB/interferon-β (IFNβ) luciferase reporter assays were used to determine transcriptional activity. RELA expression was also assessed in transfected HEK293 cells and in patient peripheral blood mononuclear cells (PBMCs) via Western blot. NF-κB and interferon-stimulated genes in patient PBMCs were assessed via quantitative polymerase chain reaction following toll-like receptor (TLR) activation. RELA^I250V, RELA^R295H and RELA^E3* displayed a loss in NF-κB transcriptional activity. RELA^I250V and RELA^R295H induced hyperactivation of the IFNβ promoter. Comparative to RELA^WT, ectopically expressed RELA^I250V protein levels were reduced. Collectively, an elevated IFN gene signature was not detected in patient PBMCs following TLR activation, however the patient heterozygous for I250V had elevated IFNβ transcripts after TLR7/8 activation. We expand upon the clinical syndromes linked to RELA dysfunction and uncover rare/novel variants that have distinct functional effects on gene transcription downstream of NF-κB and IFNβ promoter elements. These findings reinforce an important role for RELA in a range of autoimmune and autoinflammatory diseases.