Rare and novel RELA variants are common in systemic autoimmunity

Abstract

ObjectivePhenotypic diversity of autoimmune diseases presents an ongoing diagnostic and drug development challenge for clinicians and scientists. Recent discovery of mutations in RELA (encoding RELA) in patients with different diagnoses has highlighted that different pathogenic molecular mechanisms are at play and may explain the observed phenotypic diversity. We identified seven novel/rare RELA variants in patients with autoimmune diseases and examine the functional consequences on immune signalling. MethodsWild type and mutant RELA proteins were ectopically expressed in HEK293 cells. Western blot and NF-{kappa}B/IFN{beta} luciferase reporter assays were used to determine RELA expression and transcriptional activity, respectively. In patients (n=3), B and T cell populations were examined via flow cytometry and NF-{kappa}B and interferon stimulated genes in PBMCs were assessed via qPCR following toll-like receptor activation. ResultsRELAI250V, RELAR295H and RELAE3* displayed a loss in NF-{kappa}B transcriptional activity. Comparative to RELAWT, RELAI250V protein expression was reduced. Two variants, RELAI250V and RELAR295H, induced hyperactivation of the IFN{beta} promoter. An elevated IFN gene signature was not detected in patient PBMCs following toll-like receptor activation, however the patient heterozygous for I250V had elevated IFN{beta} transcripts at baseline and after TLR7/8 activation. A reduction in transitional, unswitched memory and memory B cell and cTfh (CCR6-CXCR3-) T cell subsets was shared by the patient group. ConclusionWe expand upon the clinical syndromes linked to RELA dysfunction and uncover rare and novel variants that have distinct functional effects on gene transcription downstream of NF-{kappa}B and IFN{beta} promoter elements. These findings reinforce an important role for RELA in a range of autoimmune and autoinflammatory diseases.