Rare and novelRELAvariants are common in systemic autoimmunity

Objective Phenotypic 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. Methods Wild type and mutant RELA proteins were ectopically expressed in HEK293 cells. Western blot and NF-κB/IFNβ 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-κB and interferon stimulated genes in PBMCs were assessed via qPCR following toll-like receptor activation. Results RELA I250V , RELA R295H and RELA E3* displayed a loss in NF-κB transcriptional activity. Comparative to RELA WT , RELA I250V protein expression was reduced. Two variants, RELA I250V and RELA R295H , induced hyperactivation of the IFNβ 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 IFNβ 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. Conclusion We 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-κB and IFNβ promoter elements. These findings reinforce an important role for RELA in a range of autoimmune and autoinflammatory diseases.