Abstract EN:

We have identified 2 different heterozygous mutations of RELA (a missense mutation H86N, and a non-sense R329X), coding the p65 protein, one of the transcription factors of the canonical NFκB pathway, in 3 patients presenting with adult or pediatric onset of Systemic Lupus Erythematous (SLE). The nuclear factor-kappa B (NFκB) transcription factor plays a critical role in diverse cellular processes associated with proliferation, cell death, development, as well as innate and adaptive immune responses. NFκB is normally sequestered in the cytoplasm by a family of inhibiteins kntory proown IκBs. The signal pathways leading to the nuclear accumulation of NFκB, which can be activated by a wide variety of stimuli, have been extensively studied in the past two decades. After its translocation to the nucleus, NFκB must be actively regulated to execute its function as a transcription factor. NFκB has long been considered as a target for new anti-inflammatory drugs. However, data from genetic studies in mice suggest that NFκB could be a complex therapeutic target in inflammatory diseases as it regulates proinflammatory cytokine production, but also leukocyte recruitment, or cell survival. By confocal microscopy analysis combined to molecular analysis in vitro, we showed that these mutations lead to the expression of mutant RelA and spontaneous activation of the NFκB pathway in non-stimulated patients' T cells suggesting a role of RELA mutants in the control of the adaptive immunity. Moreover, we found that patients mutated for RELA displayed a high Interferon Stimulated Genes (ISGs) expression in total Peripheral Blood Mononuclear Cells (PBMCs) as well as in activated T cells and immortalized B cells by Epstein Barr Virus (B-EBV), indicating a lymphocyte-intrinsic dysregulation of the Interferon type I (IFN-I) production. By expression of the mutants into cell lines we observed that the co-expression of the RELA wild type and mutant forms were required to activate the IFNb promoter. These results suggest that the mutant RELA is hijacking the WT RELA towards the interferon promoter, leading to an unregulated production of type-I IFN which is therefore the initial event of the SLE onset in these patients. Upregulation of the type I IFN as well as type II IFN has also been found in a patient with IPEX-like syndrome, where no mutation on FOXP3 has been identified. We identified a de novo mutation in RELB, the transcriptional factor of the non-canonical NF-kB pathway, localized in the transactivation domain of the gene, important for its transcriptional activity. First functional assays show that the mutation acts like a gain of function. Gain of function mutations of RELB has been associated with non-Hodgkin lymphomas, rather than autoimmunity. Moreover, the RNA sequencing performed on the cells of the patient shows a cross-link between canonical and non-canonical NF-kB pathway. In conclusion, the aim of this thesis was to describe the role of the NFkB pathway in autoimmune diseases and the crosstalk between this important pathway and type I and II IFN.