Novel loss of function mutations in the death domain of tumor necrosis factor superfamily receptor 1A (TNFRSF1A) in children with systemic juvenile idiopathic arthritis (sJIA)

Abstract

Abstract Systemic juvenile idiopathic arthritis (sJIA) is an inflammatory disease characterized by recurring fevers, arthritis, and hyperinflammation, but the etiology is unknown. Using family- and population-based sequencing approaches, we have identified several novel TNFRSF1A mutations. These include 2 mutations in the death domain (DD) of TNFR1 (P367S; E398K) and 1 that leads to truncation of the TNFR1 protein (K203X), fully eliminating the DD and intracellular domains. Protein modeling predicts that E398K will reduce the strength of TNFR1-TNFR1 interactions, while P367S will alter TNFR1-TRADD binding. Using flow cytometric Förster resonance energy transfer (FRET) analysis, we studied TNFR1 DD-mediated interactions. As predicted, interactions between E398K and both WT TNFR1 and TRADD are reduced, as is the interaction of P367S with TRADD. Further, proximal signaling complex formation is reduced in mutant-transfected cells by immunoprecipitation. Consistent with this, cell death is reduced in cells harboring TNFR1 mutants, while overexpression of mutant TNFR1 in NFkB reporter Jurkat cells reveals abrogated TNF responses. Analysis of soluble TNFR1 released into the supernatant of transfected cells shows K203X is released in a greatly enhanced manner unique to this mutation. Overall, we show that these mutations confer muted TNFR1 responses upon stimulation. Future studies will explore the mechanisms through which these loss of function mutations lead to an inflammatory phenotype.