Identification of a Novel Mutation in TNFAIP3 in a Family With Poly-Autoimmunity

Abstract

Haploinsufficiency of A20 (HA20) is an inflammatory disease caused by mutations in the TNFAIP3 gene classically presenting with Behcet’s-like disease. A20 acts as an inhibitor of inflammation through its effect on NF-kB pathway. Here we describe four consanguineous patients (three sisters and their mother) with a predominantly autoimmune phenotype, including thyroiditis, type I diabetes, hemolytic anemia and chronic polyarthritis. All patients had recurrent oral ulcers, with only 1 patient presenting also recurrent fever episodes, as a classical autoinflammatory feature. Next generation sequencing identified a novel heterozygous frameshift mutation (p.His577Alafs*95) that causes a premature stop codon in the zinc finger domain of A20, leading to a putative haploinsufficiency of the protein. Functional analyses confirmed the pathogenicity of the mutation. The variant was associated with decreased levels of A20 in blood cells. Accordingly, ex-vivo lipopolysaccharide (LPS)-stimulated patients’ peripheral blood mononuclear cells (PBMCs) showed higher levels of p65 NF-kB phosphorylation, as well as increased production of the proinflammatory cytokines IL-1β, IL-6 and TNF-α. Moreover, in agreement with recent observations, demonstrating a role for A20 in inhibiting STAT1 and IFNγ pathways, markedly higher circulating levels of the two IFNγ-inducible chemokines CXCL9 and CXCL10 were detected in all patients. Supporting the findings of a hyperactivation of IFNγ signaling pathway in HA20 patients, patients’ monocytes showed higher levels of STAT1 without stimulation, as well as higher phosphorylated (active) STAT1 levels following IFNγ stimulation. In conclusion, our study show that in the clinical spectrum of HA20 autoimmune features may predominate over autoinflammatory features and demonstrate, from a molecular point of view, the involvement of A20 in modulating not only the NF-kB, but also the IFNγ pathway.

Single-cell RNA sequencing combined with whole exome sequencing reveals the landscape of the immune pathogenic response to chronic mucocutaneous candidiasis with STAT1 GOF mutation

“…Previous studies have shown that A20 expression is lower in the PBMCs of patients with haploinsufficiency of A20 (HA20), which is typically manifested as Behçet’s-like disease. In vitro experiments in PBMCs of HA20 patients have shown that A20 not only inhibits inflammation through the NF-kB pathway, but also inhibits the STAT1 and IFN-γ pathways ( 25 ). In addition, A20 plays a negative regulatory role in the secretion of IL-17 by Th17 cells ( 26 ), so TNFAIP3 may be a potential pathogenic mechanism involved in CMC, although research is needed to investigate this.…”

The functional impact of two variants of uncertain significance in TNFAIP3

“…With the deepening of researches, A20 was also found to plays an important role in the interferon (IFN)-γ pathway. Recent studies have demonstrated that A20 plays a role in inhibiting STAT1 expression and regulating IFN-γ downstream genes both in mouse bone marrow cells and patients' PBMCs with TNFAIP3 mutation [33,34]. Therefore, A20 regulates a wide range of pathways, and the underlying mechanisms need further studies.…”

TNFAIP3 mutation causing haploinsufficiency of A20 with a hemophagocytic lymphohistiocytosis phenotype: a report of two cases

“…Patients with TNFAIP3 mutation can develop autoantibodies. Fluctuating levels of low-titer autoantibodies, including antinuclear antibodies, anti-double-stranded DNA (dsDNA), anti-Sm/ribonucleoprotein (RNP), anticardiolipin, and lupus anticoagulant, were found in the largest reported cohort [10][11][12]. Acute phase reactants tend to elevate with disease flares, but their levels are normal between flares, which is a characteristic of autoinflammatory syndromes [10].…”