A TBK1 mutation disrupting IRF3 activation is associated with familial recurrent myopericarditis.

INTRODUCTION: Idiopathic recurrent pericarditis (IRP) is an immune-mediated disease characterized by episodes of pericardial inflammation. While IRP is increasingly considered an autoinflammatory condition, pathogenic pathways remain poorly understood. In this context, gene discovery can reveal new disease mechanisms. METHODS: We carried out whole-exome sequencing in a pedigree where three individuals suffered from IRP presenting with myocardial involvement (myopericarditis). We first investigated mutation effects computationally, by estimating free-energy changes and undertaking molecular dynamic simulations of wild type and mutant proteins. Next, we overexpressed wild-type and mutagenized cDNAs in HEK293 cells, characterizing protein expression and phosphorylation by western blotting. Finally, we measured gene expression in primary pericardial fibroblasts, using real-time PCR. RESULTS: We identified a Y105C mutation in TBK1, a kinase that regulates antiviral responses driven by the IRF3 transcription factor. The Y105C substitution maps at the interface between the kinase and scaffold domain of TBK1. Accordingly, molecular modeling predicted a destabilizing effect of the variant, which was experimentally validated in over-expression studies. The Y105C mutation also affected kinase activity, causing a significant reduction in IRF3 phosphorylation. While TBK1 was required for TLR3-IRF3 signaling in primary human pericardial fibroblasts, TLR3 was weakly expressed in these cells. CONCLUSIONS: A TBK1 Y105C mutation that reduces IRF3 phosporylation is associated with familial recurrent myopericarditis. Given TLR3 is lowly expressed in pericardial fibroblasts, these cells may be especially vulnerable to mutations that disrupt TLR3-IRF3 signaling. Thus, our findings suggest that inherited susceptibility to viral infections may be an important factor in the pathogenesis of IRP.