A genotype-first approach reveals the molecular basis of pyrin inflammasome activation

Mutations in the MEFV gene, which encodes pyrin, are associated with a spectrum of inflammatory conditions called pyrin-associated autoinflammatory diseases (PAADs). Of the 400 MEFV variants listed in the Infevers database, most are classified as variants of uncertain significance. Thus, genetic diagnosis of PAADs remains challenging, and the molecular mechanisms underlying pyrin activation remain poorly understood. Here, we used a cell-based pyroptosis assay to stratify 265 missense MEFV variants and identified previously uncharacterized pathogenic variants. We then characterized the interaction between the pyrin B30.2 domain and CDC42, a key regulator of pyrin intracellular trafficking and activation. We found that classical familial Mediterranean fever (FMF)–related variants bind tightly to CDC42 to induce pyrin hyperactivation, whereas certain non-FMF variants induce pyrin hyperactivation independently of CDC42, indicating involvement of multiple pathways in pyrin activation. Our approach provides a proof of concept for a genotype-first approach, which may advance our understanding of complex human diseases.