A New Gain-of-Function NLRP1 Variant Is Associated with Inflammasome Activation and Disease Severity in SLC25A38 Congenital Sideroblastic Anemia Case Report

Abstract

Inflammasomes play a pivotal role in inflammation and infection, but the clinical relevance of inflammasomes goes beyond infectious disease. Here, we report a novel variant in the NLRP1 gene (p.V939M) identified in a patient with congenital sideroblastic anemia due to a homozygous SLC25A38 mutation. This patient exhibits severe anemia, iron overload, and dependence on frequent transfusions. Functional characterization of peripheral blood mononuclear cells from the patient revealed constitutive activation of the NLRP1 inflammasome in primary cells, evidenced by increased processing of NLRP1, cleavage of CASP1, and ASC oligomerization. Moreover, in a speck in vitro assay, the newly identified genetic variant increases ASC oligomerization, and using ex vivo erythroid differentiation assays with patient-derived cells, we demonstrated that pharmacological inhibition of CASP1 enhances erythrocyte formation. This patient-derived NLRP1 variant was evaluated in a newly generated human NLRP1 knockdown system using CRISPR-Cas9 in K562 cells, in combination with ferroptotic/oxidative stress induction to mimic patient clinical features, and our results indicate that the presence of NLRP1 p.V939M, together with enhanced ferroptosis, may contribute to the patient’s phenotype. Furthermore, both CASP1 inhibition and ferroptosis inhibition further enhance the restoration of erythroid colony formation from primary progenitor cells derived from the patient. Therefore, our study identifies a novel NLRP1 inflammasome variant involved in human erythropoiesis and highlights its possible contribution to the pathogenesis of congenital sideroblastic anemia, providing a basis for the development of new potential therapeutic strategies.