Somatic gene mutations expose cytoplasmic DNA to co-opt the cGAS/STING/NLRP3 axis in myelodysplastic syndromes
Amy F. McLemore, … , Alan F. List, Kathy L. McGraw
Amy F. McLemore, … , Alan F. List, Kathy L. McGraw
Published July 5, 2022
Citation Information: JCI Insight. 2022;7(15):e159430. https://doi.org/10.1172/jci.insight.159430.
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Research Article Hematology Oncology

Somatic gene mutations expose cytoplasmic DNA to co-opt the cGAS/STING/NLRP3 axis in myelodysplastic syndromes

Abstract

NLRP3 inflammasome and IFN-stimulated gene (ISG) induction are key biological drivers of ineffective hematopoiesis and inflammation in myelodysplastic syndromes (MDSs). Gene mutations involving mRNA splicing and epigenetic regulatory pathways induce inflammasome activation and myeloid lineage skewing in MDSs through undefined mechanisms. Using immortalized murine hematopoietic stem and progenitor cells harboring these somatic gene mutations and primary MDS BM specimens, we showed accumulation of unresolved R-loops and micronuclei with concurrent activation of the cytosolic sensor cyclic GMP-AMP synthase. Cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) signaling caused ISG induction, NLRP3 inflammasome activation, and maturation of the effector protease caspase-1. Deregulation of RNA polymerase III drove cytosolic R-loop generation, which upon inhibition, extinguished ISG and inflammasome response. Mechanistically, caspase-1 degraded the master erythroid transcription factor, GATA binding protein 1, provoking anemia and myeloid lineage bias that was reversed by cGAS inhibition in vitro and in Tet2–/– hematopoietic stem and progenitor cell–transplanted mice. Together, these data identified a mechanism by which functionally distinct mutations converged upon the cGAS/STING/NLRP3 axis in MDS, directing ISG induction, pyroptosis, and myeloid lineage skewing.

Authors

Amy F. McLemore, Hsin-An Hou, Benjamin S. Meyer, Nghi B. Lam, Grace A. Ward, Amy L. Aldrich, Matthew A. Rodrigues, Alexis Vedder, Ling Zhang, Eric Padron, Nicole D. Vincelette, David A. Sallman, Omar Abdel-Wahab, Alan F. List, Kathy L. McGraw

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Figure 2

cGAS is activated in SGM models and MDS bone marrow cells.

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cGAS is activated in SGM models and MDS bone marrow cells. (A) Represent...
(A) Representative immunofluorescence images of SGM mutant cell lines and MDS BM-MNCs with colocalization of cGAS to micronuclei with compromised nuclear membranes. Scale bar: 8 μm. (B) Representative immunofluorescence images of colocalization of cGAS and R-loops in SGM mutant cell lines and MDS BM-MNCs. Scale bar: 10 μm. (C) Aggregation of cGAS foci was increased in mutant immortalized SGM cells compared with WT controls (cGAS in green, DAPI in blue; original magnification, 3780×). Scale bar: 10 μm. (D) Aggregation of cGAS in MDS BM-MNCs (original magnification, 630×) compared with donor BM-MNCs (original magnification, 2940×). Scale bar: 50 μm. (E) Phospho-IRF3 was increased in SGM models compared with WT controls; representative flow histograms (n = 3 each). (F) ISG expression was increased in the immortalized SGM cells compared with WT controls (n = 3 each). (G) ISG and IFNB1 expression was significantly increased in MDS BM-MNCs (n = 213) compared with age-matched donors (n = 20). Data are presented as mean ± SEM. Images are representative of at least 2 independent experiments; Student’s t test for in vitro data; Mann-Whitney U test for G; *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001.