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 5

RNAP3 inhibition suppresses R-loop accumulation and inflammasome activity.

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RNAP3 inhibition suppresses R-loop accumulation and inflammasome activit...
(A) SGM models were treated with ML-60218 (RNAP3 inhibitor, RNAP3i) for 72 hours, and R-loop (S9.6) expression was assessed by flow cytometry (n = 2 each for Tet2 cells and n = 3 each for Srsf2 cells) with representative flow histograms. (B) Representative IF images of R-loop reduction in Tet2–/– immortalized cells treated with RNAP3i (scale bar: 10 μm) and (C) MFI quantitation of immunofluorescence (n = 10 vehicle-treated cells and n = 12 RNAP3i-treated cells). (D) Caspase-1 activity by flow cytometry with representative histograms (n = 3 each). (E) Low-risk MDS BM-MNCs treated in vitro with 10 μM RNAP3i for 72 hours (n = 3), resulting in a decrease in R-loops with representative histogram, ISGs (n = 3 each) (F), and inflammasome markers (caspase-1, IL-1β, and ASC specks (n = 3 each) (G), with representative flow histograms. Data are presented as mean ± SEM. Student’s t test; *P ≤ 0.05, **P ≤ 0.01, ****P ≤ 0.0001.