JAK/STAT signaling in development of Dnmt3a-mutant T-ALL. (A) Percentage of annexin-V⁺ (apoptotic) NICD-expressing control (Ctl) or Dnmt3a^KO (3aKO) T-ALL blasts freshly isolated from moribund recipient mice. (B) Proportion of viable T-ALL cells of indicated genotypes after 6-day in vitro coculture on OP9-DL1 cells. (C) Proportion of viable T-ALL cells of indicated genotypes after 6-day in vitro culture without stromal support. (D) GSEA plot showing enrichment of JAK/STAT gene expression in mouse Dnmt3a^KO T-ALL cells. (E) Cytometry by time of flight (CyTOF) analysis showing levels of phosphorylated Stat proteins in mouse T-ALL cells of indicated genotypes. (F) Western blot of control (Ctl) and Dnmt3a^KO (3aKO) T-ALL cells after in vitro stimulation with IL-6. (G) Western blot of MOHITO cells transduced with control (Renilla) or Dnmt3a short hairpin RNAs. (H) Western blot of human T-ALL cells after in vitro stimulation with IL-6 or IL-7.