RELA essentiality in syngeneic MPN mouse models. (A) Schematic of the Rela^flox/flox UBC-Cre-ERT2 Jak2^+/VF mouse model. (B) Relative ablation of RelA by DNA sequencing after tamoxifen induction for 5 consecutive days (n = 8 per group). (C) WBC counts of Jak2-UBC (n = 9) and Jak2-Rela^fl (n = 8) mice after tamoxifen treatment over 6 weeks. Light gray regions indicate the normal reference range. Statistics were assessed by 2-way analysis of variance (ANOVA). (D) Monocyte, PB, and BM CD45.2 myeloid cells, hematocrit, and platelet counts at end point. Statistics were assessed by 2-tailed Student t test. (E) Normalized spleen weight at end point. Statistics were assessed by 2-tailed Student t test. (F) WBC, monocyte, hematocrit, and platelet counts of control or Rela^fl (n = 10 per group) mice. Statistics were assessed by 2-way ANOVA. (G) Normalized spleen weight at end point. Statistics were assessed by 2-tailed Student t test. (H) Schematic of the Rela^flox/flox UBC-Cre-ERT2 MPL^W515L mouse model. (I) Relative ablation of Rela by DNA sequencing after tamoxifen induction for 5 consecutive days (n = 6 per group). (J) WBC counts of MPL-UBC (n = 9) and MPL-Rela^fl (n = 6) mice after tamoxifen treatment. Statistics were assessed by 2-way ANOVA. (K) Monocyte, PB, and BM CD45.2 myeloid cells, hematocrit, platelet counts, and GFP⁺ cells at end point. Statistics were assessed by 2-tailed Student t test. (L) Normalized spleen weight at end point. Statistics were assessed by 2-tailed Student t test. (M) Kaplan-Meier survival curve. Statistics were assessed by log-rank test. (N) Histology of the spleen and BM at end point. Scale bar = 75 μm. BM fibrosis was scored from 3 mice in each group.