Figure 7. RUNX1 variation and JAK3 mutation jointly drive ETP phenotype in murine bone marrow transplantation model.

(A) Peripheral leukocyte count of RUNX1^M, JAK3^M, JAK3^MRUNX1^M, and control mice. Mouse hematopoietic stem and progenitor cells were lentivirally transduced with RUNX1^M and JAK3^M constructs or EV and injected into recipient 8-week-old female mice. Peripheral blood count was monitored biweekly. (B and C) There was a significant increase in the CD8⁺ population in JAK3^M mice compared with control mice. RUNX1^M and JAK3^MRUNX1^M mice showed increases of Mac1⁺ cells and fewer CD3⁺ cells than control or JAK3^M mice at 4 months. Control, n = 7; RUNX1^M, n = 8; JAK3^M, n = 5; JAK3^MRUNX1^M, n = 6. (D) Upper panel: blood smear of JAK3^M and JAK3^MRUNX1^M mice at the time of sacrifice and control mice at 4 months. Scale bar: 50 μm. Lower panel: percentages of mice that developed leukemia in each group. JAK3^M, 100%; JAK3^MRUNX1^M, 66.7%. (E) Peripheral leukocyte count of JAK3^MRUNX1^M (n = 4) and JAK3^M (n = 5) mice at time of sacrifice and control (n = 7) mice after 4 months of transplantation. (F) Spleen weight of JAK3^M (n = 5) and JAK3^MRUNX1^M (n = 4) mice at time of sacrifice and control mice (n = 4) after 4 months of transplantation. (G and H) Thymocyte immunophenotype of JAK3^M (n = 5) and JAK3^MRUNX1^M (n = 4) mice at time of sacrifice. Coexpression of RUNX1^M and JAK3^M resulted in a drastic increase in DN1 population compared with that in mice receiving LSK cells expressing JAK3^M only. (I) In peripheral blood (n = 3), bone marrow (n = 4), and spleen (n = 4), JAK3^MRUNX1^M mice showed a significant increase in Mac1⁺ population and a reduction of the CD3⁺ population compared with JAK3^M (n = 5) mice. For E and F, P values were estimated by using Dunnett’s test. For B, C, G, H, and I, data represent mean ± SEM and P values were generated by t test. *P < 0.05; **P < 0.01; ***P < 0.001.