Fig. 1

GATA1s transgene-rescued mice develop acute megakaryoblastic leukemias. (A) The appearance of ΔNTR-M (left panel) and ΔNTR-H (right panel) embryos at E18.5 and their littermates. (B, C) Flow cytometric analysis of E18.5 fetal livers from two ΔNTR-H (B) and two ΔNTR-M (C) mice in comparison to their wild-type littermates. The frequencies of CD41⁺CD61⁺ megakaryocytes in live cells from the spleen are depicted in the panels. (D) Expression levels of Gata1 mRNA in CD41⁺ megakaryocytes. Fetal livers recovered from 3 to 4 wild-type embryos were combined and used as controls. Results are from 6 wild-type control pools, 6 ΔNTR-H, and 3 ΔNTR-M E18.5 embryos. The average value of the wild-type group was set to one, and the average values of ΔNTR-H and ΔNTR-M groups are indicated by black bars. Data were analyzed using the Mann-Whitney U test. *; P < 0.05, **; P < 0.01. (E) Survival curves of 15 G1R (black line), 53 ΔNTR-H (blue line), 39 ΔNTR-M (red line), 12 ΔNTR-MH (magenta line), and 7 ΔNTR-MM (purple line) mice. Black and magenta lines fully overlapped. Note that the early mortality of ΔNTR-M mice was partially or completely suppressed by concomitant expression of GATA1s by the ΔNT-M and ΔNT-H transgenes, respectively (purple and magenta lines versus red line, respectively). Details of mice used in this experiment are in Supplementary Table 1. (F) A summary of the Log-rank test (upper row) and Generalized Wilcoxson test (lower row) results for mortality of mice among the indicated groups. Note that ΔNTR-MH survived significantly longer than did ΔNTR-M mice. ΔNTR-MM was significantly rescued from early mortality of the ΔNTR-M, but still markedly prone to suffer from leukemia when compared to G1R, ΔNTR-MH and ΔNTR-H. n.s; not significant. (G) Enlarged spleen and liver of a representative ΔNTR-M mouse developing AMKL. (H, I) Histopathological analyses of spleen (H) and liver (I) sections with Hematoxylin-Eosin staining (H and left panel of I). Right panel of I is a silver staining of the liver section. Note that destruction of splenic architecture and marked infiltration of blast cells accompanied by increased fibrosis around the liver central vein. (J) Blast cells in peripheral blood smear samples of leukemic ΔNTR-M mice. Note that the blasts have basophilic cytoplasm, large nuclei containing several nucleoli and cytoplasmic blebs, likely representing megakaryoblastic leukemia cells. A subset of these blasts have coarse azurophilic granules in the cytoplasm (blue arrows). An abnormally large hypo-granular platelet (red arrow) is observed. (K) Flow cytometry analysis of spleen mononuclear cells from a leukemic ΔNTR-M mice. Cells in the abnormal fraction (black polygonal areas in left panels), determined by forward (FSC) and side scatter (SSC) patterns are frequently c-Kit-positive and CD41-dull (right panels). Note that the leukemic cells observed in ΔNTR-M mice harbor megakaryocytic and erythroid immunophenotypes, as seen at high frequency in Down syndrome-related AMKL cases [13]. d/o: days-old