Ineffective hematopoiesis in SALL4B transgenic mice. (A) Comparison of bone marrow of SALL4B transgenic (i) and control mice (ii). SALL4B transgenic mouse bone marrow showed increased cellularity, myeloid population (Gr-1/Mac-1 double positive), immature population (c-kit positive), and apoptosis (annexin V positive, PI negative), compared with control WT mice. (B) Increased number of immature cells and apoptosis in CFUs from SALL4B transgenic mice. On day 7 of culture, a greater number of immature cells (ii-iv, red arrows) and apoptotic cells (ii-iv, double red arrows) were observed in transgenic mouse CFUs than in control CFUs (i). Consistent with this morphologic observation, there was increased apoptosis (annexin V positive, PI negative; v) and more CD34⁺ immature cells (vi). (C) Comparison of bone marrow CFUs of SALL4B transgenic and control mice. Percentage of different types of colonies found in CFU assays of SALL4B transgenic and control mice (i). CFUs from SALL4B transgenic mice compared with control mice showed a statistically significant increase in CFU-GM (ii) (transgenic: 53.6 ± 10.3 [n = 13] vs WT: 38.1 ± 3.1 [n = 8]; P = .002) and decrease in BFU-E (transgenic: 7.8 ± 3.8 [n = 13] vs WT: 14.1 ± 2.7 [n = 8]; P = .001).