Fig. 2. Effect of induced GATA-2 on immature hematopoietic colony formation at day 7 of induction. A total of 105 day 5 induced cells were seeded onto the OP9 stroma cell layer and the cells were cultured in the presence or absence of tetracycline. All the analyses were carried out at day 7 of induction. (A) Relative number of colonies in control and Tet-regulated GATA-2 clones. Data are shown as the mean ± SD of six samples (*P < 0.01 by t-test). (B) Numbers of cells in individual colonies in the presence or absence of tetracycline. GATA-2 increased the number of cells significantly (*P < 0.01 by t-test). (C) Numbers of colonies in the culture containing various concentrations of tetracycline. (D) Typical hematopoietic colonies in the presence (left panels) or absence (right panels) of tetracycline. A colony grown underneath the OP9 stroma cells with a cobble stone appearance (pseudoemperipolesis) is shown in the right lower panel. (E) Number of colonies showing pseudoemperipolesis. Data are shown as the mean ± SD of six samples (*P < 0.01 by t-test).