Overexpression of ETS2 and ERG promote immortalization of Gata1-knockdown and Gata1s knockin fetal liver hematopoietic progenitors. (A) The numbers of total colonies derived from plating sorted GFP⁺ wild-type fetal liver progenitors transduced with MIGR1, MIGR1-ETS2, or MIGR1-ERG for 3 generations. Ten thousand cells were plated each time. No differences were significant except for the ERG third replating. P value less than .03; n = 3 in all experiments. (B) The numbers of total colonies derived from plating sorted GFP⁺Gata1-knockdown fetal liver progenitors transduced with MIGR1, MIGR1-ETS2, or MIGR1-ERG for 3 generations. Five thousand cells were plated each time. * P less than .05. (C) The numbers of total colonies derived from plating sorted GFP⁺Gata1s knockin fetal liver progenitors transduced with MIGR1, MIGR1-ETS2, MIGR1-ERG, or MIGR1-FLI1 for 3 generations. Five thousand cells were plated each time. * P less than or equal to .05.