Loss of IKZF1 alone is insufficient to recapitulate the effects of pomalidomide treatment. CD34⁺ cells were transduced with either control (luciferase) or IKZF1 lentivirus, and after this were placed in erythroid differentiation media ± 1 μM pomalidomide (N = 3). Puromycin selection was performed at 48 hours post-transduction. (A) Terminal erythroid differentiation was assessed as described. (B) Representative May-Grunwald Giemsa–stained cytopreps, and enucleation rate as determined by Syto-16 staining. (C) Western blots for IKZF1 and BCL11A at day 7 of culture. (D) Terminal differentiation of shIKZF1 knockdown in the presence of 1 μM pomalidomide. (E) Immunoblots for IKZF1 and BCL11A at day 11.