Doxycycline-induced Klf6 restores hematopoietic differentiation. (A) Doxycycline was added to culture medium on day 2 of EB differentiation in cells expressing a doxycycline-regulable Klf6. Expression of Brachyury (B) and Flk1 (C) is increased in cells following induction of Klf6 and confirmed by real-time PCR. Cells from day-5 EBs were subjected to hematopoietic colony formation assay. Colony numbers of Ery^P (D), Mac (E), and Mix (F) were counted. Bars represent SE of colony counts from 3 independent cultures. ^*P < .05 (Student t test).