Defective megakaryopoiesis in Fog^ki/ki CMP and MEP. (A) CMP, GMP, and MEP were cultured with TPO, IL-3, and IL-6 and scored at day 8. CFU-MKs were identified as AchE⁺ colonies with 3 or more MKs per colony. Other cells were identified by counterstain with Harris hematoxylin. Bars represent numbers of colonies per plated progenitors (n = 3). (B) Representative CFU-MKs derived from WT and Fog^ki/ki MEP. (C) Representative CFU-MK/G/M (left) and CFU-G/M (right) from Fog^ki/ki MEP.