MKs that overcome selinexor treatment have normal ploidy and morphology. Murine fetal liver cells were dosed with selinexor at D1 of maturation either continuously until D4 (A) or selinexor was washed out after 6 hours (B). On D4, the ploidy of the resulting MK population was quantified with FACS. *P < .05 vs vehicle control (DMSO); n = 3. (C) Representative transmission electron microscopy images of MKs showing polyploid nucleus (N), demarcation membrane (DMS), and granules (*). Bars represent 2 μM.