Wild-type (wt) and transgenic (tg) PF4-surv MKs in fresh bone marrow cytospins were quantified via positive acetylcholinesterase staining. 375 wild-type MKs and 436 tg MKs were counted and normalized to cell density as calculated using Image-Pro software (Media Cybernetics, Silver Spring, MD) and quantitation of the 4′,6-diamidino-2-phenylindole counterstain signal. The number of MKs in the tg animals is presented as a percentage of the wild-type control. A 2-tailed Student t test was used to generate a P value, indicating no difference between the 2 groups (n = 3 mice per group). — indicates not applicable.