Ectopic cyclin D1–Cdk4 does not rescue megakaryocyte terminal differentiation. mRNA was extracted from BSA gradient–purified megakaryocytes derived from wild-type fetal livers or G1KD fetal livers infected with cyclin D1 and Cdk4 encoding retroviruses (described in Figures 3 and 5). Expression levels of β1-tubulin, NF-E2, and PF4 are shown relative to wild-type expression levels. The mean ± 1 SD is shown for each study. As shown, overexpression of cyclin D1, Cdk4, or both does affect the expression of these genes.