Assessment of megakaryocyte lineage-specific Srf deletion. Bone marrow (BM) from Pf4/Srf+/+ (n = 3) and Pf4/SrfF/F (n = 4) mice was cultured for 4 days in TPO and subjected to BSA gradient separation. Quantitative RT-PCR was performed on the isolated fractions. Mean and SD are shown. P < .01.