Expression of p21 at high levels in murine polyploid megakaryocytes.

(A) Flow cytometry. Lin⁻ murine marrow cells were grown for 3 days in the presence of SCF and PEG-rHuMGDF, and cells were processed as in Figure 2. Dot plots are from a representative experiment (n = 3). (B) Immunostaining of p21. In parallel, p21 was immunodetected by indirect immunofluorescence on slides, by means of an anti-p21 mAb and a secondary TRITC-conjugated antimouse antibody, while the nuclei were counterstained with DAPI (bar 10 μm). A similar nuclear localization of p21 was observed on 250 megakaryocytes.