Cyclin B1 expression is decreased in high polyploid MKs in metaphase stage.

(A) Basic pattern of cell-cycle stages observed in megakaryocytic cells stained with anti–phospho-histone H1 + H3 antibodies; the different cell-cycle stages (G1, S, G2, metaphase, and anaphase) are indicated. (B) Double-immunofluorescence analysis by confocal laser microscopy of MKs at the metaphase stage, displaying different ploidy level, was performed by anti-H1 + H3 antibodies (in green, left panels) and anti–cyclin B1 MoAb (in red, middle panels). The yellow area (merge, right panels) indicates colocalization of histones and cyclin B1. A total of 100 MKs in the metaphase stage at different ploidy levels were analyzed. (Bar = 10 μm.)