Correlation between the number of centromeres of chromosome 1 and the cell ploidy.

Human CD34⁺ cells were grown in the presence of PEG-rhuMGDF and SCF. Day 5 megakaryocytes were treated with the PRINS and immunofluorescence procedure described in “Materials and methods.” They were cytospun, fixed with methanol/acetic acid, and permeabilized with Triton. Centromeres of chromosome 1s were probed in green by PRINS, using specific centromeric primers and FITC-labeled nucleotides. Microtubules were stained in red by indirect immunofluorescence with an anti–β-tubulin antibody, followed by incubation with TRITC-labeled antimouse F(ab′)2 fragments. Slides were examined by confocal microscopy with a 3-dimensional reconstruction and superimposition of the 2 signals. The upper-left corner of the figure shows many diploid interphase cells containing 2 dots representing 2 chromosome 1s; the lower-right corner shows a mitotic polyploid cell that contains a tetrapolar spindle and 4 chromosome 1s (white arrows). Bar, 10 μm.