Asymmetrical segregation of chromosome 1 at anaphase of megakaryocyte endomitosis.

PRINS and immunofluorescence procedures were used on day 5 megakaryocytes as previously described in Figure 1. Centromeres of chromosome 1 are probed by PRINS in green (FITC). Spindle microtubules are immunostained in red (TRITC), and nuclei are counterstained with TOTO3-iodide that appear in blue. Merging of the 3 markers is visible on the first column. (A) 4N to 8N endomitosis at anaphase: chromosomes cluster into a ring around each aster. The number of green spots on DNA area is twice the spindle poles number. Note that there are normally 2 green spots at 2 poles (white arrows), but 3 and 1 dots are observed at the 2 resting poles (yellow arrows). The other green points correspond to false signals. (B) 8N to 16N endomitosis: the number of green dots shown by white arrows is indicated when greater than one. (C) Endomitosis of high ploidy: surimposition of both PRINS-probed centromeres of chromosome 1 in green and counterstained nuclei in blue. Bar, 5μm.