Figure 6: Myc inhibition triggers micro- and multinucleation and mitotic abnormalities in U87MG cells.

(a) Normal mitosis phases in control U87MG cells. Tubulin staining (second column and in red in the merged image) shows proper centrosome maturation and spindle assembly, whereas DAPI staining (first column and in blue in the merged image) highlights correct chromosome alignment and subsequent segregation. (b) Mitotic defects in Omomyc-expressing cells. The same tubulin and DAPI staining as above show that Omomyc induces defects in all mitotic phases, ranging from abnormal multipolar spindles (prophase and metaphase panels), to chromosome misalignments, segregation errors and lagging chromosomes (anaphase and cytokinesis panels), and finally absence of midbody and failed cytokinesis (bottom panel). Mitotic abnormalities involve 14.7% of mitotic figures in Omomyc-expressing cells. (c) GFP (green) immunofluorescence and DAPI nuclear counterstain (blue) show that after 24 h of GFP-Omomyc expression, U87MG cells become multinucleated (bottom panels) whereas that is observed much less frequently in control U87MG (top panel) that express GFP alone. (d) A representative image of a multinucleated Omomyc-expressing cell: α-tubulin staining (in red) shows that all nuclei belong to the same cell. The arrowhead indicates a typical micronucleus.