Figure 6.

Loss of centrosomes and the SAC dramatically perturbs genome stability. (A–D) Karyotype assay. Loss of centrosomes or SAC alone did not dramatically disrupt the accuracy of chromosome segregation, but loss of both elevated aneuploidy and polyploidy. (B–D) Representative euploid or aneuploid/polyploid karyotypes. (E) In mad2 sas-4 brains, some CB NBs (Dpn⁺, green; Mira⁺, red) were normal sized (presumptive diploid or mildly aneuploid), whereas others were abnormally large (presumptive polyploid). E’ shows the Mira channel only, representing the cytoplasmic area of NBs; E’’ shows the Dpn channel only, showing labeling of NB nuclei. (F) Some abnormally large presumed polyploid cells in mad2­ sas-4 brains appeared to be in mitosis (arrows; PH3⁺, green; nuclei labeled by His:RFP); a normal-sized mitotic cell is also visible. F’ shows the His:RFP channel marking all nuclei; F’’ shows how PH3 staining labels on mitotic cells. (G–K) WT and single mutants did not display high levels of γ-H2Av, whereas mad2 sas-4 brains contained γ-H2Av⁺ cells. Arrows in J label cells with high levels of DNA damage. (L) sas-4 single mutant and mad2 sas-4 double mutants prolonged the time from NEB to anaphase. Error bars represent means ± SD.