KIF18A-deficient cells form MN and abnormal nuclear shapes. (A) Representative image of a micronucleated hTERT-RPE1 cell labeled with DAPI and ACA to visualize DNA and centromeres, respectively. (B–D) Plots of the percentage of cells with MN in cells treated with the indicated siRNAs for 48, 96, or 144 h (B), control and KIF18A KO hTERT-RPE1 cells (C), and MEF from Kif18a^gcd2/gcd2 mice (D). n > 600 cells for each condition; data were compared via χ² analyses. (E) Quantification of the percentage of MN containing centromeric DNA (ACA-positive) in control (black) and KIF18A siRNA (red) treated cells; data were compared via χ² analyses. (F) Quantification of MN in mouse peripheral blood reticulocytes from Kif18a^+/+, Kif18a^gcd2/gcd2, Kif18a^+/gcd2, and Atm^{tm1Awb/tm1Awb}. Data points represent the percentage of micronucleated cells from individual mice. Data were compared using a one-way ANOVA and Tukey’s multiple comparisons test. (G) Representative images of nuclear shapes and corresponding solidity values (s) observed in KIF18A KO hTERT-RPE1 cells. (H) Box and whisker plot of nuclear solidity values measured in control (n = 553) and KIF18A KO (n = 634) cells. Data distributions were compared using a Kolmogorov–Smirnov t test. (I) Plot of percentage of nuclei with solidity values two SDs below the average in control cells. Data were compared using a χ² test. In all panels, *, P < 0.01. All data were collected from three independent experiments, and error bars indicate SD.