Development of astral MTs scales to ploidy level. (A and E) Immunostaining of α-tubulin during anaphase in GFP-centrin HAP1 cells with different ploidies (A) or in RNAi-treated haploid HAP1 cells (E). Enlarged images of the astral MTs at the polar region (yellow boxes) and GFP-centrin at the spindle pole (magenta boxes in A) are shown in the bottom panels. Asterisks: neighboring interphase cells. Blue broken lines: spindle regions. (B and F) Number of astral fibers attached to the polar cortex in A or E. Values represent means ± SD of at least 10 spindle poles from three independent experiments (B) or at least 14 poles from two independent experiments (F; p-values calculated using t tests are shown). Spindle poles with different numbers of GFP-centrin foci were separately categorized in B. Examples of MT tracking are shown in Video 7. (C) Immunostaining of γ-tubulin and centrin in preanaphase cells with different ploidies. Insets show 2× enlarged images of the spindle poles indicated by magenta boxes. Bottom: An example of regions of interest (ROIs) for the quantification in D. (D) Line profiles of γ-tubulin at the spindle poles in C. Spindle poles with two centrioles were analyzed. Values represent means ± SE of at least 24 spindle poles from two independent experiments. Asterisks indicate statistically significant differences between haploid and tetraploid cells at the center of the spindle pole (*, P < 0.05, one-way ANOVA with Tukey post-hoc test).