a, Quantification of control or Deup1 siRNA-treated cells undergoing centriole amplification that contained (DEUP1+ ) or lacked (DEUP1-) DEUP1 foci. To identify cells in the process of centriole amplification we immunostained for STIL, which localizes to immature procentrioles but is absent from mature basal bodies. n = 3 cultures/genotype. b, Quantification of the intensity of DEUP1 signal in STIL+ /DEUP1+ controls or STIL+ /DEUP1- siRNA-treated cells. n = 3 cultures/genotype. The average DEUP1 intensity for the control siRNA sample was normalized to 1 for each experiment. P values, one sample t-test compared to a mean of 1. **** = p ≤ 0.0001. c, Quantification of centriole number in control and Deup1 siRNA-treated cells. Only STIL+ cells were quantified so that DEUP1 depletion could be monitored, and only cells depleted for DEUP1 (assessed by immunostaining) in the siRNA condition were quantified. n = 3 cultures/genotype. P values, unpaired, two-tailed, Welch’s t-test. n.s. = not statistically significant (p > 0.05). d, Representative images of control ependymal cells and cells with siRNA-mediated depletion of DEUP1 undergoing centriole amplification. Scale bars represent 10 μm.