Plk4 localizes to MTOCs in the mouse oocyte and facilitates microtubule growth upon resumption of meiosis. (A-E) Time-lapse series of oocytes injected with mRNA encoding EGFP-EB3 (gray, top; inverted, bottom) and histone H2B-mRFP (red, top). Oocytes were imaged as controls (A), under Plk4 inhibition by treatment with 5 µM centrinone (B), after coinjection of mRNA encoding the centrinone-resistant point mutant Plk4G95R the in presence of 5 µM centrinone (C), or while coexpressing Plk4Δkinase (D). Time (in hours:minutes) relative to NEBD. See Video 1. (E) Quantification of the size of the projected spindle area. Plk4 inhibition by expression of the dominant-negative Plk4Δkinase (GFP-ΔK; n = 13) or by treatment with centrinone at 5 µM (n = 26). Centrinone significantly reduces the kinetics of microtubule growth, as determined by the size of the spindle area, compared with controls (n = 44). Defects caused by centrinone treatment are significantly rescued by coexpression of Plk4G95R (n = 25). Error bars indicate SEM. P-values are shown in Table S1. See also Video 1. (F and G) Localization of Plk4 at MTOCs, revealed by immunostaining of oocytes with anti-Plk4, anti-CEP192, and anti–α-tubulin antibodies, in the indicated colors. DNA is shown in blue. Bars, 10 µm.