Aurora A, but not Plk1, is required for microtubule growth upon NEBD during mouse oocyte meiosis I. (A–D) Time-lapse series of mouse oocytes expressing EGFP-EB3 (green, top; gray, bottom) and histone H2B-mRFP (red, top). Depicted are controls (A), oocytes treated with 1 µM Aurora A inhibitor 1 (AurA Inh 1; B) or 500 nM MLN8237 (C), and under Plk1 inhibition by treatment with 100 nM of the Plk1 inhibitor BI2536 (D). Time in hours:minutes relative to NEBD. (E) Quantification of the duration from NEBD to establishment of spindle bipolarity. Plk1 inhibition (BI2536) and Aurora A inhibition by Aurora A inhibitor 1 or MLN8237 significantly prolongs the time until establishment of a bipolar spindle (***, P < 0.001; *, P < 0.05) compared with controls (n = 20). Error bars indicate SD of mean. (F) Time from NEBD to establishment of a metaphase I plate until polar body extrusion (PBE). Plk1 and Aurora A inhibition significantly prolongs the time spent in metaphase. Additionally, Plk1 inhibition causes an arrest at metaphase I. The time spent in metaphase is significantly shorter for oocytes treated with Aurora A inhibitor 1 or MLN8237 than for controls (***, P < 0.001; **, P < 0.01; *, P < 0.05). Error bars indicate SD of mean. (G) Measurement of the size of projected spindle area throughout time. Inhibition of Aurora A (AurA Inh 1, n = 21; MLN8237, n = 5) or Plk1 (BI2536, n = 15) significantly reduces the spindle size reached at 2 h; however, the kinetics of microtubule growth is only affected by inhibition of Aurora A. For p-values and t502h, see Tables S1 and S3, respectively. Time 00:00 corresponds to time of NEBD and is determined by invasion of the EGFP-EB3 signal within the area previously occupied by the nucleus. Error bars indicate SEM. See also Video 2.
