Patronin is required for persistent minus end polymerization. (A–C) Quantification of speed, polymerization length, and duration of minus ends of microtubules with control or Patronin RNAi. Sample sizes are 154 traces from 30 neurons for control RNAi, 229 traces from 21 neurons for Patronin RNAi 1, and 154 traces from 15 neurons for Patronin RNAi 2. (A) One-way ANOVA followed by Dunnett's multiple comparisons were used for statistics. **, P < 0.01; ****, P < 0.0001. (B and C) Kruskal–Wallis tests followed by Dunnett’s multiple comparisons were performed because of non-Gaussian distribution of these data. ****, P < 0.0001. Mean and SD are shown with black lines. (D) Quantification of persistent minus end growth events. Minus ends that polymerized for >5 min were considered persistent growth. Numbers on the graph are the total numbers of traces collected. ****, P < 0.0001 with Fisher’s exact test. (E) Representative kymographs of EB1-TagRFP-T with control or Patronin RNAi. Pink lines indicate minus ends. Horizontal bar, 5 μm. Vertical bar, 300 s. (F) Representative overview image of the comb dendrite from an EB1-TagRFP-T expressing class I ddaE neuron with control RNAi. Kymograph shows a representative persistent minus end growth event. Blue arrow points to the start and orange arrow to the end of the growth event in the overview and kymograph. (G) Schematic diagram showing Patronin is required for persistent minus end polymerization.