Interaction of GDP-tubulin-assembled microtubules with MAPs. (A) Microtubules assembled from seeds (brightest microtubule segment) and GDP-tubulin in the absence or the presence of 0.5 µM of tau or DCX. Stars (cyan) indicate non-nucleating seeds. (B) Percentages of seeds nucleating GDP-tubulin in the absence or presence of tau or DCX. n, the total number of seeds from at least three independent experiments. Triangles represent the percentage of nucleating seeds for each experiment. *P < 0.05, ****P < 0.0001 (two-sided Fisher’s test). P values were calculated relative to the control condition. (C) Microtubules assembled from seeds and 100 µM of GDP-tubulin in the presence of 0.5 µM of GFP-tau. (D) Linescan along the microtubule shown in the yellow box in C. Tau binds the microtubule lattice but is excluded from the GMPCPP seed. (E) Tau fluorescence intensity on the GDP-tubulin lattice and GMPCPP seeds. Values are means ± SD of 27 events from four independent experiments. Triangles represent the mean intensity for each experiment. ****P < 0.0001 (non-parametric Mann–Whitney test). (F) Representative kymographs of microtubules grown from seeds (S) and GTP-tubulin (8 µM) or GDP-tubulin (260 µM) in the presence of 75 nM GFP-EB1. (G) EB1 fluorescence intensity at microtubule minus end (comet) and on the lattice of both types of microtubules. Values are means ± SD of 301 (comet, GTP-tub), 124 (lattice, GTP-tub), 89 (comet, GDP-tub), and 89 (lattice, GDP-tub) events from three independent experiments. Triangles represent the mean intensity for each experiment. ****P < 0.001; ns, non-significant (Kruskal–Wallis ANOVA followed by post-hoc Dunn’s multiple comparison).