Figure 11.

The microtubule associated protein tau is required for Wnt5a induced redistribution of dynamic MTs in growth cones. (A,B) Composite images showing the redistribution of EB3 comets in the same growth cone over time 30 min before and during 30 min of application of the Wnt5a gradient (n = 361 images before Wnt5a and 601 images during Wnt5a application). The maximum intensity was computed for each pixel from the entire image stack by using algorithms in Metamorph. Using these values stacks of all images were superimposed and pixels assigned values in pseudocolor to indicate fluorescence intensity. Wnt5a was locally applied as a gradient at the right side of the growth cone. In this growth cone tau was knocked down with siRNA, which prevented the asymmetric redistribution of EB3 comets during exposure of the growth cone to Wnt5a gradients. (C) Localization of the center of intensity of EB3 comets evoked by Wnt5a gradients in four growth cones in independent experiments including the growth cone shown in (A,B). Quantitative analysis shows that Wnt5a fails to induce redistribution of EB3 comets to the far side of the growth cone after tau knockdown with siRNA (change in center of intensity not different from 0. p > 0.05, Wilcoxon signed rank test).