MTCL2 is required for the transition from bipolar to multipolar dendrite extension. A, Representative morphologies of CGNs at DIV3 visualized by GFP. Axons and dendrites were identified by staining with Ankyrin G and MAP2, respectively. Arrows and arrowheads indicate dendrites and an axon of the GFP-expressing cell, respectively. Scale bar, 20 µm. B, θ distribution of individual dendrites of CGNs at DIV3 and 5. Polar histograms of the average values from each of the three independent experiments are shown (more than 350 dendrites from the indicated number of cells were analyzed for each condition). The means ± SE are indicated. C, Distribution of the average dendritic length of the individual CGNs analyzed in B. Each data point represents the result of one neuron in three independent experiments. The means ± SD are shown for each scatterplot. D, Comparison of the direction bias (r) of the Golgi position in the GCNs at DIV3 and DIV5. Each data point represents the average value from each of the three independent experiments. The means ± SE are shown. See Figure S3C for the corresponding polar histogram. For verifying statistical significance in C and D, the Wilcoxon rank-sum test and Welch's two-sample t test were used, respectively. E, F, Representative live imaging data of GFP-expressing CGNs transfected with control (E) or MTCL2 (F) knockdown vectors. In each case, bipolar CGNs were selected at DIV3, and recordings were performed for 48 h. The frames showing the characteristic changes in the dendrite extensions are only presented for each CGN (for comprehensive images, refer to Movies 1 and 2). Arrowheads indicate axons. Arrows indicate initial stable dendrites. Note that the MTCL2-depleted CGN exhibited shrinkage of the preexisting bipolar dendrites but failed to persistently extend short dendrites in multiple directions. Instead, the cell stably extended long bipolar dendrites, again. Scale bars, 50 µm.