Figure 4(A-G) Representative frame (A, D) and a kymograph (B, F) of a simultaneous two-color movie of a hippocampal neuron expressing NPY-mCherry and either KIF1A-GFP (A, B), BDNF-GFP (D) or TfR-GFP (F). Scale bar = 20 µm (A, D), 5 µm (B, F). (C) Quantification of vesicle colocalization in cells described in (A, B) The quantifications indicate the % of KIF1Avesicles that are NPY positive - left bar quantified from images of fixed cells presented in (A) and right bar quantified from kymographs as presented in (B) (only moving fraction). (E) Quantification of vesicle colocalization in cells described in (D) - left bar indicates the % of NPYvesicles that are BDNF positive, the right bar indicates the % of BDNFvesicles that are NPY positive. (G) Quantification of vesicle colocalization in cells described in (F). The left bar indicates the % of NPYvesicles that are TfR positive, the right bar indicates the % of TfR that are NPY positive. (H, I) Quantification of run lengths (H) and velocities (I) of vesicles in dendrites of hippocampal neurons transfected at DIV10-14 for 4 days with either NPY-GFP (n = 924 movements) or TfR-GFP (n = 286) or KIF1A-GFP (n = 174) together with a morphology marker BFP. N = 2. Error bars indicate SEM; *** p < 0.001 (1-way ANOVA followed by a Tukey's Multiple Comparison Test ). (J) Scheme of live-cell imaging after photobleaching to visualize the motility of dense core vesicles labeled with NPY-GFP (H, I, K, L) or TfR positive recycling endosomes (H, I, M, N) in proximal dendrites of hippocampal neurons (DIV14). (K) Representative kymographs of NPY-GFP-labeled dense core vesicle motility in primary dendrites of transfected neurons. DIV10-14 hippocampal neurons were cotransfected, for 4 days, with plasmids encoding NPY-GFP, BFP fill and a KIF21 shRNA mix (n = 30), KIF1shRNA mix (n = 31), KIF1A shRNA (n = 19), KIF1B shRNA (n = 19) or KIF1C shRNA (n = 11). pSUPER was used as a control (n = 15). Scale bar = 5 µm. (L) Quantification of the average number of dense core vesicle entries into the primary dendrite in 100 s after photobleaching. N = 2-3. Error bars indicate SEM; *** - p < 0.001 (1-way ANOVA followed by a Tukey's Multiple Comparison Test). (M) Representative kymographs of TfR-GFP-labeled recycling endosome motility in primary dendrites. DIV10-14 Hippocampal neurons were cotransfected with TfR-GFP together with a BFP fill and a KIF1shRNA mix (n = 11). pSUPER was used as a control (n = 20). Scale bar = 5 µm. (N) Quantification of the average number of recycling endosome entries into the primary dendrite in 50 s. N = 2. Error bars indicate SEM. ns - not significant (Mann-Whitney test). (O) Representative images of hippocampal neurons (DIV4) cotransfected with an empty pSUPER (control) or pSUPER encoding an indicated shRNA together with a GFP fill fixed at DIV8 and immunostained for MAP2 and sodium channels (AIS). Scale bar = 50 µm. (P) Sholl analysis of cells described in (O) Error bars indicate SEM; * - p < 0.05, ** - p < 0.01, and *** - p < 0.001 (two-way ANOVA test followed by Bonferroni's post hoc test). (R) Analysis of the total dendritic length of cells described in (O) Error bars indicate SEM; * - p < 0.05, ** - p < 0.01 and *** - p < 0.001 (1-way ANOVA followed by a Tukey's Multiple Comparison Test). Per condition 21-24 neurons (n) were analyzed; N = 2.