Dendrite formation and motility in G15S and tsr-RNAi neurons. (A) Images show new dendrite formation in control, G15S-expressing, and tsr-RNAi–knockdown neurons. Arrowheads indicate the sites at which new buds have emerged. The images at the beginning (0 min) and the end (10 min) of the observation are shown. (B) Bar graph indicates the average numbers of new dendrites per 10,000 µm² of the dorsal posterior field. The dendritic field was live imaged for 10 min with 20-s intervals for each scan. New dendrites that had emerged during this period were scored. Numbers of neurons are 14 for control, 12 for G15S, and 11 for tsr-RNAi from 7 to 10 experiments. (C) Images show LifeAct signals (green, top) in new branches (magenta, middle and merge images at bottom) that emerged within 10 min live imaging for control (left), G15S-expressing (middle), and tsr-RNAi–knockdown (right) neurons. (D) Bar graph represents LifeAct intensities (normalized to CD4-tdTomato intensities) in new branches. Numbers of branches are 30 for control, 21 for G15S, and 22 for tsr-RNAi from seven neurons in 10 experiments for each genotype. (E) Time series of images show dendrite dynamics in 30 min with 5-min intervals. Arrowheads indicate dendritic tips to show dendrite dynamic growth. (F–H) Bar graphs show average length in tip displacement of new dendrites for 5 min (F) as well as extension (G) and retraction (H) of existing dendrites for 10 min in control, G15S-expressing, and tsr-RNAi–knockdown neurons. In F, numbers of dendrites are 25 (control), 14 (G15S), and 13 (tsr-RNAi) from six to eight neurons in four to five experiments. In G and H, number of dendrites are 81 (control), 48 (G15S), and 62 (tsr-RNAi) from 10 neurons in seven to eight experiments for each genotype, and each dot represents the average number for a neuron. Significance in comparison with control was determined by Student’s t test. **, P < 0.01; ***, P < 0.001. Error bars represent SEM.