Fig. 2.

Quality control at dendrite branch point exits regulates microtubule plus-end polymerization. (A) A dendrite region of a ddaE neuron expressing Eb1-GFP under 221-Gal4 is shown. Distal, peripheral and proximal exits are indicated with red lines. (B) A schematic diagram of success and failure growth events is shown. Microtubules (red) growing plus ends are marked with Eb1-GFP (green dots). A success event is defined as an Eb1 comet traveling through a 2-μm segment without disappearing. A failure event is defined as a microtubule plus end that stops growing after it enters the 2-μm segment. (C) An example kymograph of Eb1-GFP at the proximal exit of a control neuron is shown. A failure and a success event are marked. The red line marks the 2-μm check point segment and the yellow line indicates the branch point region. (D) Example Eb1 traces at proximal, distal or peripheral exits of control neurons. An orange frame marks success events and a blue frame marks failure events. Yellow and red lines indicate the branch point and exit, respectively. (E) Quantification of success rates at proximal, distal or peripheral exits of branch points is shown. Numbers on the bars are the number of comets recorded from control animals. ****P<0.0001 (F-test). (F) Schematics of two hypotheses that could contribute to differential success at branch point exits. (G,H) Quantification of success rates at proximal, distal, peripheral exits and inbetween branch points is shown for neurons expressing control RNAi or RNAi against candidate genes. Numbers on the bars are number of comets analyzed for that condition. *P<0.05; **P<0.01; ***P<0.001; ****P<0.0001; ns, not significant (F-test).