Figure 3

Growing microtubules do not concentrate around the centriole in developing and mature Drosophila neurons, nor in neurons after axon severing. (A) Microtubule orientation and dynamics during dendrite outgrowth were examined by tracking the movement of EB1-GFP in living embryos. EB1-GFP was expressed in neurons using 1407-Gal4. In the left images of a da neuron, an EB1-GFP comet can be seen to originate (green arrows) at an area away from the centriolar protein Fzr (right and left, red arrows), from where it traveled toward the cell body. The frames shown are from Additional file 1. Similarly, EB1-GFP movement in the cell body of da neurons can be seen to originate away from the centriole as well. This can be seen in Additional file 2. (B) Trajectories of growing microtubules in uninjured larval ddaE neurons show no origin at the centriole (arrow). EB1-GFP comets can be seen in the cell bodies of mature da neurons (top left, asterisks), although EB1-GFP dynamics are fairly quiet. EB1-GFP comets were tracked manually over multiple frames; MOSAIC Particle Tracker was used to track mRFP-Fzr. Trajectories were overlaid onto a single frame from Additional file 3. (C) Trajectories of growing microtubules were determined in larval neuroblasts. MOSAIC Particle Tracker for ImageJ was used to calculate EB1-GFP comet trajectories over multiple frames. In dividing neuroblasts, EB1-GFP comets produce a star-like pattern (top left), and their trajectories (bottom) originate at a common point from the centriole (arrow at top right). Trajectories were overlaid onto a single frame from Additional file 4. (D) Growing microtubules after axon severing of ddaE neurons do not associate with the centriole. Left: an example of an axon severed by a UV laser is shown. The blue arrow points to the site of injury, and the red arrow indicates the centriole. Twenty-four hours after severing, many EB1-GFP comets can be seen (asterisks). Tracking the comets and RFP-Fzr over multiple frames (right images) via MOSAIC Particle Tracker shows that the trajectories of the comets have no discernible origin point. Trajectories were overlaid onto a single frame from Additional file 5.