Figure 2.

Axon injury induces orientation switching of dendritic microtubules. (A) Images of EB1-GFP in a single ddaE neuron at different times before or after axon injury. Several confocal images were projected to give a complete overview of the dendrite arbor. In zoomed in movies, the direction of EB1-GFP comet movement was scored. Comets moving toward the cell body represent minus-end-out microtubules and comets moving away from the cell body represent plus-end-out microtubules. The raw data are shown in the table and represented by arrows on the overview pictures. A green arrow indicates plus-end-out microtubule orientation, a red arrow indicates minus-end-out orientation and double arrow indicates mixed orientation. Movie 3 shows microtubule dynamics in this cell. (B) Microtubule orientation was quantitated in dendrites of uninjured neurons and neurons at different times after axon severing. Comets were scored in each dendrite as in A: EB1-GFP dots in the region of the dendrite between the cell body and first dendrite branch point were counted; dendrites with four or more comets were classified as plus-end-out if 75% or more comets moved away from the cell body and minus-end-out if 75% or more moved toward the cell body. The class in between was classified as mixed and is not shown explicitly in the table. n = number of dendrites classified for each time point.