Figure 8.

Model for conversion of a dendrite to a regenerating axon after axon removal. Before axon injury, microtubules in dendrites have minus-end-out polarity (red arrows) and axonal microtubules are plus-end-out. Axon removal up-regulates JNK signaling, which switches microtubule polarity in dendrites, frequently resulting in mixed polarity (purple double arrows) and up-regulates the number of microtubules in the cell body (white circle) and throughout the dendrites. Over several days polarity resolves such that one dendrite takes on the axonal microtubule polarity and the rest return to minus-end-out polarity. After this point the process with axonal microtubule polarity initiates tip growth.