Figure 4.

The axonal diffusion barrier for Tau coincides with the axon initial segment (AIS) but depends on a different mechanism. (A) Cortical neuron (10 DIV) transfected with Tau^D2. Note the even distribution in axon (arrow), soma, and dendrites. (B) Same neuron, fixed and stained for AnkyrinG, a marker of the AIS, (C) merged images. (D) Cortical neuron (10 DIV) transfected with Tau^D2 and then treated with 10 μM nocodazol. This treatment destroys microtubules but not the localization of AnkyrinG in the AIS (E, F). (G) Green fluorescent image of a neuron (10 DIV) expressing Tau^D2 and incubated in 2.5 μM latrunculin A for 1 h to disrupt the actin cytoskeleton before photoconversion. (H) Red fluorescent image of the same neuron in the presence of latrunculin A where part of its axon was photoconverted (ROI1) (circles indicate the soma in H and I). (I) Time-lapse image after 75 min showing the blockage at the AIS (arrowhead) for Tau^D2 in the presence of latrunculin A, indicating that the barrier for Tau does not depend on the actin cytoskeleton.