Figure 2.

Stable MTs are enriched in axons. (A–H) To consider actual differences in MT stability only, MTs (green) were partially depolymerized by treatment with nocodazole and their retraction from the distal end of the processes toward the cell body was examined (see I and J). F-actin (red) outlining the neuron was used as a reference point for measuring MT retraction. In DMSO-treated control cells, MTs reach close to the distal end of both axon (B, arrow) and minor neurites (B and F, arrowheads). In nocodazole-treated cells, MTs of minor neurites retract toward the cell body (D and H, arrowheads). MTs in the axon of stage 3 cells (D, arrow) and in one of the minor neurites of stage 2 cells (H, arrowhead with asterisk) are more resistant to depolymerization. Arrows, axons; arrowheads, minor neurites. (I and J) MT retraction after nocodazole treatment in polarized stage 3 (I) and morphologically unpolarized stage 2 (J) neurons (mean ± SEM; n = 119 and 50 neurons from five and three independent experiments, respectively; ***, P < 0.001 by t test). (K–N) Polarized rat hippocampal neurons with one axon (arrow) and several minor neurites (arrowheads) after 2 DIV before (K) and after (L–N) treatment with nocodazole (5 μM for 5 min). Tyrosinated (M and N, red) and acetylated (L and N, green) MTs were assessed. Bars, 20 μm.