Figure 8

As neurons mature, the proportion of microtubules polymerizing in the anterograde direction increases to nearly 100% in axons, whereas the number of retrogradely oriented events observed in dendrites increases. (A, D) Single frames from the distal region of an axon (A) and a dendritic arbor (D) at 3 DIV, and (B, E) composite tracings of observed polymerization events, with individual EB1-GFP comet trajectories identified in the anterograde (green arrows) or retrograde (red arrows) directions. Insets depict enlarged views of the boxed regions. (C, F) The percentage of microtubule polymerization events occurring in an anterograde or retrograde direction was determined for each population of axons (C) and dendrites (F) observed throughout the developmental time-course. In axons, the total numbers of events tracked were: 833, 1 to 2 DIV; 892, 3–4 DIV; 284, 7+ DIV. For dendrites, the total numbers of events tracked were: 748, 1 to 2 DIV; 955, 3 to 4 DIV; 232, 7+ DIV. Scale bar, 10 μm. Error bars represent standard error of the mean. See Additional files 7 (axon) and 8 (dendritic arbor) for accompanying movies.