Figure 5.

Newly appearing EB1-GFP foci are at a higher density at the cell’s midzone. Trajectory map (A) for microtubule plus ends in five longitudinally oriented arrays imaged for 5 min at 3-s intervals (n = 500 frames, 5 cells, 11,512 trajectories). Color coding represents 90° bins with up (cyan), down (blue), left (green), and right (red) per legend. The positions of all newly appearing EB1-GFP foci (i.e. microtubule contributions from nucleation, rescue, and internal cell positions) were identified by hand (n = 2,139 events) and plotted with the same color coding for direction (B). Black traces represent cell perimeters. Histograms representing the total trajectory count (C) and nascent EB1-GFP events (D) as a function of the cells’ long axes (bin = 1 µm). The accumulated cell width, scaled for appearance (C, black trace), indicates a relatively uniform trajectory distribution with a depression at the midzone. Interleaved histograms representing the direction of mapped trajectories (E) and nascent EB1-GFP events (F) as a function of the cells’ long axis (bin = 1 µm) indicate a split bipolar arrangement of longitudinal events for both populations. Lateral events plotted to the left of the ordinate and longitudinal events to the right for E and F with black traces indicating the accumulated cell width. The accumulated orientation angles for the five cells (G) showing a symmetric, peaked distribution centered at longitudinal (µ = 87° ± 26°).