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. 2018 Sep 11;115(8):1614–1624. doi: 10.1016/j.bpj.2018.08.046

Figure 4.

Figure 4

Dynamic changes of the process length and MT polarity. (A) Length of simulated processes versus number of MT ends at the process tips is shown. We average the number of MT plus and minus ends located within a narrow 1 μm stripe at the tip of a process during 1 min time intervals and compare the simulation of a control cell (upper row) to the simulated dynein-inhibited cell (lower row). (i and iv) For a single simulated process (control and dynein-inhibited, respectively), these diagrams show process length (green), minus-end numbers at the tip (red bars), and plus-end numbers at the tip (blue bars) as functions of time. (ii and iii) Boxplots show distributions of minus-end (ii) and plus-end (iii) numbers at the process tips of the simulated control cell as functions of the process length. (v and vi) Distributions of minus- (v) and plus-end (vi) numbers at the process tips of the simulated dynein-inhibited cell are shown. (B) Distribution of the MT minus ends and of polymerizing plus ends in the processes longer than 6 μm is shown. We show statistics extracted from single simulation snapshots at intervals of 5 s from two 50-min-long simulations (of control and dynein-inhibited cells, respectively), with nine processes each. The positions are normalized to the interval between 0 (base) and 1 (tip). The vertical axes in histograms show the number of the minus-ends. (i) Histogram of relative minus-end positions in control show monotonic decrease toward the process tip, with relatively few minus ends at the tip. (ii) In the absence of dynein, minus ends are uniformly distributed along processes with a peak at the process tip. (iii) Percentage of retrograde plus-end-trajectories in control (1) and dynein-inhibited (2) cells is shown. Circles show the fraction of the retrograde plus ends in single processes; boxplots visualize their distributions. Mean fractions in control and dynein-inhibited cells are significantly different, with p-value p = 0.0086. (C) The upper row shows experimentally measured growth of the processes’ length (length versus time; time is measured for each individual process starting from the process initiation; see also Fig. S2). The lower row shows simulated process growth: (i and v) control; (ii and vi) dynein-inhibited; (iii and vii) control with taxol; (iv and viii) dynein-inhibited with taxol. To see this figure in color, go online.