Figure 1.

Actin-dependent dynamics of melanosomes in living Xenopus laevis melanophores. (A) Representative trajectories obtained for melanosomes moving along actin filaments (left panel) or microtubules (right panel). Both trajectories lasted for 20 s. Bars, 1 μm. (B) Average mean-square displacement determined from the analysis of 86 and 47 trajectories, during aggregation (black line) and dispersion (gray line), respectively. The error bars represent the standard error. The bottom panel show the residuals obtained by fitting the experimental data measured during aggregation (black line) and dispersion (gray line) to either Eq. 3 (continuous line) or the equation corresponding to the model proposed by Snider et al. (19): $MSD=D_{\text{app}}\left[t-{\tau }_{\text{c}}(1-e^{-t/{\tau }_{\text{c}}})\right]$, where D_app is the apparent diffusion coefficient of melanosomes along the actin network and τ_c is the characteristic time of crossover between the short- to long-time behavior (dashed lines). (C) Average β-value as a function of the lag time τ during aggregation (black line) and dispersion (gray line).