Simulating the effect of a persistence gradient on the motion of a spherical object similar in size to the nucleus. (A) Time frames from one 3D simulation of a gradient of persistence of actin-positive vesicles. The images correspond to Video 1. The nucleus is in blue, the actin-positive vesicles are in red, and the oocyte cytoplasm appears in gray. (B) Squared velocities of actin-positive vesicles as a function of the distance to the oocyte center during the centering phase. One red dot corresponds to the averaged square velocities of vesicles in the given distance bin in one simulation, taken between 30 and 60 min of simulation only. The black line represents the fit extracted from experimental data in Almonacid et al. (2015). (C) Evolution of the distance between the nucleus centroid to the center of the oocyte as a function of time for 30 different simulations. The mean curve appears in dark blue while all other curves appear in lighter blue. (D) Trajectories of the nucleus centroid from the cortex to the oocyte center for the 30 simulations in C. The coordinates of the nucleus centroid (X,Y) are given in the oocyte referential where (0,0) is the oocyte center. The running time for the trajectories is presented as a heat map of lighter blue colors (bar on the right side of the picture). The simulations show that the motion of the object representing the nucleus is rather directional to the oocyte center. (E) Measure of the radial velocity of the nucleus centroid as a function of time from the 30 simulations confronted to the experimentally measured ones. The radial velocities from the simulations are in blue (dark blue curve for the average curve and lighter blue for the standard deviation at each point of the average curve), while the experimentally measured ones (Almonacid et al., 2015) appear as dark triangles. The experimental values are in the range of the simulated ones.