Figure 1.

Sperm asters move to the egg center with persistent directionality and constant speed, in a MT- and dynein-dependent manner. (A) Time-lapse confocal images superimposed with differential interference contrast (DIC) of a male pronucleus (white arrowhead) at the center of a sperm MT aster. (B) 3D trajectories of 10 individual asters and enlarged trajectory of an aster that migrates mostly in-plane. Time is color-coded. The centration is subdivided into three phases: an initial penetration phase (P), a rapid centration phase with straight path and constant speed (C), and a final slowing-down phase (S). (C) Aster traveling distance and orientation toward the cell center as a function of time, for the sample enlarged in B. T₁ and T₂ denote the beginning and end of the rapid centration phase. (D and E) Distance and orientation time plots for 10 individual asters. Red line, mean; gray section, SD. The broken line is a guide for the eyes. (F) Time-lapse images of eggs treated with different inhibitors 3 min after sperm entry. (G) 3D trajectories corresponding to the eggs and conditions from F. Time is color-coded as in B. (H) Mean aster traveling distance as a function of time in the presence of inhibitors. The gray region indicates the period during which inhibitors are present. Red, DMSO (n = 5); blue, 20 µM latrunculin B (n = 5); green, 20 µM nocodazole (n = 7); purple, 50 µM ciliobrevin D nonactive analog (n = 6); and orange, 50 µM ciliobrevin D (n = 6). (I) Aster speed computed using the distance–time curve between 5 and 7 min. Error bars represent SD. Bars, 50 µm.