Fig. 4.

PIV analysis and MPS simulation of nmy-2-independent streaming dynamics. (A) Schematic representation of migration of the two pronuclei toward the center (f, female pronucleus; m, male pronucleus). (B, C) The flow in nmy-2(RNAi) embryos is dependent on microtubules. (B) The flow dynamics in nmy-2(RNAi) embryos. Weak but reproducible flow was observed in nmy-2(RNAi) embryos less than 1 min before pronuclear meeting. In nmy-2(RNAi) embryos treated with nocodazole, reproducible flow was not observed. (Scale bar, 5 μm.) (C) The flow velocities along the AP axis (//AP) in the posterior region of the cell are significantly reduced by nocodazole treatment. Data are means ± SD, measured at the timing when the flow was the most vigorous in each embryo [i.e., control (“WT”): ∼5–7 min before pronuclear meeting, nmy-2(RNAi): ∼1 min before pronuclear meeting]. WT: n = 6 embryos; nmy-2(RNAi): n = 6 embryos; nocodazole-treated nmy-2(RNAi): n = 7 embryos. (D) Velocities along the AP axis in the MPS simulation. Particles representing pronuclei (pronuclei particles) are shown inside the circle. Forces are applied to the pronuclei particles to move toward the central region. In the central region, the flow of cytoplasm particles was toward the center based on the movements of the pronuclei, whereas particles moved away from the center near the cortex.