Figure 5.
Membrane dynamics in an isolated blastomere treated with BFA. The multiphoton time course of a P0 blastomere labeled with FM1-43 in the presence of BFA is shown. The figure shows a sequence of 3D projections of a thick axial slice taken through the dividing cell. At the 1.5 min time point, the furrow had invaginated. By 3.0 min, the furrow had almost completed. During a period from 4.5 min to 7.5 min, the furrow stayed fully ingressed. No membrane accumulation can be seen in the vicinity of the late cleavage furrow. However, one minute after this period the furrow had regressed (9.0 min). The furrow remained ingressed for 5.5 min before regressing in the BFA-treated embryo. This time corresponds to the time in which membrane accumulation would have normally occurred in untreated blastomeres; however, no accumulation was seen, and ultimately, cytokinesis failed. At 10.5 min the cleavage furrow had completely regressed. The blastomere continued to initiate cleavage and furrows completed again, but these also failed (data not shown). The scale bar is 14 µm. See also Movie 9 in the Supplementary material.