Fig. 4. Fusion pores colocalize with openings in the actin cortex. Cells were labeled with FM4-64FX 9 minutes after a 2-minute low-pH pulse. 1 minute later, the cells were fixed and labeled with Alexa-Fluor-48–phalloidin. (A,B) xy-projections of representative contact zones (marked as 1-4) shown with membrane- and actin-labeling, respectively. (C,D) Maximum intensity projections of the image stacks of each of these zones along the z axis with membrane- (C) and, under it, actin- (D) labeling.