Fig. 2: Cortical actin flows towards the VP during CP initiation.
a, Confocal fluorescence images of maximum intensity projections of cortical actin (Utrophin-Venus) distribution in a representative oocyte during consecutive stages of CP morphogenesis. Asterisk demarcates the point of sperm entry. Arrows point at the transition zone between low- and high-intensity cortical actin domains. Arrowhead points at the vegetal bulge formed at the end of CP initiation. Dashed line demarcates the opening of the actin cortex at the AP upon fertilization. Scale bar, 30 µm. b, Plot of total actin intensity in the AP and VP hemispheres of oocytes/zygotes (N = 6 animals, n = 7 oocytes; green, left y axis) and their AR (taken from Fig. 1b, blue, right y axis) as a function of time after fertilization (0 min, dashed vertical line). Error bars, s.e.m. c, Kymograph of cortical actin flow velocity along the AV axis as a function of time after fertilization (0 min, dashed horizontal line). Colour bar indicates velocity in µm min-1 (positive velocities towards the AP, negative velocities towards the VP). d, Polar plots of sum intensity projections of cortical actin (Utrophin-Venus) over 10 central z-slides (15 µm). Angles represent the position around the oocyte (VP is at 0°, AP at 180°). The radius of the oocyte (in µm) is indicated in the concentric circles. Arrows point at the transition zone between low- and high-intensity cortical actin domains identified in a. Dashed arrows point at the opening of the actin cortex at the AP. Arrowhead points at the vegetal bulge formed at the end of CP initiation. Colour bar indicates fluorescence intensity in arbitrary units. e, Confocal fluorescence maximum intensity projection of cortical actin in an unfertilized oocyte. Arrowhead, patch of actin accumulation adjacent to the meiotic spindle at the AP. Scale bar, 30 µm. e′, Polar plot of sum intensity projections of cortical actin over 10 central z-slides of an unfertilized oocyte. Angles represent the position around the oocyte (VP, 0°; AP, 180°). Colour bar indicates fluorescence intensity in arbitrary units.
