Figure 1.
Figure 1. Abscission occurs in two stages: cytoplasmic isolation and release of the midbody/midbody ring. (A) Furrow diameter was measured in projections of the central region of z stacks of embryos (n = 10) expressing a GFP-tagged plasma membrane probe. (right) Graph plots mean furrow diameter versus time after furrow initiation. Arrow indicates the last time point when a hole can be detected (apparent closure). Error bars are the SDs. (top) Schematics illustrate shape changes during the first division in the C. elegans embryo, highlighting intercellular bridge structure. MTs, microtubules. (B, left) Schematic illustrates the method for monitoring the diffusion of photoactivated dextran between the two half-cells before and after cytokinesis. Examples of probe diffusion in embryos photoactivated before cytokinesis onset (middle; n = 12 embryos) and after apparent closure (right; n = 8 embryos, example shown is 350 s after furrow initiation). Central plane images show the embryos before activation (−5 s), immediately after activation (5 s), and 140 s after activation (140 s). Kymographs were constructed by aligning strips (narrow rectangles) from images collected at 5-s intervals. Red arrow denotes the point of photoactivation. (C) Central plane fluorescence confocal images of embryos expressing a fluorescently tagged plasma membrane probe (red in merged images) along with either the midbody marker mCherry-Mklp1ZEN-4 (n = 18 embryos) or the midbody ring marker Myosin IINMY-2–GFP (n = 14 embryos). Times are relative to anaphase of the second division (∼900 s after initiation of the first division furrow). Different embryos are shown to illustrate membrane shedding (−80 to 140–s time points) and midbody/midbody ring release (220–260-s time points). White boxes on the low magnification images mark the location of the region shown at higher magnification in the three adjacent panels. Loops and released fragments marked with the plasma membrane probe are indicated (white arrowheads). Yellow arrows denote mCherry-Mklp1ZEN-4–marked or Myosin IINMY-2–GFP-marked midbody remnants before release from the cell–cell junction. Green arrows mark the same components after release. Schematics illustrate events at each stage. Bars, 5 µm.

Abscission occurs in two stages: cytoplasmic isolation and release of the midbody/midbody ring. (A) Furrow diameter was measured in projections of the central region of z stacks of embryos (n = 10) expressing a GFP-tagged plasma membrane probe. (right) Graph plots mean furrow diameter versus time after furrow initiation. Arrow indicates the last time point when a hole can be detected (apparent closure). Error bars are the SDs. (top) Schematics illustrate shape changes during the first division in the C. elegans embryo, highlighting intercellular bridge structure. MTs, microtubules. (B, left) Schematic illustrates the method for monitoring the diffusion of photoactivated dextran between the two half-cells before and after cytokinesis. Examples of probe diffusion in embryos photoactivated before cytokinesis onset (middle; n = 12 embryos) and after apparent closure (right; n = 8 embryos, example shown is 350 s after furrow initiation). Central plane images show the embryos before activation (−5 s), immediately after activation (5 s), and 140 s after activation (140 s). Kymographs were constructed by aligning strips (narrow rectangles) from images collected at 5-s intervals. Red arrow denotes the point of photoactivation. (C) Central plane fluorescence confocal images of embryos expressing a fluorescently tagged plasma membrane probe (red in merged images) along with either the midbody marker mCherry-Mklp1ZEN-4 (n = 18 embryos) or the midbody ring marker Myosin IINMY-2–GFP (n = 14 embryos). Times are relative to anaphase of the second division (∼900 s after initiation of the first division furrow). Different embryos are shown to illustrate membrane shedding (−80 to 140–s time points) and midbody/midbody ring release (220–260-s time points). White boxes on the low magnification images mark the location of the region shown at higher magnification in the three adjacent panels. Loops and released fragments marked with the plasma membrane probe are indicated (white arrowheads). Yellow arrows denote mCherry-Mklp1ZEN-4–marked or Myosin IINMY-2–GFP-marked midbody remnants before release from the cell–cell junction. Green arrows mark the same components after release. Schematics illustrate events at each stage. Bars, 5 µm.

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