Videos of Cells and Embryos
The movie above begins right at the onset of anaphase, when duplicated chromosomes are pulled apart by the mitotic apparatus, and continues through cytokinesis.
In the first frame, the centrosomes are discrete foci – the spindle poles – but during anaphase they rapidly expand, creating “centrospheres” that swell to more than 10 µm across by the onset of cytokinesis, and revealing two nascent microtubule-organizing centers inside.
Meanwhile, although a few astral microtubules reach the cell surface before anaphase, during anaphase the asters grow tremendously, and form prominent bundles, most of which appear to penetrate the cell cortex. Some of these, which point across the midplane, are bundled together by the cleavage furrow, joining the remains of the spindle at the rapidly-diminishing canal between the two daughter cells.
Microtubule behavior during cytokinesis
March 9, 2010
Species:
Dendraster excentricus (sand dollar)
What’s in view:
One cell (a macromere) at the 16-cell stage
What’s glowing:
A probe fusing three GFPs to the Ensconsin microtubule binding domain labels all microtubules
Frame rate:
3 sec/frame @ 30 fps = 90-fold time-lapse
Points of interest:
growth of microtubule asters during anaphase; cytokinesis
Optics:
BioRad Radiance laser scanning confocal; 40x oil lens; single optical section.
Why is it orange:
Pseudo-coloring enhances the apparent brightness of single astral microtubules while retaining detail within the bright bundled microtubules of the spindle.
Filmed by:
George von Dassow, Bill Bement
More like this:
See a full-resolution version (072409_De3CEns_02-lg.mov), and one in grayscale with no annotations (072409_De3CEns_02-h6k.mov).
Please see also the Supplemental Data page and our paper “Action at a distance during cytokinesis”, which relied heavily on 3xGFP-Ensconsin to analyze the relative contribution of astral versus spindle microtubules to the spatial definition of the cytokinetic furrow.
