Video
data from "Triggering a Cell Shape Change by Exploiting Preexisting
Actomyosin Contractions"
Roh-Johnson et al., 2012
Apical constriction drives critical
morphogenetic events including gastrulation in diverse organisms and
neural tube closure in vertebrates. Apical constriction is thought to
be triggered by contraction of apical actomyosin networks. We found
that apical actomyosin contractions began before cell shape changes in
both C. elegans and Drosophila. In C. elegans, actomyosin
networks were initially dynamic, contracting and generating cortical
tension without substantial shrinking of apical surfaces. Apical
cell-cell contact zones and actomyosin only later moved increasingly in
concert, with no detectable change in actomyosin dynamics or cortical
tension. Thus, apical constriction appears to be triggered not by a
change in cortical tension, but by dynamic linking of apical cell-cell
contact zones to an already contractile apical cortex.
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Movie 1. Three-dimensional views of myosin
and plasma membrane at four timepoints during gastrulation, collected
by Bessel beam structured plane illumination microscopy. The image at
each timepoint was built from 1510 collected images: 151 z-planes in
200nm steps, using 5-phase structured illumination in each z-plane, in
two color channels. Exposed surfaces of Ea/p cells are pseudocolored
blue at the beginning of the movie. Ea/p cells fully internalized
between the third and fourth timepoint. Myosin rings can also be seen
in some AB-derived cells undergoing cytokinesis in final frame. Image
quality is best on the side facing up at the beginning of the film
because this side faces both the Bessel beam excitation objective and
the detection objective. Opposite side appears flat where the embryo
contacts the coverslip.
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Movie 2. Centripetal myosin movements in an
Ea/p cell at the early stage. Apical cell-cell contact zones are marked
in red with mCherry::PH, and myosin particles are marked in green with
NMY-2::GFP. The first frames diagram contact zone positions for this
cell at the beginning and end of the period shown (3 minutes, 5 sec
intervals between frames).
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Movie 3. Myosin movements with little
accompanying apical contact zone movements at the early stage. Left: 35
sec film, a subset of that shown above in Movie 1, with contact zones
marked in red with mCherry::PH, and myosin particles marked in green
with NMY-2::GFP. Center: Green arrows mark the centripetal paths of
some of the moving myosin particles. Dotted line outlines the region
shown in the left side of Fig. 1G. Right: Diagram includes red outlines
marking contact zones at the beginning and end of the 35 sec period (5
sec intervals between frames).
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Movie 4. Myosin movements with accompanying
apical contact zone movements at the late stage. Contact zones are
marked in red with mCherry::PH, and myosin particles are marked in
green with NMY-2::GFP. The first frames diagram contact zone positions
for this cell at the beginning and end of the period shown (3 minutes,
3 sec intervals between frames).
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Movie 5. Bessel beam plane illumination
microscopy during the transition to late stage dynamics. Myosin
particles (green) and membranes (red) are shown in a 12um-thick region
(40 planes, 300nm apart) over 6 minutes.
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Movie 6. Simulation of contracting
actomyosin cortex connected to a contact zone with 0% or 100%
efficiency. Myosin particles (green) are simulated moving centripetally
toward a point at a speed proportional to distance to the point, as for
a uniformly-contracting sheet. In the simulation, a neighboring contact
zone (red line) is connected to the contraction at 0% efficiency
(unconnected, top) to 100% efficiency (connected, bottom), with the
contact zone moving at a speed determined by the distance to the myosin
coalescence center and the assigned percent efficiency of the
connection.
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Movie 7. Drosophila ventral furrow cell, myosin movements with little
accompanying apical contact zone movements before shrinking of apical
cell profile. Cell is shown for 1min 45 secs, at 5-second intervales.
In cells at this stage, myosin can be seen to coalesce and move
(arrowheads) either toward or away from membranes that move little.
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Movie 8. Quantum Dot movements on the
apical surface of an Ea cell. Quantum Dots are in red, and an
endodermal GFP marker in green. Arrowhead in enlarged view at bottom
marks a Quantum Dot moving centripetally, converging toward Quantum
Dots that began closer to the center of the Ea apical surface.
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