Investigating Contractile Tension in the Cortex of Apically Constricting Cells
During C. elegans gastrulation, contraction of an apically-enriched actomyosin meshwork induces endoderm precursor cells (E cells) to undergo apical constriction and enter the interior of the embryo. Previous work used simultaneous live imaging of the conventional myosin motor NMY-2 and a fluorescent membrane marker and revealed rapid myosin movements which were, surprisingly, unaccompanied by corresponding movements in apical cell-cell contact zones. Later in gastrulation, myosin and membrane at the contact zones moved in concert until the E cells internalized. We confirmed this by particle image velocimetry, a computer algorithm that draws vectors depicting the magnitude and direction of myosin flow. In order to estimate whether tension in the apical cortex of E cells was increased upon coupling to the membrane, we cut the apical actomyosin network with an ultraviolet laser and measured recoil dynamics. This method has been shown to provide an estimate of tension and network viscosity. There was not a significant increase in tension upon coupling of myosin contraction to the membrane suggesting that establishing mechanical links to apical cell-cell contact zones, and not a change in the viscoelastic properties of the cortex, may be the primary difference between the early and late phases of gastrulation.
Chris' publications from his PhD work so far:
Honors and awards during Chris' PhD work: