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Triggering a Cell Shape Change by Exploiting Preexisting Actomyosin Contractions

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Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1232-1235
DOI: 10.1126/science.1217869

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A Time and a Place

The onset of morphogenetic cell shape changes is thought to be triggered by initiation of actomyosin contractions. Roh-Johnson et al. (p. 1232, published online 9 February; see the Perspective by Razzell and Martin) have now discovered in both Caenorhabditis elegans and Drosophila embryos that the actomyosin contractions driving morphogenesis run constitutively, only being engaged to trigger cell shape changes at a specific time during development.

Abstract

Apical constriction changes cell shapes, driving 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 Caenorhabitis 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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