Abstract
Epithelia represent a unique situation where polarized cells must maintain sufficiently strong cell-cell contacts to guarantee the epithelial integrity indispensable for barrier functions. Nevertheless, epithelia must also keep sufficient plasticity which is crucial during development and morphogenesis. Adherens junctions and mechanical forces produced by the actomyosin cytoskeleton are major players for epithelial integrity maintenance and plasticity regulations. To understand how the epithelium is able to meet such a challenge, it is indispensable to determine how cellular junctions and mechanical forces acting at adherens junctions are regulated. Here, we investigate the tensile forces acting on adherens junctions via cadherin during cell division in the Xenopus embryos epithelium. Using the recently developed E-cadherin FRET tension sensor and a fastFLIM prototype microscope, we were able to measure mechanical forces applied on cadherin at cell-cell junctions. We have shown that the Xenopus epithelium is under tension, approximately 3 pN which remains stable, indicating that tensile forces acting on cadherin at the adherens junction are at equilibrium. Unexpectedly, mechanical tension across cadherin was similar between dividing and non-dividing epithelial cells.
Highlights
For all the experimental approaches presented above, cell mechanics was tackled at the cellular level and the mechanical role of cadherin at its molecular level was not sensed
Is cadherin stretched by actomyosin at adherens junction to create membrane tension and deformation? Is cadherin implicated in the stability of cell-cell adhesion to preserve the tissue integrity? Can cadherin simultaneously play these two roles? To elucidate these questions, we have investigated tension applied on cadherin during cell division in Xenopus embryo epithelium
Using the EcadTSmod tension sensor described previously[14] and our CcadTSMod, we have shown that cadherin is under tension in the Xenopus blastulae epithelium and that the tensile forces are generated by the actomyosin cytoskeleton
Summary
For all the experimental approaches presented above, cell mechanics was tackled at the cellular level and the mechanical role of cadherin at its molecular level was not sensed. Using the tension sensor module developed by Schwartz and co-authors for vinculin[13], tension on cadherin was investigated in the context of substrate stretching on doublet cell adhesion[14], of border cells migration in drosophila oocytes[15] and of shear stress on endothelial cells[16]. Using this tool, different tissue-specific isoforms of cadherins were shown to exhibit differential mechanical behaviors. At the end of blastula stage, actomyosin-generated tension on cadherin is approximately 3 pN and remains stable during epithelial cell division
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