Chaminda R. Samarage1,5, Melanie D. White2,5, Yanina D. A´ lvarez2,5, Juan Carlos Fierro-Gonza´ lez2, Yann Henon1, Edwin C. Jesudason3, Stephanie Bissiere2,4, Andreas Fouras1, and Nicolas Plachta2,4
1 Laboratory for Dynamic Imaging, Faculty of Engineering, Monash University, Clayton Campus, Melbourne, VIC 3800, Australia
2 EMBL Australia, ARMI, Monash University, Clayton Campus, Melbourne, VIC 3800, Australia
3 National Health Service, Edinburgh, Scotland EH1 3EG, UK
4 Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore
5 Co-first author
Published in Developmental Cell on 24 August 2015
Every cell in our body originates from the pluripotent inner mass of the embryo, yet it is unknown how biomechanical forces allocate inner cells in vivo. Here we discover subcellular heterogeneities in tensile forces, generated by actomyosin cortical networks, which drive apical constriction to position the first inner cells of living mouse embryos. Myosin II accumulates specifically around constricting cells, and its disruption dysregulates constriction and cell fate. Laser ablations of actomyosin networks reveal that constricting cells have higher cortical tension, generate tension anisotropies and morphological changes in adjacent regions of neighboring cells, and require their neighbors to coordinate their own changes in shape. Thus, tensile forces determine the first spatial segregation of cells during mammalian development. We propose that, unlike more cohesive tissues, the early embryo dissipates tensile forces required by constricting cells via their neighbors, thereby allowing confined cell repositioning without jeopardizing global architecture.
Figure legend: Watching How Forces
Shape Mouse Embryos
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