Biophysical Society Thematic Meeting| Aussois 2019

Biology and Physics Confront Cell-Cell Adhesion

Tuesday Speaker Abstracts

BIOPHYSICS OF EPITHELIA Frank Jülicher Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

A fundamental question in Biology is to understand the collective organisation of many cells during morphogenesis. Morphogenesis often involves the dynamic remodeling of tissues involving cell rearrangements, cell divisions and cell flows. The fly wing is an important model system for the study of multicellular dynamics during morphogenesis. The growth of the wing imaginal disk is governed by characteristic patterns of cell rear-rangements and cell shape changes. During pupal stages, the early fly wing undergoes a spectacular dynamic reorganization which generates the final shape of the wing. We characterize tissue remodeling by quantifying the contributions of specific cellular processes such as cell shape changes, cell neighbor exchanges, cell division and cell extrusion to the macroscopic tissue shear. Based on this approach, we discuss tissue mechanics and dynamics with a focus on the active and passive mechanics of T1 transitions by which cells change their neighbors. HYDRAULIC FRACTURING AND ACTIVE COARSENING POSITION THE LUMEN OF THE MOUSE BLASTOCYST Jean-Léon Maître ; 1 Institut Curie, Genetics and developmental biology, Paris, France During mouse preimplantation development, the formation of the blastocoel, a fluid-filled lumen, breaks the radial symmetry of the blastocyst. What controls the formation and positioning of this basolateral lumen remains obscure. We find that accumulation of pressurized fluid fractures cell- cell contacts into hundreds of micron-size lumens. Microlumens eventually discharge their volumes into a single dominant lumen, which we model as a process akin to Ostwald ripening, underlying the coarsening of foams. Using chimeric mutant embryos, we tune the hydraulic fracturing of cell-cell contacts and steer the coarsening of microlumens, allowing us to successfully manipulate the final position of the lumen. We conclude that hydraulic fracturing of cell-cell contacts followed by contractility-directed coarsening of microlumens sets the first axis of symmetry of the mouse embryo.

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