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Séminaire LJC de Magali Suzanne

In the framework of the LJC seminars the 13th of November at 11h Magali Suzanne is giving a seminar in the big CBP conference room.

Développement de la patte de la drosophile. Implication de la mort cellulaire. Modelisation du processus.

Epithelium folding is a basic morphogenetic event essential to transform simple 2D epithelial sheets into 3D structures, in both vertebrates and invertebrates1,2. Folding has been shown to rely either on apical junction basal shifting or apical constriction that can be associated with baso-lateral shortening 3-6. The resulting cell shape changes depend on Myosin II redistribution which could be driven by mechanical signals7. Yet, the initial cellular mechanisms that trigger and coordinate cell remodelling remain largely unknown.

Here, we unravel the active role of apoptotic cells in initiating morphogenesis, thus revealing a novel mechanism of epithelium folding. We show that, in a live developing tissue, apoptotic cells exert a transient pulling force upon the apical surface of the epithelium through an unexpected maintenance of their adherens junctions which link up with an highly dynamic apico-basal Myosin II cable, specific to apoptotic cells. The apoptotic cells then induce a non-autonomous increase in tissue tension and apical constriction in the surrounding tissue, eventually resulting in epithelium folding. By integrating data from a theoretical biophysical 3D model and in vivo ectopic apoptosis experiments, our data further reveal the importance of the cumulative effect of apoptotic cells in converting a naive, flat epithelium into a folded one.

Together, our results identify an apoptotic Myosin II dependent signal as the initial signal responsible for cortical Myosin II apical stabilisation, leading to cell reorganisation and tissue folding. This work further reveals that, far from being passively eliminated as generally assumed (e.g. during digit individualisation8), apoptotic cells actively influence their surroundings and trigger tissue remodelling through regulation of tissue tension.

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