raphaël clément

During embryogenesis, living tissues constantly change their shape: they lengthen, round up, fold, form tubes, etc. Such tissue-scale changes require the coordinated action of cells in the tissue. I’m interested in the principles of cellular force generation, in the way these forces are coordinated and propagated to the surrounding tissue, and in how such forces are eventually converted into irreversible deformations to achieve morphogenesis. In that context, we have developed models and tools to study cellular mechanics in the fly embryo (optical tweezers, force inference).

During insect development, the future wing blade grows during the larval and pupal stages, and eventually folds in the confined pupal case. When the adult emerges from its pupal case, the wings are still folded. In the minutes that follow eclosion, it swallows air and increases its internal pressure, which pumps hemolymph, the insect equivalent of blood, into the folded wings. This results in very rapid wing deployment, with both unfolding and surface expansion. Using the wing as a model system, we ask how a pressure rise, isotropic in nature, can lead to fast, large-scale morphogenesis of entire organs.
[Collab. Joël Marthelot, IUSTI]

Trichoplax is said to be the simplest of all animals. No muscles, no nervous system, no organs, not even a body plan. It’s basically a flat bilayer of ciliated epithelial cells. Yet it is strikingly dynamic, and can completely change its shape in a matter of minutes. How does Trichoplax achieve such plasticity without muscles? How does it adapt the polarity of its cilia to dynamically match its rapidly changing shape?
[Collab. Andrea Pasini, IBDM]

Pediatric tumors often rely on a subset of so-called “cancer stem cells” that have the ability to sustain tumor growth. How a stable ratio of cancer stem cells is maintained in a tumor is largely unknown. We use tumors in the central nervous system of Drosophila to study this question, trying to understand how cell fate decisions are made so that tumor growth is sustained, and how a stable heterogeneity of cell types is maintained.
[Collab. Cédric Maurange, IBDM]