Accessit 2023: Dr. Alexis Villars
→ Prix de 500 €
The honorable prize for the 2023 SFBD Thesis Prize has been awarded yo Dr. Alexis Villars for his thesis entitled “Orchestration of epithelial cell elimination by effector caspases”. Alexis did his thesis under the supervision of Romain Levayer in the Pasteur Institute in Paris. His work was published in Current Biology, Developmental Cell, Current opinion in Genetics and Development, Nature Communications and Development.
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During his PhD, Alexis exploited the Drosophila pupal notum as a model system to study the phenomenon of epithelial cell extrusion, which allows dying cells to be eliminated while maintaining the integrity of the epithelial barrier. When a cell dies, its contraction brings the neighbouring cells together, thus avoiding the creation of a gap in the epithelium. Alexis focused on the link between extrusion and apoptosis, and notably on the caspases that regulate apoptosis. Careful quantitative characterisation of cell extrusion from live tissues allowed Alexis to demonstrate that apical constriction during cell extrusion is not initiated by changes of actomyosin, which is surprising since actomyosin is the main regulators of contractility. Instead, apical constriction is initiated by the caspase-driven disassembly of microtubules, whose role has never been described in this context. Alexis also used Bayesian inference to model cell sensitivity to caspases at the single cell level and showed that extrusion is linearly correlated with caspase concentration. Finally Alexis built DeXtrusion, a software that uses machine learning to automatically detect cell extrusion in vivo.
The jury was particularly impressed with the quality and rigor of the experiments, which required careful and precise measurements. The jury also appreciated the great effort that Alexis put into writing an easy to read and pedagogical thesis manuscript.