Epithelial cell extrusion underlies starvation-induced cell loss in a sea anemone

Epithelia likely predate the last common animal ancestor, yet the evolutionary origin and nutritional regulation of epithelial remodelling remain poorly understood. Here, we show that extensive, starvation-induced cell loss in the sea anemone Nematostella vectensis is associated with epidermal cell extrusion. This process involves formation of a rosette-like arrangement in which an apoptotic, extruding cell is surrounded by a phospho-ERK1/2-positive ring of cells, accompanied by basal translocation of adherens junction components. Combining chemical perturbations with computational quantification of extrusion and cell density, we show that apoptosis is necessary but not sufficient for rosette formation, and that ERK1/2 signalling limits epidermal extrusion density. Furthermore, we find increased extrusion activity during starvation, and potential nutrient recycling via phagocytosis of extruded cells. Together, our findings indicate that epithelial cell extrusion has physiological roles in sea anemones and that its key hallmarks are likely evolutionarily ancient, predating the last common cnidarian-bilaterian ancestor. This repository contains: The raw image files in tiff format pre-image-segmentation generated during confocal live imaging. The zip file contains the raw image files for the starvation, daily fed and drug treatments datasets. The rosette identification training dataset, generated through manual annotation of epithelial rosettes of previously segmented images. These annotations were used to train an automated rosette identification model for application across all datasets. Along with this zip file containing the dataset, there is a "read-me" file. The raw output tables (1-12) in csv format generated following the image segmentation and rosette ID pipeline. The tables contain cell measurements, rosette IDs and cell-level data for the starvation, daily fed and drug treatments datasets respectively. Along with this zip file containing the output tables (1-12), there is a "read-me" pdf file explaining the contents of each table.