Knockdown of one protein can obstruct the organization of sea anemone epithelia

What is it about?

Cell organization into epithelial layers precedes the formation of organs and appendages during animal development. In certain species, individual cells from dissociated embryos can re-organize and develop into living animals after re-aggregation. Because cells organize into epithelial layers as they come into direct contact, successful adhesion is often considered to be the first necessary condition for epithelialization. Moreover, in certain examples, cell adhesion helps polarize cells so that the epithelial layer acquires its unique surface-exposed and buried domains. We asked whether it is possible to identify a single protein that is essential for epithelialization of cells in aggregates and developing embryos of the sea anemone, Nematostella vectensis. We found that the conserved protein, Lethal giant larvae or Lgl, defines the lateral polarity of adherent cells and is essential for the epithelialization process. Cells with reduced levels of Lgl, were able to come into contact but were unable to organize into epithelia. Eventually, cell aggregates that failed to epithelialize, also failed to develop into living animals.

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Photo by Julia Fiander on Unsplash

Photo by Julia Fiander on Unsplash

Why is it important?

This study reveals that cell adhesion in the absence of the lateral polarity protein Lgl is not sufficient to drive the epithelialization process. This work shows that in sea anemone embryos, lateral polarization via the function of Lgl helps cells to properly position their cytoplasmic organelles and organize their shape so that new cells arising with each division can integrate homogeneously within the growing epithelium. Similarly, cells in aggregates use Lgl to establish their lateral adhesions as they come together to re-build their epithelial layers.

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