Howard Hughes Medical Institute, Chevy Chase, United States; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
Marvin Albert
Department of Molecular Life Sciences, University of Zürich, Zurich, Switzerland
William Roman
Department of Experimental and Health Sciences, Pompeu Fabra University (UPF), CIBERNED, Barcelona, Spain
Maxwell C Coyle
Howard Hughes Medical Institute, Chevy Chase, United States; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
Howard Hughes Medical Institute, Chevy Chase, United States; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
Amoeboid cell types are fundamental to animal biology and broadly distributed across animal diversity, but their evolutionary origin is unclear. The closest living relatives of animals, the choanoflagellates, display a polarized cell architecture (with an apical flagellum encircled by microvilli) that resembles that of epithelial cells and suggests homology, but this architecture differs strikingly from the deformable phenotype of animal amoeboid cells, which instead evoke more distantly related eukaryotes, such as diverse amoebae. Here, we show that choanoflagellates subjected to confinement become amoeboid by retracting their flagella and activating myosin-based motility. This switch allows escape from confinement and is conserved across choanoflagellate diversity. The conservation of the amoeboid cell phenotype across animals and choanoflagellates, together with the conserved role of myosin, is consistent with homology of amoeboid motility in both lineages. We hypothesize that the differentiation between animal epithelial and crawling cells might have evolved from a stress-induced switch between flagellate and amoeboid forms in their single-celled ancestors.
