How are the different shapes of our organs and tissues generated? To answer this question, a team forced muscle cells to spontaneously reproduce simple shapes in vitro. By confining them on adhesion discs, the biochemists and physicists observed that the cells rapidly self-organize by aligning themselves in the same direction. A circular motion is created around a vortex -- called a topological defect -- which, by orienting the cells, allows them to join forces, deforming the cell monolayer into a protrusion, a structure commonly observed in embryo development. This cylindrical protrusion is maintained by the collective rotational forces of the cells, creating a tornado-like effect. The formation of these cellular tornadoes would therefore constitute a simple mechanism of spontaneous morphogenesis, dictated by the unique properties of multicellular assemblies.
