RT Journal Article SR Electronic T1 Filopodia rotate and coil by actively generating twist in their actin shaft JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.09.20.305227 DO 10.1101/2020.09.20.305227 A1 Natascha Leijnse A1 Younes Farhangi Barooji A1 Bram Verhagen A1 Lena Wullkopf A1 Janine Terra Erler A1 Szabolcs Semsey A1 Jesper Nylandsted A1 Amin Doostmohammadi A1 Lene Broeng Oddershede A1 Poul Martin Bendix YR 2020 UL http://biorxiv.org/content/early/2020/09/20/2020.09.20.305227.abstract AB Filopodia are actin-rich structures, present on the surface of practically every known eukaryotic cell. These structures play a pivotal role in specific cell-cell and cell-matrix interactions by allowing cells to explore their environment, generate mechanical forces, perform chemical signaling, or convey signals via intercellular tunneling nano-bridges. The dynamics of filopodia appear quite complex as they exhibit a rich behavior of buckling, pulling, length and shape changes. Here, we find that filopodia additionally explore their 3D extracellular space by combining growth and shrinking with axial twisting and buckling of their actin rich core. Importantly, we show the rotational dynamics of the filamentous actin inside filopodia for a range of highly distinct and cognate cell types spanning from earliest development to highly differentiated tissue cells. Non-equilibrium physical modeling of actin and myosin confirm that twist, and hence rotation, is an emergent phenomenon of active filaments confined in a narrow channel which points to a generic mechanism present in all cells. Our measurements confirm that filopodia exert traction forces and form helical buckles in a range of different cell types that can be ascribed to accumulation of sufficient twist. These results lead us to conclude that activity induced twisting of the actin shaft is a general mechanism underlying fundamental functions of filopodia.Competing Interest StatementThe authors have declared no competing interest.