Curved crease origami at cellular scales enables hyper-extensibility of Lacrymaria olor

Eukaryotic cells undergo dramatic morphological changes during cell
division, phagocytosis, and motility. Fundamental limits of cellular
morphodynamics such as how fast or how much cellular shapes can change
without harm to a living cell remain poorly understood. Here we describe
hyper-extensibility in the single-celled protist Lacrymaria olor, a 40 μm
cell which is capable of reversible and repeatable extensions (neck-like
protrusions) up to 1500 μm in 20 seconds. We discover that a unique and
intricate organization of cortical cytoskeleton and membrane enables these
hyper-extensions that can be described as the first cellular scale curved
crease origami. Furthermore, we show how these topological singularities
including dcones and twisted domain walls provide a geometrical control
mechanism for the deployment of membrane and microtubule sheets as they
repeatably spool thousands of times from the cell body. We lastly build
physical origami models to understand how these topological singularities
provide a mechanism for the cell to control the hyper-extensile deployable
structure. This new geometrical motif where a cell employs curved crease
origami to perform a physiological function has wide-ranging implications
in understanding cellular morphodynamics and direct applications in
deployable micro-robotics.