Title: Cell motility and shape as a playground for physics
Abstract: Cells crawl and reorganize in the body to perform their functions, ranging from white blood cells finding bacteria to skin cells closing over a wound. These behaviors provide huge opportunities for physicists, not only because eukaryotic cells are actively-driven soft materials but also because cells must cope with a noisy, fluctuating environment. I will discuss a few examples of how my group has explored these topics across scales from the subcellular to the tissue scale. First, I will discuss what physics limits cells' ability to respond to electric fields, which help guide cells to help heal wounds. This analysis sets a limit bounding how accurately cells can sense the field, and predicts a universal form of the cell's directionality as a function of field strength. Secondly, I will talk about modeling "cell collider" experiments, which probe how cells respond to contact with a neighbor. I will show that the geometry of the cell's environment plays a large role in controlling the outcome of collisions. Finally, I will show how cell shape can then play a role in a tissue of thousands of cells, where anisotropic cells become aligned in patterns akin to a nematic liquid crystal. Topological defects in this liquid crystalline order then can drive changes in cell behavior, like increases in density. These increases in density can occur if cell shape regulates cell division - and we present results from experimental collaborators suggesting division is driving these density increases.