Abstract

Many types of cell in our bodies are not static but actively move around. The effects can be good, such as when immune cells search and destroy invading organisms, or bad, such as when cancer cells spread to distant parts of the body. Many biochemical circuits are implicated in cell movement, but cell fragments with no such circuits also move spontaneously—the cellular equivalent of a headless chicken. This observation suggests the presence of an autonomous “motility engine” whose operation is controlled, but not maintained, by the complex biochemical circuits present in real cells. I shall describe a simplified mathematical model for this engine, using ideas borrowed from the study of liquid crystalline materials, as found in every mobile phone and laptop screen.