Abstract: Robert Cooper '06

“Stay on Target!  The origins of persistence in amoeboid society”

Directed motion enables neutrophils (white blood cells) to hunt invaders, neural axons to find their targets, and embryonic cells to properly develop into a complete organism. Amoeboid motility has an underlying directional persistence – even in the absence of external signals – which helps cells to migrate accurately even through a noisy microenvironment. Surprisingly, this persistence results from a tendency of cells to zig-zag. To explain zig-zag motility, I propose a model in which pseudopods – the “feet” of a cell – emerge as bursts of activity from an excitable cellular cortex, and in which cells maintain an internal, membrane-bound memory of their last step. This model makes specific predictions about pseudopod dynamics, which are supported by experimental data using a new, automated pseudopod-tracking algorithm.  Quantitative cell tracking also reveals changes in the cortical structure itself as a potential source of cellular memory. This suggests a model that intimately links the memory of a pseudopod to its very existence.