Trigger for directed cell motion

When an individual cell is placed on a level surface, it does not keep still, but starts moving. This phenomenon was observed by the British cell biologist Michael Abercrombie as long ago as 1967. Since then, researchers have been thriving to understand how cells accomplish this feat. This much is known: cells form so-called lamellipodia - cellular protrusions that continuously grow and contract - to propel themselves towards signalling cues such as chemical attractants produced and secreted by other cells. When such external signals are missing - as in the observation by Abercrombie - cells begin actively looking for them. In doing so, they use search patterns that can also be observed in sharks, bees or dogs. They transiently move in one direction, stop, wiggle on the spot for a while, and then continue moving in another direction.