How to make a cell into a headless chicken.

Borisy chose to study fish skin cells – the masters of movement. In an hour they cover just under a millimeter, which on a larger scale is roughly equivalent to a person-sized bag of goo sloshing from one end of a football field to another. The cut-healing fibroblasts in humans are larger and around ten times slower ("like studying flight in an ostrich," according to one researcher); perhaps, speculates Borisy, "fish are wounded more than we are."

The fish skin cells are so fast that they can be made into headless chickens.

A moving cell fragment.

Borisy reported early in 1999 that he could make hundreds of these cell fragments by adding a chemical that turns off myosin. Actin cables kept growing and pushing out on the front of the cell. But without myosin dragging the rest of the cell forwards, the majority of the cell could not keep up. When the tension became too much the front of the cell broke away, motoring across the culture dish. It left behind the nucleus – the command-central of the cell. But still the headless-chicken cells kept going.

The headless chickens prove that there is an independent motor in the front of the cell. These cell fragments don’t need building materials from the nucleus, or large actin roadways running across the whole cell, or signals from outside the actin network telling it which way is forwards.

"The movement machinery, once polarized, propagates its own polarized state," says Borisy. The fragments’ remarkable self-sufficiency, coupled with their small size and simplicity, mean they are a great place to start understanding how movement is generated.

Making a Movement Machine