Skeletons in Space

Deep within the cells we are made of, squishy skeletons feel the effects of gravity... and respond in unexpected ways.

Sculptor Kenneth Snelson's "Needle Tower" is a fragile-looking thing. Criss-crossing rods suspended by taut wires soar perilously upward 20 meters high. Surely it ought to crumble or fall over? Yet it doesn't. When the wind blows, the Needle Tower bends, not breaks. When someone shoves it, it shoves back. The tower is lightweight, strong and curiously beautiful.

Just like the skeletons of cells.

That's right, cells have skeletons. They're not made of calcium like the bones that rattle on Halloween. Cell skeletons-biologists call them cytoskeletons - consisting of protein molecules arranged into chains. Cytoskeletons give cells their shape, help cells move, and hold the nucleus in place.

Like Snelson's sculptures, cytoskeletons have 'tensegrity' - short for tensional integrity. They balance compression with tension, and yield to forces without breaking. In the Needle Tower, the wires carry tension and the rods bear compression. In a cytoskeleton, protein chains - some thin, some thick and some hollow, take the place of wires and rods. Linked together they form a stable, but flexible, structure.

NASA is interested in cytoskeletons because cytoskeletons respond to gravity. Weight can provide both tension and compression. But what happens (during space travel, for example) when weight vanishes? Do cells behave differently when their cytoskeletons relax?

Harvard cell biologist Don Ingber is a leader among researchers who have been working to find out.