S Huang

In an orchestra that has been playing the same symphony for years, the musicians gradually start to drift: each one plays on their own, yet the notes remain the same. That is roughly what happens to cells as they age. Scientists have come up with a way to measure this discord, that is, how faithfully each cell follows the shared program of gene expression.

Picture a master switch in an old house: one flip, and lights come on in every room. The tiny worm Caenorhabditis elegans has a similar switch, except instead of light it turns on a longevity program. The flip is a signal of oxygen shortage that triggers an ancient survival mechanism called the hypoxic response.