A tiny fish will be making a big splash today when researchers at Stanford's medical school and the Broad Institute publish the whole genome sequence of 21 threespine stickleback fish in Nature. As I explain in our release:
To the uninitiated, the tiny threespine stickleback might look like nothing more than a scruffy anchovy with an attitude. But this tough little fish, with its characteristic finny mohawk, is a darling of evolutionary biologists.
That's because it exhibits some of the most recent, and most dramatic, adaptive changes of any animal alive today. Flourishing in fresh water or salty, appearing ponderously armored or slippery sleek, light-skinned or dark, this plucky pisces has made itself so uniquely at home in countless lakes, streams and oceans that early naturalists initially classified it as more than 50 separate species. It's the ultimate changeling.
The researchers, led by developmental biologist David Kingsley, PhD, discovered that the stickleback adapts to different environments by repeatedly changing the same regions of its genome. Furthermore, most of these changes occur in areas that control how and when genes are expressed, rather than in the genes themselves:
There are a lot of potential advantages to changing regulatory sequences, rather than the coding regions of genes. "Many genes work in multiple places in the body," said Kingsley. "If you change their protein product, you simultaneously disrupt everything that gene does. In contrast, if you alter the regulatory switches that control where and when a gene is expressed, it may become possible to confine a change to one part of the body, or one developmental stage, for example, and avoid possible lethal consequences."
The effect is like using a tool you know is effective in one application in a new way (let's see if I can use a nail-pounding hammer to whack this board into place), rather than trying to craft an entirely new tool with no idea if it will work at all (there's probably a good reason that you've never heard of the hamwrench).
The findings reverberate far beyond the watery domains of the tiny stickleback: They may help scientists understand how the whale lost its hind limbs when it returned to the sea, for example, or how early humans evolved variations in skin color as they migrated across our green-blue planet.