"Lindbergichthys nudifrons Gaudy notothen" by GeSHaFish / CC BY-SA 3.0

After Two Decades, a Fishy Genetic Mystery Has Been Solved

Mar 20, 2019

By Ed Yong

It has taken her two decades, but Chi-Hing Christina Cheng has finally solved her ultimate cold case—a fishy mystery that extends from one frigid end of the planet to the other.

Cheng, a Chinese-born biologist, moved to the United States as a teenager and began working in Antarctica in 1984. There, she and her partner, Arthur DeVries, studied the notothens—a group of fishes that swim in the continent’s subzero waters. These animals survive at temperatures that would kill other fish because they produce their own antifreeze—a protein that courses through their blood and prevents ice from forming.

The protein is incredibly simple. It comprises the same three chemical building blocks, repeated over and over—one threonine and two alanines. This repetitive unit, which I’ll call “thralala” for convenience, is perfectly shaped to stick to ice crystals, creating a barrier that stops water molecules from joining and prevents the crystals from growing. Hence: antifreeze.

In 1997, Cheng and DeVries found that the gene that makes this antifreeze protein had an unexpected origin—it arose from an ancestral gene that makes a digestive enzyme. Coincidentally, a tiny snippet in the middle of this digestive gene had exactly the right code for making the thralala unit. Over millions of years, that snippet must have duplicated itself, again and again, turning an old digestive gene into a new ice-binding one, and allowing the notothens to survive in Antarctic waters. Very cool.

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