How electric fish evolved to flick the switch on their genes

Have you ever dreamed of having superpowers? Maybe you wish you could manipulate some natural force like electricity?

Well, you’ve been beaten to the (epic, slow-motion) punch… by fish.

There are many fish species that have developed the ability to generate an electric field. They use it to signal each other, defend against predators, and sense other fish nearby.

But how did these flashy abilities evolve?

A new study published in Science Advances explains how a small genetic alteration allowed some fish to develop electric organs.

Fish have duplicate versions of the gene that produces sodium channels – tiny motors that control muscle contraction through electric signals. Researchers found that, in electric fish, one duplicate of the sodium channel gene is turned off in muscles and turned on in other cells. Thus, a new electric organ is formed.

“This is exciting because we can see how a small change in the gene can completely change where it’s expressed,” said co-author of the study Harold Zakon, professor of neuroscience and integrative biology at the University of Texas in Austin, US.

More on evolution: Is Darwin’s “natural selection” operating twice as fast as previously thought?

Only 20 DNA molecules long, the section of the sodium channel gene that controls whether the gene is expressed in a cell is either altered or entirely missing in electric fish.

Electric fish are found in Africa and South America. The team found that the group in Africa had mutations in the sodium channel gene control region. In South American electric fish, the control region is completely lost. Both populations converged to evolve electric organs, but from two different paths.

“If you rewound the tape of life and hit play, would it play back the same way or would it find new ways forward? Would evolution work the same way over and over again?” asks co-senior author Jason Gallant, associate professor of integrative biology at Michigan State University in the US, who breeds the South American electric fish studied by the team.

“Electric fish let us try to answer that question because they have repeatedly evolved these incredible traits. We swung for the fences in this paper, trying to understand how these sodium channel genes have been repeatedly lost in electric fish. It really was a collaborative effort.”

The team hopes to build on its results to answer how the evolution of electric fish, having turned off the sodium channel in some cells, turned the gene on in the electric organ.

So, this genetics research means we can start giving humans electrical superpowers, right?

No. But the research does have implications for us – albeit far more serious and important.

“This control region is in most vertebrates, including humans,” Zakon says. “So, the next step in terms of human health would be to examine this region in databases of human genes to see how much variation there is in normal people and whether some deletions or mutations in this region could lead to a lowered expression of sodium channels, which might result in disease.”

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