How Some Fish Developed Electric Organs – Futurity

Small genetic changes allowed electric fish to develop electrical organs, according to a new study.

The finding may also help scientists pinpoint genetic mutations behind some human diseases.

Electric organs help electric fish, such as the electric eeldo all sorts of amazing things: they send and receive signals akin to birdsong, allowing them to recognize other electric fish by species, sex, and even individually.

Evolution took advantage of a quirk of fish genetics to develop electrical organs. All fish have duplicate versions of the same gene that produces small muscle motors called sodium channels. To develop electrical organs, electric fish have turned off one duplicate of the sodium channel gene in muscles and turned it on in other cells.

The tiny motors that normally contract muscles have been repurposed to generate electrical signals, and voila! A new organ with astonishing possibilities was born.

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

In the new paper, Zakon and colleagues describe discovering a short section of this sodium channel gene — about 20 letters long — that determines whether the gene is expressed in a particular cell. They confirmed that this control area has been altered or completely missing in electric fish. And that’s why one of the two sodium channel genes is turned off in the muscles of electric fish. But the implications go far beyond the evolution of electric fish.

“This area of ​​control is in most vertebrates, including humans,” Zakon says. “So the next step in terms of human health would be to examine this region in human gene databases to see how much variation there is in normal humans and whether some deletions or mutations in this region could lead to decreased sodium channel expression.” , which can lead to disease.”

The sodium channel gene had to be turned off in muscles before an electrical organ could evolve, Zakon says.

“If they turned on the gene in both the muscle and the electrical organ, then all the new things that happen to the sodium channels in the electrical organ would also happen in the muscle,” Zakon says. “So it was important to isolate the expression of the gene to the electrical organ, where it could evolve without damaging the muscles.”

There are two groups of electric fish in the world: one in Africa and the other in South America. The researchers found that the electric fish in Africa had mutations in the control region, while electric fish in South America completely lost them. Both groups came to the same solution for developing a electric organloss of expression of a sodium channel gene in muscle, although from two different pathways.

“If you were to rewind the tape of life and hit play, would it play the same way or find new ways to move forward? Would evolution work the same way over and over again?” says Jason Gallant, an associate professor of integrative biology at Michigan State University, who breeds the electric fish from South America used in part of the study.

“With electric fish, we can try to answer that question because they have repeatedly developed these incredible traits. We waved at the gates in this article and tried to understand how these sodium channel genes have been repeatedly lost in electric fish.”

One of the next questions the researchers hope to answer is how the control region evolved to turn on sodium channels in the electrical organ.

Sarah LaPotin, a research technician in Zakon’s lab at the time of the study and currently a PhD student at the University of Utah, is the lead author of the paper. Additional co-authors are from Michigan State University and UT Austin.

The National Science Foundation and the National Institutes of Health funded the work.

Source: UT Austin

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