Charged fish, such as electric eels, can distinguish other electric fish by species, sex, and even by individual due to their electrical officers, which also enables them to send and receive messages similar to bird song. A recent study published in Science Advances describes how minor genetic alterations allowed charged fish to evolve electrically. The discovery could also help researchers identify genetic mutations that cause various human diseases.
In order for fish to obtain electrical officials, evolution must exploit a genetic anomaly. Each fish has two copies of the same gene, which creates sodium channels that function as miniature muscle motors. The charged fish turned off a copy of the sodium channel gene in the muscle and turned it on in other cells, thus evolving the electrical organ. The small motor that usually causes muscle contractions is converted into an electrical signal generator, and a completely new organ is created.
Harold Zakon, professor of neuroscience and integrative biology at the University of Texas at Austin and corresponding author of the study, said: "It's exciting because we can see that a small change in a gene can completely change where it's expressed. ”
Researchers at Michigan State University and the University of Texas at Austin report their findings in a new paper, which found that a short segment of about 20 letters in this sodium channel gene can regulate the gene's expression in specific cells. They verified that this control area was either altered or completely absent in the electric fish. Because of this, one of the two sodium channel genes is disabled in the muscles of electric fish. However, its impact far exceeds the development of electric fish.
Zakon said: "This control area is present in most vertebrates, including humans. Therefore, in terms of human health, the next step will be to examine this region in the human gene database to see how much variation there are in normal people, and whether some deletions or mutations in this region lead to a decrease in the expression of sodium channels, which may lead to disease. ”
The study's first author was Sarah LaPotin, a research technician at the time of the study at Zakon's lab and currently a doctoral student at the University of Utah. In addition to Zakon, the study's other senior authors were Johann Eberhart, a professor of molecular biological sciences at the University of Texas at Austin, and Jason Gallant, an associate professor of integrative biology at Michigan State University.
Zakon says that before the electrical organs could evolve, the sodium channel gene in the muscles had to be turned off. Zakon said: "If they turn on this gene in both the muscle and the electrical organ, then all the new things that occur in the sodium channel in the electrical organ will also occur in the muscle." Therefore, it is important to isolate the expression of this gene into the electrical organ, where it can evolve without harming 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 mutated in the control area, while the electric fish in South America completely lost control area. Both research groups came up with the same solution for developing electrical organs — losing the expression of sodium channel genes in muscle — albeit through two different pathways.
"If you play the tape of life back, will it play it back in the same way, or will it find a new way forward?" Will evolution repeat itself in the same way? Gallant said he bred electric fish from South America, which were used as part of the research. Electric fish let's try to answer this question because they have evolved these incredible traits over and over again. We wobbled in this paper to try to understand how these sodium channel genes are repeatedly lost in electric fish. This is indeed a cooperative effort. ”
One of the next questions the researchers hope to answer is how the control zone evolved to turn on the sodium channel in the electrical organ.