In 1938, a living memorial, thought to be 65 million years extinct, was accidentally caught in a trawler off the coast of South Africa.
The 2-meter (6.5-foot) long coelacanth (Latimeria chalumnae) turned out to be one of our closest fish friends – looking virtually unchanged since it recently appeared in the fossil record back from the time of non-bird dinosaurs.
Now new genetic evidence shows that this deep-sea predator has gone through growth, but widely at a genetic level – by removing genes from other species.
While searching for genetic databases for the ancestral version of a human gene involved in gene regulation, CGGBP1, the University of Toronto molecular geneticist Isaac Yellan surprisingly discovered many mutations of this gene.
Even more curiously, not all of these different mutations of the CGGBP genes shared a common ancestor. This suggests that, at some points about 10 million years ago, 62 of these genes were translocated by coelacanth from other unrelated species – through horizontal gene transfer.
These genes are called transposons, with their ability to ‘jump’ around and even between genomes a bit like viruses.
If they happen to jump into the right place in the genome, cellular machines copy them just like any other gene. But they can also jump into the wrong place, where they can be harmful and so are thought of as parasites.
At times, however, they may end up in a situation that is conducive to their host species and may lose the ability to jump around but are retained within the space. new in the genome, which is what seems to have happened in the coelacanth, several times over.
“Horizontal gene transfer goes up the picture of where the transposons came from but we know from other species that it can occur through parasites,” Yellan said. “The most likely explanation is that they have been introduced several times through the history of evolution.”
While it is common to find such transposons in many species, it is unusual to find so many.
Tube testing and computer modeling have shown at least eight of the proteins that these genes code to bind to specific strands of DNA, suggesting – like the human version – that they are involved in gene regulation. Some of them are expressed simply in specific cigarettes.
“We don’t know what these 62 genes do, but many of them encode DNA-binding proteins and appear to have a place in gene regulation, where even small changes are important in micro- growth, “explained Tim Hughes, geneticist at the University of Toronto.
Coelacanth has lobed wing-like wings and they are closer to us and our closest fish friends, the lungs, than other types of fish. Our shared ancestor far away means that the genome of coelacanth has the potential to help us discover many mysteries about our own evolution.
Unfortunately, these fish are rarely seen and endangered, so there are few opportunities to study them. But the information we have received from them is already successful.
A recent study of their genes suggests that our acid receptors may have roles beyond our protection from toxic substances, such as metabolic regulation and hormone sensitivity. Now coelacanth genes have proven that transposons have a larger role than we understand in tetrapod evolution.
“Our findings provide a very impressive example of this phenomenon of transposons contributing to the host genome,” Hughe said.
This research was published in Molecular Biology and Evolution.