A family of "jumping genes", which hop through the human genome by cut-and-pasting themselves into various different areas, have also been discovered in two octopus genomes, where they may have some seriously important functions. The genes were previously thought to have no function, but the discovery highlights this may be entirely false, and they could instead play an important role in the octopus brain.
The research was published in BMC Biology.
"Jumping genes", also called transposons, are strings of genetic information that use their own machinery to remove themselves from their current positions and insert themselves into a different position in the genome.
These transposons make up almost half (45 percent) of the human genome, and come in many different forms – long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), and many more. Scientists use jumping genes called Alu elements to trace our evolutionary history, but transposons were thought to be just that: remnants of the past with no discernible function in our modern genomes.
That may be about to change, however.
LINEs are heavily regulated in the brain, which makes sense as you cannot have transposons sneaking themselves into important genes and disrupting their function. Some scientists believe they may play a role in cognition due to their increased activity in the hippocampus, which is involved in learning processes. But, with our still-limited understanding of the human brain, this has been difficult to verify.
Much like in humans, an octopus genome is packed full of transposons, making it an ideal model for understanding them in humans.
In recent research from Stazione Zoologica Anton Dohrn and Scuola Internazionale Superiore di Studi Avanzati (SISSA), scientists have identified significant activity of a genetic element from the LINE family within a key region of the brains of two octopus species: Octopus vulgaris and Octopus bimaculoides.
This suggests it may have an important role in cognition, but also suggests LINEs within the brain may be a result of convergent evolution, meaning that despite humans and octopuses not sharing a common ancestor, both species evolved these genetic elements within the brain to perform similar tasks.
“The discovery of an element of the LINE family, active in the brain of the two octopuses species, is very significant because it adds support to the idea that these elements have a specific function that goes beyond copy-and-paste,” said Remo Sanges, director of the Computational Genomics laboratory at SISSA, in a statement.
“I literally jumped on the chair when, under the microscope, I saw a very strong signal of activity of this element in the vertical lobe, the structure of the brain which in the octopus is the seat of learning and cognitive abilities, just like the hippocampus in humans,” continued Giovanna Ponte from Stazione Zoologica Anton Dohrn.
The research is promising but does not yet tell us that LINEs are directly involved in cognition.
Scientists now know that they are active in areas involved in such tasks, as well as being present in two distinct evolutionary paths, but it is still possible that they are simply doing fun transposon things in these regions and not actually functionally active.
The team now hopes to delve further into these LINEs within the octopus, as it is analogous to many other brains in the animal kingdom, to illuminate their true (if any) functions.