A team of Italian researchers identified a group of genes that could explain the remarkable intelligence of the octopus, according to a study published in the journal BMC Biology.
The octopus is an exceptional animal with a highly complex brain and abilities not shared by any other invertebrates. In fact, you could say that it resembles more vertebrates than invertebrates. Now, researchers from the Scuola Internazionale Superiore di Studi Avanzati, Stazione Zoologica Anton Dohrn and Istituto Italiano di Tecnologia in Naples, Italy, found that some crucial genes are active both in the human brain and in the brains of some species of octopus. This discovery could help us understand the secret behind these animals’ brain abilities.
The human genome includes 45% of sequences called transposons or jumping genes. These sequences can move from one point to another in a person’s genome. In most cases, these elements stay silent and have no visible effects or lose their ability to move. Some are inactive because they have accumulated mutations over the years or are blocked by cellular defence mechanisms.
However, even in a corrupt state, these DNA fragments can still be useful and change during evolution. Among these moving elements, the most important belong to the LINE (Long Interspersed Nuclear Elements) family, which can be found in a hundred copies in the human genome and may still be active.
Until now, researchers believed that the activity of the LINE family was a remnant of evolutionary processes in the past, but recently more evidence is coming to light that their activity is finely regulated in the brain. Many now believe that LINE jumping genes are associated with complex cognitive abilities like learning new skills and memory. These genes seem particularly active in the hippocampus, the most critical area in the brain to control learning processes.
Like in humans, jumping genes are mostly inactive in the octopus. Looking at the ones that are still capable of moving, the Italian researchers identified an element of the LINE family that seems crucial to explaining the cognitive abilities of these animals. The team used next-generation sequencing techniques to analyse the presence of genes active in the nervous system of the octopus.
“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,” explained Remo Sanges, director of the Computational Genomics Laboratory at SISSA.
“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,” added Giovanna Ponte from Stazione Zoologica Anton Dohrn.
“The brain of the octopus is functionally analogous in many of its characteristics to that of mammals,” concluded Graziano Fiorito, director of the Department of Biology and Evolution of Marine Organisms of the Stazione Zoologica Anton Dohrn. “For this reason, also, the identified LINE element represents a very interesting candidate to study to improve our knowledge on the evolution of intelligence.”
Petrosino, G., Ponte, G., Volpe, M. et al. (2022) Identification of LINE retrotransposons and long non-coding RNAs expressed in the octopus brain. BMC Biol 20, 116, https://doi.org/10.1186/s12915-022-01303-5