The octopus is an exceptional organism with an extremely complex brain and unique cognitive abilities among invertebrates. So much so that in some ways it has more in common with vertebrates than with invertebrates. The neural and cognitive complexity of these animals could come from a molecular analogy with the human brain, as discovered in a research article recently published in BMC Biology and coordinated by Remo Sanges from SISSA in Trieste and by Graziano Fiorito from Stazione Zoologica Anton Dohrn of Naples. Research shows that the same “jumping genes” are active in both the human brain and the brains of two species, Octopus vulgaris, the common octopus, and Octopus bimaculoides, the California octopus. A discovery that could help us understand the secret of the intelligence of these fascinating organisms.
The sequencing of the human genome revealed as early as 2001 that more than 45% of it is composed of sequences called transposons, “jumping genes” which, through molecular copy-paste or cut-paste mechanisms, can “move” from one point of an individual’s genome to another, shuffling or duplicating. In most cases, these moving parts remain silent: they have no visible effect and have lost their ability to move. Some are inactive because they have, over generations, accumulated mutations; others are intact, but blocked by cellular defense mechanisms. From an evolutionary perspective, even these fragments and broken copies of transposons can still be useful, as “raw material” that evolution can sculpt.
Among these mobile elements, the most relevant are those belonging to the so-called LINE (Long Interspersed Nuclear Elements) family, found in about a hundred copies in the human genome and still potentially active. Traditionally, LINE activity was just a holdover from the past, a remnant of evolutionary processes involving these mobile elements, but in recent years new evidence has emerged showing that their activity is finely regulated in the brain. Many scientists believe that LINE transposons are associated with cognitive abilities such as learning and memory: they are particularly active in the hippocampus, the most important structure in our brain for neural control of learning processes.
The octopus genome, like ours, is rich in “jumping genes”, most of which are inactive. By focusing on transposons still able to copy and paste, the researchers identified a member of the LINE family in parts of the brain crucial for the cognitive abilities of these animals. The discovery, the result of the collaboration between the Scuola Internazionale Superiore di Studi Avanzati, the Stazione Zoologica Anton Dohrn and the Istituto Italiano di Tecnologia, was made possible thanks to next-generation sequencing techniques, which were used to analyze the composition molecular genes active in the octopus nervous system.
“The discovery of an element of the LINE family, active in the brain of both species of octopus, is very significant because it supports the idea that these elements have a specific function that goes beyond copy-paste”, explains Remo. Sanges, director of the Computational Genomics laboratory at SISSA, who began working on this project when he was a researcher at the Stazione Zoologica Anton Dohrn in Naples. The study, published in BMC Biology, was carried out by an international team of more than twenty researchers from around the world.
“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 capacities and cognitive, just like the hippocampus. in humans,” says Giovanna Ponte of the Stazione Zoologica Anton Dohrn.
According to Giuseppe Petrosino of Stazione Zoologica Anton Dohrn and Stefano Gustincich of the Istituto Italiano di Tecnologia “This similarity between man and octopus which shows the activity of a LINE element in the seat of cognitive abilities could be explained as an example fascinating of convergent evolution, a phenomenon for which, in two genetically distant species, the same molecular process develops independently, in response to similar needs.
“The octopus brain is functionally analogous in many of its features to that of mammals,” says Graziano Fiorito, director of the Department of Biology and Evolution of Marine Organisms at 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.”
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