The octopus brain and the human brain share the same “jumping genes”

The octopus is an exceptional organism with an extremely complex brain and cognitive abilities that are unique 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 arise from a molecular analogy to the human brain, as discovered by a recently published research paper in BMC Biology and coordinated by Remo Sanges of SISSA of Trieste and by Graziano Fiorito of Stazione Zoologica Anton Dohrn of Naples . The 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.

Sequencing of the human genome revealed as far back as 2001 that more than 45% of it is composed of sequences called transposons, so-called ‘jump genes’ which, through molecular copy-and-paste or cut-and-paste mechanisms, can ‘move’ ‘ from one point to another of an individual’s genome, shuffling or duplicating. In most cases, these mobile elements remain silent: they have no visible effects and have lost their ability to move. Some are inactive because they have accumulated mutations over generations; others are intact but blocked by cellular defense mechanisms. From an evolutionary point of view, even these fragments and broken copies of transposons may still be useful as ‘raw matter’ that can shape evolution.

Of these mobile elements, the most relevant are those belonging to the so-called LINE family (Long Interspersed Nuclear Elements), which are found in 100 copies in the human genome and may still be active. Traditionally, however, the activity of LINEs was just a relic of the past, a relic of the evolutionary processes involving these mobile elements, but in recent years new evidence has emerged showing that their activity is finely regulated in the brain. There are many scientists who believe that LINE transposons are associated with cognitive skills such as learning and memory: they are mainly active in the hippocampus, the main structure of our brain for the neural control of learning processes.

The octopus genome, like ours, is rich in “jumping genes,” most of which are inactive. The researchers focused on the transposons that can still copy and paste and identified an element of the LINE family in areas of the brain that are critical to these animals’ cognitive abilities. The discovery, the result of the collaboration between Scuola Internazionale Superiore di Studi Avanzati, Stazione Zoologica Anton Dohrn and Istituto Italiano di Tecnologia, was made possible thanks to next-generation sequencing techniques, which were used to analyze the molecular makeup of the genes that are active in the octopus’ nervous system.

“The discovery of an element of the LINE family, active in the brains of the two octopus species, is very important because it supports the idea that these elements have a specific function beyond copying and pasting,” explains Remo. Sanges, director of the Computational Genomics laboratory at SISSA, who started working on this project when he was a researcher at Stazione Zoologica Anton Dohrn in Naples. The research, published in BMC Biology, was conducted by an international team of more than twenty researchers from around the world.

“I literally jumped on the chair when I saw under the microscope a very strong signal of activity from this element in the vertical lobe, the brain structure that in the octopus is the seat of learning and cognitive skills, much like the hippocampus in people”, says Giovanna Ponte of Stazione Zoologica Anton Dohrn.

According to Giuseppe Petrosino of Stazione Zoologica Anton Dohrn and Stefano Gustincich of Istituto Italiano di Tecnologia: “This similarity between man and octopus showing the activity of a LINE element in the seat of cognitive faculties can be explained as a fascinating example 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 those of mammals,” said Graziano Fiorito, director of the Department of Biology and Evolution of Marine Organisms at Stazione Zoologica Anton Dohrn. “Also for this reason, the identified LINE element represents a very interesting candidate to study to improve our understanding of the evolution of intelligence.”

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