The octopus is a exceptional body with an extremely complex brain and cognitive abilities unique among invertebrates. However, in some ways, this animal has more in common with vertebrates. Of course, the evolutionary reason for its intelligence and the molecular mechanisms that determine it are still under investigation.
A new study, published in the journal BMC Biology, reveals that the neural complexity and octopus cognition could have its origin in a molecular analogy with the human brain. The work is the result of a collaboration between the Escuela Internacional Superior de Estudios Avanzados (SISSA) in Trieste, the Anton Dohrn Zoological Station in Naples (SZN) and the Italian Institute of Technology in Genoa (IIT).
The key: jumping genes
O human genome sequencing revealed in 2001 that more than 45% is composed of sequences called transposons. Known as ‘jumping genes’, they are DNA sequences able to pass from one point of the genome to another: through molecular mechanisms of ‘copy and paste’ or ‘cut and paste’ they can Double any mix.
In most cases, these moving parts are inactive. Sometimes because over generations they’ve accumulated mutations that have eliminated its ability to move, other times because −although its sequence is intact− the cell applies protection mechanisms that block them and disable their ability to move.
Research shows that the same ‘jumping genes’ are active both in the human brain and in the same organ of two species of this invertebrate: vulgar octopusThe common octopusY bimaculoid octopusThe california octopus. According to experts, this discovery could help to understand the secret behind the intelligence of these fascinating organisms.
“It was already known that the octopus genome is rich in transposons, but a potentially active element had never been found in these animals,” he tells SINC. Remo Sangesdirector of the SISSA Computational Genomics Laboratory.
Transposons and their relationship with memory
Among the different types of existing transposons, the most represented in the human genome are those belonging to the family called ‘LINE‘, interspersed long core elements (from Interleaved Long Nuclear Elementsin English).
Traditionally, the activity of LINEs was thought to be just a vestige of the past, a legacy of the evolutionary processes that involved these moving elements. But in recent years new evidence has emerged showing that LINE activity in the human brain is finely regulated.
In fact, they are particularly active in the hippocampusthe most important structure of our brain for the neuronal control of the processes of Learning. This evidence has led many scientists to believe that they are associated with cognitive abilities such as memory.
Focusing on transposons still able to ‘copy and paste’, the researchers identified an element of the LINE family in parts of the brain that are crucial to the cognitive abilities of these animals.
Graphic representation of an octopus. / Credits: Gloria Ros
a significant finding
The discovery was made possible by sequencing techniques of the genome last generation (next generation sequencing), which allowed the analysis of the molecular composition of active transposons in the octopus nervous system.
“The discovery of an element of the LINE family active in the brains of the two octopus species studied is highly significant and supports the idea that these elements have a specific function that goes beyond ‘copy and paste’”, adds Sanges.
“O erect wolf it is the structure of the brain that in the octopus is the seat of learning and cognitive abilities, as well as the hippocampus in the human being”, he explains. Giovanna Ponte, from the Anton Dohrn Zoological Station. “I literally jumped out of my chair when, under the microscope, I saw a very strong signal of activity from this LINE element in this area.”
“Octopus and humans are the only organisms in which the expression of LINE elements has been observed in the brain lobes that control cognitive abilities,” says Sanges.
According to Stefano Gustincichof the Italian Institute of Technology, and Giuseppe Petrosinofrom Anton Dohrn Zoological Station, “this similarity between man and octopus showing the activity of a LINE element in the origin of cognitive abilities could be explained as a fascinating example of convergent evolutiona phenomenon whereby, 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 characteristics to that of mammals”, he emphasizes. Graziano Fiorito, director of the Department of Biology and Evolution of Marine Organisms at the Neapolitan Zoological Station. “The identified LINE element represents a very interesting candidate to study to improve our knowledge of the evolution of intelligence”, he concludes.
Reference:
Petrosino and others., BMC Biology, “Identification of LINE retrotransposons and long non-coding RNAs expressed in the octopus brain”