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 originate from a molecular analogy with the human brain, as discovered by a research paper recently published in BMC Biology and coordinated by Remo Sanges from SISSA of Trieste and by Graziano Fiorito from Stazione Zoologica Anton Dohrn of Naples. The research shows that the same ‘jumping genes’ are active both in the human brain and in the brain of two species, Octopus vulgaris, the common octopus, and Octopus bimaculoides, the Californian octopus. A discovery that could help us understand the secret of the intelligence of these fascinating organisms.
Sequencing the human genome revealed as
early as 2001 that over 45% of it is composed by sequences called transposons,
so-called ‘jumping genes’ that, 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, over generations,
accumulated mutations; others are intact, but blocked by cellular defense
mechanisms. From an evolutionary point of view even these fragments and broken
copies of transposons can still be useful, as ‘raw matter’ 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 a hundred copies in the human genome and still
potentially active. It has been traditionally though that LINEs’ activity was
just a vestige of the past, a remnant of the evolutionary processes that
involved these mobile elements, but in recent years new evidence emerged showing
that their activity is finely regulated in the brain. There are many scientists
who 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 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. Focusing on the transposons
still capable of copy-and-paste, the researchers identified an element 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 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 composition of
the 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,” explains Remo Sanges, director of
the Computational Genomics laboratory at SISSA, who started working at this
project when he was a researcher at Stazione Zoologica Anton Dohrn of Naples.
The study, published in BMC Biology, was carried out by an international team
with more than twenty researchers from all over 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 and cognitive abilities, just like thehippocampus in humans,” tells
Giovanna Ponte from Stazione Zoologica Anton Dohrn.
According to Giuseppe Petrosino from
Stazione Zoologica Anton Dohrn and Stefano Gustincich from Istituto Italiano di
Tecnologia “This similarity between man and octopus that shows the activity of
a LINE element in the seat of cognitive abilities could 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 brain of the octopus is
functionally analogous in many of its characteristics to that of mammals,” says
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.”
Source: https://www.sissa.it/sites/default/files/Sanges-Fiorito%20eng_0.pdf
Journal article: https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-022-01303-5
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