.
“MicroRNAs are known as the ‘dark matter’ of the animal genome — they don’t make protein, but they regulate the expression of proteins.”
“This is the only instance in all of the invertebrates of dramatic microRNA increase and those genes are all expressed in the brain.”
Octopuses and their cephalopod relatives are exceptionally intelligent invertebrates with a highly complex nervous system that evolved independently from vertebrates. A team of scientists led by Dartmouth College and the Max Delbrück Center hypothesized that RNA regulation may play a major role in the cognitive success of these marine creatures. In their new study, the authors found that two octopus species contain a high number of microRNAs, which are linked to the development of advanced cells with specific functions.
Zolotarov et al. propose that miRNAs are intimately linked to the evolution of complex brains in octopuses and other animals. Image credit: Albert Kok / CC BY-SA 3.0.
Octopuses and their relatives are unusual among invertebrates in having a nervous system comparable to the central nervous system of vertebrates.
In 2016, an octopus named Inky made international headlines after escaping from the National Aquarium of New Zealand by slipping through a gap in his tank and pulling himself several feet across the floor to a nearly 150-foot drainpipe leading to the sea — and his freedom.
Octopuses also have been observed collecting and building shelters from discarded coconut shells, and using water currents to play catch with various objects.
“The nervous systems of octopuses and squids — which both belong to a type of mollusk known as cephalopods — evolved independently of vertebrates,” said Dartmouth College’s Professor Kevin Peterson, co-corresponding author of the study.
“Yet, the prevalence of microRNAs in both octopuses and vertebrates suggest a common role for the molecules in advanced cognition.”
“This kind of intelligence potentially stems from microRNAs’ role in diversifying cell function,” added co-author Dr. Bastian Fromm, a researcher at the University of Tromsø.
Expansion of the miRNA repertoire in cephalopods: (A) phylogeny of several animal groups with the branch lengths between nodes, or from a node to an extant species, reflecting the gains of miRNA families minus the losses; vertical lines at the end of the branches indicate the shared complement of the indicated species; the other branches lead to single species; (B) number of miRNA families (excluding species-specific novel families) versus median 3’UTR length in selected animals. Image credit: Zolotarov et al., doi: 10.1126/sciadv.add9938.
In the study, Professor Peterson, Dr. Fromm and their colleagues analyzed microRNA data from three cephalopod species: Octopus vulgaris, Octopus bimaculoides, and Euprymna scolopes.
They identified specific sequences that were either new or already found in these animals.
According to the team, the genes of two octopus species, Octopus vulgaris and Octopus bimaculoides, show an increase in microRNAs over evolutionary time that has so far only been found in humans, mammals and other vertebrates.
“When combined with the known intelligence of octopuses, the findings provide crucial support for the theory that microRNAs are key to the evolution of intelligent life,” Professor Peterson said.
“MicroRNAs are known as the ‘dark matter’ of the animal genome — they don’t make protein, but they regulate the expression of proteins.”
“This is the only instance in all of the invertebrates of dramatic microRNA increase and those genes are all expressed in the brain.”
“This was always a big test for the hypothesis, that it is not specific to vertebrates. This was a big moment — we discovered the secret to complex life, and the secret to complex life is microRNAs.”
“Cells in complex organisms perform specialized tasks, which means surrounding cells need to be calibrated to carry out additional functions,” Dr. Fromm said.
“MicroRNAs are like light switches or dimmers that can turn on and regulate the expression of thousands o0f proteins in a cell and specify what the cell can do.”
“This is a numbers game. Oysters and slugs have microRNAs, but in cephalopods — and especially the octopus — there is an explosion of them that correlates with their intelligence.”
The findings appear in the journal Science Advances.
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Grygoriy Zolotarov et al. 2022. MicroRNAs are deeply linked to the emergence of the complex octopus brain. Science Advances 8 (47); doi: 10.1126/sciadv.add9938
https://www.sci.news/biology/octopus-mi ... 11527.html