Octopus: How octopus microRNAs relate to humans
Systems biologist Rajewsky compared the microRNAs of the octopus with those of other animal species
Credit: Pablo Castagnola, Getty Images/The Image Bank RF/Hal Beral; Montage: infographic WORLD
Higher intelligence developed twice on this planet: in humans and in the octopus. The German systems biologist Nikolaus Rajewsky explains how he came up with it and hasn’t been able to eat squid since.
Nikolaus Rajewsky is a systems biologist at the Max Delbrück Center in Berlin and is one of the world’s most cited researchers in his field. Four years ago he read a paper about the octopus and how it manipulates ribonucleic acids (RNA) – the transcript of the genome that either carries the blueprint for proteins or regulates their production. He was so interested that he began to study them. In a current publication, he describes an unexpected discovery: Tiny RNA molecules control the development of the brain – also in humans.
WORLD ON SUNDAY: You’ve spent years trying to figure out the brain of the octopus to investigate. What fascinates you about this animal?
Nikolaus Rayevsky: The octopus is the only non-vertebrate creature that has evolved higher intelligence. It shows all the characteristics that we associate with intelligence: curiosity, contact, interaction. The octopus also uses tools. Behavioral scientists can tell incredible stories. There is the Aquariums worker, whom an octopus hates and whom he deliberately sprays with water. They even dream, changing their colors during the dream phase. That’s impressive, isn’t it?
WORLD ON SUNDAY: Very! In your current work, you describe how your brain development is RNA-driven.
Rayevsky: We were able to show that the development towards a complex brain is related to the occurrence of a special type of RNA, so-called microRNAs. But the really unbelievable thing is that this development happened twice in this world, independently of each other.
WORLD ON SUNDAY: How are these microRNAs related to brain development?
Rayevsky: We compared the microRNAs of the octopus to those of other animal species, both vertebrate and invertebrate, and created a pedigree. And you can see very clearly how the number of microRNAs in the vertebrate branch gradually increased, while in the invertebrate branch it increased jellyfish and worms remained very low. But then both vertebrates and invertebrates exploded in proliferation—particularly when the great apes and octopus evolved.
WORLD ON SUNDAY: One might think of this as a random correlation.
Rayevsky: But a stark correlation. How old is our common ancestor, this early form of a worm or jellyfish – a billion years? I didn’t calculate it. The point is, we can show that brain complexity and the number of microRNAs are related; we have thus found a molecular mechanism that links our own brain development with that of the octopus. It’s like meeting an alien and realizing: the complexity of its brain was created using the same class of genes. Without ever being in contact. There is something very fundamental behind it.
WORLD ON SUNDAY: What could that be?
Rayevsky: MicroRNAs are important regulators. They influence which proteins are formed in a cell. If you understand the genome present in every cell as the book of life, then every cell reads the chapter from this book that is intended for it – and microRNAs control which that is. But they can also be found in nerve cells in unusual places: in the spinous processes, where two nerve cells make contact and network. It is assumed that there, far away from the cell nucleus, they take over gene regulation, i.e. they determine which protein is produced. This could mean that they influence how nerve cells network. We now want to test this in mini-brains, i.e. organoids, for humans.
WORLD ON SUNDAY: still eat Octopus?
Rayevsky: No not more. That just doesn’t work anymore.
