When it comes to squid, you just can't help wondering.
Not only because they are slippery, but also because they have an incredible ability to genetically edit – this allows them to tune their own RNA after it has left the nucleus.
This is what it means. Genes, at least in humans, remain largely unchanged until they are recombined and passed on to the next generation.
This is the same for our messenger RNA (mRNA). Useful molecules read our DNA, create short little RNA messages, and send them outside the nucleus to tell the rest of the cell what proteins are to be built.
Once this mRNA has left the nucleus, it is believed that the genetic information it carries cannot be changed – but new research has shown that this is not the case in the nerves of squid.
“We found that squid can modify RNA at the periphery of the cell,” says Woods Hole geneticist Joshua Rosenthal of the Marine Biological Laboratory (MBL).
“It works by massively tuning the nervous system,” Rosenthal said. “This is really a new way of evolution.”
The team took neural tissue samples from an adult male long-haired squid (Doryteuthis pealeii) and analyzed the protein expression as well as the squid transcript, which is similar in genome but for mRNA.
They found that in squid nerves (or neurons), mRNA was edited outside the nucleus, in a part of the cell called an axon.
This mRNA editing allows squid to fine-tune the proteins they produce at local points. Thanks to this discovery, squid became the only creatures we know that can do this.
However, this is not the first time that squids have demonstrated their genetic prowess. Back in 2015, a team of scientists from MBL discovered that squid edit their mRNA in their nucleus to an incredible degree – orders of magnitude more than what happens in humans.
“We thought that all the RNA editing took place in the nucleus, and then the modified RNA messages are exported into the cell,” explains Rosenthal.
But the team showed that while editing occurs in both cases, it occurs significantly more outside the nucleus in the axon, rather than inside the nucleus.
Octopuses, cuttlefish, and squid use mRNA editing to diversify the proteins produced in the nervous system. This may be one of the reasons why these creatures are much smarter than other invertebrates.
“The idea that genetic information can be edited in different ways within the cell is new and expands our understanding of how a single project of genetic information can lead to spatial complexity,” the team writes in a new article.
“Such a process can fine tune the function of the protein to help meet the specific physiological needs of different cellular regions.”
While this is just an interesting genetic study of squid right now, biologists believe that ultimately this type of system may help treat neurological disorders that involve axonal dysfunction.
CRISPR has completely changed the game when it comes to editing DNA inside our cells, and RNA is significantly less constant and therefore editing can be less dangerous.
“RNA editing is safer than DNA editing,” Rosenthal said.
The study was published in Nucleic Acids Research.
Sources: Photo: Wikipedia Commons
