But when Stanford University geneticist Jin Billy Li heard about Joshua Rosenthal’s work on RNA editing in squid, his jaw dropped. That’s because the work, published today in the journal Cell, revealed that many cephalopods present a monumental exception to how living things use the information in DNA to make proteins. In nearly every other animal, RNA—the middleman in that process—faithfully transmits the message in the genes. But octopuses, squid, and cuttlefish (but not their dumber relatives, the nautiluses) edit their RNA, changing the message that gets read out to make proteins.
In exchange for this remarkable adaptation, it appears these squishy, mysterious, and possibly conscious creatures might have given up the ability to evolve relatively quickly. Or, as the researchers put it, “positive selection of editing events slows down genome evolution.” More simply, these cephalopods don’t evolve quite like other animals. And that could one day lead to useful tools for humans.
From the paper itself:
RNA editing, a post-transcriptional process, allows the diversification of proteomes beyond the genomic blueprint; however it is infrequently used among animals for this purpose. Recent reports suggesting increased levels of RNA editing in squids thus raise the question of the nature and effects of these events. We here show that RNA editing is particularly common in behaviorally sophisticated coleoid cephalopods, with tens of thousands of evolutionarily conserved sites. Editing is enriched in the nervous system, affecting molecules pertinent for excitability and neuronal morphology. The genomic sequence flanking editing sites is highly conserved, suggesting that the process confers a selective advantage. Due to the large number of sites, the surrounding conservation greatly reduces the number of mutations and genomic polymorphisms in protein-coding regions. This trade-off between genome evolution and transcriptome plasticity highlights the importance of RNA recoding as a strategy for diversifying proteins, particularly those associated with neural function.