Abstract: In eukaryotic cells, with the exception of the specialized genomes of mitochondria and plastids, all genetic information is sequestered within the nucleus. This arrangement imposes constraints on how the information can be tailored for different cellular regions, particularly in cells with complex morphologies like neurons. Although messenger RNAs (mRNAs), and the proteins that they encode, can be differentially sorted between cellular regions, the information itself does not change. RNA editing by adenosine deamination can alter the genome’s blueprint by recoding mRNAs; however, this process too is thought to be restricted to the nucleus. In this work, we show that ADAR2 (adenosine deaminase that acts on RNA), an RNA editing enzyme, is expressed outside of the nucleus in squid neurons. Furthermore, purified axoplasm exhibits adenosine-to-inosine activity and can specifically edit adenosines in a known substrate. Finally, a transcriptome-wide analysis of RNA editing reveals that tens of thousands of editing sites (>70% of all sites) are edited more extensively in the squid giant axon than in its cell bodies. These results indicate that within a neuron RNA editing can recode genetic information in a region-specific manner.
Isabel C Vallecillo-Viejo, Noa Liscovitch-Brauer, Juan F Diaz Quiroz, Maria F Montiel-Gonzalez, Sonya E Nemes, Kavita J Rangan, Simon R Levinson, Eli Eisenberg, Joshua J C Rosenthal, Spatially regulated editing of genetic information within a neuron, Nucleic Acids Research, , gkaa172, https://doi.org/10.1093/nar/gkaa172
Stay tuned. It’ll probably get stranger. Sqid are unusual in many ways and some consider them a second genesis of intelligence:
Some think that this editing ability might have slowed down the octopus’s evolution (thought to have started about 100 million years ago) by random processes. That calls into question how much evolution is due to random processes anyway. As Evolution News & Science Today notes, “The implications for Darwin’s tree of life are clear. If animals are able to “defy genetics’ ‘central dogma’” (Phys.org) and take evolution into their own hands, no wonder the tree managers are scrambling.”
News, “Is the octopus a second genesis of intelligence?” at Mind Matters News
What kind of evolution is self-editing one’s genome?