Genetic information is predominantly found in the nucleus of eukaryotic cells, with mitochondria and plastids being exceptions. This information is naturally edited via a number of processes at the level of DNA or RNA. However, no matter the level of editing, it is always the same genetic information with a few modifications depending on the cellular need. Editing of DNA or RNA was thought to be exclusively restricted to being located in the nucleus of the cell.
In a recent study by Vallecillo-Viejo et al. (link to the paper is mentioned below (1)) it was discovered that members of Doryteuthis pealeiia, a species of squid are capable of editing their genome in both the nucleus and axon of their neurons. An RNA editing enzyme ADAR2 (Adenosine deaminase acting on RNA) is expressed outside the nucleus of their neurons.
This information takes a hard hit at the concept of central dogma where genetic information is consistently and loyally transferred from DNA to RNA and lastly to protein. Here we see a gap in communication between DNA and RNA as the edits made outside the nucleus are variable and may or may not be coded by the DNA itself.
A transcriptome-wide analysis conducted by Alon et al. (link to the paper is mentioned below (2)) showed that the number of times squids edit their mRNA is multiple folds higher than that of humans, with a majority of the editing sites located at axons. This phenomenon provides them with the ability to modify their neural proteins extensively to meet localized needs of the cell.
Wardill et al. (link to the paper is mentioned below (3)) showed that nerves in the squid epidermis contribute to its uncommonly wide spectrum of shimmering hues and the rate at which they change. In addition to this, squids have been found to exhibit complicated behavioral patterns in comparison to their invertebrate relatives.
Could these unusual sightings be linked to their extraordinary gene editing skills? Only further research will be able to answer that question.
Read more at:
1. http://dx.doi.org/10.1093/nar/gkaa172
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