Death, to put it mildly, is a rather inconvenient event for a living brain. The cascade of effects that arises as oxygen vanishes sweeps like a tide down to the very way our cells transcribe and translate our DNA, scrambling in a last-ditch attempt to keep the lights on. A comparison of post-mortem brain tissue and samples taken from living patients has revealed for the first time significant differences in the way strands of RNA are modified, exposing new potential targets for disease diagnosis and treatment.
The researchers from the Icahn School of Medicine at Mount Sinai in New York focused on the way specific base codes of adenosine (A) are swapped for a completely different base, inosine (I), in messenger RNA. This A-to-I base swap is accomplished by the adenosine deaminase acting on RNA (ADAR) family of enzymes, which play critical roles in shaping a range of different tissues, including those in the brain. The process is so critical that errors in the editing process can result in a variety of neurological disorders.
To turn the genes encoded by double-stranded helixes of DNA into functional proteins, biology has to copy their sequences into a subtly different format based instead on RNA. These ‘messengers’ can then be translated into proteins by other RNA structures that piggyback the amino acid building blocks. Like a rogue editor rewording manuscripts to serve entirely new purposes, cells can tweak a gene’s messenger RNA to meet entirely different needs. Some species, most notably types of cephalopod, take RNA editing to a whole new level, rewriting their brain’s own genetic instructions as the occasion calls for it.
To determine precisely how edits to specific transcribed genes develop into life-threatening conditions, researchers have traditionally analyzed specimens collected post-mortem. However, the study conducted by the team at Mount Sinai revealed major differences in the activity of ADAR enzymes in brain tissue obtained from living patients during surgical procedures. There were hundreds of sites where editing processes were more prolific in samples from living brains, highlighting the limitations of relying solely on post-mortem tissues for studying RNA editing.
The differences in RNA editing activity observed between samples from living individuals and post-mortem tissues suggest new potential targets for disease diagnosis and treatment. Understanding the mechanisms behind these differences could lead to insights into the development of neurological disorders and other conditions related to RNA editing in the brain. Further research is needed to elucidate the functions of the identified sites and their roles in brain plasticity.
The study conducted by researchers at Mount Sinai sheds light on the intricacies of RNA editing in the brain and its implications for disease diagnosis and treatment. By comparing samples from living individuals and post-mortem tissues, the researchers were able to uncover significant differences in RNA editing activity, providing valuable insights into the biological significance of A-to-I editing. This research opens up new avenues for further exploration and potential therapeutic interventions in the field of neurobiology and genetic medicine.
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