RNA Editing
Many people have heard about the technology of genome editing with CRISPR/Cas9 molecular scissors. As you know, it allows you to remove and replace sections of DNA that are responsible for the development of certain genetic diseases. But in some cases, there is a need to change not only the genes in DNA, but also in its working copy – RNA.
Researchers from the Salk Institute for Biological Studies (USA) have modified genetic scissors, giving them the ability to edit RNA. This made it possible to correct the imbalance of proteins in the brain cells of patients suffering from dementia.
The CRISPR/CasRx system, aimed at RNA, opens up a huge potential for genetic engineering of proteins, gives researchers a powerful tool for developing new methods of gene therapy, as well as studying biological processes.
CasRx enzyme (purple) in the nuclei of human cells (gray).
RNA health plays an important role in maintaining the balance of proteins in cells. The sequence of nitrogenous bases in the composition of RNA, changing in the process of alternative splicing, leads to the synthesis of the necessary proteins. The problem is that disruptions in the connection of a disconnected chain of nucleotides sometimes leads to serious consequences: spinal muscular atrophy, atypical pulmonary fibrosis or frontotemporal dementia may develop. The development of technologies that allow RNA editing will allow to cure these diseases.
CRISPR is a special region of the bacterial genome containing DNA fragments. The Cas9 enzyme cleaves DNA at the place indicated by the RNA. This is how the DNA editing system works.
To create RNA scissors, scientists searched for a new enzyme that would dissect the RNA strand in the same way Cas9 does with DNA. A special program was developed that made it possible to identify a group of Cas13d enzymes targeted at RNA. The most suitable protein from this family turned out to be CasRx, which was obtained from the intestinal bacterium Ruminococcus flavefaciens strain XPD3002.
The CRISPR/CasRx system was tested on a cellular model of frontotemporal dementia, a neurodegenerative disease in which two types of pathological tau protein accumulate. The researchers genetically "targeted" CasRx to an RNA site involved in the synthesis of tau proteins. To do this, CasRx was packaged in a virus shell. The effectiveness of treatment was 80%, the level of pathological protein decreased sharply.
Compared to other RNA editing methods, CRISPR/CasRx has a number of advantages. Firstly, these are small sizes that allow the use of viral vectors for delivery to the core. Secondly, CRISPR/CasRx has high efficiency. And finally, there are almost no undesirable effects in the form of exposure to non-target RNA sites.
The authors write about the huge potential of the described technique in the fight against diseases associated with impaired protein synthesis. In their opinion, CRISPR/CasRx is a rich and yet unexplored resource for creating new technologies.
Article by S. Konermann et al. Transcriptome engineering with RNA-targeting Type VI-D CRISPR effects is published in the journal Cell.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Salk News: CRISPR genetic editing takes another big step forward, targeting RNA.