A great deal of the excitement around gene-editing practices, specifically the CRISPR-Cas9 technology, focuses on the skill of inserting or removing genes or repairing disease-causing mutations. A big worry of the CRISPR-Cas9 approach, in which the double-stranded DNA molecule is cut, is the cell’s response to that cut and how it is repaired. With some frequency, this method leaves new mutations in its wake with unclear side effects.
A paper which appeared in the journal Cell on 7th December stated that scientists at the Salk Institute report a modified CRISPR-Cas9 system which changes the activity, rather than the underlying sequence, of disease-associated genes. The researchers prove that this system can be used in to treat various diseases in mice.
The main idea behind the Salk technique is the use of two adeno-associated viruses (AAVs) as the machinery to introduce their genetic manipulation machinery to cells in post-natal mice. The researchers injected the gene for the Cas9 enzyme into one AAV virus. They used another AAV virus to introduce a short single guide RNA (sgRNA), which stipulates the exact location in the mouse genome where Cas9 will bind, and a transcriptional activator. The shorter sgRNA is only 14 or 15 nucleotides in comparison with the standard 20 nucleotides used in majority of CRISPR-Cas9 techniques, and this stops Cas9 from cutting the DNA.
The complex lies in the DNA region of interest and fosters expression of a gene of interest. Similar practices could be used to activate virtually any gene or genetic pathway while removing the risk of introducing potentially harmful mutations. Initial data suggest that the technique is secure and does not produce unwanted genetic mutations. Nevertheless, the researchers are hunting for further studies to guarantee safety, practicality, and productivity prior to considering bringing it to a clinical environment.