Gene-edit precision increased
US researchers claim to have developed a new gene editing technique more accurate than CRISPR.
The technique is called ‘prime editing’, and it is touted to be more precise and create fewer off-target byproducts compared to CRISPR–Cas9.
The new method avoids double-stranded DNA breaks, and in principle could correct around 89 per cent of known human genetic variants associated with diseases.
Despite exciting recent advances, the majority of the approximately 75,000 know pathologic human genetic variants cannot be corrected efficiently.
One of the difficulties with the current CRISPR/Cas9 gene-editing technology is that to work effectively a double-stranded DNA break has to be made in the cell’s DNA. This can have undesired consequences and often leads to the majority of cells containing slightly incorrect gene-edits.
The 'prime editing' approach is a CRISPR/Cas9-based tool that has been carefully engineered to eliminate the need for creating a double-stranded DNA break. As a result, precise editing efficiency is greatly increased.
In addition, other engineered improvements result in dramatically reduced off-target effects and, importantly, include the ability to make a wide range of gene-edits.
The research team from both Harvard and MIT say their new editing technology directly enables targeted point mutations, precise insertions, precise deletions, and combinations thereof without requiring double-strand DNA breaks.
The authors combined the Cas9 enzyme with a second enzyme called a reverse transcriptase. The resulting molecular machine when paired with an engineered guide RNA can both search for a specified DNA site and directly make the new genetic information containing the desired edit to replace the target DNA sequence.
They performed more than 175 edits in human cells, including correction of the primary genetic causes of sickle cell disease and Tay Sachs disease, and report that the technique is more efficient, makes fewer byproducts, and has lower off-target editing than traditional Cas9 editing.
A paper on the new development is accessible here.