A team of researchers from Harvard University and the Howard Hughes Medical Institute created a new gene-editing technique that improves upon CRISPR/Cas9 and allows scientists to edit the single letters of DNA, a breakthrough that will help in the prevention of disease in the future.
Despite the revolutionary nature of the CRISPR/Cas9 system, the fact that it cuts both strands of DNA increases error and makes results less than optimal. Furthermore, it does not allow researchers to alter single DNA letters, where point mutations occur.
CRISPR/Cas9 works by using the Cas9 enzyme to target a specific spot on the genome and, when identified, cut both strands and allow researchers to insert DNA information and make changes to the genome. However, snipping causes cell reactions and can lead to unwanted genome alteration.
In order to develop the new technique, the team disabled the Cas9 enzyme so that when it pinpoints the desired spot on the genome, it does not snip the DNA. Instead, it uses another enzyme that it carries with it to edit one DNA letter to another.
When used on isolated DNA, the new technique has been successful 44 percent of the time, a big improvement over the standard CRISPR/Cas9 gene-editing technique. The group was also able to integrate a different protein into the bundle that has the ability to remove U bases, bumping the success rate up to 75 percent when used in mouse cells linked with Alzheimer's disease.
The new technique is just one in numerous studies that are aiming to replace the Cas9 enzyme in order to increase the effectiveness of the CRISPR method. For example, some are replacing the enzyme with another called Cpf1, which is reported to have the ability to cut both RNA and DNA, as well as change shape while bound to guide RNA.
Both the current study and others looking at the potential of Cpf1 show the potential of the CRISPR system with a modified or deactivated Cas9 enzyme and the benefits not only for targeting single letters of the DNA sequence, but for increasing options for gene-editing.
The findings were published in the April 20 issue of Nature.
