Biologists have proposed a new method of gene therapy: "gentle" CRISPR

The researchers used an editing technique based on the enzyme nikase.

the difference from Cas9 "cuts" only one of the two strands of DNA.The treatment method uses a natural mechanism to repair these molecules.

Researchers explain that in many cases,people with genetic disorders have different mutations in their chromosomes inherited from their parents. This means that often a mutation on one chromosome will have a "healthy" functional sequence counterpart on another chromosome.

By destroying one of the strands of DNA that contains a harmful mutation, scientists trigger a repair mechanism that uses the “healthy” part inherited from the second parent as a basis.

Scheme of the experiment.Left: Editing with Cas9 may result in recovery, but may cause mutations. Right: The use of nickase leads to more efficient gene correction and the absence of mutagenic phenomena. Source: Guichard, Bier, UC San Diego

To test the effectiveness of your technology,the researchers used Drosophila. Normally, these fruit flies have bright red eyes. Scientists using gene editing suppressed the production of red pigment and created mutants with white eyes. Then, in a series of experiments, the biologists tried to restore the original eye color using CRISPR.

The results showed that editing withnickase proved to be even more effective than classic Cas9. A single strand cut resulted in a high level of red eye recovery almost on par with normal (not mutated) healthy flies. Success in restoring the original gene variant was 50-70% for nickase, while 20-30% with Cas9 double-stranded cleavage. At the same time, unlike the classical approach, nickase did not cause off-target mutations.

A notable advantage of this approach is itssimplicity. It is based on a very small number of components, and DNA breaks are "gentle", unlike Cas9, which produces complete DNA breaks, often accompanied by mutations.

Ethan Beer, professor at UC San Diego and study co-author

The authors note that it is not yet known whetherthe technology also work well in human cells. They believe that more research is needed and some adjustment of the method to work with humans may be required.

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