Genome Editing: Reducing Off-Target Mutations in DNA
Published:10 Dec.2023 Source:Osaka University
In a new study, researchers led by Osaka University introduced a novel technique called NICER, which is based on the creation of multiple small cuts in single DNA strands by an enzyme called a nickase. Traditional CRISPR/Cas9 editing uses small pieces of genetic code called guide RNAs and an enzyme called Cas9. The guide RNAs target a specific section of the DNA and the Cas9 enzyme initiates a break in the double-stranded DNA structure at this location. This double-strand break is key for initiating changes to the DNA. However, cellular repair of double-strand breaks can lead to unintended DNA mutations, as well as the integration of exogenous DNA to the human genome, which raises safety concerns for clinical applications of CRISPR/Cas9 technology.
To minimize these unintended mutations, the Osaka University-led research team investigated the use of Cas9 nickase, which creates single-strand breaks or "nicks" in DNA that are typically repaired without causing mutations. Each chromosome in the genome has a 'homologous' copy, Using the NICER technique, heterozygous mutations -- in which a mutation appears in one chromosome but not its homologous copy -- are repaired using the unmutated homologous chromosome as a template.
Further genomic analysis showed that the NICER technique rarely induced off-target mutations, and researchers found that NICER was able to restore the expression of disease-causing genes in cells derived from genetic diseases involving compound heterozygous mutations. Because the NICER method does not involve DNA double-strand breaks or the use of exogenous DNA, this technique appears to be a safe alternative to conventional CRISPR/Cas9 methods.