Researchers at Osaka University have introduced a novel gene editing technique called NICER (Nicking-Induced Co-conversion with Error-Prone DNA Repair), which reduces unintended mutations associated with gene editing. While CRISPR/Cas9 has revolutionized gene editing, it can sometimes lead to unintended genetic mutations.
NICER addresses this issue by using an enzyme called a nickase to create single-strand breaks or "nicks" in DNA, which are typically repaired without causing mutations. This technique is particularly effective in repairing heterozygous mutations, where a mutation appears in one chromosome but not its homologous copy, by using the unmutated chromosome as a template.
The study, published in Nature Communications, demonstrates that NICER can restore the expression of disease-causing genes in cells derived from genetic diseases involving compound heterozygous mutations. Unlike CRISPR/Cas9, NICER doesn't involve double-strand breaks or exogenous DNA, making it a safer alternative for treating genetic diseases caused by heterozygous mutations, potentially ushering in a new era of precise gene editing with fewer unintended consequences.
Lead author of the study, Akiko Tomita, explains that "each chromosome in the genome has a 'homologous' copy." NICER utilizes this feature by repairing heterozygous mutations with the unmutated homologous chromosome as a template. Initial experiments involved human lymphoblast cells with a known heterozygous mutation in a gene called TK1. When these cells were treated with nickase to induce a single cut in the TK1 region, TK1 activity was recovered at a low rate. However, when the nickase induced multiple nicks in this region on both homologous chromosomes, gene correction efficiency was enhanced approximately seventeen-fold via activation of a cellular repair mechanism.
According to senior author Shinichiro Nakada, "Further genomic analysis showed that the NICER technique rarely induced off-target mutations." This level of precision addresses a critical concern in gene editing. Moreover, since NICER does not involve DNA double-strand breaks or the use of exogenous DNA, it presents a safer alternative to conventional CRISPR/Cas9 methods. NICER holds great promise as a novel approach for treating genetic diseases caused by heterozygous mutations, potentially advancing the field of gene therapy and opening new doors for more precise and safer gene editing technologies.