Conventional gene-editing technologies, such as CRISPR Cas9, have been limited by the generation of DNA double-strand breaks, which introduce unwanted modifications into the genome. While the development of base editors has enabled the direct chemical modification of target DNA nucleotides, allowing researchers to avoid double-strand breaks, base editing technology has been limited by the number and precision of individual base modifications achievable. However, in a new study, the research team used a CRISPR-associated protein, Cas12, and guide RNAs (gRNAs). Fused with an enzyme, Cas12 can perform targeted chemical modifications on DNA at locations determined by the gRNA sequence. The team chose Cas12 for its innate ability to process an RNA template containing numerous gRNAs. To improve editing precision, the team modified the gRNAs by shortening the gRNA sequence or modifying the RNA bases. They then used the new system to successfully edit gene sequences with greater precision at 15 different sites in human cells, three times as many locations as previously designed. This improvement will not only enable the roots of complex genetic diseases, such as cancer, to be assessed, but will also guide the development of new synthetic drugs.
