Mutational rescue of the activity of high-fidelity Cas9 enzymes

Programmable DNA endonucleases derived from bacterial genetic defence systems, exemplified by CRISPR-Cas9, have made it significantly easier to perform genomic modifications in living cells. However, unprogrammed, off-target modifications can have serious consequences, as they often disrupt the function or regulation of non-targeted genes and compromise the safety of therapeutic gene editing applications. High-fidelity mutants of Cas9 have been established to enable more accurate gene editing but these are typically less efficient. Here, we merge the strengths of high fidelity Cas9 and hyperactive Cas9 variants to provide an enzyme, which we dub HyperDriveCas9, that yields the desirable properties of both parents. HyperDriveCas9 functions efficiently in mammalian cells and introduces insertion and deletion mutations into targeted genomic regions, while maintaining a favourable off-target profile. HyperDriveCas9 offers a precise and efficient tool for gene editing applications in science and medicine.