By tweaking the structure of an enzyme that cuts DNA, researchers have lowered the error rate of CRISPR–Cas9 gene editing.

Feng Zhang at the Broad Institute of MIT and Harvard in Cambridge, Massachusetts, and his colleagues engineered the Cas9 enzyme so that it is less likely to act at DNA sites that are not targeted by the RNA molecules that guide the enzyme. The team generated several versions of Cas9 that reduced off-target errors by at least tenfold compared with unaltered Cas9 enzymes. Three of those versions were just as active at their target sites as ordinary Cas9.

Even so, the error rate may need to be reduced further for CRISPR gene editing to be used for human therapies.

Science http://doi.org/9q2 (2015)