A system for editing genes has now been used to repair disease-related mutations in mice and human stem cells, highlighting the technology's therapeutic potential.

The recently developed CRISPR system uses an RNA strand matching a target gene to guide a bacterial enzyme, Cas9, to excise the gene. Jinsong Li and his colleagues at the Shanghai Institutes for Biological Sciences in China used the technique in fertilized mouse eggs to correct the mutated Crygc gene, which causes cataracts. The mice grew into healthy adults that bore normal offspring.

In a separate paper, Hans Clevers at the Hubrecht Institute in Utrecht, the Netherlands, and his team repaired the cystic fibrosis gene, CFTR, in cultured intestinal stem cells obtained from patients with the disease.

Cell Stem Cell 13, 653–658; 659–662 (2013)