The article describes a new technique for genome editing that exploits a truly ancient immune mechanism found in about half of all bacteria (eg. e. coli) and members of archaea. This immune defense works by encoding templates that match viral DNA/RNA. The RNA produced by these templates then works together with a protein (Cas9) to bind to and destroy matching DNA. Interestingly, some of the segments of the destroyed DNA may be spliced back into the genome to form new templates — an adaptive, heritable immune defense.
To use this technique in genetic editing, scientists synthesize the RNA that guides the binding of the Cas9 protein to code for the spot in the genome that they want to cut. Once the genome is severed cleanly, the normal DNA repair mechanisms can be used to splice in the desired edits. A team from Shanghai used this technique to repair a single mutation that causes cataracts in mice. As described in the New Scientist article, experiments with this technique are already underway on human cells.