Mini Enzyme Moves Gene Editing Closer to the Clinic

A tweak to a technique that edits DNA with pinpoint precision has boosted its ability to correct defective genes in people. Called CRISPR, the method is already used in the lab to insert and remove genome defects in animal embryos. But the genetic instructions for the machinery on which CRISPR relies — a gene-editing enzyme called Cas9 and RNA molecules that guide it to its target — are simply too large to be efficiently ferried into most of the human body’s cells.

This week, researchers report a possible way around that obstacle: a Cas9 enzyme that is encoded by a gene about three-quarters the size of the one currently used. The finding, published on 1 April in Nature, could open the door to new treatments for a host of genetic maladies (F. A. Ran et al. Nature http://dx.doi.org/10.1038/nature14299; 2015).

“There are thousands of diseases in humans associated with specific genetic changes,” says David Liu, a chemical biologist at Harvard University in Cambridge, Massachusetts, who was not involved in the latest study. “A fairly large fraction of those...