For all its well-earned fame, the gene-editing tool CRISPR is, in reality, pretty hard on the genome. It’s a pair of DNA scissors that cuts the double helix, and what’s called “editing” is actually a cell’s hasty attempt to patch things back together. That often introduces errors: critics have even called these unpredictable unintended changes a form of “genome vandalism.”
So researchers are searching for ways to make CRISPR live up to its reputation as a real search-and-replace function for genes. In the words of David Liu, a Harvard University biologist, the ultimate aspiration of genome engineers is “the ability to make virtually any targeted change in the genome of any living cell or organism.”
Today, in the latest—and possibly most important—of recent improvements to CRISPR technology, Liu is introducing “prime editing,” a molecular gadget he says can rewrite any type of genetic error without actually severing the DNA strand, as CRISPR does.
The new technology uses an engineered protein that, according to a report by Liu and 10 others today in the journal Nature, can transform any single DNA letter into any other, as well as add or delete longer stretches. In fact, Liu claims it’s capable of repairing any of the 75,000 known mutations that cause inherited disease in humans.
CRISPR 1.0 is harnessed most often to disable genes—making it useful for research and possibly in treating a subset of diseases where a DNA delete button is what’s called for. More extensive gene replacements are also possible with this tool but aren’t easy to control.