It’s not hyperbolic to say that the CRISPR-Cas9 gene-editing technique has been a revolutionary breakthrough, allowing scientists the ability to quickly, easily and precisely edit sections of DNA. But questions over how precise the CRISPR tool is have been raised in a new study from Columbia University Medical Center, which shows this gene-editing technology can introduce hundreds of unintended mutations into the genome.
CRISPR has sparked a flurry of new avenues of research around the world, from targeting cancer to HIV, with the first human trials involving CRISPR-edited cells already underway in China and a US trial slated for 2018. But this new study urges caution moving forward, suggesting we are still yet to understand the greater genomic effects of the tool.
The team of scientists involved in the study had previously been working with the CRISPR tool to treat a serious eye disease called retinitis pigmentosa, which leads to blindness. They decided to examine the entire genome of the CRISPR-treated mice from their previous experiments, looking for any potential mutations, even those that altered just a single nucleotide.
Generally, when scientists are trying to identify whether a CRISPR edit has resulted in an off-target mutation or deletion they use computer algorithms to identify areas most likely to be affected and focus their attention on those.
“These predictive algorithms seem to do a good job when CRISPR is performed in cells or tissues in a dish,” says co-author of the study, Professor Alexander Bassuk, “but whole genome sequencing has not been employed to look for all off-target effects in living animals.”
In examining the entire genome from the CRISPR-treated mice, they found that the tool had successfully corrected the specific gene they were targeting, but it also potentially caused a great deal of other genetic changes. In two CRISPR-treated animals, more than 100 large gene deletions or insertions and over 1,500 single-nucleotide mutations were identified.