Researchers identify CRISPR/Cas9 "off-switch"

In a manuscript published in Cell, researchers identified three families of naturally-occurring protein inhibitors of CRISPR/Cas9 gene editing, which they said could be used for spatial, temporal or conditional control of Cas9 activity. The scientists said the anti-CRISPR proteins could have applications in tissue-specific or developmental stage-specific gene editing.

Scientists at the University of Toronto and University of Massachusetts Medical School used genomic searches to identify regions near mobile genetic elements -- left in bacterial genomes by bacteriophages -- that share a genomic localization across bacterial species with genes known to inhibit type I CRISPR systems, which do not use Cas9. Cloning of candidate sequences yielded proteins that bound directly to the Cas9 protein of Neisseria meningitidis and completely inhibited gene editing in human embryonic kidney cells, with no signs of cellular toxicity...