Has CRISPR-Cas9 Met Its Match?

According to researchers from Cornell University, CRISPR-Cas3 can efficiently erase long stretches of DNA from a targeted site in the human genome, a capability not easily attainable in more traditional CRISPR-Cas9 systems.

"My lab spent the past ten years figuring out how CRISPR-Cas3 works. I am thrilled that my colleagues and I finally demonstrated its genome editing activity in human cells," said Ailong Ke, professor of molecular biology and genetics and a corresponding author of a paper published earlier this week in Molecular Cell. "Our tools can be made to target these viruses very specifically and then erase them very efficiently. In theory, it could provide a cure for these viral diseases."

The CRISPR-Cas3 technology also allows researchers to scan through the genome and detect non-coding genetic elements, and it could be used to efficiently screen for non-coding genetic elements and erase long sequences of DNA.

CRISPR-Cas9 systems use a bacterial RNA as a guide pairs with and recognizes a sequence of DNA. When a match is found, the guide RNA directs CRISPR-associated (Cas) proteins to that precise string of DNA. Once located, the Cas9 protein snips the target DNA at just the right place. CRISPR-Cas3 uses the same mechanism to locate a specific sequence of DNA, however, instead of snipping the DNA in half, its nuclease erases DNA continuously, for up to 100 kilobases.  The Cornell team successfully deleted sequences of up to 100 kilobases of targeted DNA in human embryonic stem cells as well as in HAP1.

While CRISPR-Cas3 holds the potential for a more impactful genome-editing tool than CRISPR-Cas9, the researchers are working to control how long a section they delete. "We can't quite define the deletion boundaries precisely, and that is a shortcoming when it comes to therapeutics," Ke said.