For the past five years, CRISPR-Cas9 technology has revolutionized the field of gene editing due to its ease and low cost. But although this technology reliably finds and cuts the targeted stretch of DNA sequence, fixing that cut as desired has been something of a hit-or-miss process. Error rates as high as 50 percent are a particular problem when the goal is to correct typos in the DNA that cause genetic disease.
Now, a team of researchers led by Krishanu Saha, a professor of biomedical engineering at the University of Wisconsin–Madison, has made the fix less error-prone and published its approach today (Nov. 23, 2017) in the journal Nature Communications.
Compared to standard CRISPR technology, the new method improves the likelihood of rewriting the DNA sequence exactly as desired by a factor of 10. The researchers achieved this much greater precision by taking advantage of a molecular glue, called an RNA aptamer, to assemble and deliver a complete CRISPR repair kit to the site of the DNA cut.
“The kit provides not only the molecular scissors, but also the correct template for the cell machinery to fix the DNA cut with,” Saha says. “Since the RNA aptamer is strong and very stable, everything we need is getting to the right place within the cell in one fell swoop.”
In standard CRISPR technology, the bacterium-derived Cas9 protein (the scissors) and a guide RNA molecule (to locate the targeted DNA sequence) are delivered to the cell. When the scissors cut open the DNA molecule, the cell mends the gap with nearby DNA templates, but more faithful rewriting results from attaching the desired templates to the Cas9/RNA package with the molecular glue.