Oligonucleotides make for cleaner CRISPR


Researchers from the Christiana Care Health System have used short segments of synthetic single-stranded DNA, or oligonucleotides, to achieve a “cleaner ‘cut’” of the gene in CRISPR/Cas9.

“If you want to repair a genetic mutation, you can’t allow the DNA to be ripped apart when CRISPR makes a cut. You need it to remain intact to execute the repair, and that’s what the oligonucleotide enables us to do,” said Eric Kmiec, lead author of the study and director of the Gene Editing Institute at the Christiana Care Health System in Wilmington, DE, in a statement.

Kmiec likened CRISPR to cutting or tearing ribbons: “CRISPR can leave frayed ends in the DNA,” he said in the statement. “It’s as though you’ve tried to tear a ribbon in two. But for gene therapy you want a clean cut at a precise spot with minimal fraying, like cutting a ribbon with scissors, so that the ends can re-close.” The oligonucleotide holds the ends of the cuts together, like a bandage, he said.

In previous work, Kmiec noticed that using the oligonucleotide in CRISPR resulted in an edited gene that was “healthier and nearly intact.” He and his team then determined that the oligonucleotide was not merely helping to fix the mutation, but prevented the gene from tearing, according to the statement.

Back in June, a federal biosafety and ethics panel unanimously approved the first use of CRISPR/Cas9 in a human trial. Kmiec’s team plans to move on from lab model cells to human progenitor cells.