ChristianaCare’s Gene Editing Institute, located in Newark, Delaware, recently announced an innovation that could accelerate CRISPR gene editing work. CRISPR, which stands for “clustered regularly interspaced short palindromic repeats,” is a defense mechanism found in bacteria that can recognize and slice up the DNA of invading viruses. Scientists have learned how to modify this mechanism so it can be directed to “edit” specific sequences of DNA code, with the goal of repairing DNA mutations that cause debilitating diseases like sickle cell disease and cystic fibrosis. The technique has proven highly successful, but is not without some risk. Sometimes CRISPER subtly affects nearby portions of the genetic code unrelated to the disease and that can have unintended consequences. The ability to rapidly detect these minor changes represents an important advancement that promises to enhance patient safety.
According to Eric Kmiec, Ph.D., director of the Gene Editing Institute, the new process rapidly screens all edits made by CRISPR, and quickly reveals unintended and potentially harmful changes introduced by a gene editing process. What typically required up to two months of costly and complicated DNA analysis can be completed in just 48 hours. The process was described in a study published in Nature Research’s journal Communications Biology on December 6, 2019. Dr. Kmiec was a principal author, along with lead author Brett Sansbury and Amanda Hewes.
“We’ve developed a new process for rapidly screening all of the edits made by CRISPR, and it shows there may be many more unintended changes to DNA around the site of a CRISPR repair than previously thought,” Dr. Kmiec said. While most errant edits may be harmless, Dr. Kmiec added, insights are essential to gauge patient risk. He also cautioned that the unintended changes revealed by their work involve “subtle mutations” to DNA around the immediate site of the genome targeted for repair. That’s very different, he said, from the hotly debated concern about the risk of CRISPR causing “off-target” mutations by drifting far afield from the intended site and making random cuts across the genome.
Most tools for analyzing CRISPR gene edits are best suited for verifying that the repair was successful, not for revealing alterations that may occur to nearby strands of DNA. He said going further and screening for these unintended edits has required extracting and analyzing an enormous amount of DNA code from a cell, a sort of needle-in-a-haystack process that can take up to two months. Scientists at the Gene Editing Institute found a way around this problem by working with a system they have developed that performs gene edits on circular segments of DNA extracted from the cell, which are known as plasmids.
“It’s important to note that in all instances we were still seeing CRISPR achieve a fantastic level of successful repairs that would have been unimaginable even five years ago,” said Sansbury. “But we saw a lot of other changes to DNA near the site of the repair that need to be better understood so that when we correct one problem, we’re not creating another.”