MIT Study Shows New Way to Improve Prime Editing Accuracy

Researchers at MIT have developed a new approach to reduce errors in prime editing, a genome-editing technique with potential for treating numerous genetic diseases. The study, led by senior authors Phillip Sharp and Robert Langer and published in Nature, demonstrates how modified protein versions used in prime editors can dramatically lower the error rate, providing a more precise editing tool.

Prime editing transforms faulty genes by making targeted edits without requiring double-stranded DNA cuts, unlike older approaches. Instead, a modified Cas9 enzyme cuts just one DNA strand to create a flap where a new DNA sequence is inserted using a guide RNA template. However, the edited strand must compete with the original strand to be successfully incorporated, and when the old strand prevails, errors can arise. These mistakes, while often harmless, could sometimes lead to serious complications like tumor development.

In this study, the MIT team leveraged findings from a 2023 paper showing that certain mutated Cas9 proteins can cut DNA slightly off the usual position, destabilizing the original strand and facilitating replacement without error. By combining pairs of these mutations and improving the RNA template’s stability, they created a prime editor named vPE that lowered the error rate to just one in 101 edits for the standard mode and one in 543 for a high-precision mode. This represents a reduction to 1/60th of the original error rates, tested in both human and mouse cells.

“This paper outlines a new approach to doing gene editing that doesn’t complicate the delivery system and doesn’t add additional steps, but results in a much more precise edit with fewer unwanted mutations,” said Phillip Sharp. Robert Langer added, “For any drug, what you want is something that is effective, but with as few side effects as possible... I would think this would ultimately be a safer, better way of doing it.” 

Lead author Vikash Chauhan highlighted the technology’s broad potential: “In principle, this technology could eventually be used to address many hundreds of genetic diseases by correcting small mutations directly in cells and tissues.” 

The MIT team is continuing to refine prime editing efficiency and explore delivery methods for specific tissues. They hope other researchers will adopt this optimized system to study diverse biological questions, from tissue development to cancer evolution and drug response, expanding prime editing’s impact beyond therapeutics.