Researchers at MIT have made a significant advancement in the field of gene therapy by discovering a method that substantially reduces errors during the gene editing process. By modifying the key proteins involved in editing, the team believes this innovative approach could enhance the safety and practicality of gene therapy for a myriad of diseases. According to Phillip Sharp, an Institute Professor Emeritus at MIT and a senior author of the study, this new method simplifies the delivery system while achieving more precise edits with minimal unintended mutations.
Using their refined technique, the MIT team dramatically decreased the error rate in prime editing from approximately one in seven edits to about one in 101 for the most common editing type. In a more precise editing mode, the error rate improved from one in 122 to one in 543. Robert Langer, a David H. Koch Institute Professor at MIT, emphasized that an effective drug should have minimal side effects. He believes that this new approach to genome editing will ultimately provide a safer and more effective solution for various diseases.
The journey of gene therapy began in the 1990s with the use of modified viruses to insert new genes into cells. However, these early efforts faced challenges. Subsequent techniques using enzymes like zinc finger nucleases allowed for direct gene repair, but they were often slow and cumbersome. The introduction of the CRISPR system revolutionized gene editing, utilizing an enzyme called Cas9 to cut DNA at specific locations, making the process faster and more adaptable.
In 2019, scientists at the Broad Institute of MIT and Harvard unveiled prime editing, an even more precise version of CRISPR that minimizes unintended effects on the genome. This technology has shown promise in treating rare disorders like chronic granulomatous disease (CGD) by directly correcting small mutations in cells and tissues, potentially addressing hundreds of genetic diseases.
One of the standout features of prime editing is its ability to avoid double-stranded cuts in DNA. Instead, it employs a modified version of Cas9 that creates a single-strand cut, allowing for the insertion of a new sequence. The guide RNA delivered alongside the prime editor acts as a template for this new sequence. This gentler approach reduces the risk of unintended errors, although some mistakes can still occur, potentially leading to serious health issues.
To address the issue of errors, the MIT team leveraged insights from a 2023 study. They discovered that certain mutated versions of Cas9 show a tendency to cut DNA at varied locations, which can destabilize the old DNA strands, making it easier for new strands to be integrated without errors. By identifying these mutations, the researchers were able to reduce the error rate to 1/20th of its original value. Further modifications combined pairs of these mutations, resulting in an even lower error rate of 1/36th.
To enhance accuracy further, the researchers incorporated their new Cas9 proteins into a prime editing system that includes an RNA binding protein, which stabilizes the RNA template ends more effectively. The final version of their editor, referred to as vPE, achieved an impressive error rate of just 1/60th of the original, ranging from one in 101 to one in 543 edits, depending on the editing mode. These promising results were validated in both mouse and human cells.
The MIT team is actively working on improving the efficiency of prime editors through additional modifications of Cas9 and the RNA template. They are also focused on developing effective delivery methods for these editors to specific tissues, a persistent challenge in gene therapy. The researchers hope that their innovative prime editing approach will inspire other laboratories to integrate these techniques into their research, further exploring the applications of genome editing.
As prime editors continue to be utilized in various research contexts, including studies on tissue development, cancer evolution, and cellular responses to drug treatment, the therapeutic potential of this technology is becoming increasingly exciting. Research scientist Vikash Chauhan, who led the study, expresses enthusiasm about seeing how the scientific community will adopt their editors into ongoing research workflows.
This groundbreaking research was funded by several prestigious organizations, including the Life Sciences Research Foundation, the National Institute of Biomedical Imaging and Bioengineering, the National Cancer Institute, and the Koch Institute Support Grant from the National Cancer Institute.
