Modified gene editing tool reduces unintentional mutations by 70%
Researchers have developed a CRISPR-based gene editing tool that is less likely to lead to unintended changes.Researchers at Rice University have modified CRISPR-based gene editing technology to reduce the number of unintended mutations. Separating the tool used to make point changes in the genome improves editing accuracy.
Point mutations, which involve changes to individual DNA base pairs, cause thousands of diseases. Traditional CRISPR technology uses either an adenine (ABE) or cytosine (CBE) editor to modify a single nucleotide. By targeting a specific stretch of DNA, the hybrid ABE protein dots a misplaced adenine with guanine, while the CBE protein replaces cytosine with thymine.
Researchers at Rice University split ABE into two separate proteins that remain inactive until a molecule of sirolimus (rapamycin) is added. This is a drug with antitumor and immunosuppressant properties that is used to prevent rejection in organ transplants and to treat certain types of cancer.
"Once this small molecule is administered, two separate inactive fragments of the adenine base editor are glued together and become active. As the body metabolizes rapamycin, the two fragments separate, deactivating the system," Hongzhi Zeng, co-author of the study.
CRISPR genetic editing technology has revolutionized medical research. But the classical method has a significant disadvantage, the study authors explain: the editor remains in the cell in an active state, which leads to a large number of unwanted mutations. Creating an activation and deactivation mechanism reduces the number of unplanned changes in the genome by 70% and increases the accuracy of editing.
The researchers tested their method by targeting the PCSK9 gene in the liver of mice. This gene produces a protein that regulates the amount of cholesterol in the bloodstream, so it has therapeutic value for humans. By packaging rapamycin-activated split ABE into an adeno-associated virus (AAV) vector, the researchers found that it converts one A͵T base pair into a G͵C base pair.
This conversion is useful because mutations in which G͵C mutates into an A͵T base pair account for nearly 50% of point mutations associated with human genetic diseases.