In a newly published study, a research team from Leipzig's Max Planck Institute for Evolutionary Anthropology describes improvements in the methods by which mutations can be introduced into human and other genomes. These make the methods much more efficient and less error-prone.
When editing genomes, researchers often want to place a letter (the DNA bases Adenim, Guanine, Cytosine and Thymin) with another one. To do this, they use reagents that cut the two strands of DNA near the site to be changed. They then add DNA molecules containing the desired new letter to the cell in the hope that the cell's repair systems will use them to incorporate the desired mutation as they repair the DNA break. However, since different repair systems in cells compete with each other and only one of them is able to introduce the desired new mutation, applications of precision genome editing have been limited by low efficiency and unintended byproducts.
Through the combined inhibition of two repair pathways that compete with the desired pathway, the team has now succeeded in inducing intended point mutations in up to 93 percent of cell population chromosomes. Importantly, this method largely prevents unwanted DNA sequence changes in the area of the desired mutation, as well as unintended changes elsewhere in the genome. This greatly increases the precision and reliability of DNA editing.
Effects of mutations
The researchers demonstrated the efficiency of the new method in the laboratory by changing 58 different target sites in human cells. The method should find diverse applications in basic research. "With this method, we can more easily introduce genetic changes into cells and thus study the effects of mutations that distinguish modern humans from Neanderthals," says Svante Pääbo, who was involved in the study.
The scientists also corrected disease-causing mutations in cells derived from patients suffering from the genetic diseases anemia, sickle cell anemia or thrombophilia. “The potential for treating human disease is enormous. One could imagine taking cells from patients, treating them with this method and then giving them back to the patients,” says Stephan Riesenberg, who led the study. "However, there is still a long way to go from proving that the method works in the laboratory to application in patients," emphasizes Riesenberg.
Efficient high-precision homology-directed repair-dependent genome editing by HDRobust
Nature Methods, July 20, 2023, DOI: 10.1038/s41592-023-01949-1