A new genome engineering method called prime assembly has been described in a study published in the journal Nature. This technique allows for the insertion of long DNA fragments into specific, programmable locations within living cells. Such precision could lead to the development of universal gene therapies—treatments that could be applicable to many patients with genetic disorders. Prime assembly builds on prime editing, a technology that enables precise, small modifications to DNA, such as insertions, deletions, or changes to individual bases. However, for diseases involving multiple mutations, current methods often require several separate edits. Prime assembly, on the other hand, could correct multiple mutations with a single, targeted approach. The method uses prime editing to insert short DNA "flaps" into specific positions in the genome. These flaps act like hooks that can bind to DNA fragments with matching ends. The resulting DNA inserts—sometimes consisting of one or more full-sized genes—become permanent changes in the genome. Daniel Bauer, M.D., Ph.D., director of the Gene Therapy Program at Boston Children's Hospital and co-senior author of the study, explained that the method allows for precise control over where the DNA replacement begins and ends. Since prime assembly is based on the more precise prime editing technique, it is less likely to cause unintended changes in the genome compared to other gene-editing methods. One of the risks associated with gene editing is off-target effects, where changes occur in unintended parts of the genome. These can lead to harmful outcomes, including the activation of genes that might cause cancer. Prime assembly avoids this risk by using targeted insertion methods. Additionally, it does not rely on double-strand breaks in DNA or on double-strand donor DNA, both of which can be harmful and cause stress in cells. Unlike other gene-editing methods that primarily work on dividing cells—cells that are rare in the body and more prone to errors—prime assembly functions in nondividing cells, making it potentially more versatile for therapeutic use. The research team plans to further explore the molecular mechanisms that could make the prime assembly method even more efficient and precise. As they refine the technology, they hope it will have practical applications in clinical settings. The ability to correct multiple mutations at once could lead to broad solutions for treating genetic disorders. Bauer noted that the team is working on improving the delivery of prime assembly components to specific human cells within the body, such as hematopoietic stem cells used in blood disorder treatments. They are also exploring how prime assembly might be used to deliver genetic therapies that restore gene function for serious inherited diseases with few existing treatments.