Researchers in New York have tested an improved gene-editing method on healthy human embryos donated for research. The study shows mixed success in making precise DNA changes while avoiding some unintended mutations.
Dieter Egli and colleagues at Columbia University used base editing on two-cell embryos. One targeted change succeeded in three-quarters of cells with no unwanted effects detected. The second change succeeded in only about half the cells and often produced off-target alterations. The team attributes the differences to guide RNA design and believes further optimization could reduce errors. However, the method did not edit every cell in any embryo, leaving a mosaicism issue unresolved. Mosaicism means some cells would carry the intended edit while others would not. This raises concerns that gene-edited children could still develop the conditions the edits aimed to prevent. The findings appear in a May 30 bioRxiv preprint. The researchers note that editing sperm or egg cells before fertilization might eventually address mosaicism, but that step has not yet been achieved in humans.
