For the first time in the United States, researchers have used gene editing to repair a mutation in human embryos.
Molecular scissors known as CRISPR/Cas9 corrected a gene defect that can lead to heart failure. The gene editor fixed the mutation in about 72 percent of tested embryos, researchers report August 2 in Nature. That repair rate is much higher than expected. Work with skin cells reprogrammed to mimic embryos had suggested the mutation would be repaired in fewer than 30 percent of cells.
In addition, the researchers discovered a technical advance that may limit the production of patchwork embryos that aren’t fully edited. That’s important if CRISPR/Cas9 will ever be used to prevent genetic diseases, says study coauthor Shoukhrat Mitalipov, a reproductive and developmental biologist at Oregon Health & Science University in Portland. If even one cell in an early embryo is unedited, “that’s going to screw up the whole process,” says Mitalipov. He worked with colleagues in Oregon, California, Korea and China to develop the embryo-editing methods.
Researchers in other countries have edited human embryos to learn more about early human development or to answer other basic research questions (SN: 4/15/17, p. 16). But Mitalipov and colleagues explicitly conducted the experiments to improve the safety and efficiency of gene editing for eventual clinical trials, which would involve implanting edited embryos into women’s uteruses to establish pregnancy.