Normal eight-cell human embryoWIKIMEDIA, RWJMS IVF PROGRAMJust more than a month after MIT Technology Review reported on the imminent publication of a paper in which researchers describe editing human embryos using the CRISPR/Cas9 system, investigators from Sun Yat-sen University in Guangzhou, China, report their work editing human tripronuclear zygotes—nonviable early embryos that had one egg nucleus and two sperm nuclei—in an April 18 Protein & Cell article. The Sun Yat-sen team used CRISPR/Cas9 to cleave the endogenous β-globin gene, which is mutated in patients with the blood disorder β thalassemia, but observed some off-target effects.
Study coauthor Junjiu Huang told Nature that he and his colleagues were surprised by the number of off-target effects they observed, including some in remote locations in the genome. If the system were to be applied to edit the genome in normal embryos, “you need to be close to 100%” on target, Huang told Nature, adding: “That’s why we stopped. We still think [the technology is] too immature.”
“I believe this is the first report of CRISPR/Cas9 applied to human pre-implantation embryos and as such the study is a landmark, as well as a cautionary tale,” stem-cell researcher George Daley of Harvard Medical School told Nature. “Their study should be a stern warning to any practitioner who thinks the technology is ready for testing to ...
