This week, a team of Chinese researchers used a gene editing technique to try to modify several human embryos. The results have raised concern among many in the scientific community, including those who developed the technique.
The gene-editing technique, called CRISPR-Cas9, allows scientists to add or remove genetic material, which has significant implications for a variety of health problems. As TIME recently reported in the TIME 100 issue, CRISPR could, in theory, edit any human gene.
However, as science writer Carl Zimmer writes in National Geographic, scientists including those who developed the technology have publicly said it should not yet be used for any human engineering and that it’s not ready for clinical use. Researchers at Sun Yat-sen University recently tested the technique on human embryos (notably, embryos that would not have ever grown into a human). Zimmer writes:
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All told, the researchers injected 86 embryos, 71 of which survived long enough for them to study. CRISPR only managed to cut DNA in a fraction of the embryos, and in only a fraction of those embryos did cells manage to take up the new version of the target gene (called beta-globin).
The experiment “came out poorly,” Zimmer says; in some cases, DNA was placed in the wrong spot and “off-target” mutations were discovered in the DNA. As Zimmer reports, scientists behind the CRISPR technique are arguing it was not ready for use. Jennifer Doudna, one of the creators of CRISPR, told Zimmer: “Although it has attracted a lot of attention, the study simply underscores the point that the technology is not ready for clinical application in the human germline. And that application of the technology needs to be on hold pending a broader societal discussion of the scientific and ethical issues surrounding such use.”
Read more of Zimmer’s coverage of the new study at National Geographic.