By David Cyranoski
The meeting where He Jiankui explained his extraordinary claim to have helped produce the first babies — twin girls — born with edited genomes came to a close with a statement that came down hard on the scientist.
“We heard an unexpected and deeply disturbing claim that human embryos had been edited and implanted, resulting in a pregnancy and the birth of twins,” reads the statement released by the organizing committee of the Second International Summit on Human Genome Editing in Hong Kong on 29 November. “Even if the modifications are verified, the procedure was irresponsible and failed to conform with international norms.”
Similar criticism rained down since the revelation earlier this week that He had used the CRISPR–Cas9 to modify the CCR5 gene in two embryos, which he then implanted in a woman. The gene encodes a protein that many strains of HIV use to infect immune cells, in two embryos, which he then implanted in a woman.
As researchers take stock of the week’s events, Nature summarizes six big questions that are still unanswered.
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