Six months ago, Chinese researchers reported that an enzyme called NgAgo could be used to edit mammalian genes – and that it might be more accurate and more versatile than the popular CRISPR-Cas9 gene-editing technique. But almost immediately, other scientists complained on internet forums that they could not replicate the experiment. Now, a paper with 20 authors, published in Protein & Cell, lists multiple attempts that failed to replicate the original experiment – while another, published in Cell Research, suggests that NgAgo may only block, but not edit, genes when it is injected into zebrafish (Danio rerio) embryos. The debacle has raised questions about a 224-million yuan (US$32-million) gene-editing centre that Hebei University of Science and Technology announced that it would build, to be paid for with local government money.

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