On Aug 2, Nature published a study in which US-based researchers successfully edited the genome of a human embryo using the CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9) system to correct a genetic defect implicated in a potentially fatal heart condition. Although this is not the first time CRISPR has been used for genome editing in embryos, the introduction of the editing molecules at an earlier stage led to a much higher targeting efficiency than that in previous studies (72% vs 14–25%). The researchers also managed to avoid mosaicism, in which some cells in the embryo have the corrected version of the gene but others still have the mutation.
The work has raised hopes for new treatments based on genome editing, as well as fears over so-called designer babies. But both are still a long way off. Read more in The Lancet Child & Adolescent Health.