Researchers say CRISPR edits to a human embryo worked. But critics still doubt it

Reports that a heart disease–causing version of a gene had been corrected remain contested

human embryos

ALTERED OR NOT?  These human embryos were edited with CRISPR/Cas9 to repair a gene that can cause heart failure. A follow-up study claims to confirm the result, but other scientists contend the embryos might not have been fixed.

Salk Institute

When researchers announced last year that they had edited human embryos to repair a damaged gene that can lead to heart failure, critics called the report into question.