Correction of a pathogenic gene mutation in human embryos
Genome editing could be applied to correct disease-causing mutations in human embryos, but concerns about efficacy and safety are paramount. Shoukhrat Mitalipov and colleagues use CRISPRCas9 to correct a heritable cardiomyopathy mutation in human embryos. By optimizing the experimental conditions, the authors show very reduced mosaicism, and report that for this heterozygous mutation, CRISPRCas9-induced breaks seem to be preferentially repaired using the wild-type allele as a template in human embryos. The results advance our understanding of the promises and challenges of editing the human germline.