Scientists at Oregon Health Sciences University, a member of America’s Essential Hospitals, for the first time have used a gene editing technique to remove disease from a human embryo.

Gene editing is used to correct disease-causing gene mutations in human embryos. OHSU researchers used a technique called CRISPR-Cas9, which involves removing the disease-causing section of a genome and replacing it with new segments of DNA by injecting as enzyme that acts as molecular-scale scissors.

OHSU scientists used this technique to extract a mutation that causes hypertrophic cardiomyopathy, a congenital heart disease that can lead to heart failure and death. It was the first time scientists have reported testing the method with clinical-quality human embryos.

This breakthrough not only removes disease from the embryo, but also removes their entire lineage moving forward. That provides opportunity to prevent certain genetic diseases in entire families and larger populations if the technique is perfected and brought to scale.

The project was successful in part because researchers were able to avoid mosaicism, a gene-editing problem in which not all cells are repaired and some continue to carry the mutation. OHSU scientists prevented mosaicism by introducing the Cas9 enzyme during fertilization, when the embryo can replace breaks in the disease-causing gene with normal sections from a second source or parent.

Despite reaching this milestone, researchers say there is a long way to go before implementing the technique in clinical practice. To ensure safety, researchers must employ methods to avoid unintended outcomes, like subsequent mutations in other parts of the genome.

Researchers in this field seems to agree that further research is needed to fully understand the method’s potential and implications, and there are ethical debates in the field about when the practice is appropriate. Several groups, including the American Society of Human Genetics, caution that this gene-editing technique should be used to correct genetic mutations only in babies that already are born or in utero, rather than using it before implantation.