In late July, news broke that an international team led by scientists at the Oregon Health and Science University had successfully used the genome editing tool CRISPR to modify a gene in human embryos. This was not the first example of CRISPR being applied to viable human embryos – in April this year a Chinese research group reported they had edited embryos to become resistant to HIV (in both cases, the embryos were only allowed to grow for a few days and were not intended for implantation). However, it was the first time the technique was used to “correct” a disease-causing genetic variant in viable embryos – in this case, one that causes hypertrophic cardiomyopathy, a major cause of sudden death in young athletes. This current experiment also seems to be more successful than previous attempts, in terms of the number of embryos edited, the percentage of embryos where all of the cells received the modification (rather than being “mosaics” where only some of the cells within the embryo were modified), as well as the apparently low amount of “off-target” changes that were made. Moreover, the study’s results seem to hint at a previously unknown mechanism by which fertilized eggs repair their genomes.

Even though the current study is widely regarded as technically impressive, there is still a long way to go before the procedure is safe and effective enough for use in the clinic (in addition to policy changes that will be required if such applications were to occur in the US, Canada and much of Europe). A recent analysis also suggests that, due to naturally occurring small differences in DNA sequence within the human population, it might be harder to make precise edits to our genomes than previously thought.

Many scientists are also quick to point out that this new study doesn’t mean that “designer babies” will be a reality anytime soon. However, they acknowledge that it is now more important than ever for society to discuss the ethical implications of being able to make genetic modifications to our offspring, and balance them with the potential health benefits. pgEd will continue to engage all communities in these conversations.

Pam Belluck, “In Breakthrough, Scientists Edit a Dangerous Mutation From Genes in Human Embryos” (New York Times)

Heidi Ledford, “CRISPR fixes disease gene in viable human embryos” (Nature)

Ed Yong, “The Designer Baby Era Is Not Upon Us” (The Atlantic)