Groundbreaking study demonstrates promise and controversy of gene editing in embryos

— -- In a groundbreaking experiment, an international team of scientists on Wednesday officially reported the successful elimination of a genetic disease from human embryos.

It’s potentially a huge step for medicine -- but also a controversial one. While these embryos, which a team led by researchers at the Oregon Health and Science University edited using a novel gene-editing procedure known as CRISPR-Cas9, were destroyed rather than implanted into a womb, some say this type of genetic manipulation opens the door to other possibilities in human engineering.

Below are answers to some of the common questions about this research.

What did this experiment show?

In short, this experiment showed that it is potentially possible to correct a genetic disease in an embryo with a high chance of success. In order to show this, the researchers created human embryos designed to have a specific genetic mutation responsible for a type of heart disease known as hypertrophic cardiomyopathy. This genetic disease, which occurs in one out of 500 people, can cause sudden death, as well as a host of other cardiac problems such as heart failure and arrhythmias.

Using a technique known as CRISPR-Cas9, the scientists were able to target the faulty genes as the cells in the embryo divided -- swapping them out for a properly functioning form of the gene. What was novel about this study is that researchers were able to nudge the embryo to use its own native machinery to perform the repair with a high degree of efficiency using a correct form of the gene already present in the cell. In this particular experiment, the researchers used CRISPR-Cas9 on 58 embryos containing the mutation. After the procedure, they found that the mutation was corrected in 42 embryos -- a success rate of 72 percent.

Why is this important?

If a feat similar to that seen in this experiment could be achieved in an afflicted embryo that was allowed to develop into a person, it would prevent the condition in this individual -- and it would also prevent their future sons and daughters from inheriting this condition as well.

Moreover, there are thousands of genetic diseases, ranging from cystic fibrosis to sickle cell anemia, for which such a procedure could be relevant. Tests currently exist to diagnose many diseases prior to birth; however, at this time there is no therapy in use that actually alters the DNA of embryos prior to birth. Of course, the use of such a technique would inevitably raise the prospect of exerting all kinds of control over human reproduction -- as well as a host of new ethical questions.

Is such gene editing likely to become reality?

It’s not likely, at least for now. Currently, the U.S. Food and Drug Administration is barred from reviewing investigational medical studies involving editing of human embryos -- something which would be required in order to proceed with moving this research into practice. Additionally, the National Institutes of Health, which is an important source of science research funding in the United States, will not financially support research on gene editing of embryos. The research in this study was not supported by funding from the National Institutes of Health.

So what lies ahead for human embryo editing research?

Right now, it is unclear. Importantly, even though this experiment was considered to be successful, it is not known how this method would perform in other cases -- for example, a case in which both copies of the gene were mutated rather than just one, which was the case in this experiment. Also, since the scientists destroyed these embryos at a very early stage of development, it is not possible to tell for sure how viable these embryos would actually have been in the long run, or whether there would have been any unforeseen complications with their development.

But along with these scientific questions are also big ethical questions -- ones that will only be answered as scientists, ethicists and the public reflect further on this groundbreaking step.

Will Garneau, M.D., is an internal medicine resident at the Johns Hopkins Hospital.