Gene Editing

Ten years ago, a paper was published, describing a revolutionary discovery that since had a profound impact on many aspects of science and medicine. Eight years later, the two women behind this discovery won a Noble prize in chemistry. They, and others, found a way to use a biological phenomenon called CRISPR to edit DNA in ways that are safer, more precise, and less expensive than in the past. If you think of DNA as a language, CRISPR – much like a word processor – allows to make edits at the level of a specific letter.

Editing DNA allows us to modify the genetic basis of many traits in plants, animals, and humans. When we consider that many diseases are caused by ‘mistakes’ (or a ‘typos’) in our DNA, we can instantly see why this technology has enormous medical potential. Imagine a world in which thousands of currently incurable genetic diseases, some caused by one single mistake (mutation), can be cured by an injection that ‘corrects’ them. Clinical trials that attempt to do just that are currently underway worldwide, giving thousands of families new hope.

Now, imagine that instead of curing an already sick patient, you could prevent the disease altogether by correcting the mistake before the patient was born! This is feasible if we consider that we could edit the DNA in sperm, eggs, and embryos. In-Vitro Fertilization (IVF), a 44-year-old technology that is considered by now safe and socially acceptable, gives us access to embryos at an early stage, when they consist of just a few identical cells. If we correct the genetic mistake in those few cells, the correction will be present in all the cell of the body later on. The fetus that would then develop, and the child that could potentially result, would be completely free of the genetic disease we targeted and would require no additional treatment or intervention.

This obviously raises great hopes, but alas also deep concerns. Since we would be modifying all the cells in the body of this potential person, we would also be introducing the change into reproductive cells (also called ‘germ’ cells): into the sperm if it is a male and the egg if it is a female. This means that if this person has children, the change we made would pass on to them as well, and to all the subsequent generations they might conceive.

If we succeed, the reward is enormous: we eradicate genetic disease for generations to come. But if we fail and cause harm, it would be suffered not just by one person (as in the case of using CRISPR to treat one patient), but rather - if we consider the impact on an evolutionary scale - by potentially millions. The damage we could do by misusing this technology is therefore unprecedented.

Therefore, since the discovery of CRISPR, ethicists and regulators have been developing guidelines to address these concerns. While most endorse clinical trials that use CRISPR on the cells of the body (called ‘somatic’ cells), most have argued that using this technology on germ cells or embryos is too risky.

Recently, however, some argue that as our understanding of CRISPR grows, there will come a time when we should try to edit germ cells cautiously and responsibly, if we at first limit our efforts and only target ‘serious’ genetic disease. This raises the complex question of how we should understand what ‘serious’ means.

Should we only target genes that cause a disease that is incurable? Fatal? Appears at a young age? Extremely expensive to treat? These questions are now being discussed within the field of bioethics, since without a clear answer we cannot determine what a responsible use of CRISPR on germ cells would be. I invite all of us to think about this complex issue and ask ourselves what we consider to be a ‘serious’ disease and why.