What is Human Gene Editing?
Gene editing is a way of making changes to specific parts of a genome. Scientists have been able to alter DNA since the 1970s, but in recent years, they have developed faster, cheaper, and more precise methods to add, remove, or change genes in living organisms. Researchers are working to develop therapies that use gene editing to treat children or adults for a range of conditions, including sickle cell, hemophilia, and some forms of cancer and blindness.
Since 2015, a few laboratories have been experimenting with a far more controversial use of CRISPR: editing the genomes of early human embryos, eggs, and sperm. If edited embryos are used to start a pregnancy, the changes affect every cell in the body of any resulting child, that child’s offspring, their offspring, and so on. Dozens of countries already prohibit any attempt to start a pregnancy with edited embryos, yet some scientists seem eager to proceed.
In November 2018, researcher He Jiankui from Shenzhen, China announced the birth of the first gene-edited babies: twin girls publicly referred to as Lulu and Nana. In a reckless and widely condemned experiment, He had edited the DNA of two embryos and used them to start a pregnancy. The babies were born prematurely and their current health status is unknown.
Vast economic inequalities and the resurgence of overt xenophobia and racism in many parts of the world mean that we must emphasize the serious societal risks of human gene editing in any discussions of how we might use this technology in the future. Human gene editing is a political and social justice issue, not just a scientific one.
Gene Therapy: Changing genomes to treat disease
There are two distinct ways gene editing might be used in humans. Gene therapy, or somatic gene editing, changes the DNA in cells of an adult or child to treat disease, or even to try to enhance that person in some way. The changes made in these somatic (or body) cells would be permanent but would only affect the person treated. One way this is already being done is by editing a person’s immune cells to help them better fight cancer. Clinical trials will soon be underway to use CRISPR to edit blood cells as a treatment for sickle cell anemia and other blood disorders. Gene therapy raises many of the same social and ethical issues as other high-tech medical treatments, including ethical research practices, safety and effectiveness, unequal access to expensive treatments, and how we allocate resources, but is widely supported as a promising way to treat disease.
Germline Editing: Changing the genomes of future generations
But there is a much more controversial way that human gene editing could be used. In germline modification, gene editing would change the DNA of embryos, eggs, or sperm. Because germline DNA is passed down to all future generations, any changes—whether they had beneficial or harmful effects—would be as well. Some have proposed that germline editing could be used to prevent inherited diseases, but this would carry unacceptably serious safety, ethical, and social risks. And it’s unneeded, since we already have safe and effective ways to prevent passing on an inherited disease. People at risk can use preimplantation genetic diagnosis (PGD), a way to screen embryos created through in vitro fertilization (IVF) and select one that is unaffected; this allows parents to have a genetically related child without passing on an inherited disease. PGD certainly raises its own ethical questions, particularly around disability rights and justice, but it poses fewer safety and societal risks than germline editing would.
Understanding the Social and Ethical Risks
New technologies often raise ethical questions about their unknown risks and benefits. These questions become especially tricky -- and essential -- when we are talking about something like human germline editing, which affects future generations who obviously can’t consent to the changes being made to their DNA. And how could potential parents make informed decisions when there would be unknown health risks that might emerge during pregnancy for the woman and the fetus, epigenetic effects, and health issues that might not develop until adulthood or old age (or even in future generations). It would be extremely difficult, if not impossible, to do the kind of follow-up that would be necessary to definitively say that germline editing is safe enough to use in reproduction. Would there even be ethical ways to conduct these experiments?
But focusing on these obvious safety risks takes too narrow a view and overlooks the many serious social and ethical risks that germline editing would pose. Consider the potential effects on groups that have less power in society and are already discriminated against, including people with disabilities, people of color, and women. Imagine wealthy parents being able to purchase enhancements (real or perceived) for their children, and the kind of world that would result if children’s education and life chances were thought to be determined at birth by their DNA. Imagine the long-term consequences of imposing the preferences and biases we hold today on the genes of all future generations. The major social inequalities that already shape our lives would increase even more rapidly, and new forms of inequality could be introduced, leading to a new form of eugenics.
While it might seem possible to avoid such dire outcomes by limiting the use of germline gene editing to the prevention of serious diseases, this would be extremely difficult. The line between therapy and enhancement is fuzzy and would be nearly impossible to enforce. How would we determine which diseases or disabilities are serious enough to edit out? And who would decide? Many people with disabilities value their differences as a form of human diversity and do not think they need to be “treated” or “cured.” Allowing just some uses of germline gene editing for reproduction would mean opening the door to all uses. For these reasons, over 40 countries have banned human germline modification.
Who gets to decide?
Human germline editing is not just a scientific or technical issue. It affects how we understand ourselves as humans and what kind of future we want to build. It has implications for society as a whole, not just individuals. Therefore, decisions about whether to permit germline modification should not be made by small groups of scientists or bioethicists, by biotechnology companies, or by wealthy elites. Human germline editing is an urgent social justice issue; we need public discussions of it that are open to all.