He Jiankui tried to use CRISPR to make individuals immune to HIV, but many believe the most-compelling case for gene editing before birth is to prevent genetic disorders.
Most disorders caused by mutations in a single gene, such as cystic fibrosis, can already be prevented. One way of doing this is to screen IVF embryos for harmful mutations before implanting them.
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However, such preimplantation genetic diagnosis has limitations, particularly when you only need to inherit the mutation from one parent to develop the condition, as is the case with Huntington鈥檚, a neurological disorder. If one parent has this condition, half the embryos will carry the gene, halving a couple鈥檚 chances of successfully having children without the condition through IVF. Some mutations, including the cancer-causing BRCA1, can affect fertility, meaning women produce fewer eggs per IVF cycle, lowering their chances of success.
Embryo screening is also of little use if the aim is to prevent children inheriting more than one harmful mutation, as the chances of finding a healthy embryo in such cases is much lower.
In all these cases, using gene editing to repair mutations in embryos, rather than discarding them, would increase a couple鈥檚 chances of having children.
Gene editing could also help men who can鈥檛 produce sperm due to mutations in the cells that make sperm. Correcting these mutations may restore their fertility 鈥� something that has been done in mice but isn鈥檛 yet possible in people.
We all have thousands of harmful mutations that make us more prone to cancer, heart attacks or dementia. In principle, everyone could live longer, healthier lives if these were repaired, but we are still a long way from being able to achieve this.
This article appeared in print under the headline 鈥淲hat could we use gene editing for?鈥�
