Scientists have for the first time managed to edit genes in a human embryo to repair a genetic mutation, fuelling hopes that such procedures may one day be available outside laboratory conditions. In results announced in Nature this week, scientists fixed a mutation that thickens the heart muscle, a condition called hypertrophic cardiomyopathy. The cardiac disease causes sudden death in otherwise healthy young athletes and affects about one in 500 people overall. It is caused by a mutation in a particular gene and a child will suffer from the condition even if it inherits only one copy of the mutated gene. Correcting the mutation in the gene would not only ensure that the child is healthy but it would also prevent the mutation from being passed on to future generations. In an attempt to remove the small portion of mutation, the researchers injected sperm of a man affected by hypertrophic cardiomyopathy and the gene-editing tool called CRISPR-Cas9, that cuts the DNA near the position of the mutation, into the egg at the same time. The gene-editing tool cut the DNA at the correct position in all embryos and 42 out of the 58 embryos did not carry the mutation. Though the research marks a major milestone in genome editing of embryos, it will be a long while before it becomes available as a tool to produce healthy embryos. For instance, even research on embryos using federal funding is not permitted in the U.S., where the research was carried out. The embryos were produced with the clear intention of using them solely for research and not for implanting them in women.
While several diseases can potentially be prevented by using this technique, including some cancers, the announcement has also revived fears about designer babies being within the realm of possibility. In retrospect, every advancement in reproductive health, starting from in vitro fertilisation to the recent birth of a baby through the “three parent” technique for mitochondria-related disease, has initially been mired in controversy but has ultimately come to stay. In the same way, the use of CRISPR-Cas9 gene-editing tool when proven safe for preventing certain hereditary disease-causing mutations from being passed on to the child should be allowed, especially when no other treatment is available. In February this year, the U.S. National Academies of Sciences and Medicine allowed scientists to use the tool for research and said the technique to edit embryos will become acceptable for clinical use. But for that to happen, rigorous research involving multiple locations has to be carried out to address all safety concerns and ethical issues. To that end, the researchers have already addressed an inherent problem of producing embryos containing a mosaic of unrepaired and repaired cells by introducing the gene-editing tool and the sperm together into the egg. Meanwhile, Nonetheless, the philosophical and ethical debates will rage on.
