However, “treatment” does not mean helping existing sufferers. Rather, the techniques might allow a small subset of women with mitochondrial disease (in the UK, roughly 10 to 20 annually) to reduce the risk that their children will inherit the mutation — at the cost of setting a precedent with serious potential consequences.
In addition to national legislation, international treaties like the Council of Europe Convention on Human Rights and Biomedicine (which the UK has not signed) specifically prohibit human germline genetic modification. The easy explanation for this prohibition would be moral aversion to eugenics, the pseudoscience of improving a population’s genetic composition, which was popular in the West in the first half of the 20th century, before being discredited by the example of the Nazis.
Unlike eugenicists, proponents of altering mitochondrial DNA simply hope to free future generations from deadly diseases. Nonetheless, critics fear the slippery slope. After all, breaching the ethical and legal barrier to permanent genetic modification could make it more difficult to block its application for treating non-lethal conditions, or even for enhancing qualities like cognitive ability or athletic prowess.
The more urgent threat is that any kind of germline genetic modification could do long-term, permanent damage. The HFEA’s own expert panel reported that the safety of mitochondrial techniques is far from being proven for current users. There is no telling what it could mean for their descendants.
According to Joanna Poulton, an expert in mitochondrial research at Oxford University, it is not yet appropriate to offer treatment with so little knowledge of the potential consequences when reasonable alternatives — such as egg donation from a woman unaffected by mitochondrial disease or pre-implantation genetic diagnosis (PGD) — are available.
“There are very few families who don’t want to use donated oocytes [eggs], where PGD would not work and where the risk of having severely affected babies is so high that it might be worth trying the new techniques,” she says.
In fact, mitochondrial studies have already begun to produce unexpected results. For example, scientists in Oregon recently observed abnormal fertilization in some of the human eggs that they had manipulated. Given that the defective eggs miscarry naturally, more eggs than expected would be needed for the technique — possibly posing a risk to the donors. Indeed, in their study, the team used 106 eggs from seven women, one of whom donated a total of 28 eggs, indicating possible ovarian hyperstimulation, which can be dangerous or even fatal.
Like all human endeavors, science gets some things wrong. Germline genetic modification threatens to make such errors permanent. The UK scientific and charitable organizations advocating mitochondrial research are proud of the permissive legislative framework that has enabled them to establish an “international lead.” However, extending that leniency to human germline genetic modification may well cause future generations to view their actions very differently.