A Trip Across The Rubicon

In June, the Government announced that it would be putting together regulations on the creation of so-called “three-parent embryos”- that is embryos containing mitochondrial and nuclear DNA from different mothers- taking us a step closer to the conception and birth of children as a result of these technologies. The ostensible rationale for this development is to “treat” mitochondrial disease resulting from inherited defects in the mitochondrial DNA, which can have horrific consequences. This is very much the angle that has been pushed in the media, with this technology portrayed as a medical technology to treat these horrific diseases. Nevertheless I remain troubled by this move.

Little noted, but important to bear in mind, is the fact that this process will not cure any children currently living with mitochondrial disease. It will allow mothers to avoid passing on the defective DNA, but only those who know they are at risk, and are willing and able to undergo IVF treatment. This group already have options, most notably conceiving using a whole donor egg. Thus, mitochondrial transfer is as much a reproductive technology, as it is a medical one. The question this leads to, which hasn’t received as much attention during this debate, is how far is it acceptable to go to enable parents to have a child that shares their nuclear DNA?

To answer that question we need to look at what the process entails. In theory there are two separate processes that could be used, as outlined by the BBC . The first method involves the removal of the nucleus from the donor egg and the replacement of it with the nucleus from the effected mother’s egg. The resulting egg, which is genetically descended from the effected mother, but is free of the defective mitochondria, is then fertilised resulting in an embryo that is implanted back into the prospective mother. The second, more problematic method involves creating two embryos: one using the donor egg, the second using an egg from the effected woman. The nucleus of the donor created embryo is removed and destroyed, to be replaced with that of the prospective parents’ embryo.

In both cases the resulting embryo is genetically descended of both prospective parents, but with healthy mitochondria from a donor woman’s egg. Advocates of this process have objected to the term “three-parent embryo” with its frankensteinian connotations, correctly pointing out that the genetic contribution of the donor is very minor. “What makes us us” is wholly contained within the nuclear DNA. But therein lies the key to the problem with the whole process: the creation of the donor embryo with its complete genetic code defining it and “making it itself,” to borrow the phrase. Currently, this donor created embryo can be implanted and continue to develop, and this is commonly done, in women who, for whatever reason, cannot conceive with their own eggs. Instead, in the proposed process, it is stripped for spare parts and discarded. This is no longer a hypothetical individual of the kind who shuffle in and out of existence depending on happenstance and our personal choices. In another recent development, fertility specialists have developed a way of screening IVF embryos using time-lapse images, to determine those with the greatest chance of survival. I was struck when viewing the resulting videos by the embryos dividing and growing under their own power, with some of them heading inexorably, given the right environment, on the path that leads to each one of us. The alternative proposed method is less problematic, amounting to little more than a mitochondria transplant, but is still likely to require embryo manipulation and destruction in the experimental phases.

Of course this bridge has already been crossed multiple times and for multiple reasons, but that doesn’t mean that each fresh trip across the rubicon shouldn’t result in a pause to take stock.