Mitochondria in the media

Consider the plight of a woman who wants children but comes from a family in which her offspring run the risk of being born with an incurable mitochondrial inherited disease (MiD). If she's happy to adopt or to undergo IVF using an egg donated by a woman whose mitochondria are healthy, she can sidestep the problem. But if the genetic connection is important to her, the options available to minimise the risk (PGD or prenatal diagnosis) may be unreliable, or inappropriate, or both.

Small wonder that affected families are keen to see the advent of another option in which variants of IVF technology would be used to rehouse the parental genetic material in a donor cell with healthy mitochondria. The genetic material of the resulting embryo would be 99.9 percent that of the parents.

Two methods of achieving this end look increasingly promising, but both raise a number of ethical issues. Our report set out to examine them and to decide if, following further research on safety and efficacy, they would be acceptable for clinical use. Subject to a number of conditions, we believe they would.

These conditions include the need to provide prospective parents with proper counselling and a full explanation of what are, after all, novel and complex interventions. We also think that, if used clinically, the treatments should be provided only by centres that specialise in MiD. And they should also be carried out as part of a clinical study extending over several generations. This is because their influence would be felt not only by the child born through their use, but by the female descendants of that child. These technologies are not just gene therapies; they are germline gene therapies. They cross into what is still forbidden territory.

It's with this in mind that I've been reflecting on the media coverage of our report, in particular on the way that most journalists have framed the story. As on previous occasions when these technologies have made the news, most of the focus has been on what now seems doomed to be labelled the 'three parent' issue. As already mentioned, a fraction of one percent of the child's DNA (37 mitochondrial genes, as opposed to more than 20,000 nuclear genes) would come not from its mother and father, but from a third party.

Both legally and biologically our group found no evidence to suggest that this would cause distress or confusion to a child who learned of his or her slightly unusual inheritance. The only known function of mitochondrial genes is to provide the cell with the energy it needs. Vital, certainly; but of no significance for what is usually regarded as an individual's sense of identity.

The big ethical development as far as I'm concerned is that we have endorsed what we choose to describe as a germline therapy. I say 'choose' because there are those who prefer not to so label these techniques. Our view is that if you knowingly influence the genetic make up of generations as yet unborn, you're changing the germline.

Gene therapists have often emphasised that what they aim to do affects only the person being treated. They are aware that any attempt to alter our descendants is likely to induce nervousness and suspicion; it comes with a deal of historical and emotional baggage. So why did our working party feel able to endorse such a controversial enterprise? Because our approval was limited to techniques used only for the prevention of MiD, and only those forms caused by possession of mutant mitochondrial genes (mitochondrial disease can also be caused by mutant nuclear genes).

We are, of course, aware that some will see this as a justification for germline interventions in nuclear genes.  It is not. There is a clear demarcation between the two enterprises, and our endorsement is confined to mitochondrial genetic material. But we recognise that it does cross a line.

This, and not the 'three parent' froth, is the deeper significance of our report. Yet few commentators in the media and elsewhere seem to see it that way.

This is regrettable. Sooner or later a researcher somewhere is going to claim to have found a safe way of altering, replacing or otherwise manipulating a nuclear gene in a human egg or early embryo. This would be orders of magnitude riskier than anything considered in our report. And even if it really were safe, would we want to change our descendants in a manner that might go far beyond the prevention of a debilitating disease?

The debate on this issue, when it comes, will be far tougher, far more complicated, and with far more at stake than any issue confronting our working party during the past six months. It is a pity that our report has, so far, been little used to prompt that particular discussion. It does however appear to have made a considerable contribution to supporting a level-headed discussion of mitochondrial donation.

Throughout June, BioNews is running its own poll on the question 'Should Government allow variations of IVF using genetic material from three people to prevent children from inheriting mitochondrial diseases?', to which you can respond here.