Swapping Mitochondrial DNA: Ethically Sound or Excessive?

Headlines about “three-parent designer babies” have been inciting controversy since initial research on pronuclear transfer (PNT) was published two years ago. This treatment is aimed at stopping the maternal transmission of mutated mitochondrial DNA (mtDNA). The disorders caused by mutated mtDNA range in severity, but can be devastating and are incurable. One of the most common mitochondrial disorders, Leigh’s syndrome, sparked a heated end-of-life debate in the ‘Baby Joseph’ case last year. PNT would cure Leigh’s syndrome and other mitochondrial disorders by supplementing an embryo from the intending parents with healthy mitochondria from a donor egg.

While laws in the UK currently prohibit implanting “admixed embryos” into women, some researchers are hopeful that with enough support and a change in legislation, the treatment could be available within three years. Seeking approval of PNT in the U.S. would likely face stronger aversion and greater challenges because of fertility laws that differ by state and continuing controversy over treatments affecting embryos. Long before this becomes a reality though, the ethical implications of PNT must be addressed. On June 12th, following a six month review, the UK’s Nuffield Council on Bioethics released an extensive ethical review of the therapeutic treatment.¬ The Council ultimately concluded that it is ethical to study the treatment further, and if proven safe and effective, it may be used to treat mitochondrial disorders.

There has been a widely expressed concern over the psychological and legal identity of a child produced from the genetic material of three people. The Council ruled that because the genetic contribution of mtDNA is so miniscule (about 0.1% of our total genes), there is no valid biological or legal sense of the proclaimed “third parent” or “second mother”. Rather, an analogy was made likening the switching of mtDNA in an embryo to changing the batteries in a camera – it doesn’t matter what type of batteries you use, as long as they’re present the camera will function in the same way. Some opponents contend that being disabled is part of one’s identity, and this attempt to “save only health lives” by preventing disability is dehumanizing.

When the Council consulted mothers of children with mitochondrial disorders who were supportive of the treatment, some said they would tell the child of their unique genetic origins because they would be “a miracle of science”. Others said they would not disclose in hopes of preventing a negative “psychological effect”. However, the Council’s recommendation for researchers to require parents undergoing PNT to consent to “very long-term follow-up of their children” would likely make nondisclosure to the children impossible. While the Council focused on this need for follow-up to ensure the safety of the treatment, they did not address the larger mental effect such precautions may have on the children, namely making them feel like experiments.

The fact that mtDNA is only passed maternally has caused debate about how to proceed with future generations of children created through this treatment. It has been suggested that until the long-term effects have been determined, embryos made by PNT should be restricted to males. This way, any unforeseen negative effects would not be passed to subsequent generations. This adds an entirely different question about whether parents should have the right to choose the sex of their child to the ethical quandary.

This treatment also contributes to one of the most contentious questions in genetics and scientific research today: do all couples have the right to have a healthy, biological child? It seems science is responding affirmatively and going to great lengths to ensure that parents-to-be with less-than-perfect genotypes can produce a genetically perfect child. But at what point do we reach extraordinary measures in the attempt to provide everyone a biologically related child? And is it morally justifiable to go to such “extraordinary measures” when there are over 100,000 children in need of parents in the US alone? Finally, as inheriting mutated mtDNA carries no guarantee of a poor quality of life, we arrive at the question of where the line between preventing suffering ends and perfecting begins.

Grace VanNoy is a Summer Intern at the Montefiore-Einstein Center for Bioethics. She is a pre-med student at Bates College where she is studying Biology and Anthropology with a concentration in Public Health.

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