Three cheers for three-person embryos

On February 3 2015, the UK made history when MPs approved the draft Human Fertilisation and Embryology (Mitochondrial Donation) Regulations 2015, with 382 in the House of Commons voting in favour and 128 against. This meant that, in principle, they supported the creation of ‘three-person embryos’ through mitochondrial donation.

This is a new type of fertility treatment in which a tiny amount of DNA from a healthy donor is used to prevent mothers passing on congenital genetic disorders to their children. It is thought that around one in 6,500 children is born with a serious mitochondrial disorder due to faults in mitochondrial DNA (mtDNA). Or, to put it another way, every 20 minutes a child is born who will develop mitochondrial disease by the age of 16.

These diseases can appear at birth or develop later in life, and can cause early infant death or lead to a range of possible diseases in those who survive. These are usually degenerative and can affect major organs such as the brain and heart, or other parts of the body including bone marrow and muscles. More information on associated problems can be accessed here.

When the draft regulation was approved by the House of Lords later that month, in a vote of 280 to 48, the UK became the first country in the world to legislate for the use of mitochondrial donation techniques in treatment. Now the Human Fertilisation and Embryology Authority (HFEA) can consider applications from fertility clinics for licences to perform mitochondrial donation. The decision to grant these licences will be at the discretion of the HFEA, subject to rigorous criteria and the framework of the UK's system of regulation. Regulators in the United States are also considering whether to allow this new technique.

Professors Doug Turnbull and Alison Murdoch, two of the researchers at Newcastle University who have pioneered mitochondrial donation techniques, welcomed the result, saying: 'This is wonderful news for patients and families affected by mitochondrial disease.' They added: 'We hope to be able to submit a treatment application to the HFEA when regulatory policies have been determined.'

So what is the science behind mitochondrial donation? It’s simple but brilliant. The DNA in our cell – our mitochondria – can go awry. Because we only inherit mtDNA from our mother, scientists have learned how to remove the healthy nucleus from the mother's cell and transfer it into a donor cell (with its healthy mitochondria) from another woman. This means that diseases we inherit from our mother can be prevented.

Conceiving a child via mitochondrial donation therefore involves using biological material from three people – the child's parents (an egg from the mother, sperm from the father) plus a female mitochondrial donor. 'Three-person embryo' is already entering the medical lexicon and is becoming shorthand for this new development. It has also been labelled ‘three-parent embryo', but this is inaccurate – mitochondrial donation will not result in children with three parents. A child conceived via this method will inherit nuclear DNA from two parents in the usual way; the only DNA that the child will inherit from a donor is the donor's mitochondrial DNA.

That is why the regulations do not require a mitochondrial donor and a person conceived using their donation to be identifiable to one another. This is because mitochondrial donation creates neither observable nor other shared characteristics between the two individuals (except for the fact that both of them will be free of mitochondrial disease).

Mitochondrial donation is the only way that patients with high levels of faulty mitochondria can have a child who is both genetically related to them and unaffected by mitochondrial disease. Patients in this predicament – not to mention the health professionals, researchers, charities and politicians who seek to help them – have been engaged in a long uphill struggle against devastating and fatal diseases.

Olivia Seaby, a 19 year old with mitochondrial disease, said of legislative decision: 'I'm so happy because it means that women will be able to go on to have children who are free from this condition.'

Contrary to what some critics have suggested, work on avoiding the transmission of mitochondrial diseases does not detract in any way from ongoing attempts to develop treatments for those who already have these diseases. The two endeavours are complementary, with the same clinicians and researchers, including the pioneering mitochondrial donation team, working on these in tandem.

Two charities played important roles in this world-first development. The Lily Foundation was set up by, and is for, families affected by mitochondrial disease. It has funded research to improve diagnosis and increase treatment options for patients. The Progress Educational Trust has done exemplary work in this area, first reporting on mitochondrial donation as a hypothetical possibility back in 1999. As research progressed and the possibility moved from theory to reality, the trust continued to monitor closely the relevant scientific and ethical issues, winning hearts and minds in the process.

About the author

Bríd Hehir is a writer and researcher who worked in the NHS as a nurse, midwife, health visitor and senior manager. To read her blog click here.