A Harvard Law School event on 17 April was the first in a series of meetings to persuade the US government to lift the ban on mitochondrial donation. Although a 2015 report from the US National Academies of Science Engineering and Medicine said that it would be ethically acceptable to use the technique, an amendment introduced to US law just months before forbade the US Food and Drug Administration (FDA) from considering applications for trials involving genetically altering human embryos.
Most of a cell's genetic material is found in the nucleus, but a small amount is located in the mitochondria – self-contained structures within cells that generate the energy needed to grow and survive. Mutations in this DNA can cause mitochondrial diseases, which are often fatal. As mitochondria are usually inherited solely from the mother, female carriers are highly likely to have children affected by these conditions.
Mitochondrial donation involves taking the nucleus containing the parental DNA from an egg or embryo and transferring it to a donor egg or embryo that contains healthy mitochondria but has had its nucleus removed. The egg can be fertilised with the father's sperm before or after the transfer takes place. The resulting embryo contains nuclear DNA from the mother and father as well as a small amount of mitochondrial DNA from the donor – hence the method has been called 'three person IVF'.
Dr Dietrich Egli, assistant professor of developmental biology at Columbia University, New York, announced at the event that he has used this method to create embryos for four women who are carriers of mitochondrial disorders. The embryos have been frozen as the FDA forbids genetically altered embryos from being transferred to the womb.
'They would be ready for transfer if a legal path could be found,' said Dr Egli. His team do not plan on transferring the embryos outside the US. 'We would like to advance the regulatory framework here,' he said.
In the UK, mitochondrial donation is only legal to prevent transmission of mitochondrial disease, but the procedure has been trialled in Greece and Ukraine to treat infertility.
Opponents say that there is insufficient evidence to know if the technique is safe and that it is possible that the disease could re-emerge later in life. However, supporters argue that the technique provides another option to a relatively small group of women and would allow them to eliminate devastating diseases.
Professor Robin Lovell-Badge, a researcher at the Francis Crick Institute (and chair of trustees of the Progress Educational Trust, which publishes BioNews), said: 'As other countries, notably Australia and Singapore, consider changing their laws in line with the UK on this, it is appropriate that the US does so as well.'