News Debating mitochondria replacement Spring will see the government consider the public’s views on the use of new medical techniques that could allow women to avoid passing on genetically inherited mitochondrial diseases to their children. These diseases are usually degenerative and can affect the functioning of muscles and major organs as well as the nervous system and the cardio-vascular system: for example, Leigh disease, Barth syndrome and many myopathies. The techniques, which are in vitro fertilisation (IVF)-based, involve modification of human embryos or eggs. The law would need to change before they are permitted. At the request of the government, The Human Fertilisation and Embryology Authority (HFEA) has carried out a public consultation to gather views on the social and ethical impact of making these techniques available to patients. Genetic modification Mitochondria are inherited from the mother and are present in almost all human cells. They are often referred to as the cell’s ‘batteries’ as they generate most of a cell’s energy supply. Mitochondrial disease can either be caused by faults in the genes within a cell’s nuclear DNA or within the small amount of DNA that exists within the mitochondria themselves. The HFEA consultation considered techniques that would avoid faults in mitochondrial DNA being passed on. The new mitochondria replacement techniques involve a degree of genetic modification by transferring parental nuclear DNA into a donated embryo or egg that contains healthy mitochondria. Two techniques are being developed: one dealing with an embryo, and the other with an egg. In each case, the parental nuclear DNA is removed and transferred from an embryo or egg which contains defective mitochondria, and the donor nuclear DNA is extracted from the donor embryo or egg before it receives the parental nuclear DNA. Scientists are still working on these techniques to find out which will be the safest and most effective. If both or either of the techniques are proven safe and are approved for use in clinics, it will mean that women with mitochondrial disorders will be able to have genetically related children who are free from disease. In addition, the risk of passing on mitochondrial disease down the family line to future generations will be eliminated. New issues These techniques involve some medical firsts and therefore raise new ethical and social issues, which need to be carefully considered. For example, this would be the first time that a genetically modified embryo would be transferred into a woman with the hope of achieving pregnancy. How might the child born feel about this? And although the law would only allow this particular form of mitochondrial modification, would it soften us to demands for more trivial use of the technology in the future? Another issue is the impact of inheriting mitochondrial DNA from a donor rather than the intended mother. The physical impact on the resulting child is likely to be negligible, but would their sense of themselves be affected? And what should our perception of a mitochondria donor be? Are they just like bone marrow donors, for instance, or more like egg donors who are required to be identifiable to any children resulting from their donation? Consultation to decide The HFEA, working with Sciencewise and research partners, involved the public through an open and independent consultation to explore what people think about the possible use of these techniques in treatment. The consultation was carried out in several phases, including a public dialogue exercise, a survey, an online questionnaire, public meetings and a focus group. The HFEA will consider the outcomes of the consultation, and decide what advice to pass on to government regarding the public’s views on the social and ethical impact of making these techniques available to patients.