The avoidance of mitochondrial disease

Previous Ethics briefings reported on research developments involving mitochondrial transfer to allow women to avoid passing on a serious mitochondrial disease to their daughters.1 This update reports on the beginning of the legal process that could see the procedure used in clinical practice. The Human Fertilisation and Embryology Act 1990 (as amended) allows for regulations to be passed that permit techniques that alter the mitochondrial DNA of an egg or embryo to be used in assisted conception to prevent the transmission of serious mitochondrial disease. This involves the pronuclei (containing the genetic material from the egg and sperm) being removed from a fertilised oocyte and transferred into a fertilised donor egg that has had its own pronuclei removed—this is called pronuclear transfer (PNT). Another option is maternal spindle transfer (MST) whereby the spindle containing the woman's nuclear genetic material is transferred into an enucleated donor egg, which is then fertilised with the man's sperm. In both cases the resultant fertilised egg contains nuclear DNA from the father and mother and mitochondrial DNA from the donor. If successful, these techniques would avoid mitochondrial disease in the resulting child and also in future generations.

In February 2011 the Secretary of State for Health asked the Human Fertilisation and Embryology Authority to carry out a scientific review into the effectiveness and safety of these forms of mitochondrial transfer. Having carried out a detailed analysis of the existing research base, the Human Fertilisation and Embryology Authority concluded that there was no evidence that these techniques were unsafe but that some further safety experiments needed to be carried out before either technique could be introduced into clinical practice.2 It recommended the following minimum set of basic experiments that needed to be undertaken before the techniques could be assessed as safe for use in …