Use of Mitochondrial Donation
Mitochondria are organelles that generate energy required for biochemical reactions in cells. They contain a small genome, mitochondrial DNA (mtDNA), which encodes a variety of protein and RNA molecules required for energy production. Individuals inherit mtDNA only from their mother, and if this maternal mtDNA contains a disruptive mutation, it may result in diseases in offspring, which are frequently devastating and life-limiting. Mitochondrial donation (MD), or mitochondrial replacement, comprises a group of related embryological techniques that can be used to prevent or reduce transmission of mtDNA from mother to offspring in order to avoid disease transmission. It does so by replacing the mtDNA of an egg or embryo with that of a donor egg or embryo. The clinical use of two of these techniques, maternal spindle transfer (MST) and pronuclear transfer (PNT), for the prevention of transmission of mitochondrial diseases is lawful in the United Kingdom. This chapter describes the role of mtDNA in mitochondrial disease, the basics of the methodologies of MST and PNT, and issues that must be addressed in their technical refinement. MD has attracted much attention due to the fact that it modifies the inheritance of mtDNA by altering constituents of the germ line (eggs or embryos). Such germ line interventions are opposed by some people, for a variety of reasons. Here, several arguments that have been deployed against the clinical use of mitochondrial donation are evaluated. Finally, mitochondrial donation is considered in the context of assisted reproductive technologies more broadly and comparisons are made with other lawful and nonlawful germ line interventions.