Maternally inherited mitochondrial DNA (mtDNA) mutations are a common cause of genetic disease. However, to date, there has been very little success in developing effective treatments for mtDNA disease. Nuclear genome transfer techniques are a promising approach for the prevention of transmission of human mtDNA disease. (1,2) Recently, metaphase II spindle transfer between unfertilised metaphase II oocytes has successfully been performed in oocytes from non-human primates, resulting in live offspring in which no donor mtDNA was detectable. (3)