Four rhesus macaques have been created in a laboratory at the Oregon National Primate Research Center, USA, using a technique that could prevent the genetic transmission of diseases carried in mitochondrial DNA (mtDNA), as reported in Nature. By taking the nuclear DNA from one egg and transferring it into another egg from which the nucleus had been removed, the researchers could eliminate defective mitochondria and use this 'reconstructed' egg for in vitro fertilization.

Mutations in mtDNA, which is inherited from the mother, are known to have a role in a wide range of human diseases, including myopathies and cancer. As genetic tests showed no traces of mtDNA from the egg that the nuclear DNA originated from, it might be “possible to use this therapy in mothers carrying [mtDNA] diseases so that we can prevent those diseases from being passed on to their offspring,” said Shoukhrat Mitalipov, who led the research ( Science Daily , 27 Aug 2009). He hopes that their work can be “rapidly translated into clinical trials for humans, and, eventually, approved therapies.” ( guardian.co.uk , 26 Aug 2009.)

Nevertheless, there are safety concerns, as the treatment introduces permanent genetic changes, and mtDNA and nuclear DNA from different donors might not be compatible. Follow-up tests will help to clarify these issues in monkeys, but investigating the effects in humans will be difficult as there are few human egg donors, and genetically modifying human eggs is controversial and illegal in most counties. However, a spokesman for the Human Fertilisation and Embryology Authority, UK, said that if safe and effective treatments are developed in the future “Parliament would have to pass secondary legislation to allow [them] to take place” ( The Independent , 27 Aug 2009).