The Human Fertilisation and Embryology Authority (HFEA) has granted permission for doctors to create the UK's first 'three-person' children by mitochondrial donation.

Doctors at Newcastle Fertility Centre successfully applied to treat two women and are now allowed to create embryos by combining fertilised eggs created through IVF with mitochondria from a female donor. The resulting embryos will be implanted in the two women.

Mitochondrial donation was developed for use where women carry disease-causing genetic mutations in their mitochondria. Mitochondria are small structures located in the cell which produce energy and also house their own distinct DNA, separate from the main bulk of DNA located in the cell nucleus.

To avoid passing on these mutations to their children, the healthy nuclear DNA of the intended parents is removed from a fertilised egg and transplanted into the fertilised egg of a female donor whose nuclear material has been removed, resulting in an embryo with nuclear DNA from two parents and the mitochondrial DNA of the donor. An alternative method involves performing the DNA transfer before fertilisation.

The decision by the HFEA has already been warmly welcomed by UK advocacy groups. Liz Curtis, founder of the British mitochondrial disease charity The Lily Foundation, said: 'The first patient licence for mitochondrial donation has been a long time coming, but now at last women with mitochondrial disease have a chance to have children without fear of passing on this devastating condition.'

In both of the currently approved cases, the women carry a genetic mutation for a condition called MERRF syndrome. The disease is characterised by twitching, weakness and progressive tightness in the muscle fibres. This can lead to symptoms such as difficulty coordinating movement, seizures and heart disease.

Professor Salvatore DiMauro, an expert in mitochondrial disease at Columbia University in New York, said: 'It's good to do this. MERRF is a crippling disease. It's the only way to be sure it is not passed on.'

Newcastle Fertility Centre, which has pioneered much of the research in this field, received a licence to perform mitochondrial donation techniques last March from the HFEA, but it has taken nearly a year for these two specific cases to be approved. 

Responding to the news, Sarah Norcross, Director of the Progress Educational Trust, said: 'The pace at which these treatments are being rolled out may seem slow, but this highly regulated and measured approach will ensure the highest standards of treatment and follow-up research. Options which for many years have been tantalisingly out of reach to patients are now a step closer.'

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