mitochondrial disease

Baby leaps into a brave new world

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Each year around 100 children in Britain are born with a form of mitochondrial disease. The conditions, which range from deafness to heart disease and brain disorders, are often fatal. In 2016 a cure will come closer. Britain will become the first country to allow babies to be born using mitochondrial donation, creating children with genes from three people rather than two. It will inspire other countries to follow suit.

Mitochondria are the power-packs providing energy to cells. They live in the part of the cell outside the nucleus, and have their own genomes, which are passed down through the maternal line. Around 2,500 women in Britain carry mitochondria with mutations that could adversely affect their children. At the moment, genetic diagnosis can test embryos for some of these. But such screening (allowing the selection of disease-free embryos) is fully effective only in certain cases.

By contrast mitochondrial donation is an outright cure. The likeliest procedure involves removing the nucleus from an egg that comes from two parents through in-vitro fertilisation (IVF) and inserting it into an egg from a donor with healthy mitochondria which has had its nucleus removed. The embryo will then inherit the genes of three different people, though the contribution of the third party is modest: mitochondria contain only 37 of the roughly 20,000 genes which make up a human. Nuclear DNA, which provides the other 99.8%, will not be changed in the process, so inherited traits such as eye colour, a propensity for baldness and personality quirks will still come from two parents.

Some oppose the procedure on religious or ethical grounds. A few worry that babies born this way will be sterile. Others dislike the idea of “three-parent babies”, as the media have dubbed them, or fret that, as mitochondria are passed down in eggs, any female children born from the process will pass the changed genes to their children. Those opposed will probably still create a fuss as the first procedures go ahead.

World’s first ‘three-parent’ babies could be born in the UK

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MPs will be asked to vote on whether to allow mitochondrial transfer technique to prevent inherited genetic diseases
A newborn baby
The IVF technique involves using healthy mitochondrial DNA from a donor to replace the defective DNA responsible for a host of debilitating inherited diseases.

A newborn baby

A further step towards creating babies using DNA from three people has been taken by the UK government with the announcement of new regulations to be put before parliament. The move was hailed as a “milestone” by the head of one charity representing those affected by mitochondrial diseases, which the controversial fertility technique aims to prevent.

MPs will be asked to vote on whether the UK should become the first country in the world to legalise the procedure, an IVF technique that uses genetic material from a mother and a father as well as a donor egg – minus its nucleus – from another woman.

The donor contributes healthy mitochondrial DNA (mtDNA) to replace defective mtDNA responsible for a host of serious inherited diseases. Housed in the mitochondria – the cell’s “power plants” – and not the cell nucleus, mtDNA accounts for only 0.1% of a person’s genetic make-up.

Mitochondrial diseases are rare, affecting around one in 5,000 of the population, but can be devastating for families. They cause a wide range of different conditions affecting muscles, nerves and organs, and can lead to blindness, deafness, autism and learning difficulties.

One of the regulations laid before parliament says that the donor would not be classed as a parent related to the child. Others say that the fertility regulator must assess each case for a significant risk of disability or serious illness, and that fertility clinics would need to obtain a special licence to offer the treatment.

In addition, any child born as a result of the technique would have no automatic right to information about the donor.

Robert Meadowcroft, chief executive of the Muscular Dystrophy Campaign, which helps people suffering from mitochondrial diseases, said: “Today’s news is an important milestone for families affected by mitochondrial disease.

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“For years, many have been hoping for access to this IVF technique and a debate in parliament is a huge step forward towards achieving this.

“This technique has moved successfully through the necessary ethical and public reviews, and a positive result in this debate is now vital to allow further progress.”

Dr Jeremy Farrar, director of the Wellcome Trust, said: “Over the past seven years, Britain has been engaged in an exemplary process for evaluating scientific, ethical and public opinion about mitochondrial donation, which has revealed broad support on all three fronts.

“A parliamentary vote is the next logical step, and we urge MPs to support regulations that will allow the law to catch up with public and scientific opinion.

“Parents who know what it means to care for a sick and suffering child with mitochondrial disease are the people best placed to decide, with proper medical advice and safeguards, whether mitochondrial donation is right for them.

“They should not have to wait any longer to be able to make this choice.”

But Dr David King, director of Human Genetics Alert, argued that there are already reliable ways of avoiding the conditions: “This is high-tech medicine at its worst and most unnecessary.

“Medical researchers are crossing the crucial ethical line that will open the door to designer babies based on scientific misinformation,” he said.

Consultation on technique to prevent mitochondrial disease launched in UK

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Controversial technique, currently banned, would prevent women from passing mitochondrial diseases to their children
  • Mitochondria
Around one in 200 children born in the UK has some form of mitochondrial disorder. The most serious affect the heart, brain, muscles and liver. Illustration: Getty Images

The Department of Health has launched a three-month consultation on the draft regulations for a radical procedure that aims to prevent mothers from passing on serious genetic diseases to their children, a controversial technique because it leads to babies with DNA from three people.

Mitochondrial transfer has never been tried in humans and is prohibited in Britain under laws that ban the placing of an egg or embyro into a woman if the DNA has been altered. But scientists working on the technique said it offered hope of preventing life-threatening diseases for which there were no cures.

The government announced last June that it intends to allow the procedure, but the regulations must be finalised, debated and approved by parliament before the Human Fertilisation and Embryology Authority (HFEA) can allow clinics to offer the treatment.

About one in 200 children born in the UK have some form of mitochondrial disorder. The most serious affect the heart, brain, muscles and liver. Under the procedure, the nucleus is removed from an affected woman’s egg or from a cell in an embryo and transferred to a donor egg or embryo that has healthy mitochondria.

As a result, a baby will have DNA from the biological parents and a female donor who provides healthy mitochondria, the tiny biological batteries that power most cells in the body. The fraction of a cell’s DNA that is in mitochondria is minuscule and affects only how cells are powered. It does not influence the child’s physical appearance or personality.

Another reason the procedure is controversial is that it would be the first to introduce genetic changes that are passed on not only to the intended child, but to all subsequent generations. One concern is that any harmful and unexpected side-effects might then damage the health of people born long into the future.

Launching the consultation, Dame Sally Davies, the chief medical officer, said: “Allowing mitochondrial donation would give women who carry severe mitochondrial disease the opportunity to have children without passing on devastating genetic disorders. It would also keep Britain at the forefront of scientific development in this area.”

She added: “I want to encourage contributions to this consultation so that we have as many views as possible before introducing our final regulations.”

Under the draft regulations, donors of mitochondrial DNA would remain anonymous, but could request details from the HFEA of the number and sex of any children born from their material. If someone aged 16 or over asked the HFEA if they were born after mitochondrial transfer, the authority would be required to tell them.

Doug Turnbull, a neurologist at Newcastle University and the leader of mitochondrial transfer research in Britain, welcomed the draft regulations. “This is very good news for patients with mitochondrial DNA disease and an important step in the prevention of transmission of serious mitochondrial disease,” he said.

Last year, the HFEA published results of a national consultation on mitochondrial transfer, which found broad public support for the procedure. Tests in monkeys suggest that the procedure is safe, but research to perfect the technique is ongoing.

Mitochondrial diseases can affect single or multiple organs and tend to worsen with age. One disorder, called Leigh syndrome, usually develops in babies before the age of two, and causes progressive degeneration of the brain and nervous system.

Jeremy Farrar, director of the Wellcome Trust, encouraged the government to bring the regulations before parliament as soon as the consultation period finished in May. “Once further public consultation on the detail of these regulations is complete, we urge the government to move swiftly so that parliament can debate the regulations at the earliest opportunity and families affected by these devastating disorders can begin to benefit,” he said.