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Why mitochondrial donation is not about making ‘designer babies’

by Guest Author on 29 Aug 2014

A cell with the nucleus and mitochondria labelled (Image credit: Wellcome Images)

A cell with the nucleus and mitochondria labelled (Image: Wellcome Images)

The UK Government is considering legalising a specialised form of IVF called mitochondrial donation, which aims to prevent potentially fatal mitochondrial disease. As Parliament prepares to debate the issue on Monday 1 September, Jane Bunce tries to clear up confusion over the science behind the technique ― and explains why it will not lead to creation of “designer babies”.

What is mitochondrial disease?

An estimated one in 6,500 children will develop a serious mitochondrial condition, which is passed down from mother to child. There is no cure and symptoms include seizures, strokes, blindness, deafness, heart and liver failure ― and in serious cases, death at a young age.

The diseases are due to faults in a child’s mitochondria, which are often described as the “battery packs” of our cells. These mitochondria are small structures in human cells that convert the food we eat into energy we need to stay alive. If these mitochondria don’t work correctly, cells don’t have enough energy and the tissues or organs they make up do not function properly.

What is mitochondrial donation?

The MRC and other research funders such as the Wellcome Trust have supported research into mitochondrial donation, an IVF technique that aims to prevent mitochondrial disease developing in a child. Normally, a child receives all their mitochondria from their mother’s egg. The technique would instead use a donated egg from a woman who has healthy mitochondria.

The genetic material is removed from the nucleus of the donated egg, and replaced with the nuclear DNA of the mother. Depending on which precise technique is used, the egg is fertilised (becoming an embryo) either before or after nuclear DNA transfer. The healthy embryo ― now containing the mother’s nuclear DNA and the donor’s mitochondria ― is implanted into the mother’s uterus in the same way as in conventional IVF.

Will it create designer babies?

Opponents of the regulation appear to be concerned that it will lead to the creation of “designer babies”. However, some of this concern may be due to confusion around the very separate role that mitochondrial DNA and nuclear DNA play in the body. The vast majority of genetic material in the body is contained in the nucleus of the cell. This nucleus contains all the genetic material that determines our personality and appearance ― an estimated 30,000 genes in total.

The regulations being proposed will maintain the ban on altering this nuclear DNA. This means there is no way the technique can be used to choose hair colour, personality traits, intelligence or any other characteristic associated with creating “designer babies”.

The mitochondria are separate structures to the nucleus and contain a very small amount of DNA. This DNA includes exactly 37 genes, which control the function of the mitochondria and how they produce energy. These are the genes that are faulty in children with mitochondrial disease. Scientists would not be allowed to tinker with the DNA code, but would replace the whole, faulty, set with another, normal, set.

Children born after mitochondrial transfer would be free of mitochondrial disease ― and would eventually pass this healthy mitochondrial DNA on to their own children.

Importantly, the genes in the mitochondria are entirely separate from the genes in the nucleus. They cannot combine with each other. The only genes that would be affected by the technique would be the damaged mitochondrial genes. A child born using this technique would still receive all its nuclear genetic material ― controlling its physical and psychological traits ― from its mother and father.

What happens next?

Current UK law allows scientists to investigate these techniques in a laboratory, but not to treat patients. In July, the Government announced it would proceed with putting regulations before Parliament that would permit the technique to proceed into clinical trials, to determine whether it is safe and effective.

Clinicians would need to apply to the independent regulator ― the Human Fertilisation and Embryology Authority ― which will be responsible for deciding when the treatment can be offered. The Government decision followed four years of consideration, including a scientific review and public consultations. And like IVF before it, the new reproductive technique will now receive the full scrutiny of Parliament.

Jane Bunce

Senior Public Affairs and Policy Officer

On 1 September after 5.30pm, backbench MPs will hold a debate in House of Commons on mitochondrial donation techniques, specifically the motion to ‘delay the laying of the regulations to allow the licensing of mitochondrial donation techniques through parliament’. A full debate in both houses of Parliament will be held when the regulation is tabled, which is expected later this year.

Update 29 January 2014: the House of Commons will debate and vote on these regulations on 3 February 2015.

More information:

Government response to consultation

Nuffield Council on Bioethics ethical review

Wellcome Trust

The Lily Foundation


Update: Many thanks to Professor Robin Lovell-Badge, Head of the Division of Stem Cell Biology and Developmental Genetics at the MRC National Institute for Medical Research, for pointing out that some mitochondrial disease are caused by mutations in nuclear DNA. The proposed techniques would only be relevant to those mitochondrial diseases linked to mutations in the mitochondrial DNA.

author avatar by Jane Bunce on 29-Aug-2014 16:22

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