A decision by the UK to support further research and development of a new IVF technique to enable women carrying defective mitochondrial DNA to have healthy babies has made headlines worldwide. Professor Michael Hanna, Consultant Neurologist at The Physicians’ Clinic and Director of the MRC Centre for Neuromuscular Diseases
was interviewed widely when the news broke, providing comment for Sky News, Aljazeera Live and other major news outlets. Here, he explains the facts behind the media coverage.
“The UK is leading the world in this development, which is a modification of the technique used widely for in vitro fertilisation (IVF). Routine IVF gives couples facing infertility the opportunity to become parents; this new technique gives women known to be carrying a potentially fatal disease the chance to not only have a baby, but to have a baby that survives more than a few days or weeks and is healthy,” says Professor Hanna.
What are mitochondria?
Mitochondria (see diagram of a human mitochondria, above right) are small components that are present in every cell in the body. They act as a type of rechargeable battery and provide the energy for everything that the cell does. If all your mitochondria were to suddenly stop working, you would die within minutes because your muscles, heart and brain would have no energy to maintain essential functions.
Whether we are male or female, we all inherit our mitochondria from our mother. Mitochondria have their own small amount of DNA containing about 37 genes. Compared with the DNA in the cell nucleus, commonly known as the genome, which has 20,000 genes, it’s tiny.
The sole function of mitochondrial genes is to allow the mitochondria to produce energy. Mitochondrial DNA does not determine a person’s physical characteristics, which are all controlled by those 20,000 genes located in the nucleus of every body cell.
These mitochondrial genes can become damaged (mutated), just like any other genes. If a mutation arises in the mitochondrial DNA, all the mitochondria that a mother passes onto her children will be potentially defective.
What is mitochondrial disease?
There are many different kinds of mitochondrial disease. All affect the ability of mitochondria to produce energy for the cell and all can be passed on from one generation to the next.
A genetic mitochondrial disease may affect a baby from birth or may cause serious neurological disease in childhood. A woman may be healthy but she may have a mutation in the mitochondrial genes in the mitochondria in her eggs. This means that although she can produce eggs, and the DNA within the nucleus of that egg is capable of combining with a sperm to produce a healthy baby, she may not pass on healthy mitochondria.
All of her children will inherit defective mitochondria. One woman, Sharon Bernardi
, supports the new IVF technique to prevent mitochondrial disease because she lost all seven of her children. Only two survived more than a few days; one lived to be two years old and her only son to reach adulthood died in 2012 aged just 21.
How many people are affected?
Around 10 babies are born in the UK each year with a mitochondrial disease that is either fatal within a few days or that leads to extreme health problems that shorten life.
Because mitochondrial disease is difficult to diagnose; a couple might have two or more babies die before the problem is diagnosed. Until now there was no way to provide reproductive choices so that these couples, already traumatised by losing one child or more, could have a healthy baby.
How can the new IVF technique help?
For women diagnosed as carriers of mitochondrial disease, it means a chance to have a baby that is healthy. As Sharon Bernardi has said to the BBC, it’s not about designing a baby with ‘desirable’ features, or saying that disable children or adults cannot live productive lives. It’s about providing these women and their partners with the choice to decide whether to remain childless or to have a baby that has a good chance of living.
What does the new IVF technique involve?
Eggs and sperm are taken from the biological parents, as with any IVF cycle. The nucleus from the mother’s egg is removed from the egg casing and transferred into a donated egg from another woman. This has had its nucleus and the entire nuclear DNA removed; only the healthy mitochondria and the egg casing remain. This egg is then fertilised using the father’s sperm in vitro, and the resulting embryo is implanted into the womb.
“The headlines that have referred to ‘3-parent babies’ and ‘designer babies’ are misleading,” stresses Professor Hanna. “A child born as a result of this IVF technique would have two parents, the mother and the father. The egg donor is simply providing the healthy mitochondria, which then divide and enter each of the embryo’s cells, allowing them to function normally.”
Safeguards and public consultation
The announcement, by Professor Dame Sally Davies, Chief Medical Office, that the UK will produce draft regulations on this technique later in 2013 follows a public consultation that resulted in widespread support.
“This is a new technique and ground-breaking. Some people are opposed to it because they think it will lead onto using IVF for sinister reasons, but that is never going to happen,” says Professor Hanna. “The regulations in the UK are the strictest in the world and this new IVF technique will be available under very severe restrictions for women diagnosed with a mitochondrial disorder. For them, it means regaining the hope of having a healthy baby and a family life.”