In April of this year the world’s first three-parent baby was born and is reported to be healthy. This is a huge milestone in mitochondrial therapy, a year after the procedure was legalised in the UK, the only country in the world (so far) to have explicitly permitted the technique.
The procedure was overseen by doctors from the US (where the procedure is currently illegal) and took place in Mexico to Jordanian parents. This technique, which combines the mitochondrial DNA from a ‘third parent’ donor with the nuclear DNA of the mother and father, is shrouded in ethical debates and disputes. Many concerns are about the technique itself and whether there has been enough research into the long-term effects on the child and their future fertility. Moreover, as with any genetic modifications, there are additional ethical concerns about the aspect of human intervention at the embryonic stage and whether it is ethically right, with the term ‘designer-babies’ being thrown about.
Mitochondrial disease affects around 1:5,000 babies born and is often devastating, with most patients dying before or during adolescence. The mitochondria in our cells are responsible for producing energy. So when something goes wrong with the mitochondria, tissues and organs which require high levels of energy, like the brain and muscles, suffer the most. This leads to symptoms such as blindness, deafness, neurological problems and muscle weakness amongst many others.
Mitochondrial disorders can arise from mutations in nuclear genes which code for proteins that are involved in maintaining and/or replicating the mitochondrial DNA. Other mitochondrial disorders are caused by mutations in the mitochondrial DNA itself. The mitochondrial genome is small, but compact. This means that mutations in the mitochondrial DNA, which provides the instructions for making the machinery responsible for energy production in our cells, are often fatal.
We inherit our mitochondrial DNA solely from our mother but the mechanism of inheritance is not as well understood, nor as simple, as that of nuclear DNA. What this means is that often, mothers who are healthy but are carrying copies of mitochondrial DNA with mutations, pass on these mutations to their offspring. These offspring can then suffer huge developmental problems and so this frequently results in miscarriage or infantile death. Many mothers across the world who carry such mitochondrial DNA mutations have suffered heartbreak and turmoil when trying to start a family.
The current available treatments for mitochondrial disorders are lacking. Because of the vast range of mutations which can cause the disease, as well as the variety of symptoms and affected organs, it is extremely difficult to treat. But now, we have been afforded an opportunity to prevent mitochondrial disease and it is often said that prevention is better than cure. And it is certainly easier in this case!
As with any procedure, it is not 100% certain that this IVF approach will completely abolish any risk of transmission of disease, but for parents who have suffered multiple miscarriages and family tragedy, the risk is greatly reduced. Professor Sir Doug Turnbull, Director of the Wellcome Trust Centre for Mitochondrial Disease at Newcastle University is pioneering the procedure in the UK and following his latest research says:
“Our studies on stem cells does express a cautionary note that it might not be 100% efficient in preventing transmission, but for many women who carry these mutations the risk is far less than conceiving naturally”
It is clear that following the success of this new 3-parent baby, progress is likely to be swift. It is an exciting time in science that we are able to present mothers with mitochondrial DNA mutations a chance to have a healthy child of their own. The ethical debates will continue, no doubt. But it is a wonderful example of the power of science. Many of us [scientists] work for years to make some small contribution to the knowledge of mankind, and ultimately to improve the lives of others. The birth of the first 3-parent baby is a perfect example of what years of hard work and good science can achieve and that all the long hours in the lab are not in vain. This isn’t just a great achievement for science but for society as a whole and I’m excited for the future of mitochondrial therapy.
Chloe Moss is a PhD student from UCL in the UK studying Mitochondrial DNA replication in ageing and disease. Her personal blog can be found here.