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Inside every cell in the human body are mitochondria, tiny molecular machines which ‘power’ the cell by providing chemical energy. When these mitochondria don’t work properly, the consequences can be fatal.

Treating mitochondrial diseases has historically been challenging, since they are a diverse family of diseases with a wide spectrum of symptoms.  Mitochondrial disorders often target nerve tissue, and the results range from debilitating (MERRF syndrome) to fatal in the first few years of life (Leigh’s disease).

Recently, a powerful but controversial therapy has emerged to prevent these diseases, and it just became legal in the UK. Here’s the story of this treatment, which will eventually see babies being born with the genetic material from three parents.

The Procedure

Of the components of the cell, mitochondria are unique in an important way — mitochondria are actually the remnants of a very old species of microbe, which evolved a symbiotic relationship with animal cells before being fully integrated in our life cycle.  Mitochondria live inside our cells but have their own organelles, their own DNA, and their own cell wall.  This makes it very difficult to fix them when they have problems.

The idea behind the new therapy is very simple: if the mother has a disease carried in the mitochondrial DNA, you can remove the defective mitochondria and replace them with new, healthy ones from a donor.  The mitochondrial transfer procedure itself is revolutionary, and can be performed in two ways, depending upon the state of fertilization.

The first technique is done prior to the fertilization of the egg. This procedure is known as Maternal Spindle Transfer, and it works by taking an unhealthy egg with defective mitochondria, and removing the nucleus, which contains the majority of the cell’s DNA, and acts as the command center of the cell. This is implanted into a donor egg which lacks the defective mitochondria, and has had its own nucleus removed.  The hybrid cell can then be fertilized, and will mature normally.



The second is done after the egg has been fertilized, and is called pronuclear transfer. Here, the nucleus from the fertilized, but unhealthy, egg is removed and transplanted into a healthy egg. This is then transplanted back in to the biological mother to gestate.

Both procedures eliminate the risk of a child being born with mitochondrial disorders. With 1 in 200 children being born with some form of mitochondrial disorder, and 1 in 6,500 having a disease that will eventually result in early death, the benefits of this are overwhelmingly obvious. So, why the controversy?

The Controversy

This legislation, which passed the first time around, has attracting criticism from the usual suspects in reproductive rights conversations, namely the religious right and social conservatives in general.

The Catholic Church, known for their strong stance when it comes to sexual and biological ethics, decried the ‘Three-Parent Baby’ law as one which trivializes life, with Bishop John Sherridon saying that it makes ‘human life disposable[…]’

“Whilst the Church recognizes the suffering that mitochondrial diseases bring and hopes that alternative methods of treatment can be found, it remains opposed on principle to these procedures where the destruction of human embryos is part of the process.”

Speaking to the Catholic Herald, he continued:

“The human embryo is a new human life with potential; it should be respected and protected from the moment of conception and not used as disposable material.”

The Anglican Church – which is the official state church of the United Kingdom, and is generally less hardline than the Catholic Church when it comes to reproductive and biological issues – was relatively reserved, although in the days leading up to the vote, they made an official statement raising concerns about the safety aspects of the procedure.

“The Archbishops Council, which monitors this issue, does not feel that there has been sufficient scientific study or informed consultation into the ethics, safety and efficacy of mitochondria transfer. Without a clearer picture of the role mitochondria play in the transfer of hereditary characteristics, the Church does not feel it would be responsible to change the law at this time.”

This said, it’s neither fair nor accurate to characterize all concern about the procedure as coming from religious quarters. Social conservatives have also raised concerns about mitochondria transfer procedures. The most notable critic of the procedure is Conservative backbench MP Jacob Rees-Mogg, who in an interview on The Today Program on BBC Radio 4 said:

“At the moment there is a very clear boundary that babies cannot be genetically altered and once you’ve decided that they can, even for a small number of genes, you have done something very profound and then it’s merely a matter of degree as to what you do next.”

Rees-Mogg (with his usual subtlety) then went on to tweet:

Seemingly, the biggest criticisms of the Three-Parent Baby procedure are very similar to the criticisms leveled against transhumanism How Technology May Be Influencing Human Evolution How Technology May Be Influencing Human Evolution There's not a single aspect of the human experience that hasn't been touched by technology, including our very bodies. Read More . Namely, that science is transforming what it means to be a person, and the consequences are incredibly hard to predict.

Cutting Through The Noise

Mitochondrial replacement therapies are inherently divisive, especially given the sensitive matter of genetics and parentage are considered. But what are the facts?

Well, let’s start off by saying that the term ‘three parent baby’ which has been rapturously adopted by the British press is a bit of a misnomer. Although the egg does indeed come from a third party donor, and some genetic material from that donor is passed on, the reality is that only a tiny portion of genetic material will be passed on to the baby. In total, less than 0.2% of genetic material will be passed on.


Another concern (and another massive can of worms) is that this procedure could eventually pave the way for ‘designer babies’, in which humans seize genetic control of their own development, to engineer smarter, stronger, and healthier children — a scenario that was explored in frightening detail in the film GATTACA.

The genetics required to modify nearly all of a person’s characteristics are stored in the cell’s nucleus, which is not changed by the mitochondria transfer procedure. Furthermore, at the time of writing, it is illegal to modify the nucleus of a human baby in the United Kingdom, and in a great many other countries. Accusing this therapy of leading inevitably to designer babies is simply a non sequitur.

It’s also worth noting that, in the grand scheme of things, a mitochondrial transfer isn’t the most unorthodox transplant we’ve ever really seen. Researchers have already worked out how to transplant a genetically modified pig heart Researchers Create a Pig Heart That Can Survive in Primates Researchers Create a Pig Heart That Can Survive in Primates Last week, researchers announced that they'd implanted the heart of a transgenic pig into a baboon, and kept it alive for a year. Here's why you should care. Read More into a primate, and we’re already examining the possibility of replacing human organs and bones with ones that came from a 3D printer How 3D Printing Humans Might Be Possible Some Day How 3D Printing Humans Might Be Possible Some Day How does bioprinting work? What can be printed? And will be ever be able to print a full human being? Read More . Some people have even voluntarily embedded magnets and electronic circuits Biohacking: The Creepy but Exciting Trend in Body Modification Biohacking: The Creepy but Exciting Trend in Body Modification "Sorry about the mess," says Steve Haworth, as we walk down the stairs to the surgical theater, where he merges consumer technology and the human body to produce uniquely functional body modifications. Read More into their body.  If conservatives can’t cope with a mitochondrial transplant, they’re not going to like the next few decades at all.

A Great Leap Forwards

Each year in the UK, 150 babies are born with severe, life-limiting (or life ending) mitochondrial diseases.  Many more go on to develop less fatal mitochondrial diseases, which produce an array of horrifying symptoms. This treatment could save all of those people from needless suffering and death.  Are we venturing into unknown territory? I think so. Is it worth it? Absolutely.

So where you do you stand?  Do you know anyone who suffers from a mitochondrial disorder?  Do you think this kind of therapy should be legal? Let us know in the comments.  

Photo Credit: Laughing Baby (SvetlanaFedoseyeva – Shutterstock), artificial insemination (Koya979 – Shutterstock), Digital illustration of Mitochondria in colour background (RAJ CREATIONZS – Shutterstock) 

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