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

Treatment of mitochondrial diseases has historically been challenging as they are a diverse group of diseases with a wide range of symptoms. Mitochondrial disorders often target neural tissue, and results range from debilitating (MERRF syndrome) to fatal in the first few years of life (Lie’s disease).

A powerful but controversial therapy has recently emerged to prevent these diseases and has just become legal in the UK. Here is the story of this treatment, which will eventually lead to the birth of children with genetic material from three parents.


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

The idea of ​​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 on the state of fertilization.

The first method is done before the fertilization of the egg. This procedure is known as mother spindle transfer, and it works by taking an unhealthy egg with defective mitochondria and removing the nucleus, which contains most of the cell’s DNA, and acts as the cell’s command center. This is implanted in a donor egg that does not have defective mitochondria and its own nucleus has been removed. The hybrid cell can then be fertilized and mature normally.


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

Both procedures eliminate the risk of having a child with mitochondrial disorders. For 1 in 200 children born with some form of mitochondrial disorder and 1 in 6,500 children with a disease that will eventually lead to premature death, the benefits are clear. So why the dispute?


This law, which was passed for the first time, drew criticism from the usual suspects in the reproductive rights talk, namely religious law and social conservatives in general.

The Catholic Church, known for its strong stance on sexual and biological ethics, has denounced the Three Parents Act, which makes life easier, and Bishop John Sherridon said it does » human life disposable […]».

“While the Church acknowledges the suffering that mitochondrial diseases bring and hopes that alternative treatments can be found, it fundamentally opposes these procedures where the destruction of human embryos is part of the process.”

Addressing the Catholic Herald, he continued:

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

The Anglican Church, which is the official state church of the United Kingdom and is generally less rigid than the Catholic Church when it comes to reproductive and biological issues, has been relatively low-key, although in the days leading up to the vote they issued an official statement raising concerns about about the safety aspects of the procedure.

“The Archiepiscopal Council, which is monitoring this issue, does not believe that there has been sufficient scientific research or sound advice on the ethics, safety, and efficacy of mitochondrial transfer. Without a clearer understanding of the role that mitochondria play in the transmission of hereditary traits, the Church does not hold itself responsible for changing the law at this time.”

It said that it is not fair or accurate to characterize all concerns about the procedure as coming from religious quarters. Social conservatives have also raised concerns about mitochondrial transfer procedures. The most notable critic of the procedure is Conservative backbench MP Jacob Reese-Mogg, who, in an interview with BBC Radio 4’s Today programme, said:

“Currently, there is a very clear line that children cannot be genetically modified, and once you decide that they can, even for a small number of genes, you have done something very deep, and then it is just a matter of degree that you will do next.

Rees-Mogg then (with his usual subtlety) tweeted:

Apparently, the biggest criticism of the three-parent procedure is very similar to the criticism directed against transhumanism. Namely, this science is changing what it means to be human, and the consequences are incredibly difficult to predict.

cut through the noise

Mitochondrial replacement therapy is inherently divisive, especially given the sensitive issue of genetics and lineage. But what are the facts?

Well, let’s start by saying that the term «child with three parents», which has been enthusiastically received by the British press, is a bit of a misnomer. Although the egg does come from a third party donor and some of the genetic material from that donor is passed on, the reality is that only a tiny fraction of the genetic material will be passed on to the child. In total, less than 0.2% of the genetic material will be transferred.


The other issue (and another big worm) is that this procedure could eventually pave the way for «designer kids» in which humans master the genetic control of their own development to develop smarter, stronger, healthier kids — the scenario. which was explored in frightening detail in the film GATTACA.

The genetics required to change almost every human characteristic is stored in the nucleus of the cell, which is not changed by the transfer of mitochondria. Also, at the time of writing, it is illegal to modify the core of a human baby in the United Kingdom and many other countries. The accusation that this therapy inevitably leads to designer children is simply not true. consequence .

It’s also worth noting that, in the grand scheme of things, mitochondrial transfer is not the most unorthodox transplant we’ve ever actually seen. Researchers have already developed how to transplant a genetically modified pig heart into a primate, and we are already exploring the possibility of replacing human organs and bones with a 3D printer. Some people even voluntarily embed magnets and electronic circuits. in their body. If conservatives can’t handle mitochondrial transplantation, they won’t like the next few decades at all.

Big Leap Forward

Every year in the UK, 150 babies are born with severe, life-limiting (or life-ending) mitochondrial diseases. Many others go on to develop less-fatal mitochondrial diseases that cause a host of horrifying symptoms. This treatment can save all these people from unnecessary suffering and death. Are we venturing into unknown territory? I think so. Is it worth it? Absolutely.

So where are you standing? Do you know anyone who suffers from a mitochondrial disorder? Do you think this type of therapy should be legal? Let us know about it in the comments.

Photo credit: Laughing Baby (Svetlana Fedoseeva — Shutterstock), artificial insemination (Koya979 — Shutterstock), digital illustration of mitochondria on a colored background (RAJ CREATIONZS — Shutterstock)

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