Insights into Editorial: World’s first three-parent baby born
The birth of the world’s first “three-parent baby,” a child who carries genetic information from three different people, was recently announced.
How was it done?
The baby was created via an IVF (in vitro fertilization) procedure that involved three people: the mother, the father and a woman who donated eggs. This specialized IVF procedure is called spindle nuclear transfer.
- Scientists took DNA from the nucleus of the mother’s egg cell and inserted that genetic material into an egg cell from the donor.
- The nucleus of the donor egg had been removed, but the egg still contained a bit of DNA from the donor woman: That is, it contained genetic material from the mitochondria, or the cell’s energy powerhouses, which have their own DNA. The egg was then fertilized with sperm from the father.
What was the need for it?
In this case, the procedure was done because the eggs of the mother contained faulty mitochondria. This caused four miscarriages and the death of two of her children from a neurological condition called Leigh syndrome.
About the procedure:
In the spindle nuclear transfer in this case, the scientists took five egg cells from the mother and removed a cellular part called the spindle, which carries the mother’s chromosomes. The researchers inserted these spindles into five donor eggs that had their nuclei removed, but which contained healthy mitochondria. The donor eggs then underwent in-vitro fertilization and developed for several days in a dish. Of the five early stage embryos, just one had a normal number of chromosomes. It was implanted into the mother, who gave birth to a healthy boy after 37 weeks of pregnancy.
What is the problem the procedure solves?
A small number of children each year are born with faults in their mitochondrial DNA which can cause diseases. Mitochondria are small structures that sit inside our cells and provide them with energy. They have their own set of 37 genes which are separate from the 20,000 or so genes that shape who we are.
How do the diseases affect people?
Mitochondrial diseases tend to strike in childhood and get steadily worse. They often prove fatal before adulthood. The parts of the body that need most energy are worst affected: the brain, muscles, heart and liver. Conditions include Leigh’s disease, progressive infantile poliodystrophy and Barth syndrome. Faulty mitochondria have also been linked to more common medical problems, including Parkinson’s, deafness, failing eyesight, epilepsy and diabetes.
Why do doctors want to do this?
There are no treatments for mitochondrial diseases, which affect about 1 in 6,500 babies in the more serious forms. Women at risk of passing them on have few options available to them if they want to give birth to healthy children. They could opt for using donor eggs or, in some cases, a form of pre-natal genetic diagnosis before one of their own IVF embryos is placed back into their womb. Creating IVF embryos using mitochondrial donation offers an opportunity of having their own, genetically related children who are free of mitochondrial defects. Furthermore, the process could mean that mitochondrial diseases are eliminated completely from future generations of that family.
What objections do people have to the procedure?
Mitochondrial transfer passes on genetic changes from one generation to another. That raises ethical concerns because any unexpected problems caused by the procedure could affect people who are not yet born, and so cannot give their consent to have the treatment. Mitochondria are not completely understood, and the DNA they hold might affect people’s traits in unknown ways. For that reason, some scientists believe mitochondria should be better understood before the procedures are legalised.
- Some people are opposed on religious or ethical grounds, particularly with pro-nuclear transfer technique which involves creating and then destroying a fertilised egg in order to treat another embryo.
- Others believe that there will be inevitable “carry over” of defective mitochondria from the affected mother’s fertilised egg to the donor egg. These mutant mitochondria could multiply during embryonic development to cause disease, perhaps in way we do not yet understand. This is why, they say, we need to do more research before allowing it to be used on people.
What’s not so good about this technique?
- Experts have warned that three-parent babies could be at greater risk of cancer and premature ageing, and would need to be monitored all their lives.
- Since this is uncharted territory and the children born from this technology would have heritable genetic changes, there are also significant unknown risks to future generations.
- There are numerous serious risks associated with this technology. These include most notably the possibility that developmentally disabled or deceased babies will be produced.
- Aberrations could also lead to developmental defects in babies or also manifest in later life as increased rates of ageing of cancer.
Where is it legalized?
The UK is the only country to have introduced laws to permit the technique. The European country legalized the treatment in 2015.
There ought to be a better understanding of the implications and the completion of review of outstanding experiments on their safety before they are actually taken up.