This is the name given to babies born thanks to a new assisted reproductive technology which allows the creation of embryos with genetic material from 3 different people. We should call it two genetic parents technology, though, since only 0.002% of the third person's genetic material is used.
This new technology might be the reproductive solution for more than 150 couples that, each year, cannot have children due to mitochondrial diseases.
Approval in the United Kingdom
The House of Commons of the United Kingdom has passed, on February 3rd, a new law that gives green light to this technology. With 382 votes in favour and 128 against, the technique has been authorized. However, it has been the focus of ethical debates and opposed by the Anglican Church. The church rejects the technique and believes it destroys and manipulates the embryo.
With the approval of the Senate, the UK will become the first country to allow the so-called three parents technology. Now, the Human Fertilisation and Embryology Authority must license the technology so that it can be used in clinics. The birth of the first baby with "three parents" is not expected until 2016.
What does this technique involve?
Cells have two main components: the nucleus and the cytoplasm. The genetic material, DNA, is found in the nucleus. The cytoplasm is formed by several organelles, responsible for different DNA functions. Mitochondria are a type of organelle, which contains a small portion of DNA.
In some cases, mitochondrial errors lead to mitochondrial diseases, which are genetically transmitted by the mother. They can have serious consequences for the baby, such as brain damage, loss of muscle mass, heart failure and blindness within the first year of life.
The transplant of healthy mitochondria is the solution for these diseases. For the transplant to be effective and for all the organism's mitochondria to be changed, it should be done after conception. This is only possible by means of in vitro fertilization.
The transplant is carried out as follows: two eggs are fertilized using spermatozoids from the man. One is the egg of the woman who suffers from a mitochondrial disease and, the other, a donated egg (with healthy mitochondria). The core of the two embryos is extracted and only the one carrying the genetic material of the parents is preserved. The preserved core is introduced in the donor's embryo, that is to say, in the donor's cytoplasm. The embryo is then transferred to the mother's uterus.
There is a variant of the technique that consists of switching the nucleus before the fertilization. Either way, the future baby has the core's material (i.e. the vast majority of his parents' genetic material) and the donor's healthy mitochondria.
According to specialists, this technology is hopeful and not overly complex. However, there are risks.
Risks of the technique
The three parents technology has two main disadvantages:
- Mitochondrial activity is not only regulated by the DNA they carry, but also by the nucleus' DNA. Since the mitochondria are from one person and the nucleus from another, the possibility of incompatibility between nuclear and mitochondrial proteins exists. This possibility would cause alterations of energy and of the primary function of mitochondria, creating pathologies that we were trying to avoid.
- When the nucleus of the mother whose mitochondria are damaged is transferred to the cytoplasm of the donor, unhealthy mitochondria can be transferred. If few mitochondria exist, the risk of disease in the foetus is very low, even if the female foetuses are carriers and transmitters of defective mitochondria.
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