© The Indian Express Pvt Ltd
Tags:
Journalism of Courage
In a first, eight children in the United Kingdom are leading healthy lives because of a groundbreaking but controversial IVF (in-vitro fertilisation) procedure that uses genetic material from three parents — the mother, the father and the mitochondrial donor to create an embryo in a lab. The procedure helps women with faulty mitochondria (powerhouses of cells) to have children without passing on the incurable, potentially fatal disease.
Researchers from the UK’s Newcastle Fertility Centre — the only centre in the country authorised to perform the three-parent IVF — reported that four boys and four girls were born using the procedure. The oldest of the children is now over two years old and the youngest under five months. Another pregnancy is currently under way. Altogether 22 women underwent the procedure. UK is the only country that legalised this form of IVF in 2015.
Mitochondrial diseases can be varied — ranging from mild with little or no symptoms to severe that can affect different organ systems and can be life-threatening. They tend to affect parts of the body that require a lot of energy, like our brain, muscle, kidney and heart. The estimated prevalence of diseases resulting from faulty mitochondria is estimated to be one in 5,000. “Mitochondrial disorders can be devastating, often causing organ failure or death in early childhood. They are incurable and only passed through the mother’s mitochondrial DNA. The three-parent technique seems to effectively prevent these conditions,” says Dr Neelam Suri, senior consultant, gynaecology, Indraprastha Apollo Hospital, New Delhi.
Researchers from the Newcastle Fertility Centre used a technique called Pronuclear Transfer. In this technique, the mother’s egg is fertilised using the father’s sperm in a laboratory setting. The genetic material from the mother and the father are contained in two separate membranes called the pronuclei. The two pronuclei are removed from the fertilised egg on the first day of development, which leaves most of the mother’s faulty mitochondria behind.
Then a donor egg is fertilised using the father’s sperm or donated sperm. Again, on the first day of development, the pronuclei are removed from the egg. The pronuclei extracted from the first egg is then injected into the donor egg. So, the embryo consists of the genetic material from the parents along with the healthy mitochondrial DNA from the donor. “We found that mitochondrial donation through pronuclear transfer was compatible with human embryo viability,” the researchers said.
There is another technique that scientists can use for creating such three-parent babies called Maternal Spindle Transfer. This technique modifies the egg before fertilisation. The genetic material contained in the nucleus of the mother’s egg is removed and inserted into a donor egg whose genetic material has also been removed. This egg containing the genetic material from the mother and mitochondrial DNA from the donor is then fertilised using the father’s sperm.
Yes. Almost all of the genetic material comes from the parent, with around 0.1 per cent coming from the donor egg. The mitochondrial DNA makes up for only 37 genes out of the nearly 20,000 that make up a human genome. As children inherit mitochondria only from the mother — and not the father — mitochondrial DNA is sometimes used to trace ancestry, which would not be possible for these children.
Three of the eight children born so far did carry some proportion of the faulty mitochondria from the mother — ranging between five and 16 per cent. These levels of faulty genes, however, are not enough for the diseases to manifest. Of the three children who do carry the faulty mitochondria, two are female and may pass it on to their children.
The three-parent technique is not about designer genes or selecting a baby’s physical or intellectual traits. It only replaces faulty mitochondria to prevent disease and does not alter the nuclear DNA that carries the vast majority of our hereditary characteristics. “Ethical and social concerns exist because changes to mitochondrial DNA are inherited by future generations, raising long-term safety and unforeseen risks. However, current scientific consensus views the technique primarily as a life-saving intervention for families affected by specific mitochondrial disorders,” says Dr Suri.
Opponents say the procedure is unnecessary as it is risky, can have health consequences for the donors as they need to undergo hormonal stimulation of eggs and an extraction procedure.
