The NHMRC invited all Australians to provide their views on the use of a new assisted reproductive technology that might prevent certain rare mitochondrial diseases, but which requires careful social consideration.
As a priest with expertise in Christian ethics and moral theology, I was one of the experts the campaign made available for consultation. The other experts included medical and legal professors. Australian law currently prohibits the creation of babies using DNA from more than two people, and also prohibits making changes to an embryo or egg that can be passed down to future generations. NHMRC was asking the Australian community to consider the ethics associated with mitochondrial donation, with a view to providing advice to the Federal Government.
Mitochondrial donation might be able to prevent mitochondrial DNA disease in an estimated 60 children born each year in Australia. The social and ethical issues relate to the use of mitochondrial DNA from a donor (using IVF) that results in a child having DNA from three people; the rights of children to know their full genetic heritage; the potential risks and benefits of the technology; and the implications for future generations.
Human beings are made up of billions of cells, most of which contain a nucleus. The nucleus holds most of our DNA — somewhere between 20,000 and 30,000 genes on 46 chromosomes. Most of our cells also contain many mitochondria, which provide the cell with energy and support other important functions. I think of them as tiny batteries. Mitochondria also contain some DNA — 37 genes in all.
Mitochondrial DNA disease occurs when there is a defect in one or more of the mitochondrial genes. Affected mitochondria do not function properly, and therefore do not provide the cell with the energy that it needs. There are more than 300 different mitochondrial diseases. Symptoms range from fatigue to deafness, intellectual disability, diabetes, liver failure, heart failure, respiratory failure, seizures and strokes. One in 5000 Australian babies is born with a severe or life-threatening form of mitochondrial DNA disease. Many of these babies die as children. Many other Australians (about one in 200) are born with defects in their mitochondrial genes that could lead to mitochondrial DNA disease at some stage in their lives.
We inherit our mitochondria from our mother. Mitochondrial donation attempts to prevent the transmission of mitochondrial DNA disease from mother to child. There are at least four techniques. Each of them involves IVF, which is not approved of by the Catholic Church. Each also involves the father’s sperm, the mother’s egg (with defective mitochondria), and a donor egg (with healthy mitochondria). The aim is to produce a zygote or early embryo that contains the nuclear DNA from the father’s sperm, the nuclear DNA from the mother’s egg, and the healthy mitochondria from the donor egg. This zygote would then be implanted into the mother’s womb, and hopefully would develop free of mitochondrial disease.
If mitochondrial donation is permitted in Australia, the technique most likely to be used would be pronuclear transfer or PNT. In this technique, both the mother’s egg and the donor egg are fertilised by sperm from the father. The nuclear DNA in the zygote produced from the donor egg is then replaced with the nuclear material from the zygote produced from the mother’s egg. If all goes well, this should produce a zygote who is genetically related to both his or her mother and father, but who also possesses healthy mitochondria from the donor egg.
The ethical concern is that pronuclear transfer involves producing and then destroying human life. Two zygotes are produced. Each of them is a unique human life. Each of them is what all of us once were at the earliest moment of our existence. But one of these zygotes is destroyed so that some of its parts can be used. I feel very strongly about this issue because I know that I was once a zygote and an embryo in my mother’s womb, and this zygote is my brother or my sister. It is wrong to destroy human life even from that moment when that life begins.
Mitochondrial donation is new, and we know little about how effective or safe it might be. There is some risk of a carryover of the defective mitochondria — which means there is some risk of the child still developing serious mitochondrial disease. There is an alternative to mitochondrial donation that is safer and less ethically troubling.
The alternative is simply to fertilise the donor egg with the father’s sperm. It means there will be no genetic relationship between the child and their mother, but just as parents of adoptees love their children, these parents will love their child too. And this alternative eliminates any risk of their child developing mitochondrial disease.
Mitochondrial donation introduces changes that could be heritable — that is, changes that could be passed on to any progeny of this child. What effect could this have on the human genome in the future? The United States does not permit mitochondrial donation for this reason.
Australian law does not currently permit mitochondrial donation. Might it be better and safer to leave this ban in place?