How the future of fertility will challenge ideas of parenthood
When Britain’s House of Lords gave doctors its blessing this year to proceed with the seemingly harmless- sounding “mitochondrial replacement therapy,” the country’s tabloids went to work: “Threeparent babies risk future of human race,” screamed the breathless Daily Mail.
Now, with the first of those babies expected early in 2016, doctors and ethicists are awaiting the births with mixed excitement and dread. The procedure, which is illegal in Canada, involves essentially swapping genetic material between two women’s eggs.
Mitochondria work like miniature power plants, supplying energy to virtually every cell in the body, except red blood cells. When the genes in mitochondria contain mutations, they can cause devastating, often fatal, diseases, including brain disorders, diseased heart muscles, strokes, seizures, dementia, deafness and blindness.
Now, researchers can extract the nucleus from the egg of a woman with diseased mitochondria, and transfer it to a donated and “enucleated” egg of one with normal mitochondria.
The “new” egg contains the nuclear DNA of the “social” mother — the woman who will parent the child — and the mitochondrial DNA of the egg donor. The egg is then fertilized in a lab with the male partner’s sperm via in vitro fertilization (IVF), and the resulting embryo transferred to the mother’s uterus.
Since most DNA is packaged into chromosomes within the nucleus, the mother and father provide 99.9 per cent of the total genetic material. The remainder — 0.1 per cent — comes from the egg donor. ( Mitochondrial DNA is passed down only through females. Women can be carriers, but not discover the problem until they give birth.)
While the mitochondrial DNA contribution is exceedingly small, “it’s the first time in human history that we’re altering the genome,” says Dr. Neal Mahutte, a past president of the Canadian Fertility and Andrology Society. “I think the families who suffer from these diseases make a very compelling case that it’s worth trying under an appropriately supervised system.”
In Britain, the procedure could benefit 150 births a year; in the U. S., 778. The U.S. Institute of Medicine has been asked by the Food and Drug Administration to issue its own report on the ethical and social considerations of mitochondrial replacement therapy.
Canada’s Assisted Human Reproduction Act says no person shall knowingly “alter the genome of a cell of a human being or in vitro embryo such that the alteration is capable of being transmitted to descendants.”
Dalhousie University bioethicist Françoise Baylis, who doesn’t think there’s a compelling case for mitochondrial replacement, questions the “time, talent and energy” being spent on helping a few women have genetically linked children, when there are other ways of having a family, including adoption, or stan- dard IVF using a donor egg. “They’re saying, ‘I don’t want any child. I want this child — this child that’s genetically connected to me.’ And I want to say, why is that important?”
Some of the steps involved in mitochondrial therapy, Baylis argues, “would otherwise look very similar to cloning.” Others worry the procedure could lead society down a path to genetic enhancement
Baylis says science is nowhere near being able to select for something as complex as, say, memory. Still, she asks, “Will we, as a species, try? Will we forge ahead? Might we eventually succeed? I think so.”
She grounds her concerns in capitalism and hubris. “The minute somebody knows how to do it, and make it, they’re going to sell it. And the minute it’s for sale, people are going to want to buy it.”
Dr. Mark Tarnopolsky, an expert in mitochondrial disorders, doesn’t see any ethical issues. “I’ve seen people from the first few days of life, to people in their 60s and 70s die from these diseases,” says Tarnopolsky, a pediatrics prof at Hamilton’s McMaster University. He views mitochondrial replacement as a minor alteration of standard IVF. “There are always people who take things to hyperbole,” he says.
But, “I’m watching kids and people die (from fatal disease). If we can stop that with this somewhat sophisticated twist on a current practice, it seems progressive and appropriate to do so.”