A Potential But Controversial Fix For Genetic Disease
Scientists in Oregon have developed a technique that could be used to prevent certain genetic diseases. They've demonstrated it in monkeys and are anxious to try it in people. The technique raises ethical questions, however, because it makes a permanent genetic change not just in an individual, but in all generations that follow.
The technique involves an unusual set of genes in the human body. Most of our genes are in our chromosomes, which are in the cell's inner sanctum, the nucleus. But 37 human genes are outside the nucleus. They are contained in tiny bodies called mitochondria, which float around in our cells. Mitochondria are the mini power plants for our cells. And mutations in the genes inside mitochondria can cause disease.
Shoukhrat Mitalipov and his colleagues at Oregon Health and Science University are trying to figure out how to treat this class of rare genetic diseases. They've been working with the eggs of rhesus monkeys. If you fix a genetic problem in an egg, you will fix it in all the cells the egg grows into — the whole animal.
"So, basically, we construct this experimental egg, which contains nuclear genes from one female, but mitochondrial genes from another female," he says.
In short, they can remove the nucleus from an egg that has defective mitochondrial genes, and put it into an egg that has healthy mitochondria. So the mother's chromosomes end up in an egg that has healthy mitochondria, albeit from a different female.
The technique worked quite well in monkeys, according to a study the journal Nature has published online. The researchers made this transfer with 15 eggs, fertilized them, and ended up with four baby monkeys.
"So what we showed is these manipulated eggs acted like normal eggs, and most importantly they resulted in births of healthy offspring," Mitalipov says.
The monkeys are only a few months old so far. It will take four or five years before the scientists know whether they are able to reproduce successfully. It could take even longer to notice any long-term health effects. But Mitalipov says he doesn't want to wait that long — he wants to try the technique in people.
To do that, he would need to convince the Food and Drug Administration that the technique is safe. And he will also have to deal with a key ethical issue. Art Caplan at the University of Pennsylvania says the issue is that modifying the genes in an egg doesn't merely affect one individual — the modification ends up in the eggs of the individuals, too.
"It goes on forever, because it's passed on from generation to generation," Caplan says.
This kind of manipulation is called "germ line" therapy, and it's been considered taboo. For one thing, if there are health risks, they will affect multiple generations. For another, it could open the door to genetically engineering a lineage of people with supposedly superior qualities. This is called eugenics, and many people find that repugnant.
"It does breach the principle: no germ line engineering," Caplan says. "It breaches a promise that many geneticists have made, that whatever else, they're not going down that road. I always thought that promise would be difficult to keep. This particular experiment shows why."
Caplan argues the egg manipulation in this case isn't seeking to make an improved person, just a healthy one. And he's OK with that.
But George Annas at Boston University is uneasy — both for ethical reasons and for practical ones.
"I don't think anything should be totally off the table, although this would be pretty extreme," he says. "I would probably have a presumption it shouldn't be done, and the burden of poof would be on the people who propose doing it: that it's safe, and that it's not going to create problems — not just for the children, but for the children's children."
Annas says it will take a lot more than just four apparently healthy baby monkeys to make that case.
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Scientists in Oregon have developed a technique that could be used to prevent certain genetic diseases. They've demonstrated it in monkeys and are now eager to try it in people. But the technique raises ethical questions because, as NPR's Richard Harris reports, it makes a permanent genetic change not just in an individual, but in all generations that follow.
RICHARD HARRIS: You need to know just a bit of biology before you can understand what these guys are doing. Most of our genes are in our chromosomes, which are in the cell's inner sanctum, the nucleus. But 37 human genes are outside the nucleus. They are contained in tiny bodies called mitochondria, which float around in our cells. Mitochondria are the mini power plants for our cells. And mutations in the genes inside mitochondria can cause disease.
Shoukhrat Mitalipov and his colleagues at Oregon Health and Science University are trying to figure out how to treat this class of rare genetic diseases. They have been working with eggs of rhesus monkeys. If you fix a genetic problem in an egg, you'll fix it in all the cells the egg grows into - the whole animal.
Dr. SHOUKHRAT MITALIPOV (Researcher, Oregon Health and Science University): So basically, we construct this experimental egg, which will contain, you know, nuclear genes from one female, but mitochondrial genes from another female.
HARRIS: In short, they can remove the nucleus from an egg that has defective mitochondrial genes, and put it into an egg that has healthy mitochondria. So the mother's chromosomes end up in an egg that has healthy mitochondria, albeit from a different female.
And the technique worked quite well in monkeys, according to a study Nature magazine has published online. The researchers made this transfer with 15 eggs, fertilized them, and ended up with four baby monkeys.
Dr. MITALIPOV: So we showed these manipulated eggs behave like normal eggs and most importantly, they resulted in births of healthy offspring.
HARRIS: The monkeys are only a few months old so far. It will take four or five years before the scientists know whether they are able to reproduce successfully. And it could take even longer to notice any long-term health effects.
Mitalipov says he doesn't want to wait that long. He wants to try the technique in people. To do that, he would need to convince the Food and Drug Administration that the technique is safe. And he will also have to deal with a key ethical issue.
Art Caplan, at the University of Pennsylvania, says the issue is that modifying eggs means that the change doesn't merely affect one individual.
Professor ARTHUR CAPLAN (Center for Bioethics, University of Pennsylvania): It goes on forever because it's passed on from generation to generation.
HARRIS: This kind of manipulation is called germ line therapy, and it's been considered taboo. For one thing, if there are health risks, they will affect multiple generations. For another, it could open the door to genetically engineering a lineage of people with supposedly superior qualities. This is called eugenics, and many people find that repugnant.
So Caplan says the proposal to try this technique in humans deserves special attention.
Prof. CAPLAN: It does breach the principle: no germ line engineering. It breaches a promise that many geneticists have made, that whatever else, they're not going down that road. I always thought that promise would be difficult to keep. This particular experiment shows why.
HARRIS: Caplan argues the egg manipulation in this case isn't seeking to make an improved person, just a healthy one, and he's okay with that.
But George Annas at Boston University is uneasy, both for ethical reasons and for practical ones.
Professor GEORGE ANNAS (Bioethics and Human Rights, Boston University): I don't think anything should necessarily be totally off the table, although this would be pretty extreme. This would certainly be at that end that I would probably have a presumption it shouldn't be done. And the burden of proof would be on the people who are proposing it to show that it's safe and that it's not going to create problems, not just for the children, but for the children's children.
HARRIS: And he says it will take a lot more than just four apparently healthy baby monkeys to make that case.
Richard Harris, NPR News. Transcript provided by NPR, Copyright National Public Radio.
