TOPICS > Health

Three-parent DNA treatment for rare defect raises debate

February 3, 2016 at 6:25 PM EDT
When women have defective mitochondria, their children can inherit terrible, sometimes fatal problems. A new technology, pioneered in England, adds healthy cellular structure from a third person, meaning that children are born with DNA from three people. William Brangham learns more from Jeffrey Kahn of Johns Hopkins University and Marcy Darnovsky of the Center for Genetics and Society.

GWEN IFILL: Now to questions surrounding a significant advance in reproductive technology with DNA and embryos.

The change on the horizon was pioneered and approved in England and it is now being considered for use in the U.S. Proponents believe it may eliminate dangerous disease in children, but others have raised ethical concerns.

Today, the National Academy of Sciences recommended that clinical trials go forward in the U.S.

William Brangham has our look.

WILLIAM BRANGHAM: This new technology is called mitochondrial replacement technique, or MRT for shot.

Mitochondria are tiny structures that exist in nearly all the cells in our bodies, and have their own unique DNA. The problem is, a very small number of women have defective mitochondria, and if they have children, those kids inherit their mom’s mitochondria and can suffer terrible, sometimes fatal, problems, including brain damage and heart failure.

This new technology would, in essence, replace that original mitochondria in either the mother’s egg or in the parents’ embryo with healthy mitochondria from a third person. A child born this way would then be carrying the DNA of three different people.

Earlier today, patient advocate Laurie Strongin told us why the advance was so important for a small group of parents.

LAURIE STRONGIN, Patient Advocate: One of the things that we have found is that parents’ desire to have genetically related offspring is a widely held desire. It’s not universal, but it’s widely held.

And the potential to use MRT to have offspring who are genetically related to both parents is something that families who carry mtDNA disease really want. And not everyone is going to pursue it, but for the family for whom having children who are — who have a nuclear genetic connection to them, this is something that will just be one of numerous options available to them.

WILLIAM BRANGHAM: Joining me now to discuss the technology and its implications are Johns Hopkins bioethics Professor Jeffrey Kahn, who chairs the panel at the National Academy of Medicine that recommended moving forward with the technology, and Marcy Darnovsky, who writes widely on these issues and is the executive director of the Center for Genetics in Society.

So, Jeffrey Kahn, I would like to start with you.

I wonder if you could just tell us a little bit more about this technology. To my ear, this sounds like what we know of as some sort of modified version of in vitro fertilization. Can you tell us a little bit more? What is this technology?

JEFFREY KAHN, Johns Hopkins University: Yes.

It is, in fact, a modified version of in vitro fertilization, as you noted. However, it’s picking up the nuclear DNA, the DNA that we think of as creating the traits that make us who we are, and picking that up and putting it into a healthy environment of mitochondria.

As you noted in the intro, there are women who suffer from mutations in addition those mitochondrial DNA that will cause really terrible diseases in their offspring. So, this is a way to avoid that and preserve the genetic relationship. The difference, or the challenges, this has never before been done in a human.

And so the FDA, which is charged with regulating license applications in new areas like this, asked the National Academy of Medicine to hold the consensus committee to evaluate the ethics, social, and policy issues related to this technology.

And that’s the report that was released today.

WILLIAM BRANGHAM: So, just so — I know there are some viewers who are wondering. We’re not talking about tweaking the DNA that affects our hair color or our intelligence or things like that.

JEFFREY KAHN: No, that’s right.

And so the mitochondria actually are quite important. Otherwise, there wouldn’t be this need, because people who have defective mitochondria have terrible disease issues. So, mitochondria create energy for every cell in our body. And they also have some other implications at the cellular development level.

And so, no, it isn’t actually a way to change the things we think of as making us who we are, eye color, hair color. You mentioned intelligence, athletic ability, all the kinds of things we might think of in the so-called designer baby problems. It wouldn’t do that.

It’s really picking up a healthy population of mitochondria and replacing that for those that are diseased, and a way forward which we think we have crafted which allows a responsible, ethically acceptable way forward, but with great precaution and numerous restrictions.

WILLIAM BRANGHAM: I’m just curious. We mentioned this is a relatively small number of people who would use this. How many people are we talking about?

JEFFREY KAHN: In the hundreds of people, so not — across the entire country. And part of that is because it’s a very homogeneous disease.

It’s really hard to detect and diagnose, and only a small number of people have a severe enough version that we know for sure that they’re going to pass it on and that the children who are born will be affected. That said, they very desperately want to have a way to have children who are related to them.

The alternative for those individuals, otherwise, is adoption, not having children, or egg donation. And that is a different thing for those individuals. And it’s an area we thought needed to be respected on the part of people who wanted it.

WILLIAM BRANGHAM: All right, Marcy Darnovsky, I want to turn to you.

I know you have some concerns about this technology. What is it that troubles you?

MARCY DARNOVSKY, Center for Genetics and Society: Well, I think for people who are in the situation that has just been described, they have to make a very difficult decision about whether to subject their future child to the risks of what’s really a quite biologically extreme procedure, whether that’s worth what their — their preference to have a genetically related child is.

All people that have this problem, this terrible problem, can have healthy children, children who are not affected by these mitochondrial diseases, in the ways that Jeff just mentioned, and some of them can actually use an embryo screening technology as well. And that would further reduce the number of people who would be candidates for this procedure.

And so, for the rest of us, I think we have to weigh the preferences of those — that small number of people for a genetically related child against — which is a benefit, but it’s a social benefit, not really a medical benefit, because it’s not about healthy children.

We have to weigh that against the big deal it is to do this for the first time, to make changes that would be passed down to future generations. And this problem of whether we should do it or not is a subject right now of huge controversy around a different technique called gene editing.

And on that technique, the conclusion of a 500-person meeting that was held in December was that it would be irresponsible to proceed unless and until there was a broad, societal consensus that it would be OK.

But, on the other hand, the committee, although I appreciate very much the cautions and the limitations that they have recommended, but this committee is saying it’s OK to go forward now.

WILLIAM BRANGHAM: Jeffrey, what do you make of that? Is this the slippery slope to gene editing or some of these more troubling outcomes?

JEFFREY KAHN: I would say no, and here’s why.

As Marcy rightly pointed out, there are real concerns about crossing the germ line, so creating genetic modifications that could be inherited by future generations. And among the recommendations in our report was that the initial investigations be limited to the implantation of male embryos, because the mitochondrial DNA is only passed from mother to offspring.

So by limiting the offspring to males, you wouldn’t allow that germ line modification to happen. There would be no possibility of passing those alterations to future generations. So, we thought we could find a way to allow people who very much wanted to have genetically related offspring to pursue a new reproductive technology.

And I think it’s important to say there are many new reproductive technologies introduced in this country and around the world that do not get this level of scrutiny. This is the first time the Food and Drug Administration in our country has, from the beginning, prior to the initial investigation of a new reproductive technology, has asked for this level of scrutiny, and, depending on what they do with the recommendations from this report, implement them in a way that will really control the introduction of a new technology of this sort.

WILLIAM BRANGHAM: Marcy, what do you make of that? Do you feel that the conditions can be placed on this technology to keep it in check that would make you comfortable with this?

MARCY DARNOVSKY: Well, the condition that I would like to see placed on this before we go forward would be for the United States to join the dozens of other countries around the world that have actually written laws saying that we’re not going to alter the nuclear DNA that’s passed down to our children and future generations.

I think that would make us able to evaluate this technology in a better way. And the limitations are better than nothing, but they are temporary, as the report notes, and I think we’re already seeing this approval being characterized as a green light for going ahead, and it’s being used as an argument for doing the full-out kinds of genetic engineering that would create the designer baby scenarios.

WILLIAM BRANGHAM: All right, this is a very interesting discussion.

Marcy Darnovsky and Jeffrey Kahn, thank you both very much for being here.

JEFFREY KAHN: Thank you.