AUDIE CORNISH, HOST:
CRISPR is a powerful gene-editing technique scientists use to modify genes. NPR has learned that a group of scientists in New York is using it in a new way. They're trying to edit genes in human sperm, and the changes they make could be passed down for generations. NPR health correspondent Rob Stein recently got exclusive access to the lab conducting this controversial experiment. He joins us now in the studio.
Welcome back, Rob.
ROB STEIN, BYLINE: Hey, Audie.
CORNISH: This isn't the first time scientists have tried to make changes in human DNA in a way that could be inherited. Haven't they done this kind of thing before with human embryos, though?
STEIN: Yeah, that's right. Scientists have used CRISPR to edit the DNA in human embryos. In fact, you might remember there was a Chinese scientist who announced last year that he'd created the world's first genetically modified babies using embryos that he had edited in his lab and was widely condemned around the world as irresponsible and unethical. And the big reason is is that no one knows if it's safe to do that sort of thing.
CORNISH: So why are researchers trying to edit DNA now using human sperm?
STEIN: Well, one reason is that it could be safer than editing DNA in human embryos. One of the big safety concerns about editing human embryos is that you might only end up editing some and not all of the cells in any babies you try to make from an edited embryo. But if you start with sperm, at least theoretically, you can be more confident that all the cells of any resulting baby would have the changes that you're trying to make.
CORNISH: Can we go back to the issue of safety, though - right? - and the controversy around using CRISPR to edit genes? What are some of the other concerns that people have?
STEIN: Yeah. Yeah, there's a lot more concerns other than just safety. And, you know, the - one of the big concerns is that, you know, if you make any changes in DNA in babies that could be passed down for generations, somebody someday could try to use the same technology to make, you know, so-called designer babies, where parents pick and choose the traits of their children. And that raises all kinds of sort of scary sci-fi scenarios about genetic haves and genetic have-nots.
CORNISH: And scientists still see this as worth doing. What are their hopes for the technology?
STEIN: Yeah, so this group of scientists in New York, they're doing this really for two reasons. One is to possibly find new ways to prevent male infertility by, you know, understanding more about how sperm works and the genetics of sperm. The other one is to try to fix genetic mutations that cause diseases that men pass down to their children. Here's Gianpiero Palermo. He runs the Weill Cornell Medicine lab in New York City, where this experiment is being conducted.
GIANPIERO PALERMO: Somebody has a certain genetic abnormality carried in their genome. This can be removed so make sure that the offspring will be void from these abnormalities. Theoretically, in principle, that would be a major, major benefit to society.
CORNISH: You actually went to the lab to see this research in action. Can you tell us what it was like?
STEIN: Yeah, it was really fascinating. So what they're trying to do, as I said, is used CRISPR to edit the DNA in human sperm. And the hard thing about sperm is that the DNA is packed really tightly in the head of each sperm cell. So what they're doing is they're literally zapping the sperm with a jolt of electricity to loosen up the DNA to try to get the CRISPR gene-editing tool in there. Let's listen to a little moment that occurred when I was with June Wang. She's a lab technician in the lab in New York.
JUNE WANG: I am now taking the sample into the pipette.
STEIN: That's the sperm and the CRISPR together.
WANG: Now it's going into the machine.
STEIN: So the CRISPR and the sperm are in this zapping machine.
WANG: Here. I'm going to click start. It's very quick.
STEIN: So that's it. It just did it.
STEIN: Now, it's important to emphasize that these scientists haven't figured out a way to make it work yet, and, you know, they may never. It could turn out to be technically just too difficult, but they're going to keep trying to see if they can possibly make it work.
CORNISH: That's NPR health correspondent Rob Stein.
Thanks for explaining it.
STEIN: Oh, sure thing.
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