CRISPR And Human Embryo Experiments Underway In The U.S. : Shots - Health News Despite outrage over gene editing in China that affected the birth of twins, research is underway in the U.S. to assess the safety and effectiveness of CRISPR tools to edit genes in human embryos.
NPR logo

New U.S. Experiments Aim To Create Gene-Edited Human Embryos

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
New U.S. Experiments Aim To Create Gene-Edited Human Embryos

New U.S. Experiments Aim To Create Gene-Edited Human Embryos

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


A Chinese scientist stunned the world last year when he announced that he had created the first gene-edited babies. Now NPR has learned about a new experiment aimed at creating gene-edited human embryos. It's being conducted by a scientist in the United States. Let's be clear. He is not trying to make genetically modified babies yet, but that could be the ultimate goal. NPR health correspondent Rob Stein brings us this exclusive story from inside the scientist's lab.

ROB STEIN, BYLINE: It's early in the morning at one of Columbia University's research towers in New York City. I meet Dieter Egli in his office on the sixth floor.

Hi, Rob Stein from NPR.

DIETER EGLI: (Laughter) You came in with a microphone.

STEIN: Yeah, sorry, sorry. I was...

EGLI: I guess that's your job. That's what you do.

STEIN: Yeah, we have to kind of record every little thing for our stories.

Egli leads me down the hall to a tiny windowless room. It's jammed with scientific equipment - two microscopes, lab dishes. He's going to show me how he's trying to fix mutations in human embryos.

EGLI: I'm going to wear gloves because we want to keep things clean.

STEIN: Egli wants to know if it's really possible to use the revolutionary gene-editing technique known as CRISPR to safely repair genes in human embryos.


STEIN: Egli is trying to repair a genetic defect that causes blindness to maybe, someday, help blind people carrying the mutation have children who can see.

EGLI: Preventing inherited forms of blindness would be wonderful and very important for affected families.

STEIN: One big reason the world condemned the Chinese scientist is he rushed ahead without doing enough careful research first to prove it works and is safe.

EGLI: We can't just do the editing and then hope everything goes right and implant that into a womb. That's not responsible. We have to first do the basic research to see what happens. That's what we are doing here.

STEIN: But even just doing the basic research to see if this might be possible is really controversial, but more about that later. Right now, Egli is ready to start his editing experiment. He turns to a big, black microscope behind him and slides a round glass dish under the lens. That dish contains the CRISPR gene-editing tool, along with sperm from a blind man who carries the defect that Egli is trying to fix. Egli gently adds a human egg to the dish.

EGLI: I'm starting with just one egg. You'll be able to see it shortly once I go to higher magnification.

STEIN: I can see everything he's doing under the microscope magnified on a computer monitor.

The big round thing is the egg. It looks like the moon.

EGLI: Yeah, it's a beautiful cell. I would say it's one of the most beautiful cells.

STEIN: Egli maneuvers a tiny glass needle towards one of the sperm.

EGLI: So you can see I'm moving sperm over here. I'm picking it up. The sperm is in the needle. Now I'm dipping it in the CRISPR tool.

STEIN: Once the sperm is inside the needle with the CRISPR gene-editing tool, Egli points the needle's tip at the egg.

EGLI: Oh, no. No. The sperm is swimming away. Oh, here it is.

STEIN: Once that runaway sperm is back in the needle, Egli pierces the egg.

EGLI: The membrane is broken, breached. There we go. Sperm and CRISPR tool in the egg.

STEIN: Oh, you did it.

EGLI: Yeah, got it.

STEIN: That's nerve-wracking.

EGLI: Very.

STEIN: The idea is that CRISPR will slice out the mutation in the sperm, and the healthy DNA in the egg will fix it.

EGLI: Hopefully the CRISPR tool will cut the mutation, and then the egg will replace that with a version that no longer causes disease. The genome from the mother would be rescuing the mutant genome from the father.

STEIN: Scientists in Oregon who developed this approach are also trying to prove the technique can safely fix genetic mutations in human embryos, including one of the breast cancer genes.

EGLI: OK, next.

STEIN: For the next two hours, Egli painstakingly fertilizes and edits one egg after another.

EGLI: There we go. That one definitely worked - beautiful.

STEIN: It may be beautiful to Egli, but this kind of research is making some people very nervous.

FYODOR URNOV: This is really disturbing.

STEIN: Fyodor Urnov is a scientist at the Altius Institute for Biomedical Sciences in Seattle. He worries this kind of research will encourage more scientists to go rogue and misuse this technology.

URNOV: As we've learned from the events in China, it is no longer a hypothetical that somebody will just go ahead and go rogue and do something dangerous, reckless, unethical. Anyone with a connection to the Internet will be able to download the recipe to make a designer baby. And then the question becomes, what's to prevent them from using it? And as we learned in the past year, apparently nothing.

STEIN: So Urnov wants a halt to such research until scientists can figure out how to prevent more abuse.

URNOV: We need to hit the pause button and keep it pressed until we understand how do we proceed in a way that minimizes the risk of people going rogue.

STEIN: And society has had a chance for a broad debate about whether there's really any good reason to ever try to make anymore gene-edited babies when there are so many other ways to prevent genetic diseases. But many others disagree.

ALTA CHARO: This is valid research, and I think it's important research.

STEIN: Alta Charo is a bioethicist at the University of Wisconsin.

CHARO: It has value not only for the possible use in the future for some number of conditions that would involve a live birth, but it has value for basic understanding of embryology, basic understanding of human development. Of course I think you should be doing that research. Why wouldn't you do that research?

STEIN: Two hours later back in Egli's lab...

EGLI: OK, that's it. That's the last one.

STEIN: Fourteen fertilized and edited eggs are safely back in storage.

Wow, so that was a lot of work.

EGLI: Yeah, well, that - it was.

STEIN: Egli stresses he's nowhere near trying to make any gene-edited babies this way. He stops his embryos from developing right away to study them.

EGLI: Right now we're not trying to make babies. We are working with human embryos for research purposes only. None of these cells will go into the womb of a person.

STEIN: What if it does work safely, Egli says? This gene editing could someday prevent a long list of horrible diseases - Tay-Sachs, cystic fibrosis, Huntington's; not make designer babies.

EGLI: If we ultimately find ways to prevent diseases, that will be wonderful.

STEIN: While this debate rages, the National Academies of Science and Medicine, the World Health Organization and others are trying to come up with tougher guidelines for how scientists could safely and ethically edit human embryos. Rob Stein, NPR News, New York.


Copyright © 2019 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.