Five Things to Know About the Latest Gene Editing Breakthrough

While it’s not the first case of genetically modifying human embryos, the study has reignited a long-running controversy

By editing a gene soon after fertilization, scientists were able to successfully fix a disease-causing mutation in human embryos OHSU

A new study this week has pushed the boundaries of gene editing, demonstrating again that scientists can now successfully repair certain disease-causing mutations in human embryos. Published yesterday in the journal Nature, the results garnered many headlines, with news of the move even leaking early last week. While not the first case of human embryo editing, the announcement has re-ignited the controversy over the ethics of gene editing. Here are there five things you should know about this latest research.

1. CRISPR strikes again

In this study, scientists worked with the CRISPR-Cas9 gene editing system, which is kind of like cut and paste on for genes. It's based on a naturally occurring immune system found in many bacteria species in which the microbes keep a "hit list" of virus DNA in their genomes so they can recognize future dangerous intruders. If any of that DNA is present, the bacteria deploys enzymes called Cas (CRISPR-associated proteins), which precisely and efficiently snip out that DNA.

In the latest study, scientists used this tool to remove a mutation in the gene MYBPC3 that leads to a thickening of the heart muscle—a potentially fatal condition, reports Emily Mullin of MIT Technology Review. After successfully snipping it out, they then copied a healthy version into the sliced section.

2. It's not the first editing of its kind done of human embryos

This research was notable for its use of viable embryos, or embryos that could likely develop into a baby if allowed to grow, reports Dina Fine Moran for Scientific American. This is the first time this has ever happened on U.S. soil, but scientists in China have already been pushing the envelope for years. In 2015, a group of Chinese researchers genetically modified embryos for the first time. And earlier this year, another group of researchers modified the genes of viable embryos for the first time.

The U.S. government and its affiliates, including big regulators like the Food and Drug Administration, are banned from funding research that involves human embryos, meaning researchers had to draw on private or institutional funds for this study, reports Heidi Ledford for Nature. A report in February cautiously opened the door for possible future U.S. government funding of embryo gene editing research, but it's not clear when that recommendation will make its way into regulations.

3. The next step may move overseas

The next step for this research is to see whether the embryos modified in this way can actually grow in a healthy way, reports Ian Sample of The Guardian. But the U.S. strictly forbids clinical trials of this nature, and it doesn't seem likely that the rules will change any time soon.

“It’s still a long road ahead,” study author Shoukhrat Mitalipov tells Sample. “It’s unclear when we’d be allowed to move on.”

To move forward, the researchers might need to head somewhere more permissive, reports Kate Lunau of Vice Motherboard"We would be supportive of moving this technology to different countries," Mitalipov tells Lunau.

4. There's controversy

A slew of think-pieces and editorials accompanied the news of this research yesterday, with many expressing concerns about how far this research pushes science into unknown territory—and urging caution.

"There’s too much we don’t know about the safety of gene editing to allow engineered humans who can pass down mutations to roam the Earth. What are the potential health effects of even slight editing mistakes? We don’t know yet," Alessandra Potenza writes for The Verge about a report released yesterday by an international group of geneticists.

"Public policy and the field of bioethics have not caught up with the science of genetic intervention," the editorial board of the Los Angeles Times writes. "It’s paramount that we get human gene editing right rather than just getting it soon."

Others championed the news as providing hope for those struggling with inherited diseases. This includes Alex Lee, who suffers from Leber’s hereditary optic neuropathy, a rare mitochondrial disease. He writes for The Guardian:

"It’s easy for those unaffected by genetic diseases to dismiss scientific progress as a step towards a future in which we start selecting a criterion of eye or hair color from a design-your-own-baby catalog. But for people like me, affected by an incurable genetic disease that caused me to go blind, scientific advancements into gene editing and mitochondrial replacement therapy offer nothing but hope."

5. We're not designing babies (yet)

“This has been widely reported as the dawn of the era of the designer baby, making it probably the fifth or sixth time people have reported that dawn,” bioethicist​ Alta Charo tells Ed Yong of The Atlantic. “And it’s not.”

For one thing, reports Megan Molteni of Wired, choosing traits willy nilly for a child is actually much more difficult than this process. Scientists in this study took one gene and modified it to get to the embryo to copy a healthy DNA sequence instead of a mutated one.

“Everyone always talks about gene editing. I don’t like the word editing. We didn’t edit or modify anything,” Mitalipov tells Molteni. “All we did was unmodify a mutant gene using the existing wild type maternal gene.”

Traits like height, hair color and eye color are controlled by hundreds or thousands of separate genes in ways that scientists don't fully understand yet. And they would require splicing in whole new DNA sequences that would have to be created or drawn from other people. Still, researchers foresee a future where that could be discussed, and hope to see it reasonably controlled.

“There’s the worry that this could be used for enhancement, so society has to draw a line,” Mitalipov tells Yong. “But this is pretty complex technology and it wouldn’t be hard to regulate it.”

Get the latest stories in your inbox every weekday.