Health

CRISPR Editing of Human Embryos Brings Us Closer to GMO Babies

A new development in CRISPR technology ignites ethics debates about how much control we should have over our own genome.

Matthias Kulka/Getty Images

The experiment would be the first of its kind in the US, but not in the world. In 2015, scientists in China announced that they had edited the genome of human embryos for the first time, setting off a wave of controversy. The new study reportedly differs from the Chinese study in two key ways. First, these scientists were able to use a larger number of human embryos. Secondly, and most importantly, they were able to be a lot more precise.

“I think it’s a step forward, it sounds encouraging,” Richard Hynes, a cancer researcher at MIT and co-chair of the Committee on Human Gene Editing, an advisory group formed by the National Academy of Sciences, remarked to Seeker. This past February, the committee released a report that supported the use of editing human embryos in certain specific situations — for example, to mitigate genetic disease.

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In the Chinese study, one of the issues was that although they could edit the human genome, they weren’t able to edit it well. A lot of mistakes were made, including “mosaicism,” an error that occurs when some cells of an organism contain the edited genome and others do not. The 2015 study also produced many “off-target” effects, where CRISPR edits unintended parts of the genome in addition to the intended parts. When working with human DNA, it’s obviously best to be as accurate as possible.

The latest study has managed to correct many of these errors, the Technology Review claims. The research was led by Shoukhrat Mitalipov of Oregon Health and Science University, who created the first cloned monkeys a decade ago. If this claim holds up, Mitalipov will have taken a crucial step forward in the possibility of human germline engineering. But it also raises tough ethical questions whose answers no one can seem to agree on.

In different parts of the scientific community, human germline engineering is both a hope and a fear. The idea is that once genes have been changed in an embryo, those same modified genes are then passed down to that embryo’s offspring, and in turn to their offspring’s descendants. In the case of a genetic disease, it could be the difference between eliminating the genetic disease from one generation and eliminating it from an entire lineage. And while for decades this seemed like a sci-fi fantasy, the invention of CRISPR in 2012 sparked a frenzy of scientists trying to make it a reality.

Since then, CRISPR has been a hot topic in the scientific community. CRISPR is short for CRISPR-Cas9, a gene editing system that’s made possible by several players. CRISPR (an acronym for Clustered Regularly Interspaced Short Palindromic Repeat) refers to naturally-occurring repeated DNA sequences inside microbes, used for immune system defense. But to edit genes, CRISPR needs to be paired up with Cas9 (short for CRISPR-associated protein 9). Cas9 is a large enzyme that acts as the “scissors” in the system, cutting strands of DNA in precise areas. The snipped DNA can then be modified or replaced with other sequences.

The CRISPR system can also be used to control or mute certain genes.

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The tool has generated so much hype in recent years because the possibilities for editing genes seem almost limitless. In recent years it has been used to create malaria-resistant mosquitoes, blight-resistant plants, and, for some reason, super muscular beagles. But many scientists are most excited about the possibility of using it to tackle the hundreds of viral and genetic diseases that still plague humanity.

Mitalipov, the lead researcher of the new study, has done a lot of previous research in mitochondrial diseases, such as the one that afflicted Charlie Gard in the UK. These are often devastating genetic diseases, with no current cure. If CRISPR could be used to prevent these types of illness, it would likely be a welcome relief for many couples trying to have children.

But not everyone agrees about the uses of this technology. Marcy Darnovsky, executive director of the Center for Genetics and Society, a public interest group based in California, called this latest research “a really disturbing development.”

It’s not the science itself that Darnovsky is opposed to. She told Seeker that human embryo editing likely has relevant uses, particularly in research of miscarriages and infertility. However, she noted, we don’t currently have the policy in place to ensure that this type of research is used appropriately.

“While we do have some guidelines,” Darnovsky said, “we don’t have it really written into law.” She pointed out that unlike 25 other countries around the world, the US has no legally binding ban on the books that restricts human embryo experimentation.  

“Once you let this out of the box,” Darnovsky cautioned, “you’re not going to be able to shove it back in.”

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But, Hynes said, not just any scientist can decide to study human embryos. Experimentation on human embryos is highly regulated by oversight boards, and the laws on it vary from state to state in the US. It is also subject to funding restrictions from the federal government.

“I think it’s going to be very well regulated,” said Hynes. “It’s not something you’ll be able to do in the garage.”

“Congress has included a provision in the budget which says FDA is not permitted to consider any request to begin such trials,” confirmed R. Alta Charo, a legal scholar and bioethicist at the University of Wisconson-Madison, in an e-mail to Seeker. “For now it cannot legally be done in the US.” Charo is also a co-chair of the Committee on Human Gene Editing along with Hynes.

The claim that germline editing will impact the trajectory of human evolution is also hyperbolic, she wrote.

“Even if there were a small number of children born in the future whose disease-causing traits had been edited,” Charo said, “it would not affect the vast number of people then or in the future.”

Furthermore, Charo pointed out, many of the “designer baby” traits that people are worried about, such as selecting for higher intelligence, are so complex that they are currently impossible.

Josephine Johnson, Director of Research at The Hastings Center, told Seeker that she personally thinks it’s “absolutely appropriate” to use CRISPR technology on human embryos in the case of eliminating genetic diseases and the resulting suffering. But, she pointed out, we are already in the era of designer babies.

Couples today can look for egg donors with certain characteristics, or screen and then abort embryos with genetic diseases.

“We are on that path already,” Johnson said. “The question is how far down it we want to go.”