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August 1, 2017

Scientists edit genes of human embryos for the first time in US

Daily Briefing

A team of biologists in Oregon reportedly have conducted the first known experiment in the United States using the gene-editing technique CRISPR to genetically modify viable human embryos.

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The experiment, first reported last week in MIT Technology Review, is not the first of its kind: Three previous studies that used CRISPR to edit human embryos were all conducted in China. However, it is believed to be the first such study completed in the United States, and according to MIT Technology Review, the scope of the study goes beyond the previous research in terms of the number of embryos tested and the research findings.

According to the Associated Press, officials at Oregon Health and Science University confirmed that the research was conducted at the university and said results are pending publication in a journal.

Congress has barred FDA from approving any clinical trials using genome-editing technology in human embryos.

Study details

Shoukhrat Mitalipov, the director of the Oregon Health and Science University Center for Embryonic Cell and Gene Therapy, led the study but declined to share specific details about the research while it awaits publication.

According to the Technology Review, the study centered on a process known as germline engineering, which entails altering human embryos' DNA in an effort to eradicate or correct genes that cause inherited diseases.

People familiar with the experiment have said it involved "many tens" of "clinical quality" human embryos created using donated sperm from men with a specific genetic mutation that researchers planned to repair with CRISPR. None of the embryos involved in the study developed for more than a few days, and researchers never intended to implant any of them into a womb, according to the Technology Review.


The research appears to have avoided problems that arose in previous studies, in which CRISPR caused editing errors and intended DNA changes sometimes affected some of an embryo's cells but not others—an effect known as mosaicism, the Technology Review reports.

A scientist familiar with the experiment said the results are "proof of principle that [using CRISPR to edit human embryos] can work," because the researchers "significantly reduced mosaicism." According to the Technology Review, the latest experiment may have had more success than past research by "'getting in early' and injecting CRISPR into the eggs at the same time they were fertilized with sperm."

The scientist said, "I don't think it's the start of clinical trials yet, but it does take it further than anyone has before."


Scientists and ethicists have expressed a range of sentiments over such experiments—from awe to alarm, the Technology Review reports.

While scientists say the approach could one day be used to avoid genetic diseases, some have raised concerns that it could lead to "designer babies." Further, according to STAT News, some fear that "such manipulations could alter the course of human evolution" because the edited cells could be passed down to future generations, if a germline edited embryo were implanted, born, and grown to adulthood.

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However, R. Alta Charo, a legal scholar and bioethicist at the University of Wisconsin-Madison, said, "We still have regulatory barriers in the United States to ever trying this to achieve a pregnancy," adding that the public would have "plenty of time" to weigh in on whether such embryos should be implanted in a womb.

Charo said the study "is the kind of research that is essential if we are to know if it's possible to safely and precisely make corrections" in human embryos. He added that "while there will be time for the public to decide if they want to get rid of regulatory obstacles to these studies, [he does] not find them inherently unethical."

The National Academy of Sciences (NAS) and the National Academy of Medicine earlier this year gave the first green light to such research, saying scientific advancements have made the use of gene-editing technology on human reproductive cells "a realistic possibility that deserves serious consideration." But the groups said such research would need to be strictly regulated.  

Robert C. Green, a medical geneticist at Harvard Medical School, called the prospect of editing embryos to avoid disease "inevitable and exciting." He said that "with proper controls in place, it's going to lead to huge advances in human health" (Begley, STAT News, 7/26; Beasley, Reuters, 7/27; Connor, MIT Technology Review, 7/26; AP/New York Times, 7/27).

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