CRISPR Cas9 explainer natpkg_00010203.jpg
Emmanuelle Charpentier explains CRISPR Cas9 gene editing (2016)
01:50 - Source: CNN

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A first in the US, scientists reportedly edit the genes of human embryos using CRISPR

Yet the research hasn't been published and researchers remain tight-lipped

CNN  — 

America reportedly has moved ahead in a controversial race to tinker with human DNA – but the scientific feat is shrouded in unanswered questions.

The MIT Technology Review published on Wednesday a news report about the first-known experiment to create genetically modified human embryos in the United States using a gene-editing tool called CRISPR.

Shoukhrat Mitalipov, director of the Oregon Health & Science University’s Center for Embryonic Cell and Gene Therapy, reportedly led the new research. Mitalipov and the university would not confirm details of the research to CNN.

“Results of the peer-reviewed study are expected to be published soon in a scientific journal. No further information will be provided before then,” according to an emailed statement from the university’s press office. Another researcher cited in the MIT report, the Salk Institute’s Jun Wu, did not reply to CNN’s request for comment.

Mitalipov also declined to comment in the MIT Technology Review report, referencing that the research results have not been published yet in a peer-reviewed scientific journal, which is considered the gold standard for scientific research. The author of the MIT report would not confirm to CNN whether he had seen the paper.

Previously, Mitalipov and his colleagues reported the first success in cloning human stem cells in 2013, successfully reprogramming human skin cells back to their embryonic state. In 2007, a research team led by Mitalipov announced they created the first cloned monkey embryo and extracted stem cells from it.

The MIT Technology Review reported that the researchers in Portland, Oregon, edited the DNA of a large number of one-cell embryos, specifically targeting genes associated with inherited diseases in those embryos. The MIT Technology Review could not determine which disease genes had been chosen for editing in the new research.

“I’m not surprised that they were looking at genetic diseases to try and see if they could target them, because that’s exactly where I think the future inevitably leads,” said Arthur Caplan, a professor and founding head of the division of bioethics at New York University Langone Medical Center, who was not involved in the research.

CRISPR research and controversy

Previously, scientists in China were the first in the world to reveal attempts to modify genes in human embryos using CRISPR. Three separate papers were published in scientific journals describing various studies in China on gene editing in human embryos.

When it comes to the new research, “my reaction was, this is an interesting incremental step, and boy, I bet it’s going to get blown up as being more important than it is,” said Hank Greely, professor of law and genetics at Stanford University, who was not involved in the research.

“It’s not the first time anybody has CRISPR-ed human embryos. It’s not the first time anybody’s CRISPR-ed viable human embryos. It’s certainly not the first time people have CRISPR-ed viable mammalian embryos,” Greely said. “It’s the first time it’s been done in the US, but the embryos don’t care where they are.”

Yet the research has already generated attention and controversy.

“This is pushing the research faster than I thought we would see,” said Dana Carroll, professor of biochemistry at the University of Utah, if the MIT Technology Review report rings true. Carroll has used CRISPR in his own studies, but was not involved in the new research.

He pointed out that the new research reportedly involved earlier, more delicate embryos, and CRISPR reportedly was still demonstrated as efficient.

“From the perspective of research that would ultimately make germline editing safer and more effective, the earlier embryos will provide more relevant information,” he said.

CRISPR – an acronym for clustered, regularly interspaced, short palindromic repeats – allows scientists to cut and edit small pieces of DNA at precise areas along a DNA strand, essentially modifying DNA.

Once scientists discovered that they could develop a system that modifies pieces of DNA, they tested the gene-editing technology in microbes, then non-human mammals, then non-human primates, and then, by 2015, human embryos.

The controversy surrounding gene-editing in human embryos partly stems from concern that the changes CRISPR makes in DNA can be passed down to the offspring of those embryos later in life, from generation to generation. Down the line, that could possibly impact the genetic makeup of humans in erratic ways.

“There is also considerable concern about off-target effects, such as making mutations at sites in the genome other than the intended target,” Carroll said. In other words, an edit made in one area of DNA possibly could cause problems in another, as a ripple or domino effect, which could be concerning.

Some CRISPR critics also have argued that gene-editing may give way to eugenics and to allowing embryos to be edited with certain features in order to develop so-called designer babies.

Though, not all experts are too concerned.

Treating diseases

“Some people are worried about, where’s this all going to head? Are we going to wind up with super babies and eugenics? And to me, I don’t find that an interesting objection. It’s too soon for that objection,” Caplan said. “Clearly, if we’re going to let this research proceed, it’s going to be to treat diseases and prevent diseases.”

The enthusiasm surrounding gene-editing in human embryos partly stems from the promise CRISPR has shown in editing away and treating devastating intractable diseases. Earlier this year, the National Academies of Sciences, Engineering, and Medicine published a report on human genome editing, addressing potential applications of gene editing, including the possible prevention or treatment of disease.

“I hope the applications will be for the treatment of serious diseases and in cases where a sensible alternative is not available, as the National Academies’ report proposes,” Carroll said.

Greely said: “The National Academy of Sciences came out with a big report on Valentine’s Day this year about genome editing in humans, and I thought they very usefully divided it into three categories: basic research, treating living people, and making changes that will pass down from generation to generation.”

As for the reported new research, “this is category one. This is basic research,” he said. “Category three is the ethically crucial one; this isn’t that. We’re still a long way from that.”

What’s next

Other strides have been made recently in CRISPR research. Scientists at the Memorial Sloan Kettering Cancer Center in New York used the technology to genetically engineer immune cells to target and kill tumor cells in mice.

The mouse study was published in the journal Nature in February. More research is needed to determine whether similar results would appear in humans.

Last year, scientists in the Netherlands published a study in the journal PLOS Pathogens demonstrating that CRISPR could be used to edit the DNA of three types of herpes viruses in a petri dish. More research is needed to see whether this tool could be used to fight herpes in actual humans.

Other examples of diseases where CRISPR could show promise as a treatment or preventive approach in the future include cystic fibrosis, sickle cell, hemophilia, and mitochondrial diseases, such as the rare degenerative condition that the terminally-ill British infant Charlie Gard has, Caplan said.

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    “There are what are called point mutations where you can go in and fix one genetic error. The simpler the genetic error, the easier it might be to try to repair it using a CRISPR gene-insertion technique,” Caplan said about genetic diseases.

    “I think rather than trying to treat cystic fibrosis, or treat sickle cell, or treat hemophilia, it does make ethical sense to figure out ways to prevent it,” he said. “Now, obviously if it’s too risky we won’t do it. If it’s too dangerous or maybe it won’t work, we still don’t know. We’re in the early, early days (of research), but I don’t think it’s fear of eugenics that should stop us.”