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Emmanuelle Charpentier explains CRISPR Cas9 gene editing (2016)
01:50 - Source: CNN
CNN  — 

Two women have won the Nobel prize in chemistry for the development of a revolutionary gene editing tool that’s been described as “rewriting the code of life.”

The technique discovered by Emmanuelle Charpentier, the director at the Max Planck Institute for Infection Biology, and Jennifer A. Doudna, a biochemist at the University of California Berkeley, is known as CRISPR/Cas9.

It hit the headlines in 2018 when a Chinese scientist used the technology to create the first gene-edited babies, shocking the world and sparking a highly charged ethical debate about its use.

What is CRISPR (pronounced “crisper”) and why has it been controversial?

How it works

DNA is like the instruction manual for life on our planet, and CRISPR/Cas9 can target sites in genetic material.

This allows scientists to change it by knocking out a particular gene or inserting new genetic material at a predetermined site in our DNA.

Cas9, a type of modified protein, acts like a pair of scissors that can snip parts of DNA strands. CRISPR stands for clustered regularly interspaced short palindromic repeats – a repeated DNA sequence in genomes.

“Doudna and Charpentier showed that CRISPR works like a pair of scissors that can be targeted to cut specific DNA sequences, said Andrew Holland, an assistant professor in the Department of Molecular Biology and Genetics at Johns Hopkins School of Medicine. “After cutting, the repair of the DNA code enables it to be altered. This has allowed scientists to change the DNA code in a targeted way to help understand and treat genetic disease,” he told CNN via email.

The technology has worked in pretty much every organism that it has been used on, including plants, microbes and humans.

“What the system does is that it can recognize (a) certain specific gene in the genome of ourselves and correct mutations, do some copy pasting, do some editing like we edit a text. The system can edit the genome and change the properties of the genes,” Charpentier said in 2016 when she was interviewed by CNN.

How is it used?

It is already having a major impact on biomedical research, clinical medicine and agriculture. For example, it’s been used to grow rice that accumulates lower levels of potentially toxic heavy metals and create livestock with more desirable traits.

It was used for the first time in humans in 2016 and a trial is underway in the United States to use the experimental technology to treat a dozen patients with sickle cell disease, a group of inherited blood disorders.

Related technologies may be able to potentially correct up to 89% of genetic defects, scientists have said.

“It’s not an exaggeration to say that the technology that arose from Doudna and Charpentier’s discoveries has revolutionized the field,” Jessica Downs, the deputy head of the Division of Cancer Biology at the Institute of Cancer Research in the UK, told the Science Media Centre in London.

“We adopted the technology in our lab to investigate molecular changes that lead to cancer development. It’s been transformative in terms of what we can achieve, but there is also great potential for using this technology in the clinic. And on a more personal level, it’s inspiring and uplifting to see two women honored for their work in this way.”

Why has it been controversial?

While it has immense potential to transform our lives, the technology has raised many ethical questions.

Chinese scientist He Jiankui was jailed for three years in 2019 after announcing that twin girls had been born with modified DNA to make them resistant to HIV, which he had managed using the gene-editing tool CRISPR/Cas9 before birth.

An associate professor at the Southern University of Science and Technology in Shenzhen at the time, he said that he was “proud” of the achievement. But he was condemned by many of his peers, with the experiment labeled “monstrous,” “unethical” and a “huge blow” to the reputation of Chinese biomedical research.

Claes Gustafsson, secretary of the Nobel committee in chemistry and a professor of biochemistry and biophysics at Stockholm University, said that with “every really powerful technology, in life sciences or elsewhere, there’s a possibility of misuse.”

“Clearly this Chinese researcher was way out of line in applying it in this particular way,” he told CNN.

“Everyone has agreed that it cannot be used for germline engineering. You can’t make heritable changes to human DNA. That is far too uncertain at this point,” added Gustafsson. “There are specific genetic diseases you can think of curing for the individual but not in a heritable way.”

Scientists have called for a moratorium on human germline editing, while efforts are being made to better regulate use of the technology. An international commission said in September it was too early for gene-edited human embryos to be used to create a pregnancy.

Doudna has expressed deep concern about He’s work, telling CNN it was not medically necessary and there was no way to defend using an experimental technology when there were established ways of avoiding HIV transmission.