What is CRISPR? What to know about transformative gene-editing tools

Over the past 10 years, CRISPR has been transformative for research, enabling fast, simple and precise gene editing, experts say.

The first paper showing that CRISPR could be used to edit mammalian genes was published 10 years ago this month. Since then, it has been used in research laboratories around the world and is being tested in the treatment of cancer and rare diseases, and in developing crops resistant to cardiovascular disease and climate change.

CRISPR gene editing is fast, simple and precise, researchers say.

“There are many examples that without CRISPR, our lives as scientists would be much more difficult,” said Beverly Davidson, a neuroscientist at the Children’s Hospital of Philadelphia.

Gene editor Fyodor Arnov compared DNA sequencing – the detailed reading of the genome – to a powerful telescope. CRISPR, meanwhile, “allows us to fly to these newly discovered galaxies and do something useful once we’re there,” he said. “This gives us completely unprecedented insight into the functioning of every biological system, from tiny yeast to humans.”

CRISPR has already been used to discover the biological basis of diseases, which then leads to treatments, he said. “And that’s within 10 years.”

Here’s what to know.

What is CRISPR used for?

In nature, CRISPR, an acronym for “clustered regularly interspaced short palindromic repeats,” acts as a defense system for bacteria. Scientists have repurposed it to make gene editing more precise and easier to use.

CRISPR has the ability to find a specific spot on a strand of DNA and cut, add or replace a genetic “letter” or even a word.

Advanced forms of CRISPR allow researchers to quickly screen diseased cells compared to normal cells, looking for targets for gene editing.

University of California San Francisco pediatric and fetal surgeon Dr. Scientists spent years and “tons of money” breeding genetically altered mice similar to those of humans with rare genetic diseases, Tippi McKenzie said. “Now you can do it in a few weeks.”

Has CRISPR been used on humans?

In November 2018, Chinese scientist He Jiankui sparked a global scandal by admitting to using a gene editing tool to edit embryos and create “CRISPR babies”.

Most scientists and medical ethicists support the idea of ​​using gene editing to improve the lives of people with dreaded diseases. Such changes help address the illness while the person is alive.

But mainstream scientists and companies are not working on so-called germline editing, although there may be some rogue actors considering it.

Chairman and CEO of Intelia Therapeutics, which develops CRISPR-based therapies for rare diseases and cancer, John Leonard said, “It makes no sense”. Almost all conditions that could benefit from germline editing can be treated or otherwise prevented, he said.

Since 2016, CRISPR has been used in clinical trials to treat patients with blood cancer. Recent research has tested CRISPR gene editing in people with rare diseases caused by single gene mutations.

“We’re really trying to create answers for people with diseases,” Leonard said.

What is CRISPR-Cas9?

In June 2012, biochemists Jennifer Dudna and Emmanuel Charpentier published a paper describing how CRISPR works as a bacterial immune system. They revealed that Cas9, short for CRISPR-associated endonuclease 9, acts like scissors, cutting DNA. These two women won the 2020 Nobel Prize in Chemistry.

“The protein Cas9 to DNA is like your mouse cursor that you use to click on the section of text you want to change,” said Arnove of the University of California, Berkeley.

With RNA delivered to the correct location, Cas9 cuts both strands of the DNA fragment. When the strands are put back together, some letters of the genetic text are lost. Researchers use that ability to get rid of toxic genes.

In people with sickle cell disease, for example, researchers are using Cas9 to make a genetic snip to enable the patient’s body to make a substance called fetal hemoglobin again. Fetal hemoglobin, normally shut down in the first year of life, causes sickling of red blood cells causing severe pain and organ damage in patients.

Using CRISPR to treat sickle cell, Urnov said, is basically like taking a spare tire out of the trunk to replace a flat.

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