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CRISPR genome editing

Emmanuelle Charpentier and Jennifer A. Doudna were awarded the 2020 Nobel Prize for Chemistry “for the development of a method for genome editing,” for what is commonly known as CRISPR, first published in 2012.

But what is the CRISPR/Cas9 system? 

CRISPR is a method of gene editing. CRISPR finds a specific bit of DNA inside a cell. After that, the next step in CRISPR gene editing is usually to alter that piece of DNA. CRISPR is also used to turn genes on or off without altering their sequence.

CRISPR is sometimes referred to as genetic scissors and is a much cheaper and easier system of gene editing than previous methods.

The discovery came from Doudna’s research into a bacterial immune system against viruses. Bacteria use a form of CRISPR to slice up viral DNA, rendering it harmless to the bacteria. 

Doudna and Charpentier showed they could program a small strip of what they called “guide RNA” to carry a bacterial CRISPR-associated (Cas) enzyme to exact DNA sequences, allowing them to target specific genes. 

The Cas9 protein targets and binds to specific DNA sequences, Cas then cuts the double-stranded DNA. This starts the normal cell DNA repair system but without a repair template, the process creates insertion/deletion mutations, and can be used to knock out specific genes.

Knocking out a gene in this way and stopping it working is an effective way to study its normal role. CRISPR also allows researchers to insert a new stretch of DNA at the cut site.

CRISPR stands for clustered regularly interspaced short palindromic repeats.

CRISP has been very widely applied. Here are just a few examples. 

Making pig organs available to people

CRISPR has been used to manipulate pig DNA, making it a better match to human DNA in hopes of engineering safer pig organs for human transplants. The pig genome has 62 copies of porcine endogenous retroviruses which researchers were able to eliminate in pig embryos in the lab using CRISPR. The modified pig cells were unable to pass the retrovirus on to human cells and with more research it is hoped that modified animal organs will one day be used for human transplants.

Professor George Church, geneticist at Harvard University said,

"It was kind of cool from two stand points. One is it set a record for Crispr or for any genetic modification of an animal, and it took away what was considered the most perplexing problem to be solved in the xenotransplantation field. With immune tolerance, that completely changes the landscape as well. These two things, immune tolerance and now getting rid of all the retroviruses, means we have a clear path." 

Gene-editing tool, Crispr-Cas9, stunts tumour growth in mice 

Dr Weiren Huang and his team from Shenzhen University, in China, used the gene-editing tool Crispr-Cas9 to stunt tumour growth in mice. Mice with the reprogrammed code developed tumours that were much smaller than cancers in mice that did not get this treatment. Whilst experts call the study promising more research is needed to see whether the technique would work in humans.

CRISPR used to treat haemophilia in mice

CRISPR/Cas9 is showing promise for efficient correction of disease-causing mutations. For the first time, researchers from the Perelman School of Medicine at the University of Pennsylvania have developed a dual gene therapy approach to deliver key components of a CRISPR/Cas9-mediated gene targeting system to mice to treat haemophilia B.

CRISPR-based treatment destroys two cancer types

Scientists at Tel Aviv University (TAU) have developed a lipid nanoparticle-based delivery system that specifically targets cancer cells and destroys them by genetic manipulation. This novel system, which they call CRISPR-LNPs, carries a genetic messenger (messenger RNA), which encodes for the CRISPR enzyme Cas9 that acts as molecular scissors to cut the cells' DNA.

Last edited: 11 February 2021 11:08

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