Changing DNA

Will CRISPR revolutionise genetic engineering?

by Kimmy Kwok

From cloning to genetic engineering, humans have revolutionised genome editing technology. However, the most recent discovery in the science of gene modification is known as CRISPR; clustered regularly interspaced short palindromic repeats. This technology allows us to change genetic material in living organisms. As represented in Fig 1, the cells are being broken apart to allow natural DNA repair processes to take over. A technology that isn’t even ten years old and can already perform surgery on our genes. It is the cheaper, faster, and more accurate process of changing an organism’s DNA. It is said that ‘the future of CRISPR is now’.

Cas9 has revolutionised life sciences, including targeted gene editing. It was originally adapted from a naturally occurring process that bacteria use as a defence mechanism. When the bacterium detects the presence of the virus DNA, it produces two different short pieces of RNA. One containing a sequence that matches the virus. The two RNAs form an enzyme known as Cas9. Cas9 acts as a pair of ‘molecular scissors’ as its job is to cut DNA. Cas9 proteins cut out a segment of the viral DNA, disabling the virus. It will stitch the taken segment into the bacterium’s CRISPR region. The viral code is then copied to short pieces of RNA where it binds to Cas9.

CRISPR in the future?

The testing of CRISPR had started in labs, but it has slowly advanced to the testing in humans (Drillinger, 2021). Scientists discovered to replace a mutant gene with a healthy one, they had to add another piece of DNA that carries the desired sequence. The CRIPSR system will make a cut, allowing the DNA template to pair up with cut ends, which combines and replaces the original sequence with the new one. It is an exciting advancement of science and medicine where it could even be a potential cure for cancer.

Why use CRISPR?

A lot of attention has been on using CRISPR to cure sickle cell disease. Cells are extracted and treated before inserted back into patients and it happens right in front of their eyes. Unlike other genetic engineer methods, CRISPR can be used to target large areas at once. This is extremely practical for complex human diseases that are caused by many genes acting together. It accelerates research into diseases such as cancer and mental illnesses. Not only can it happen to humans, but it has also been tested on animals. CRISPR can cure mice with Duchenne muscular dystrophy – DMD (Kaiser, 2015). CRISPR will simply snip out part of the defective gene in mice, allowing the organism to make its own essential muscle protein. This approach was the first time CRISPR has been successfully delivered throughout the body to treat animals with a genetic disease.

What is CRISPR?

From living organisms to foods, CRISPR has made advanced breakthroughs, starting from its discovery in 1993 to 2005. Francisco Mojica was the first researcher to characterize this technology. The discovery of Cas9 was made in 2006, by a scientist studying at an Agricultural Research Institute. Scientists have discovered if one would like to edit genes, one would have to use the technology known as CRISPR. The technology was designed to locate a desired piece of DNA inside a cell and genetically alter it. The discovery of CRISPR-

Top breakthroughs made by CRISPR

13,000 edits in a single cell

A student at MIT known as George Church has made a breakthrough by using CRISPR. He made 13,000 edits in a single cell without killing it (Fan, 2019). Church led a study to wipe out PERV - a virus that are integrated in the genome of all pigs. CRISPR has successfully mutated every PERV gene in the pig’s cell which was roughly 62 copies. While doing this study, he found if one made too many edits, a cell could commit suicide. This was due to CRISPR breaking the double helix multiple times.

No hangover wines

A team of researchers at the University of Illinois have genetically modified the yeast that is used to ferment wine. They achieved no hangover wines by increasing a chemical known as resveratrol, thus decreasing your hangover. Resveratrol is found in the skin of grapes used to make wine (Patsnap, 2022). The yeast being modified is called Saccharomyces cerevisiae. It has many copies of its own gene, making it highly adaptable and difficult to genetically modify with older methods. Researchers have successfully used CRISPR to cut every copy of a desired gene in one go, increasing the amount of resveratrol. Thus, leaving those hangovers in the dust.

Faster racehorses

How far should we be allowed to go in transforming human race?

Some are suggesting using CRISPR on early embryos to change the genetics at an early stage. But due to safety, social, and ethical reasons, scientists say that’s a step too far. However, that didn’t stop He Jiankui. Jiankui was the rogue scientist behind the creation of the world’s first CRISPRmodified babies, twin girls known as Lulu and Nana (Patsnap, 2022). Said by Dr Kiran Musunuru, who studied stem cell and regenerative biology at the Harvard University, ‘No babies should be born at this point of time following the use of this technology. It’s simply too early, too premature.’ Jiankui altered a gene to protect them from HIV because their father has AIDS. But he did it while the twins were still in a petri dish. Which leads to the problem of his use of CRISPR technology. He genetically altered sperm line cells – the sperm and the egg. In this case of the twin girls, a fertilised egg at the singlecell stage. By changing the DNA at that stage, it will appear in every cell in a person’s body. One may call that effective, however, they are permanent and will be passed onto future generations. There is a real chance that an edit can cause a mutation in the genome, leading to worse case scenarios. Another problem was consent. The twin girls had no authority to say no in the changes made to their bodies.

This sort of technology would only be available for people with status or significant wealth. By encouraging them to use CRISPR, it has the potential to increase inequality in our world. To regulate it, 75 countries have banned the use of CRISPR in human reproduction. But many scientists and governments agree there should be more rules to guarantee its prohibition.

What if there was a way to make certain horses run faster or stronger? Researchers have discovered that different versions of the myostatin gene, an inhibitor of skeletal muscle growth, accounts for the speed of a horse. Argentinian KheironBiotech is using CRISPR to edit the genome of racehorses making breeds that are faster, stronger, and better jumpers (Patsnap, 2022). Thus, increasing their rate of winning. They have a success for removing the myostatin gene with 96.2% efficiency. This includes creating horse embryos with the genetically altered edit. Looking to the long term, we hope to identify more alleles that give horses a natural advantage.

Discussion questions

1. What other scientific uses can CRISPR be used for beyond genetic engineering?

2. Can embryos consent to the use of CRISPR?

3. Will CRISPR increase wealth inequality?

Interested in learning more?

Here’s a YouTube video you may enjoy:

References

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Broad Institute (2018). CRISPR Timeline. [online] Broad Institute. Available at: https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/ crispr-timeline [Accessed 14 Feb. 2023].Drillinger, M. (2021). CRISPR Study Is First to Change DNA in Participants. [online] Healthline. Available at: https:// www.healthline.com/health-news/crispr-study-is-first-to-change-dna-inparticipants#How-does-retinal-dystrophy-gene-correction-work? [Accessed 13 Feb. 2023].

Fan, S. (2019). New CRISPR Method Can Edit Over 13,000 Spots in a Single Cell. [online] Singularity Hub. Available at: https://singularityhub.com/2019/04/10/ new-crispr-method-can-edit-over-13000-spots-in-a-single-cell/ [Accessed 13 Feb. 2023].

Genotipia. (n.d.). Genome Editing Image courtesy of Stephen Dixon and Feng Zhang solo apra noticias51426_web. [online] Available at: https://genotipia. com/genetica_medica_news/edicion-crispr-linfocitos-t/genomeediting-image-courtesy-of-stephen-dixon-and-feng-zhang-solo-apranoticias51426_web/ [Accessed 10 May 2023].

Greely, H.T. (2019). CRISPR’d babies: Human Germline Genome Editing in the ‘He Jiankui affair’*. Journal of Law and the Biosciences, 6(1). doi:https://doi. org/10.1093/jlb/lsz010. [Accessed 13 Feb. 2023].

Jazeera, A. (2021). CRISPR: What is the future of gene editing? | Start Here. [online] www.youtube.com. Available at: https://www.youtube.com/ watch?v=pVIVSpUgR44 [Accessed 15 Feb. 2023].

Kaiser, J. (2015). CRISPR helps heal mice with muscular dystrophy. [online] www.science.org. Available at: https://www.science.org/content/article/ crispr-helps-heal-mice-muscular-dystrophy#:~:text=Three%20groups%20 report%20today%20in [Accessed 13 Feb. 2023].

Kurzgesagt – In a Nutshell (2016). Genetic Engineering Will Change Everything Forever – CRISPR. YouTube. Available at: https://www.youtube. com/watch?v=jAhjPd4uNFY [Accessed 14 Feb. 2023].

Liu, A. (2021). TALEN gene editing tool more efficient than CRISPR-Cas9 in compact DNA: study. [online] Fierce Biotech. Available at: https://www. fiercebiotech.com/research/talen-gene-editing-tool-more-efficient-thancrispr-cas9-certain-dna-study#:~:text=A%20research%20team%20from%20 the [Accessed 14 Feb. 2023].

McGovern Institute (2014). Genome Editing with CRISPR-Cas9. YouTube. Available at: https://www.youtube.com/watch?v=2pp17E4E-O8 [Accessed 13 Feb. 2023].

MedlinePlus (2020). What are genome editing and CRISPR-Cas9? [online] medlineplus.gov. Available at: https://medlineplus.gov/genetics/ understanding/genomicresearch/genomeediting/ [Accessed 13 Feb. 2023]. PatSnap. (2022). 7 Innovations Driving CRISPR Technology Forward. [online] Available at: https://www.patsnap.com/resources/blog/7-innovationsdriving-crispr-technology-forward/#:~:text=The%20applications%20of%20 CRISPR%20technology [Accessed 14 Feb. 2023].

P. Zipes, D. (2019). Transcription Activator-Like Effector Nuclease - an overview | ScienceDirect Topics. [online] www.sciencedirect.com. Available at: https://www.sciencedirect.com/topics/biochemistrygenetics-and-molecular-biology/transcription-activator-like-effectornuclease#:~:text=Transcription%20activator%2Dlike%20effector%20 nucleases%20(TALENs)%20are%20synthesized%20by [Accessed 14 Feb. 2023]