Progression in the gene editing field through CRISPR has now made it possible for genes to be altered inside the body, coining the term “gene surgery” and representing a bright prospect in advancements of medicine.
What is CRISPR?
CRISPR is a gene-editing tool used by scientists which rose to popularity for its simplicity and efficiency compared to other techniques. This method was discovered in the immune systems of bacteria such as e-coli, which fights deadly viruses that infect the bacteria.
Clustered Regularly Interspaced Short Palindromic Repeats (aka CRISPR) and CRISPR-associated proteins (Cas) are the two main components that come together and splice the DNA of the invading virus in the cell.
The immune system of bacteria follows the Cas proteins, taking a segment of the virus’s DNA and implementing it into the cell’s DNA. Then that viral DNA is copied as RNA and attaches itself to a Cas9 protein (a type of Cas protein), the next time the virus enters the cell again the RNA will detect its DNA sequence and kill the viral DNA.
This inspired scientists to implement this method in targeting any DNA in all organisms.
How Does CRISPR-based Gene Surgery Work?
Firstly, the CRISPR gene editing process follows scientists creating a guide RNA which matches the gene sequence that needs to be edited and is then attached to a Cas9 protein. The guide RNA takes the protein to the location of the gene sequence, and the protein recognizes and cuts that DNA sequence. This act of “cutting” gave rise to the term “molecular scissors” when referring to CRISPR.
Once the cut DNA is discarded, the body tries to heal and recreate the same DNA sequence through the process of non-homologous end joining, but it will fail, leading that specific portion of the gene to be inactive. Scientists can leave it at this stage, or they can add a DNA template to their CRISPR equation which will lead to the body generating the new DNA sequence in place of the inactive sequence through homology-directed repair.
Until 2020, all gene editing was done in vitro, meaning that the process was done outside the body in a lab by extracting a sample of cells from the body. However, this changed on March 4th, 2020, when the first in vivo gene surgery called Brilliance was performed at Oregon Health and Science University. It took place to cure a severe form of hereditary blindness called Leber Congenital Amaurosis Type 10.
The goal was to inject the gene editing drug into the body to eliminate the mutation on the photoreceptor cells. To achieve this, a sub-retinal injection was performed to place a cannula which would transport the gene editing drug under the retina. Once the CRISPR formula is in the body, the molecular scissors will cut away the mutated gene sequence, correcting the genetic code.
What Does This Mean for the Future?
The ability to conduct in vivo gene surgery opens the door to curing various diseases. The reason being inherited diseases related to certain organs such as the kidneys, brain, and types of muscle tissue cannot be done through in vitro gene editing because their sample of cells cannot be collected and tested in a lab.
Hence why in vivo gene surgery serves as a leap into the future for medicine as it can mean we will be able to cure many types of diseases such as cancer and genetic disorders such as sickle cell anemia through the powerful tool, CRISPR.
Works Cited:
Behr, Matthew, et al. “In Vivo Delivery of CRISPR-Cas9 Therapeutics: Progress and Challenges.” Acta Pharmaceutica Sinica. B, U.S. National Library of Medicine, Aug. 2021,https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8424283/
Henle, Andrea M. “HOW CRISPR Lets You Edit DNA – Andrea M. Henle.” YouTube, YouTube, 24 Jan. 2019, https://www.youtube.com/watch?v=6tw_JVz_IEc
Network, JAMA. “Gene Editing inside the Body Using CRISPR.” YouTube, YouTube, 28 Apr. 2020, https://www.youtube.com/watch?v=EPTeaXMVcyY
Tabb, Michael, et al. “What Is CRISPR, and Why Is It so Important?” Scientific American, 20 Feb. 2024,https://www.scientificamerican.com/video/what-is-crispr-and-why-is-it-so-important/
White, Franny. “OHSU Performs First-Ever CRISPR Gene Editing within Human Body.” OHSU News, 4 Mar. 2020,https://news.ohsu.edu/2020/03/04/ohsu-performs-first-ever-crispr-gene-editing-within-hum an-body
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