Gene Editing with CRISPR

How CRISPR works

How CRISPR works

There have been several relatively recent medical breakthroughs, but the one with the most potential is easily CRISPR – Cas9. This modern iteration of gene editing first experimented in 2009, but there have been constant developments since then.

CRISPR – Cas9 is based on a natural system used by bacteria to protect themselves from viral infection. When the bacteria detect the presence of a virus, it makes two strands of RNA, one of which has a sequence that corresponds to the DNA of the virus. These two strands combine with a protein to make a nuclease called Cas9. When the matching sequence in the RNA, called the guide RNA, matches up with the corresponding segment of virus DNA, it cuts it, disabling the virus. Scientists discovered that if they edit the guide RNA, the Cas9 nuclease will cut any segment of DNA. They also realized that by engineering the Cas9 in such a way, it can also carry a replacement strand of DNA that goes in the place of the cut-out segment. Thus, CRISPR can edit human DNA to remedy genetic mutations and diseases.

Until now, CRISPR has only been used in eggs and living cells outside the body which are then reintroduced to the body where the edited cell can multiply allowing the change to take place. However, in March 2020 one of the first trials was done with directly injecting the Cas9 into somebody.

Researchers from Oregon Health Science Institute injected fluid that delivered the Cas9 with the replacement DNA fragments directly into a patient’s eye in the hope that it will reverse an uncommon genetic condition called Leber congenital amaurosis, which causes blindness early in childhood. The researchers are monitoring the health and development of the subject, but right now it looks as if the treatment is improving his eyesight. Within a month we will know the outcome of the trial and if it is deemed effective the treatment will be used on others with the same condition.

Even though this is one of the only executed uses of CRISPR-Cas9 in March, there is constant research to increase the scope of this tool. Recently, a paper was released outlining plans to use CRISPR on three major species of mosquitos to neutralize their ability to spread disease. These species are the Anopheles gambiae, An. coluzzii, and Aedes aegypti which together transmits malaria, dengue, chikungunya, yellow fever, and Zika. This new method is sorely needed because current methods aren’t working due to insecticide resistance. Using gene-editing to combat the spread of disease through mosquitos isn’t a new concept, but recent developments such as improving Cas9’s effectiveness by combining it with other nucleases made this idea much more feasible.

This major development with the successful use of CRISPR-Cas9 to treat Leber congenital amaurosis spells a bright future for further testing and treatment. This along with the constant developments in research for new applications of CRISPR makes it clear that it will save many more lives in the future.