A recent study shows the first success of CRISPR being directly injected into the bloodstream, reducing the effects of a toxic protein, caused by a genetic mutation, for up to 1 year. CRISPR-Cas9 is a fairly new genetic technology that allows scientists to edit and manipulate specific DNA sequences; it can remove, add, or alter specific sections of DNA. There are two key components that are involved in the CRISPR-Cas9 technology. Cas-9, an enzyme, works to untwist and unzip the DNA at a specific location. This Cas-9 enzyme is very similar to the helicase enzyme. As we learned in AP Biology, helicase untwists and unzips the DNA. However, unlike the Cas-9 enzyme, helicase unzips the whole DNA strand as the DNA is preparing to replicate. The second key component to CRISPR is guide RNA or gRNA. Guide RNA works to guide the Cas-9 enzyme to make sure it cuts the right part of the DNA. 

CRISPR-Cas9 mode of action

A condition called transthyretin (TTR) amyloidosis, inherited from a gene mutation, causes numbness, nerve pain, and heart failure in adults. These symptoms are caused by a buildup of nerves and organs of misfolded TTR proteins, which are made by the liver. Intellia Therapeutics and Regeneron Pharmaceuticals funded research in which scientists figured out a way to fix the genetic mutation. They created a fat particle that contained messenger RNA that codes for Cas-9, CRISPR’s cutting enzyme. This fat particle was then injected into the subjects. Once injected, the gRNA guides the Cas-9 enzyme to cut out the mutated TTR genetic code from the DNA in liver cells. Once this code is cut out, the cells repair the DNA code to a non mutated form; this stops the production of the TTR protein. 

One month after six patients received this injection, these companies reported that the levels of TTR in the patients blood fell drastically. While the symptoms of these patients have not improved, the blood levels gave enough evidence to prove that the injections of CRISPR-Cas9 were successful. In addition, this form of treatment has led to no safety issues. These companies and many others are continuing to test this technology with TTR patients as well as patients with other genetic mutations. 


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