Progress Update: DUX4 mRNA silencing using CRISPR-Cas13

Lay progress update submitted by Afrooz Rashnonejad
See original grant DUX4 mRNA silencing using CRISPR-Cas13

FSHD is caused when the DUX4 gene turns on in muscle. The DUX4 gene produces a protein (also called DUX4) that is toxic to muscle cells, and over time, enough damage can accumulate to cause muscle weakness in FSHD. Considering this, many FSHD therapy studies are now focused on turning the DUX4 gene “off” in FSHD muscle. CRISPR is a hot new technology that can be used to accomplish this. CRISPR-Cas9 is perhaps the most well-known system as it has received a lot of news coverage in the past few years. The Cas9 enzyme works to edit DNA, creating permanent modifications in our genes. However, a more recent CRISPR system uses an enzyme called Cas13, which can only target RNA, not DNA. RNA is an important molecule in our cells. Messenger RNA (mRNA) transfers information from hereditary material (DNA) into the functional molecules (proteins) in the cells. Therefore, any strategy that can silence mRNA could prevent toxic DUX4 protein formation without modifying the DNA that makes up our genes.

In this study, we tried to test our theory that CRISPR-Cas13 could reduce the amounts of DUX4 mRNA in the FSHD cells and animal models, and protect cells from death caused by toxic DUX4 protein. In the past 9 months, we used several molecular methods to show that Cas13 could reduce DUX4 toxicity in cells on a petri dish or in animal muscles. In the first step, we found that this system efficiently reduced DUX4 mRNA and consequently DUX4 protein in FSHD cells. Then, we packaged the CRISPR-Cas13 elements into the Adeno Associated Virus (AAV) vectors, which are used to deliver gene therapies, and delivered them into adult and newborn FSHD mouse models. Both models had DUX4 levels and their muscles showed protection from damage. At this time, we are trying to increase the efficiency of this treatment using various methods. We believe our results show that CRISPR-Cas13 gene therapy could be an efficient approach for treating FSHD disease in the near future.