Cystic Fibrosis — Developing targeted therapy for patients
Background
Cystic Fibrosis is a rare disease that builds up an abnormal amount of mucus inside the lungs, the digestive track, and other areas of the body. These symptoms are detrimental as they can lead to lung infections and digestive problems. Statistically, around 1/2000 Caucasians are born with this disease, showing how common this disease is.
Key Terms
1) NMD (Nonsense-mediated Decay) — NMD is a defense mechanism in our cells that is responsible for decaying bad proteins.
2) ASOs (Antisense oligonucleotides) — ASOs are DNA sequences that bind complementary to their target mRNA (messenger RNA), which degrade or alter the sequence.
3) EJCs (Exon-Junction Complexes) — A protein complex that forms at the junction between two exons of the mRNA and oversees any issues of the mRNA before it is translated into a protein (In this case, they can recruit NMDs that degrade the mRNA).
The Problem
Cystic Fibrosis begins with mutations that occur within a particular gene that is responsible for many important bodily functions.
In an experiment, researchers looked at a particular gene, CFTR-W1282X. This gene ranks as the sixth most common CF-causing mutation, expressing a dangerous form of cystic fibrosis in the form of a truncated protein. This form of cystic fibrosis is found in 1.2% of CF patients worldwide, 2.2% of U.S. CF patients, and up to 40% of Israeli CF patients.
Ironically, the problem that causes the truncated protein lies not in the mutated gene. The problem lies with NMD, the defense mechanism that gets rid of bad proteins.
The EJCs that bind to the mRNA recognize the bad RNA and immediately activate NMD. However, NMD does not get rid of the mRNA completely. As a result, the mRNA is now in an even worse form than when it began. As the mRNA makes its final journey outside of the cell’s cytoplasm, the mRNA is translated into a deadly protein.
This past May, an article from Nature Communications was published by researchers and scientists from the Stony Brook University School of Medicine stating their experiments of finding a possible therapy option for patients that have cystic fibrosis.
Experiment
In this experiment, the researchers’ goal was not to create global NMD suppression in the cell. Instead, their goal was to have gene-specific stabilization of the CRTF mRNA that prevented a certain NMD pathway from interfering.
This goal required finding the most optimal ASO cocktail that could create healthier CRTR proteins without NMD interference. Although these proteins would not be necessarily 100% healthy, they would be healthy enough for CFTR gene function to increase. Additionally, the quantity of these proteins created is also an important goal. For the gene to be completely expressed, there needs to be enough protein.
In this experiment, the ASO cocktails are a mixture of a unique ASOs and correctors, a mix of DNA sequences that enhance gene function and processing. More specifically, these modified ASO cocktails were modified to go under the radar and disrupt EJCs, effectively stopping NMDs from recognizing the bad mRNA and degrading it.
This experiment utilized four ASOs and two correctors previously known from past experiments to increase the number of CFTR proteins created. In total, 11 tests were conducted using a concoction of different ASO’s and correctors. These tests also included ASO cocktails that were absent of any ASOs.
Results and Discussion
The results after the experiment were astounding. First, the ASO known as LC-15 was found to increase CFTR protein the most when there was a high concentration of the ASO.
Second, whenever the ASO was combined with the corrector VX-770/661/445 (Trikafta), the CFTR activity jumped to 10–30% CFTR gene function. This percentage might seem insignificant, but the data was enough to set the stage for clinical development of an allele-specific therapy for cystic fibrosis.
Whether or not the ASO cocktail effectively reduces toxicity or other problems will require further research and investigation. However, one thing is for certain: ASOs can modulate clinically relevant NMD, expanding the current RNA and oligonucleotide therapeutics toolbox to reduce the deadly effects of diseases.
As a result of these findings, researchers can begin the next stage of testing the ASO cocktail on mice, looking for ways to increase optimization of the ASO for potential cystic fibrosis therapy. Another step for researchers would be to find ways for patients to consume these ASO cocktails. More specifically, researchers have already began thinking of developing aerosolized ASOs that can enter the lungs and airways of patients. With medical technology rapidly and exponential growing, it will not be a surprise that more therapeutic options will be available for patients that struggle with cystic fibrosis.
If you are interested in reading more research on this topic, you can find similar research in The Journal for Cystic Fibrosis.
Grove City College students can find any of these journals by simply searching the journal name in Discover on the Henry Buhl Library’s homepage. And don’t forget — if you’d like to find more related resources, the library maintains a list of A-Z Databases with an entire tab dedicated to biology!
