"The pig model could help us develop and test more corrector drugs, and it will also help us better understand why the protein is misprocessed in the first place," Stoltz added. "If we understand what is going wrong, we may be able to develop new therapies that can target the problem and allow more of the CFTR to make it to the cell surface, which may alleviate the disease symptoms."
In 2008, the UI team and colleagues at University of Missouri created pigs that were missing the CFTR protein. These animals developed CF disease symptoms that closely mimicked the human disease. In the new pig model, the animals have two copies of the CFTR gene containing the most common CF-causing mutation, which is known as the delta F508 mutation. These pigs also develop CF symptoms similar to the human disease. In particular, the CF pigs are born with gastrointestinal disease and develop lung disease over time.
By studying the protein in the pigs, the researchers were able to show that most of the CFTR protein is misprocessed and gets degraded, but a small amount of the protein does get to the cell membrane where it is able to form active chloride channels. However, the level of activity is only about 6 percent of the activity found in normal pigs with fully functional CFTR channels. The study shows that this small amount of CFTR activity is not sufficient to prevent CF disease in the pigs.
CF is a recessive disease, meaning a person with one mutated copy and one good copy of the CFTR gene is a "carrier" but does not have CF. This suggests that 50 percent of normal CFTR activity is sufficient for health. The question has always been, 'Is there a minimal amount of active CFTR
|Contact: Jennifer Brown|
University of Iowa Health Care