It's been more than 20 years since scientists first discovered the gene that causes cystic fibrosis (CF), yet questions about how the mutated gene causes disease remain unanswered.
Using a newly created pig model that genetically replicates the most common form of cystic fibrosis, University of Iowa researchers have now shown that the CF protein is "misprocessed" in the pigs and does not end up in the correct cellular location. This glitch leads to disease symptoms, including gastrointestinal abnormalities and lung disease in the pigs, which mimic CF in humans. The findings are published in the March 16 issue of the journal Science Translational Medicine.
The findings match earlier laboratory experiments that suggested the gene mutation disrupts the process whereby the CF protein is folded into its correct shape and shipped to the membranes of cells that line the airways and other organs.
When it is correctly located at the cell membrane, this protein -- called cystic fibrosis transmembrane conductance regulator (CFTR) -- forms a channel to allow chloride ions to move in and out of cells. This ion movement is a critical component of the system that maintains salt and water balance across cell membranes in the lung as well as other organs and supports normal membrane function including eradicating bacteria from cell surfaces.
The new study shows that in pigs, the CFTR protein behaves the same way in a living animal as it does in experimental cell systems, suggesting that these experimental systems are useful for learning about the CFTR protein's properties. The cell systems and the new pig model may also be helpful in testing therapies designed to increase the amount of protein that gets to the cell membrane, or boost the activity of the protein that is located at the membrane.
"Instead of just trying to treat the symptoms of CF, current research is moving toward therapies that target mutations in the CFTR gene," said David Stoltz, M.D., Ph.D., UI assistant professor of internal medicine and senior study author. "For example, there already are drugs known as "correctors" being tested. These drugs help CFTR move from inside the cell to its correct location on the cell surface.
"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 that would be enough to protect people from the disease symptoms?'
"We know that people with 50 percent CFTR function have no disease, and now we know that 6 percent of full activity is not enough to prevent disease in the pigs," Stoltz said. "We still don't know how much CFTR is enough to prevent the disease, but this model animal could give us a way to investigate."
In addition to Stoltz, the UI research team included senior author Michael Welsh, M.D., UI professor of internal medicine and molecular physiology and biophysics and a Howard Hughes Medical Institute investigator, and co-first authors, Lynda Ostedgaard, Ph.D.; David Meyerholz, D.V.M., Ph.D.; and Jeng-Haur Chen, Ph.D.
This work was a collaboration between UI scientists and scientists at the University of Missouri including Dr. Randall Prather and members of his research team.
Researchers from the UI Departments of Internal Medicine, Pathology, Surgery and Pediatrics were also part of the team.
The study was funded in part by grants from the National Institutes of Health and the Cystic Fibrosis Foundation.
Jennifer Brown | EurekAlert!
Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care
Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses