Gene Editing to Determine MUC5B Mucin Polymer Targets in Lung Injury, Repair, and Fibrosis
Abstract
This proposal directly addresses the Peer Reviewed Medical Research Program Topic Areas of Pulmonary Fibrosis and Lung Injury by studying mechanisms of lung fibrosis in mice. The purpose of the research is to develop the scientific knowledge needed to prevent and potentially reverse the progression of Idiopathic Pulmonary Fibrosis (IPF), a common form of pulmonary fibrosis that is currently incurable with treatments other than lung transplant. Research proposed will focus on an emerging concept that aberrant mucus defense in small airways (bronchioles) leads to injury and scarring of delicate gas exchange surfaces (alveoli). This is an area of need in PF research that is largely unmet. Due to the time and scope of the work proposed, this approach is ideally suited for a Discovery Award. IPF affects five million worldwide, and even though it is likely underdiagnosed, IPF is increasing in frequency in susceptible civilian, Veteran, and military populations. IPF risk factors include both environmental and genetic components. Environmental challenges that promote IPF include cigarette smoking and combat-related particulate exposures. Among genetic risk factors, IPF is known to disproportionately affect men, to increase with age, and to be inexplicably increasing in overall prevalence even though it is likely underdiagnosed. Accordingly, IPF is a significant source of morbidity and mortality among military personnel and Veterans. Unfortunately, patients with IPF are usually diagnosed after the disease has caused permanent and extensive damage to alveoli, resulting in severely limited oxygen/carbon dioxide gas exchange. Given the irreversible nature of disease, even approved treatments for IPF only modestly slow progression, and therapies have not been shown to alter the poor 2- to 3-year survival timeline after diagnosis. It is thus crucial to investigate earlier stages of lung injury and IPF-related exposures before extensive alveolar damage has occurred. To this end, airway inflammation, injury, and repair are important areas of needed exploration. Recently a gene called MUC5B, which encodes a sugar-rich mucin protein ordinarily found in the mucus layer that protects airway surfaces, was found to be strongly associated with the risk of developing IPF. At least one-third of the risk of disease is accounted for by a single DNA base mutation in MUC5B. Thus, even though the MUC5B gene is important for host defense in the lungs, its protective role is hijacked in IPF. The lungs produce more than 10 times higher levels of MUC5B in IPF than normal. This overly exuberant level of production is directly linked to the DNA mutation in MUC5B, which itself causes anywhere from 5-35 times more production. This application tests the hypothesis that gene-editing will elucidate sites required for Muc5b polymer assembly, thus revealing targets for reducing lung injury, inflammation, and aberrant fibrotic repair. This hypothesis will be tested by conducting studies focused on specific aims that seek to determine the following: Aim 1: How conserved N- and C-terminal cysteines cause Muc5b polymerization and Aim 2: How selective inhibition of Muc5b disulfide polymerization sites can restore mucus gel function, thus reducing lung injury and fibrosis in vivo. The Research Plan centers on innovative methods and concepts. Working with mucin polymers in isolation is challenging, especially if attempts are made to instill mucus gels into airspaces for functional assessments. Hence, the proposed studies employ cutting-edge gene-editing techniques to address a highly novel conceptual question. Mice will be engineered to determine whether Muc5b polymers are formed in a similar fashion as that seen with a blood-clotting factor called von Willebrand factor, an evolutionary relative to mucins. Successful completion of the proposed aims could identify novel targets for treating lung injury and preventing or slowing the progress
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910172
Entities
People
- Christopher M Evans
Organizations
- United States Army
- University of Colorado Denver