BACKGROUND The mutations that have been implicated in pulmonary fibrosis account for only a small proportion of the population risk. METHODS Using a genomewide linkage scan, we detected linkage between idiopathic interstitial pneumonia and a 3.4-Mb region of chromosome 11p15 in 82 families. We then evaluated genetic variation in this region in gel-forming mucin genes expressed in the lung among 83 subjects with familial interstitial pneumonia, 492 subjects with idiopathic pulmonary fibrosis, and 322 controls. MUC5B expression was assessed in lung tissue. RESULTS Linkage and fine mapping were used to identify a region of interest on the p-terminus of chromosome 11 that included gel-forming mucin genes. The minor-allele of the single-nucleotide polymorphism (SNP) rs35705950, located 3 kb upstream of the MUC5B transcription start site, was present at a frequency of 34% among subjects with familial interstitial pneumonia, 38% among subjects with idiopathic pulmonary fibrosis, and 9% among controls (allelic association with familial interstitial pneumonia, P = 1.2×10−15; allelic association with idiopathic pulmonary fibrosis, P = 2.5×10−37). The odds ratios for disease among subjects who were heterozygous and those who were homozygous for the minor allele of this SNP were 6.8 (95% confidence interval [CI], 3.9 to 12.0) and 20.8 (95% CI, 3.8 to 113.7), respectively, for familial interstitial pneumonia and 9.0 (95% CI, 6.2 to 13.1) and 21.8 (95% CI, 5.1 to 93.5), respectively, for idiopathic pulmonary fibrosis. MUC5B expression in the lung was 14.1 times as high in subjects who had idiopathic pulmonary fibrosis as in those who did not (P<0.001). The variant allele of rs35705950 was associated with up-regulation in MUC5B expression in the lung in unaffected subjects (expression was 37.4 times as high as in unaffected subjects homozygous for the wild-type allele, P<0.001). MUC5B protein was expressed in lesions of idiopathic pulmonary fibrosis. CONCLUSIONS A common polymorphism in the promoter of MUC5B is associated with familial interstitial pneumonia and idiopathic pulmonary fibrosis. Our findings suggest that dys-regulated MUC5B expression in the lung may be involved in the pathogenesis of pulmonary fibrosis. (Funded by the National Heart, Lung, and Blood Institute and others.)

Respiratory surfaces are exposed to billions of particulates and pathogens daily. A protective mucus barrier traps and eliminates them via mucociliary clearance (MCC)1,2. However, excessive mucus contributes to transient respiratory infections and to the pathogenesis of numerous respiratory diseases1. MUC5AC and MUC5B are evolutionarily conserved genes that encode structurally related mucin glycoproteins, the principal macromolecules in airway mucus1,3. Genetic variants are linked to diverse lung diseases4-6, but specific roles for MUC5AC and MUC5B in MCC, and the lasting effects of their inhibition, are unknown. Here we show that Muc5b (but not Muc5ac) is required for MCC, for controlling infections in the airways and middle ear, and for maintaining immune homeostasis in the lungs. Muc5b deficiency caused materials to accumulate in upper and lower airways. This defect led to chronic infection by multiple bacterial species, including Staphylococcus aureus, and to inflammation that failed to resolve normally7. Apoptotic macrophages accumulated, phagocytosis was impaired, and IL-23 production was reduced inMuc5b−/− mice. By contrast, in Muc5b transgenic (Tg) mice, macrophage functions improved. Existing dogma defines mucous phenotypes in asthma and chronic obstructive pulmonary disease (COPD) as driven by increased MUC5AC, with MUC5B levels either unaffected or increased in expectorated sputum1,8. However, in many patients, MUC5B production at airway surfaces decreases by as much as 90%9-11. By distinguishing a specific role for Muc5b in MCC, and by determining its impact on bacterial infections and inflammation in mice, our results provide a refined framework for designing targeted therapies to control mucin secretion and restore MCC.

Background Given strong environmental influence on both epigenetic marks and allergic asthma in children, the epigenetic alterations in respiratory epithelia may provide insight into allergic asthma. Objective To identify DNA methylation and gene expression changes associated with childhood allergic persistent asthma. Methods We compared genomic DNA methylation patterns and gene expression in African American children with persistent atopic asthma[N=36] versus healthy controls[N=36]. Results were validated in an independent population of asthmatic children[N=30] using a shared healthy control population[N=36] and in independent population of Caucasian adult atopic asthmatics[N=12] and controls[N=12]. Results We identified 186 genes with significant methylation changes, differentially methylated regions(DMRs) or differentially methylated probes(DMPs), after adjustment for age, gender, race/ethnicity, batch effects, inflation, and multiple comparisons. Genes differentially methylated included those with established roles in asthma and atopy, genes related to extracellular matrix, immunity, cell adhesion, epigenetic regulation, and airflow obstruction. The methylation changes were substantial (median 9.5%, range:2.6–29.5%). Hypo- and hyper-methylated genes were associated with increased and decreased gene expression respectively (P<2.8x10−6 for DMRs and P<7.8x10−10 for DMPs). Quantitative analysis in 53 differentially expressed genes demonstrated that 32(60%) have significant methylation-expression relationships within 5kb of the gene. 10 loci selected based on the relevance to asthma, magnitude of methylation change, and methylation-expression relationships were validated in an independent cohort of children with atopic asthma. 67/186 genes also have significant asthma-associated methylation changes in nasal epithelia of adult Caucasian asthmatics. Conclusions Epigenetic marks in respiratory epithelia are associated with allergic asthma and gene expression changes in inner-city children.

The gain-of-function MUC5B promoter variant rs35705950 is the dominant risk factor for developing idiopathic pulmonary fibrosis (IPF). Here we show in humans that MUC5B, a mucin thought to be restricted to conducting airways, is co-expressed with surfactant protein C (SFTPC) in type 2 alveolar epithelia and in epithelial cells lining honeycomb cysts, indicating that cell types involved in lung fibrosis in distal airspace express MUC5B. In mice, we demonstrate that Muc5b concentration in bronchoalveolar epithelia is related to impaired mucociliary clearance (MCC) and to the extent and persistence of bleomycin-induced lung fibrosis. We also establish the ability of the mucolytic agent P-2119 to restore MCC and to suppress bleomycin-induced lung fibrosis in the setting of Muc5b overexpression. Our findings suggest that mucociliary dysfunction might play a causative role in bleomycin-induced pulmonary fibrosis in mice overexpressing Muc5b, and that MUC5B in distal airspaces is a potential therapeutic target in humans with IPF.

Background Epigenetic marks are heritable, influenced by the environment, direct the maturation of T lymphocytes, and in mice enhance the development of allergic airway disease. Thus it is important to define epigenetic alterations in asthmatic populations. Objective We hypothesize that epigenetic alterations in circulating PBMCs are associated with allergic asthma. Methods We compared DNA methylation patterns and gene expression in inner-city children with persistent atopic asthma versus healthy control subjects by using DNA and RNA from PBMCs. Results were validated in an independent population of asthmatic patients. Results Comparing asthmatic patients (n = 97) with control subjects (n = 97), we identified 81 regions that were differentially methylated. Several immune genes were hypomethylated in asthma, including IL13, RUNX3, and specific genes relevant to T lymphocytes (TIGIT). Among asthmatic patients, 11 differentially methylated regions were associated with higher serum IgE concentrations, and 16 were associated with percent predicted FEV1. Hypomethylated and hypermethylated regions were associated with increased and decreased gene expression, respectively (P < .6 × 10−11 for asthma and P < .01 for IgE). We further explored the relationship between DNA methylation and gene expression using an integrative analysis and identified additional candidates relevant to asthma (IL4 and ST2). Methylation marks involved in T-cell maturation (RUNX3), TH2 immunity (IL4), and oxidative stress (catalase) were validated in an independent asthmatic cohort of children living in the inner city. Conclusions Our results demonstrate that DNA methylation marks in specific gene loci are associated with asthma and suggest that epigenetic changes might play a role in establishing the immune phenotype associated with asthma.