Project description:Background: Asthma, a complex chronic lung disease affecting the airways, has striking disparities across ancestral groups, but the molecular underpinning of these differences is poorly understood and minimally studied. A major goal of the Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) is to understand multi-omics signatures of asthma risk in the nasal epithelium focusing on populations of African ancestry. Methods: DNA methylation (DNAm) quantification was performed using Illumina’s Infinium MethylationEPIC array® using genomic DNA from nasal airway epithelial cells collected across the 4 US recruitment sites (Baltimore, Chicago, Denver, and Washington DC) for 331 subjects (N=149 asthma cases, N= 182 never asthmatic controls). We performed association analysis to identify eQTMs (CpG-gene associations) for DEGs limiting to CpGs ≤5kb from the transcription start site or within enhancer regions identified through promoter-capture HiC in bronchial epithelial cells. CpGs from significant eQTMs (p<0.05) were tested for differential methylation by asthma (DMCs) to assess the relative contribution of expression and methylation in asthma risk. All models were fully adjusted for ancestry, sampling site, and appropriate latent factors. Findings: Multi-omic analysis identified FKBP5 as a key contributor to asthma risk, where the association between nasal epithelium gene expression is likely regulated by methylation and is associated with increased use of inhaled corticosteroids. FKBP5 is a co-chaperone of glucocorticoid receptor signaling and known to be involved in drug response in asthma. Interpretation: Our analyses reveal genes and networks in asthma that are differentially expressed in nasal epithelium of current asthma cases of African ancestry in CAAPA. Importantly, this work reveals molecular dysregulation on three axes – increased Th2 inflammation, decreased capacity for wound healing, and impaired drug response – that may play a critical role in asthma within the African Diaspora.
Project description:Childhood asthma is a complex disease historically defined by partially overlapping clinical features, including recurrent respiratory symptoms and reversible airway obstruction. However, the heterogeneity observed in clinical disease and airway pathology suggests that the “traditionally” defined asthma population is composed of multiple subgroups (i.e., endotypes), each with a distinct pathogenesis. Gene expression profiling of bronchial airway brushings identified the type 2-high asthma endotype, defined by excessive airway inflammation driven by type 2 cytokines, which was found in ~50% of subjects. Importantly, response to inhaled corticosteroid treatment was limited to this type 2-high endotype. The clinical utility of type 2-high asthma endotyping and the discovery of other endotypes have been limited by the need to perform an invasive bronchoscopy to obtain the bronchial brushings for analysis. Moreover, research bronchoscopies cannot be performed in children. Less invasive methods for the identification of asthma endotypes are needed. To this end, we found that the type 2-high asthma endotype can be identified by gene expression profiling of minimally invasive nasal airway epithelium brushings. Moreover, we found high nasal expression of the type 2 cytokine, IL-13,4 was associated with higher risk of asthma exacerbations among Puerto Ricans, who have the highest asthma morbidity and mortality in the U.S. Herein, we propose to use whole transcriptome sequencing of nasal airway epithelial brushings from Puerto Rican children with asthma to identify the type 2-high and other asthma endotypes, which relate to severity and drug response.
Project description:Severe asthma is a clinically and physiologically heterogeneous disease. Benralizumab is a monoclonal antibody which binds the alpha chain of the interleukin-5 receptor and used for severe eosinophilic asthma worldwide. However, not all eosinophilic asthma patients will benefit from benralizumab due to heterogeneity of this disease. Therefore, we performed comprehensive gene expression analysis of whole blood cells that examine severe asthma disease heterogeneity in response to benralizumab. This study is the first to perform comprehensive transcriptome analysis of whole blood cells to identify transcriptomic endotypes of severe asthma clusters that correlate with benralizumab response. The identified transcriptomic endotypes of severe asthma clusters are associated with gene signatures of eosinophils and neutrophilis.
Project description:Perinatal smoke/nicotine exposure alters lung development and causes asthma in exposed offspring, transmitted transgenerationally. The mechanism underlying the transgenerational inheritance of perinatal smoke/nicotine-induced asthma remains unknown, but germline epigenetic modulations may play a role. Using a well-established rat model of perinatal nicotine-induced asthma, we determined the DNA methylation pattern of spermatozoa of F1 rats exposed perinatally to nicotine in F0 gestation. To identify differentially methylated regions (DMRs), reduced representation bisulfite sequencing was performed on spermatozoa of F1 litters. The top regulated gene body and promoter DMRs were tested for lung gene expression levels, and key proteins involved in lung development and repair were determined. The overall CpG methylation in F1 sperms across gene bodies, promoters, 5’UTRs, exons, introns, and 3’UTRs was not affected by nicotine exposure. However, the methylation levels were different between the different genomic regions. 81 CpG sites, 16 gene bodies, and 3 promoter regions were differentially methylated. Gene enrichment analysis of DMRs revealed pathways involved in oxidative stress, nicotine response, alveolar and brain development, and cellular signaling. Among the DMRs, Dio1 and Nmu were the most hypermethylated and hypomethylated genes, respectively. Gene expression analysis showed that the mRNA expression and DNA methylation were incongruous. Key proteins involved in lung development and repair were significantly different (FDR < 0.05) between the nicotine and placebo-treated groups. Our data show that DNA methylation is remodeled in offspring spermatozoa upon perinatal nicotine exposure. These epigenetic alterations may play a role in transgenerational inheritance of perinatal smoke/nicotine induced asthma.
Project description:Rationale: DNA methylation plays a critical role in asthma development, but differences in DNA methylation associated with asthma severity, especially among adults, are less well-defined. Changes in DNA methylation are influenced by exposure to air pollution, which is a risk factor for asthma exacerbation and severity. Here, we examined how DNA methylomic patterns in adult asthmatics differ by asthma severity and exposure to different components of air pollution. Methods: Peripheral blood CD3+ T cells from adult asthmatics in Beijing, China were serially collected from 37 patients (130 samples total) and analyzed for global DNA methylation using the Illumina MethylationEPIC Array. Measurements and Main Results: Significant differences in DNA methylation were noted among subjects with different degrees of asthma severity, as measured by fraction of exhaled nitric oxide, forced expiratory volume, and asthma control test scores. Differences in DNA methylation were annotated to genes that were enriched in pathways related to asthma or T cell function, and included gene ontology categories related to cellular adhesion, developmental pathways, and calcium signaling. Notable genes that were differentially methylated based on asthma severity included RUNX3, several members of the HLA family, PDGFRA, CDH1, CAV1, and NOTCH4. Differences in DNA methylation also varied by exposure to ambient air pollution, with different components of pollution effecting methylation of different groups of genes. Conclusion: These findings demonstrate how adult asthmatics possess widespread differences in the DNA methylation that associated with varying asthma severity and how air pollution might contribute to more severe asthma via changes in DNA methylation.
Project description:Asthma is a chronic inflammatory disease of the airways driven by complex genetic-environmental interactions. Epigenomic mechanisms including histone modifications and DNA methylation are altered in key cell types of asthma. However, genome-wide studies of histone modifications in the airway epithelium of asthmatics have yet to be undertaken. We undertook genome-wide profiling of an enhancer (regulatory domain)-associated histone modification H3K27ac in bronchial epithelial cells (BECs) from asthmatic and healthy control individuals. We identified 49,903 (P<0.05) regions exhibiting differential H3K27ac enrichment in asthma and found they clustered predominately at genes associated with Th2-high asthma (e.g. CLCA1) and epithelial processes (e.g. EMT). We determined asthma had a dramatic influence on the enhancer landscape of BECs and identified asthma-associated Super-Enhancers encompassing genes encoding transcription factors (e.g. TP63) and enzymes involved in lipid metabolism (e.g. NOX4). We integrated published protein expression, epigenomic and transcriptomic datasets and identified epithelium-specific transcription factors associated with H3K27ac in asthma (e.g. TP73) and dynamic relationships between asthma-associated changes in H3K27ac, DNA methylation, genetic susceptibility and transcriptional profiles. Finally, using a CRISPR-based approach to recapitulate the H3K27ac landscape of asthma in vitro, we provide proof of principal that asthma-associated gene expression (e.g. SERPINB2) is driven in part by aberrant histone acetylation. This report identifies the influence of asthma on the epigenome of airway epithelium and provides evidence that aberrant epigenomic mechanisms exert functional consequences in key cell types of asthma, validating the combination of genome-wide and epigenome-editing approaches in identifying and deciphering the molecular mechanisms underlying asthma pathogenesis.
Project description:Background: Asthma is common chronic inflammatory disease of the airways with a heterogenous clinical presentation. Individual differences in asthma susceptibility remain poorly understood, although genetics is thought to play a major role. Aim: To build a polygenic risk score (PRS) for asthma and determine whether predictive genetic variants can be epigenomically linked to specific pathophysiological mechanisms. Methods: PRSs were constructed using data from genome-wide association studies and performance was validated using data generated in the Rotterdam Study, a Dutch prospective cohort of 14,926 individuals. Outcomes used were asthma, childhood-onset asthma, adulthood-onset asthma, eosinophilic asthma and exacerbations. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) data from 14 primary cell types, including lung epithelial cells and T lymphocytes was used for epigenomic PRS partitioning. Results: All PRSs successfully predicted risk to develop asthma and related outcomes, with the strongest predictive power (2.42 odds ratios per PRS standard deviation, area under the curve of 0.736) achieved for childhood-onset asthma. PRSs allowed for stratification of the Rotterdam Study cohort into groups at low or high risk to develop asthma. PRS partitioning using genome-wide epigenomic profiles identified 5 clusters of variants within gene regulatory regions linked to specific asthma-relevant cells, genes and biological pathways. Conclusions: PRSs can predict whether individuals in a Dutch cohort developed asthma and asthma-related phenotypes, which is most effective for childhood-onset asthma. Importantly, we show that PRS partitioning based on epigenomics data dissects a genetic risk score into blocks of regulatory variants with differential predictive power, which likely represent distinct genetically driven disease pathways. These findings have potential implications for personalized risk mitigation and treatment strategies.