Genome-wide profiling of an enhancer-associated histone modification reveals the influence of asthma on the epigenome of the airway epithelium.

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. Overall design: H3K27ac Chip-Seq in primary bronchial epithelial cells from Healthy and Asthma volunteers.