Defining the Recurrent Airway Obstruction Restricted Lung Transcriptome

Summer pasture associated recurrent airway obstruction (SPARAO) is an adult onset respiratory disease affecting horses housed on pasture in hot humid climates. Recurrent airway obstruction (RAO), a similar syndrome, affects horses maintained indoors in temperate climates. Both conditions resemble severe asthma, being characterized by exacerbations of reversible airway obstruction, neutrophil influx, and mucus accumulation in the airways in response to inhaled aeroallergens. To discover novel cell signaling in SPARAO and to identify signaling pathways that are shared with asthma, we contrasted transcriptomes from lung of horses with SPARAO and from unaffected controls. Two SPARAO affected and 2 control horses were sampled during seasonal disease exacerbation and again during seasonal disease remission. Transcriptomes derived using Illumina sequencing of total RNA identified 21,664 unique gene products from each of 8 lung samples, confirming sequencing depth that identified all known/predicted equine gene products in each sample at the time of sequence analysis. For individuals, genes with significant differential expression (DEGs) between summer and winter seasons were identified at a 5% false discovery rate. 1645 gene products were identified as differentially expressed during seasonal disease exacerbation (relative to seasonal remission) in both SPARAO horses. 269 of the 1645 ‘SPARAO-associated’ gene products were also differentially expressed between summer and winter samples in control horses. 1376 DEGs were unique to SPARAO (not differentially expressed in control horses) during seasonal SPARAO exacerbations. The 1376 SPARAO-unique DEGs include gene products of interest in asthma and signaling pathways not previously described in asthma.