Original Article Differential microRNA epression in asthma and the role of miR-1248 in regulation of IL-5

Asthma is a chronic inflammatory disease that can be difficult to manage due to a lack of diagnostic bio- markers and an incomplete understanding of the molecular pathogenesis. MicroRNAs (miRNAs) are small, single- stranded, non-coding RNAs with increasing importance in regulation of immune function and as biomarkers. We profiled miRNAs in the serum of asthmatics and non-asthmatic controls to identify miRNAs that could serve as diag- nostic markers and potential regulators of allergic inflammation. Differential expression of miR-1248, miR-26a, Let- 7a, and Let-7d were observed in asthmatic patients compared to controls. Predictive algorithm analyses of these miRNAs revealed their specificity for different Th2 cytokines, including IL-5, which has not previously been shown to be post-transcriptionally regulated. Using multiple approaches, we showed that miR-1248 physically interacts with the IL-5 transcript in the 3' untranslated region and serves as a positive regulator to increase IL-5 expression. Col- lectively, our results demonstrate a previously uncharacterized mode of regulation of IL-5 expression and potential use for miRNAs in the diagnosis and clinical management of asthma.