Novel MicroRNA Involved in Host Response to Avian Pathogenic Escherichia coli Identified by Deep Sequencing and Integration Analysis.

Avian pathogenic Escherichia coli (APEC) causes one of the most common bacterial diseases of poultry worldwide. Effective control methods are therefore desirable and will be facilitated by a better understanding of the host response to the pathogen. Currently, microRNAs (miRNAs) involved in host resistance to APEC are unknown. Here, we applied RNA sequencing to explore the changed miRNAs and deregulated genes in the spleen of three groups of broilers: nonchallenged (NC), APEC-challenged with mild pathology (CM), and APEC-challenged with severe pathology (CS). Twenty-seven differentially expressed miRNAs (fold change >1.5; P value <0.01) were identified, including 13 miRNAs between the NC and CM, 17 between the NC and CS, and 14 between the CM and CS groups. Through functional analysis of these miRNA targets, 12 immune-related biological processes were found to be significantly enriched. Based on combined analyses of differentially expressed miRNAs and mRNAs within each of the three groups, 43 miRNA-mRNA pairs displayed significantly negative correlations (r < -0.8). Notably, gga-miR-429 was greatly increased in the CS group compared to levels in both the CM and NC groups. In vitro, gga-miR-429 directly repressed luciferase reporter gene activity via binding to 3' untranslated regions of TMEFF2, NTRK2, and SHISA2. Overexpression of gga-miR-429 in the HD11 macrophage cell line significantly inhibited TMEFF2 and SHISA2 expression, which are involved in the lipopolysaccharide-induced platelet-derived growth factor (PDGF) and Wnt signaling pathways. In summary, we provide the first report characterizing the miRNA changes during APEC infection, which may help to shed light on the roles of these recently identified genetic elements in the mechanisms of host resistance and susceptibility to APEC.