chicken gga-mir-19a targets zmynd11 and plays an important role in host defense against mycoplasma gallisepticum (hs strain) infection

Mycoplasma gallisepticum (MG), one of the most pathogenic Mycoplasmas, can cause chronic respiratory disease (CRD) in chickens. It has been suggested that micro-ribonucleic acids (miRNAs) are involved in microbial pathogenesis. However, little is known about the roles of miRNAs in MG infection. Previously, we found by deep sequencing that gga-miR-19a was significantly up-regulated in the lungs of MG-infected chicken embryos. In this work, we confirmed that gga-miR-19a was up-regulated in both MG-infected chicken embryonic lungs and MG-infected DF-1 (chicken embryo fibroblast) cells. At 72 h post-transfection, we found that the over-expression of gga-miR-19a significantly enhanced the proliferation of MG-infected DF-1 cells by promoting the transition from the G1 phase to the S and G2 phases, while a gga-miR-19a inhibitor repressed the proliferation of MG-infected DF-1 cells by arresting the cell cycle in the G1 phase. Moreover, we found that gga-miR-19a regulated the expression of the host zinc-finger protein, MYND-type containing 11 (ZMYND11), through binding to its 3ʹ untranslated region (3ʹ-UTR). DAVID analysis revealed that ZMYND11 could negatively regulate the NF-kappaB (NF-κB) signaling pathway in chickens (Gallus gallus). Upon MG infection, gga-miR-19a, NF-κB, MyD88 and TNF-α were all up-regulated, whereas ZMYND11 was down-regulated. The over-expression of gga-miR-19a in the DF-1 cells did not affect the above gene expression patterns, and gga-miR-19a inhibitor repressed the expression of NF-κB, MyD88 and TNF-α, but enhanced the expression of ZMYND11. In conclusion, gga-miR-19a might suppress the expression of ZMYND11 in MG-infected chicken embryonic lungs and DF-1 cells, activate the NF-κB signaling pathway, and promote pro-inflammatory cytokines expression, the cell cycle progression and cell proliferation to defend against MG infection.