Expression and significance of miR - 20b in retinal photoreceptor cells exposed to PCB1254

Previous studies have shown that PCB 1254 has an adverse effect on zebrafish retinal development, but the basic mechanism behind it is not clear. The purpose of this study was to investigate the molecular mechanisms of PCB-induced retinal dysplasia. RT-qPCR, immunoblotting, HE staining and immunofluorescence were adopted to detect the expression at mRNA and protein level. Functional experiments were carried out in 661w cells including CCK-8 assay, caspase-3 assay, and the flow cytometry, while the functional role of miR - 20b was further investigated by using the zebrafish model. The result showed that PCB 1254 exposure inhibited cell proliferation and increased the apoptosis of the 661w cells, and the dose-response relationship between the retinal development-related genes (SWS1, CRX, Rho), miR-20b expression and PCB 1254 exposure was also discovered. We confirmed that miR-20b targeted FGF2 and GRB2 by constructing a dual luciferase reporter gene and suppressed the cell function as well as PCB 1254 . In the miR-20b overexpression zebrafish model, we found abnormal retinal morphology characterized by sparse and irregular photoreceptor cells and the thick photoreceptor cell layers. Our results demonstrate for the first time that PCBs target the MAPK/ERK signaling through miR-20b, affecting retinal cell development and leading to visual impairment.