Copper-induced deregulation of microRNA expression in the zebrafish olfactory system

Although environmental trace metals, such as copper (Cu), can disrupt normal olfactory function in fish, the underlying molecular mechanisms of metal-induced olfactory injury have not been elucidated. Current research has suggested the involvement of epigenetic modifications. To address this hypothesis, we analyzed microRNA (miRNA) profiles in the olfactory tissues of Cu-exposed zebrafish. Our data revealed 2, 10, and 28 differentially expressed miRNAs in a dose response pattern to three increasing Cu concentrations. Numerous deregulated miRNAs were involved in neurogenesis (let-7, miR-7a, miR-128 and miR-138), indicating a role for Cu-mediated toxicity via interference with olfactory neurogenesis. Putative gene targets of deregulated miRNAs were identified when interrogating our previously published microarray database, including those involved in olfactory cell growth and proliferation, cell death, and cell morphology. Moreover, several miRNAs (miR-203a, miR-199*, miR-16a, miR-16c, and miR-25) were inversely correlated with the depression of key genes within olfactory signal transduction pathways, which likely contributed to the inhibition of olfactory function. Our findings provide novel insight into the epigenetic regulatory mechanisms of metal-induced neurotoxicity of fish olfactory system, and identify novel miRNA biomarkers of metal exposures. 12 one-year-old adult AB strain zebrafish were exposed to Cu concentrations of 0, 6.3, 16 and 40 ppb Cu.