Relationship between miR-203a inhibition and oil-induced toxicity in early life stage zebrafish (Danio rerio)

IHNV induced miR-19-3p modulates immune response of rainbow trout (Oncorhynchus mykiss) by targeting DHX58-dependent RLR signaling pathway

miR-19-3p has been implicated in various pathological and physiological processes, including immune response, inflammation, oncogenesis and cell damage. However, its function in rainbow trout (Oncorhynchus mykiss) has not been well elucidated. In this study, the expression patterns of miR-19-3p and target gene DExH-Box helicase 58 (DHX58) in rainbow trout infected with infectious hematopoietic necrosis virus (IHNV) were detected, and regulatory mechanism and function of miR-19-3p were investigated by overexpression and inhibition experiment in vitro and in vivo. Expression patterns showed that miR-19-3p and DHX58 displayed significant time-dependent changes in IHNV-infected rainbow trout intestines, skins, gills, and liver cells, and their expression were negatively correlated at multiple time points. In vitro, the targeting relationship between miR-19-3p and DHX58 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay, and overexpression of miR-19-3p significantly suppressed the expression of DHX58 and downstream genes interferon regulatory factor 3 (IRF3), interferon regulatory factor 7 (IRF7), interferon (IFN), myxovirus 1 (MX1), interferon-stimulated gene 15 (ISG15), nuclear factor kappa-B (NF-κB), and interleukin-1 beta (IL-1β), whereas the expression levels of DHX58 and downstream genes were significantly increased after transfecting miR-19-3p inhibitor. In vivo, agomiR-19-3p significantly inhibited the expression of DHX58, and then reduced the expression levels of IRF3, IRF7, IFN, MX1, NF-κB, IL-1β, tumor necrosis factor-α (TNFα), and ISG15. Additionally, overexpression of miR-19-3p significantly increased IHNV copies and cell proliferation number, and suppressed apoptosis, while the opposite results were obtained after miR-19-3p repressing. This study confirmed that miR-19-3p regulates rainbow trout antiviral immune by DHX58-mediated interferon pathway in vitro and in vivo, which provides potential for using miRNAs as anti-viral target drugs.

Incorporating Primer Amplification Efficiencies in Quantitative Reverse Transcription Polymerase Chain Reaction Experiments; Considerations for Differential Gene Expression Analyses in Zebrafish

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) is commonly used to measure the mRNA expression of target genes in zebrafish. Gene expression values from RT-qPCR are typically reported as relative fold-changes, and relative quantification of RT-qPCR data incorporates primer amplification efficiency values for each target gene. We describe the influence of the primer amplification efficiency analysis method on RT-qPCR gene expression fold-change calculations. This report describes (1) a sample analysis demonstrating incorporation of primer amplification efficiency into RT-qPCR analysis for comparing gene expression of a gene of interest between two groups when normalized to multiple reference genes, (2) the influence of differences in primer amplification efficiencies between measured genes on gene expression differences calculated from theoretical delta-Cq (dCq) values, and (3) an empirical comparison of the influence of three methods of defining primer amplification efficiency in gene expression analyses (delta-delta-Cq [ddCq], standard curve, LinRegPCR) using mRNA measurements of a set of genes in zebrafish embryonic development. Given the need to account for the influence of primer amplification efficiency along with the simplicity of using software programs (LinRegPCR) to measure primer amplification efficiency from RT-qPCR data, we encourage using empirical measurements of primer amplification efficiency for RT-qPCR analysis of differential gene expression in zebrafish.

Fish to learn: insights into the effects of environmental chemicals on eye development and visual function in zebrafish

Vision is the most essential sense system for the human being. Congenital visual impairment affects millions of people globally. It is increasingly realized that visual system development is an impressionable target of environmental chemicals. However, due to inaccessibility and ethical issues, the use of humans and other placental mammals is constrained, which limits our better understanding of environmental factors on ocular development and visual function in the embryonic stage. Therefore, as complementing laboratory rodents, zebrafish has been the most frequently employed to understand the effects of environmental chemicals on eye development and visual function. One of the major reasons for the increasing use of zebrafish is their polychromatic vision. Zebrafish retinas are morphologically and functionally analogous to those of mammalian, as well as evolutionary conservation among vertebrate eye. This review provides an update on harmful effects from exposure to environmental chemicals, involving metallic elements (ions), metal-derived nanoparticles, microplastics, nanoplastics, persistent organic pollutants, pesticides, and pharmaceutical pollutants on the eye development and visual function in zebrafish embryos. The collected data provide a comprehensive understanding of environmental factors on ocular development and visual function. This report highlights that zebrafish is promising as a model to identify hazardous toxicants toward eye development and is hopeful for developing preventative or postnatal therapies for human congenital visual impairment.

Transcriptomic profiling of miR-203a inhibitor and miR-34b-injected zebrafish (Danio rerio) validates oil-induced neurological, cardiovascular and eye toxicity response pathways

The global sequencing of microRNA (miRNA; miR) and integration to downstream mRNA expression profiles in early life stages (ELS) of fish following exposure to crude oil determined consistently dysregulated miRNAs regardless of the oil source or fish species. The overlay of differentially expressed miRNAs and mRNAs into in silico software determined that the key roles of these miRNAs were predicted to be involved in cardiovascular, neurological and visually-mediated pathways. Of these, altered expression of miRNAs, miR-203a and miR-34b were predicted to be primary targets of crude oil. To better characterize the effect of these miRNAs to downstream transcript changes, zebrafish embryos were microinjected at 1 h post fertilization (hpf) with either a miR-203a inhibitor or miR-34b. Since both miRs have been shown to be associated with aryl hydrocarbon receptor (AhR) function, benzo(a)pyrene (BaP), a potent AhR agonist, was used as a potential positive control. Transcriptomic profiling was conducted on injected and exposed larvae at 7 and 72 hpf, and eye morphology assessed following exposure at 72 hpf. The top predicted physiological system disease and functions between differentially expressed genes (DEGs) shared with miR-203a inhibitor-injected and miR-34b-injected embryos were involved in brain formation, and the development of the central nervous system and neurons. When DEGs of miR-203a inhibitor-injected embryos were compared with BaP-exposed DEGs, alterations in nervous system development and function, and abnormal morphology of the neurosensory retina, eye and nervous tissue were predicted, consistent with both AhR and non-AhR pathways. When assessed morphologically, the eye area of miR-203a inhibitor and miR-34b-injected and BaP-exposed embryos were significantly reduced. These results suggest that miR-203a inhibition and miR-34b overexpression contribute to neurological, cardiovascular and eye toxicity responses that are caused by oil and PAH exposure in ELS fish, and are likely mediated through both AhR and non-AhR pathways.