Phenotypic anchoring for OMICS-guided assessment of liver toxicity in zebrafish

The zebrafish (Danio rerio) has become a popular model organism for studying embryonic development, genetics, and toxicology. As vertebrates sharing 70 % of their coding genes with humans, zebrafish are also widely used for modelling human diseases. Their small size, external development, transparent embryos, easy husbandry and breeding, and the large number of eggs they lay make them a valuable model for drug and toxicity screening. Already the older embryos possess a functional liver, allowing to assess compound effects on this organ in vivo.
In the context of PrecisionTox (www.precisiontox.org), a large-scale EU project aiming at OMICS based toxicity prediction using invertebrate and early life stage vertebrate model organisms, we wish to establish a workflow for identifying compounds with adverse effects on the zebrafish embryonic liver.
The selected test compounds are known or suspected liver toxicants. To assess overall toxicity, we used the vibration/startle response of zebrafish embryos as a phenotypic read-out, employing a custom-built system. Embryos were exposed to different concentrations of the compounds for 48 h, and benchmark doses (BMD) were determined using a customized KNIME workflow. ... mehrLiver integrity was specifically examined by Oil red O staining. Compound effects on glucocorticoid signalling activity were measured with the Glucocorticoid Responsive In vivo Zebrafish Luciferase activitY (GRIZLY) assay previously developed by our laboratory [1].
Within the PrecisionTox consortium, transcriptome and metabolome data will be acquired for all tested compounds at BMD10 and 25 as determined by the vibration/startle assay. To anchor these OMICS data with respect to adverse liver phenotypes, we measured the size of the embryonic liver and assessed its lipid content by Oil Red O staining after 48 h of exposure. Furthermore, the GRIZLY assay examined whether glucocorticoid signalling, one important regulator of liver function, was altered by the compounds.
Our workflow aims at enabling rapid assessment of liver toxicity in zebrafish embryos, providing phenotypic data that complement the OMICS data generated by the PrecisionTox consortium. With this phenotypic anchoring, we hope to be able to identify novel transcriptomic and metabolic marker patterns that are predictive for liver toxicity