Toxicogenomic signatures in zebrafish embryos provide a resource for mode-of-action-informed ecotoxic hazard screening.

Depending on their application, chemicals may enter the environment and exert harmful effects on organisms, necessitating environmental hazard assessment (EHA) as part of most approval processes. However, the increasing number of chemicals and the substantial resources required for EHA - in terms of time, cost, and animal use - pose major challenges for legacy and future chemical management. Here, we employ toxicogenomic profiling in the 3R-compliant zebrafish embryo model to explore candidate molecular signatures that may support mode of action (MoA)-informed hazard screening. Using data from published studies and data newly collected in this study, a total of 32 substances representing 19 distinct MoA were analyzed using differential gene expression analysis, followed by random forest-based identification of candidate MoA-associated gene-expression signatures, biological processes following gene set enrichment analysis and Connectivity Mapping (CMap). The resulting publicly available dataset provides a foundation for pre-regulatory hazard screening and substance prioritization, contributing to the development of resource-efficient and animal-reduced approaches for EHA.