February 05, 2018
Author: Sarah Beckman, BioTek Instruments, Inc., Winooski, VT USA
Zebrafish are a powerful model organism used for studying numerous biological processes. Some of the benefits of the zebrafish model include that they mature within a short period of time, are optically transparent, develop outside of the mother’s body, and are vertebrates. Because of these, and other reasons, zebrafish are used in a wide variety of applications including drug discovery, developmental biology, and molecular genetics. One specific application that zebrafish are well-suited for is toxicity testing. The zebrafish is an excellent model organism for identifying and understanding the genes that regulate sensitivity and resistance to developmental toxins.
Most toxicology screens use cultured cells, which limits the assays to cell-autonomous phenotypes or those end points that can be observed in relatively simple culture systems. A cell monolayer in a dish fails to capture the complexity of a complete organism, and cell based reporters give little indication of disease phenotype modulation. Furthermore, small molecules may act differently in whole organisms compared to cell culture. In contrast, zebrafish screens are carried out in living zebrafish embryos, which possess fully integrated vertebrate organ systems. As such, a much broader range of phenotypes can be assayed in zebrafish than cultured cells. Whole organism screening has the advantage of being less targeted than cell-based screens, allowing the drug to interact with any biological pathway. The readout is an alteration of a whole organism phenotype which relates well to disease.
In this study, we take advantage of the utility of the zebrafish organism to assess the effect of the known toxicant ethanol on cell death. After 24 hours of ethanol treatment, we evaluate the effect of ethanol on cell death using acridine orange staining in combination with automated microscopy. Spot count analysis was performed which allows the determination of the number of acridine orange positive cells per zebrafish.