The small size and rapid development of the zebrafish make it a useful vertebrate model for assessing potential effects of chemicals on development in a mid- to high-throughput manner. The embryonic zebrafish model has been used for this purpose in pharmaceutical development and in high-throughput screening programs at NTP and the U.S. Environmental Protection Agency. However, deficits in several key areas hinder the broader adoption of the zebrafish model for toxicological screening:
NTP established the Systematic Evaluation of the Application of Zebrafish in Toxicology (SEAZIT) program, led by NICEATM and other NTP scientists, to address these deficits and enable the broader adoption of zebrafish for toxicological screening. Summarized below are four key SEAZIT program activities:
In 2016, SEAZIT team members conducted a series of interviews with researchers considered to be experts in the use of zebrafish in toxicology studies. These interviews identified areas key to development of a harmonized testing protocol for embryonic zebrafish studies and important sources of variability among laboratories. Outcomes of this effort included:
Key issues being addressed by SEAZIT include the variability among laboratories in the endpoints measured and the nomenclature used for each endpoint. On behalf of SEAZIT, NICEATM presented a webinar series in February and March 2017 that considered how these issues might be addressed by implementation of standardized nomenclature systems, also known as ontologies. The webinars in this series:
The interlaboratory study described above will determine the influence of chorion removal and exposure media renewal on study outcomes. Participating laboratories will use in-house protocols to test a defined chemical set while varying the two protocol elements under investigation. The chemical set, which was designed to provide overlap with other NTP studies, includes chemicals with a range of physico-chemical properties and developmental effects. Many of the chemicals have in vivo reference data available from rodent and other zebrafish studies. The interlaboratory study will also include a pilot effort on chemical kinetics in support of future studies of absorption, distribution, metabolism, and excretion in zebrafish.
An important SEAZIT goal is to develop best practices for data analysis. To this end, the data generated in this study will be made publicly available so that any interested investigators could contribute to developing a means of compiling all data generated by the study to yield a single toxicity value for each chemical.
A best practices workshop, currently planned for Fall 2018, will serve as a public forum where experts from various fields can discuss continued development and standardization of assays, as well as practices for collecting, analyzing, and reporting of data. The objectives of the workshop will be to:
The workshop will include presentations, discussion sessions, a poster session, and a breakout session during which participants will employ use cases to develop common language for endpoints and effect phenotypes. A report from the workshop, which will be published in the peer-reviewed literature, will include recommendations for the conduct and reporting of zebrafish screening assays.