National Toxicology Program

National Toxicology Program

SEAZIT: Systematic Evaluation of the Application of Zebrafish in Toxicology

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:

  • Consistency of experimental protocol elements
  • Understanding of mechanisms of chemical absorption, distribution, metabolism, and excretion in zebrafish
  • Consistency of informatics approaches used for classification of outcomes

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:

  • Zebrafish information gathering
  • A webinar series (2017) focused on using informatics to improve data analysis for zebrafish screening studies
  • An interlaboratory zebrafish study and data challenge
  • A zebrafish best practices workshop (2018)
Timeline of planned SEAZIT activities through 2018; refer to webpage text for details

Timeline graphic shows activities planned for the SEAZIT project through 2018 and their status as of March 2017

Information Gathering

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:

  • A meeting of researcher experts and data scientists to discuss how to improve zebrafish screening data analysis using ontologies (standardized nomenclature) (April 2017). The meeting will produce an outline of a recommendations document that will:
    • Capture best practices for data production and analysis
    • Identify tools to be developed and other needs to advance the application of the zebrafish model in toxicology
  • An interlaboratory study designed to examine the influence of chorion removal and renewal of exposure media on toxicity estimates
  • A manuscript incorporating the meeting discussions within a SEAZIT literature review.

Webinar Series

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:

  1. Summarized some of the barriers to routine use of zebrafish in toxicological evaluations
  2. Reviewed the concept of ontologies
  3. Considered how ontologies could be applied to harmonize procedures used for zebrafish screening studies

More information about the webinars

Interlaboratory Study

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.

Best Practices Workshop

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:

  • Identify best practices for conducting zebrafish screening assays
  • Define the state of the science for data analysis of zebrafish screening assays and develop guidelines for analyzing and reporting data
  • Define minimum essential endpoints for zebrafish screening assays
  • Develop common terminology for endpoints and effect phenotypes in zebrafish screening assays
  • Define opportunities for improvement and greater utilization of the data generated in screening assays

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.

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.