The hypothalamic-pituitary-thyroid (HPT) axis is known to play a crucial role in the development of teleost fish. However, knowledge of endogenous transcription profiles of thyroid-related genes in developing teleosts remains fragmented. We selected two model teleost species, the fathead minnow (Pimephales promelas) and the zebrafish (Danio rerio), to compare the gene transcription ontogeny of the HPT axis. Control organisms were sampled at several time points during embryonic and larval development until 33 days post-fertilization. Total RNA was extracted from pooled, whole fish, and thyroid-related mRNA expression was evaluated using quantitative polymerase chain reaction. Gene transcripts examined included: thyrotropin-releasing hormone receptor (trhr), thyroid-stimulating hormone receptor (tshr), sodium-iodide symporter (nis), thyroid peroxidase (tpo), thyroglobulin (tg), transthyretin (ttr), deiodinases 1, 2, 3a, and 3b (dio1, dio2, dio3a and 3b), and thyroid hormone receptors alpha and beta (thrα and β). A loess regression method was successful in identifying maxima and minima of transcriptional expression during early development of both species. Overall, we observed great similarities between the species, including maternal transfer, at least to some extent, of almost all transcripts (confirmed in unfertilized eggs), increasing expression of most transcripts during hatching and embryo-larval transition, and indications of a fully functional HPT axis in larvae. These data will aid in the development of hypotheses on the role of certain genes and pathways during development. Furthermore, this provides a background reference dataset for designing and interpreting targeted transcriptional expression studies both for fundamental research and for applications such as toxicology.
Bibliographical noteFunding Information:
This work was supported by the European Chemical Industry Council (Cefic) Long-range Research Initiative (LRI-ECO20 and LRI-ECO20.2) with support of ECETOC, by the Belgian Federal Public Service of Health, Food chain safety and Environment (TRANSGGO), and by Universiteit Antwerpen (BOF-KP 2015 ID 31088 and DOCPRO 2015-2019 ID 31405). Lucia Vergauwen was supported by the LRI-ECO20 and LRI-ECO20.2 projects. The USEPA authors’ contributions were supported by the Chemical Safety for Sustainability research program. The funding sources were not involved in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.
© 2018 Elsevier Inc.
- Early development
- Endocrine system
- HPT axis
- Thyroid hormone
- mRNA expression