Gene transcription ontogeny of hypothalamic-pituitary-thyroid axis development in early-life stage fathead minnow and zebrafish

• Published in: General and comparative endocrinology Vol. 266; pp. 87 - 100
• Main Authors: Vergauwen, Lucia, Cavallin, Jenna E., Ankley, Gerald T., Bars, Chloé, Gabriëls, Isabelle J., Michiels, Ellen D.G., Fitzpatrick, Krysta R., Periz-Stanacev, Jelena, Randolph, Eric C., Robinson, Serina L., Saari, Travis W., Schroeder, Anthony L., Stinckens, Evelyn, Swintek, Joe, Van Cruchten, Steven J., Verbueken, Evy, Villeneuve, Daniel L., Knapen, Dries
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-09-2018
• Subjects: Animals; Cyprinidae - embryology; Cyprinidae - genetics; Early development; Embryonic Development; Endocrine system; Fish; Fish Proteins - metabolism; HPT axis; Hypothalamo-Hypophyseal System - metabolism; Larva - metabolism; mRNA expression; Principal Component Analysis; Species Specificity; Thyroid Gland - metabolism; Thyroid hormone; Transcription, Genetic; Zebrafish - embryology; Zebrafish - genetics; EDC; tsh; rpnl; dio; HPT; Early development; mRNA expression; rp18; bactin; nis; Fish; qPCR; dpf; dph; hpf; T3; T4; AOP; Endocrine system; qRT-PCR; trh; LSW; tpo; tg; ttr; TH; Thyroid hormone; HPT axis; trhr; thr; tshr
• ISSN: 0016-6480; 1095-6840
• DOI: 10.1016/j.ygcen.2018.05.001

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•Control fish were sampled at 25 time points covering embryo-larval development.•Transcript levels of 12 thyroid-related genes were profiled.•Maternal transfer of almost all transcripts was confirmed in unfertilized eggs.•Increasing transcript levels up to larval period suggest active HPT-axis in larvae.•Inter-species comparison of profiles showed an overall high similarity.
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.