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Published on: March 1, 2022
Thyroid Hormones Regulate Zebrafish Melanogenesis in a Gender-Specific Manner
Raúl Guillot1, Borja Muriach2, Ana Rocha1
1Department of Fish Physiology and Biotechnology, Instituto de Acuicultura de Torre de la Sal, Consejo Superior de Investigaciones Científicas, (IATS-CSIC), Ribera de Cabanes, Castellón, Spain, 12595.
Abstract:
Zebrafish embryos are treated with anti-thyroidal compounds, such as phenylthiourea, to inhibit melanogenesis. However, the mechanism whereby the thyroidal system controls melanin synthesis has not been assessed in detail. In this work, we tested the effect of the administration of diets supplemented with T3 (500microg/g food) on the pigment pattern of adult zebrafish. Oral T3 induced a pronounced skin paling in both adult female and male zebrafish that was reversible upon cessation of treatment. The number of visible melanophores was significantly reduced in treated fish. Accordingly, treatment down-regulated expression of tyrosinase-related protein 1 in both sexes. We also found sexually dimorphic regulation of some melanogenic genes, such as Dct/Tyrp2 that was dramatically up-regulated in females after T3 treatment. Thus, we demonstrated that melanogenesis is reversibly inhibited by thyroid hormones in adult zebrafish and make the discovery of gender-specific differences in the response of melanogenic gene expression. Thus, fish gender is now shown to be an important variable that should be controlled in future studies of fish melanogenesis.
Insights
Thyroid hormone (T3) administration reversibly inhibits melanogenesis in adult zebrafish, reducing melanophores and down-regulating tyrosinase-related protein 1. Gender-specific gene expression differences were observed, highlighting fish sex as a key factor in future studies.
Area of Science:
- Endocrinology
- Developmental Biology
- Genetics
Background:
- Thyroid hormones regulate various physiological processes, but their detailed role in melanogenesis is not fully understood.
- Previous studies used anti-thyroidal compounds in zebrafish embryos, necessitating investigation in adult fish.
- Melanin synthesis is crucial for pigmentation and camouflage in aquatic species.
Purpose of the Study:
- To investigate the effect of triiodothyronine (T3) on the pigment pattern and melanogenesis in adult zebrafish.
- To determine if thyroid hormone-induced changes in melanogenesis are reversible.
- To explore potential sex-specific differences in the regulation of melanogenesis by thyroid hormones.
Main Methods:
- Adult male and female zebrafish were fed diets supplemented with T3 (500microg/g food).
- Skin pigmentation, melanophore counts, and expression of melanogenic genes (e.g., tyrosinase-related protein 1, Dct/Tyrp2) were analyzed.
- Fish were monitored during and after T3 treatment to assess reversibility.
Main Results:
- Oral T3 administration caused significant skin paling in both male and female zebrafish.
- Treated fish exhibited a reduced number of melanophores and down-regulated expression of tyrosinase-related protein 1.
- Sexually dimorphic gene expression was observed, with Dct/Tyrp2 significantly up-regulated in females post-T3 treatment.
- The observed paling was reversible upon cessation of T3 administration.
Conclusions:
- Thyroid hormones reversibly inhibit melanogenesis in adult zebrafish.
- Melanogenesis is subject to gender-specific regulation by thyroid hormones in zebrafish.
- Fish sex is a critical variable to consider in future research on fish melanogenesis and pigmentation.
