Expression Profiles of Reproduction- and Thyroid Hormone-Related Transcripts in the Brains of Chemically-Induced Intersex Frogs

Abstract

Endocrine disrupting chemicals can induce intersex animals in amphibians and fish. Our previous study in frogs demonstrated that chemically-induced intersex animals can display different hepatic profiles of transcript levels than normal animals. In this study, we extend the observations to the developing frog brain. We investigated the effects of finasteride and fadrozole known to induce female- and male-biased sexual development on Silurana tropicalis brain mRNA levels. Real-time RT-PCR analysis of transcript levels of sex steroid- and thyroid hormone-related genes in the brain demonstrated that in finasteride-induced intersex animals, the mRNA levels of aromatase, estrogen receptor α, thyroid hormone receptor β and deiodinase type 3 were higher compared to both control males and females. Furthermore, finasteride-induced intersex animals expressed higher mRNA levels of both androgen receptor and estrogen receptor β compared to control females and to control males, respectively. Furthermore, fadrozole did not affect any of the genes analyzed in the brain but was effective at reducing aromatase activity. Intersex animals display different profiles of transcript levels in the brain whether the intersex condition was induced by an anti-androgen or anti-estrogen treatment. Finally, we conclude that a complex relationship exists between thyroid hormone-responsive genes and androgen status in frogs.