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Gen Comp Endocrinol
2018 Oct 01;267:172-182. doi: 10.1016/j.ygcen.2018.07.001.
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Thyroid hormones and androgens differentially regulate gene expression in testes and ovaries of sexually mature Silurana tropicalis.
Campbell DEK
,
Langlois VS
.
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A series of ex vivo exposures using testicular and ovarian tissues of sexually mature Western clawed frogs (Silurana tropicalis) were designed to examine molecular mechanisms of thyroid hormone (TH) and androgen crosstalk sans hypophyseal feedback as well as investigate potential sex-specific differences. Tissues were exposed ex vivo to either triiodothyronine (T3), iopanoic acid (IOP), one co-treatment of IOP + 5α-dihydrotestosterone (5α-DHT), 5α-DHT, 5β-dihydrotestosterone (5β-DHT), or testosterone (T). Direct exposure to different androgens led to androgen specific increases in thyroid receptor and deiodinase transcripts in testes (trβ and dio1) but a decrease in expression in ovaries (trβ and dio3), suggesting that male and female frogs can be differently affected by androgenic compounds. Moreover, exposure to select androgens differentially increased estrogen-related transcription (estrogen receptor alpha (erα) and aromatase (cyp19)) and production (estradiol) in ovaries and testes indicating the activation of alternate metabolic pathways yielding estrogenic metabolites. Sex-steroid-related transcription (i.e., steroid 5α-reductase type 2 (srd5α2) and erα) and production (i.e., 5α-DHT) were also differentially regulated by THs. The presence and frequency of transcription factor binding sites in the putative promoter regions of TH- and sex steroid-related genes were also examined in S. tropicalis, rodent, and fish models using in silico analysis. In summary, this study provides an improved mechanistic understanding of TH- and androgen-mediated actions and reveals differential transcriptional effects as a function of sex in frogs.
Fig. 1. Promoter analysis of M. musculus, S. tropicalis, and O. latipes TH-related genes (trβ) and androgen-related genes (ar, srd5α2) (A), and estrogen related genes (erα, and cyp19) (B). For information on tr and ar half-site motifs in thyroid- and androgen-re;ated genes please refer to Flood et al. (2013). All sequences used for analysis were collected from the Ensembl Project (http://www.ensembl.org). Putative transcription factor binding sites within the putative promoter (−2000 to + 1) were identified using PROMO (v.3.0.2; Farré et al., 2003) and FIMO (v.4.11.1; Grant et al., 2011) software. TREs are shown in blue, AREs are shown in green, and EREs are represented by purple arrows. This figure was adapted from Fig. 1 in Flood et al. (2013). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 2. Expression of trs (trβ) and dios (dio1, dio2, and dio3) in testes (A, C, E, and G, respectively) and ovaries (B, D, F, and H, respectively) exposed ex vivo to testosterone (T; 1 μM), 5α-dihydrotestosterone (5α-DHT; 1 μM), and to 5β-dihydrotestosterone (5β-DHT; 1 μM) for 6 h. Symbols represent individual samples (n = 6–8 per treatment). Gene expression data are normalized to odc and presented as fold changes relative to the control treatment. Significant differences between treatments and the control (*) were identified by one-way ANOVAs followed by post hoc Dunnett’s tests (p < 0.05). Note that the scales of the y-axis vary.
Fig. 3. Expression of trs (trβ) and dios (dio1, dio2, and dio3) in testes (A, C, E, and G, respectively) and ovaries (B, D, F, and H, respectively) exposed ex vivo to triiodothyronine (T3; 50 nM), iopanoic acid (IOP; 10 μM), and to a co-treatment of IOP (10 μM) + 5α-dihydrotestosterone (5α-DHT; 1 μM) for 6 h. Symbols represent individual samples (n = 5–8 per treatment). Testis and ovary gene expression data are normalized to odc and rpl8, respectively and presented as fold changes relative to the control treatment. Significant differences between treatments and the control (*) were identified by one-way ANOVAs followed by post hoc Dunnett’s tests (p < 0.05). Significant differences between treatments were identified by two-tailed t tests (p < 0.05). Note that the scales of the y-axis vary.
Fig. 4. Expression of erα, cyp19, and dax-1 in testes (A, C, and E respectively) and ovaries (B, D, and F respectively) exposed ex vivo to testosterone (T; 1 μM), 5α-dihydrotestosterone (5α-DHT; 1 μM), and to 5β-dihydrotestosterone (5β-DHT; 1 μM) for 6 h. Symbols represent individual samples (n = 6–8 per treatment). Gene expression data are normalized to odc and presented as fold changes relative to the control treatment. Significant differences between treatments and the control (*) were identified by one-way ANOVAs followed by post hoc Dunnett’s tests (p < 0.05). Note that the scales of the y-axis vary.
Fig. 5. Expression of erα, cyp19, and dax-1 in testes (A, C, and E, respectively) and ovaries (B, D, and F, respectively) exposed ex vivo to triiodothyronine (T3; 50 nM), iopanoic acid (IOP; 10 μM), and to a co-treatment of IOP (10 μM) + 5α-dihydrotestosterone (5α-DHT; 1 μM) for 6 h. Symbols represent individual samples (n = 5–8 per treatment). Testis and ovary gene expression data are normalized to odc and rpl8, respectively and presented as fold changes relative to the control treatment. Significant differences between treatments and the control (*) were identified by one-way ANOVAs followed by post hoc Dunnett’s tests (p < 0.05). Note that the scales of the y-axis vary.
Fig. 6. Expression of ar, srd5α1, srd5α2, and srd5α3 in testes (A, C, E, and G, respectively) and ovaries (B, D, F, and H, respectively) exposed ex vivo to triiodothyronine (T3; 50 nM), iopanoic acid (IOP; 10 μM), or a co-treatment of IOP (10 μM) + 5α-dihydrotestosterone (5α-DHT; 1 μM) for 6 h. Symbols represent individual samples (n = 5–8 per treatment). Testis and ovary gene expression data are normalized to odc and rpl8, respectively and presented as fold changes relative to the control treatment. Significant differences between treatments and the control (*) were identified by one-way ANOVAs followed by post hoc Dunnett’s tests (p < 0.05). Note: scales of the y-axis vary.
