Histological and transcriptomic effects of 17α-methyltestosterone on zebrafish gonad development

Abstract

BackgroundSex hormones play important roles in teleost ovarian and testicular development. In zebrafish, ovarian differentiation appears to be dictated by an oocyte-derived signal via Cyp19a1a aromatase-mediated estrogen production. Androgens and aromatase inhibitors can induce female-to-male sex reversal, however, the mechanisms underlying gonadal masculinisation are poorly understood. We used histological analyses together with RNA sequencing to characterise zebrafish gonadal transcriptomes and investigate the effects of 17α-methyltestosterone on gonadal differentiation.ResultsAt a morphological level, 17α-methyltestosterone (MT) masculinised gonads and accelerated spermatogenesis, and these changes were paralleled in masculinisation and de-feminisation of gonadal transcriptomes. MT treatment upregulated expression of genes involved in male sex determination and differentiation (amh, dmrt1, gsdf and wt1a) and those involved in 11-oxygenated androgen production (cyp11c1 and hsd11b2). It also repressed expression of ovarian development and folliculogenesis genes (bmp15, gdf9, figla, zp2.1 and zp3b). Furthermore, MT treatment altered epigenetic modification of histones in zebrafish gonads. Contrary to expectations, higher levels of cyp19a1a or foxl2 expression in control ovaries compared to MT-treated testes and control testes were not statistically significant during early gonad development (40 dpf).ConclusionOur study suggests that both androgen production and aromatase inhibition are important for androgen-induced gonadal masculinisation and natural testicular differentiation in zebrafish.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3915-z) contains supplementary material, which is available to authorized users.

Immune genes, IL1β and Casp9, show sexual dimorphic methylation patterns in zebrafish gonads

“…In human ovaries, IL1 mediates inflammatory processes during ovulation, fertilization and oocyte implantation (Polan et al, 1991;Garcia-Velasco and Arici, 1999) and is highly expressed in ovarian cancers (Aggarwal and Gehlot, 2009). In this work, we report a higher expression of IL1 in testes when compared to ovaries in adult zebrafish according to that previously found by Lee et al (2017), thus indicating that IL1 is expressed in a sex-dependent manner in fish. In sea bream gonads, IL1 was found in the cytoplasm of spermatogonia, spermatocytes and oogonia and its expression was higher during reproductive cycles suggesting a role in promoting proliferation in gametogenesis and spermatocyte differentiation (Chaves-Pozo et al, 2008).…”

Immune genes,IL1βandCasp9,show sexual dimorphic methylation patterns in the zebrafish gonads

“…The two cytokines, IL1β and TNFα modulated the in vitro testosterone production in goldfish testis indicating their role in regulating sex steroids (Lister and van der Kraak, 2002). In the present work, we report a higher expression of IL1β in testes when compared to ovaries in adult zebrafish according to what previously found by Lee et al (2017), thus indicating that IL1β is expressed in a sex-dependent manner in fish. We did not find significant difference in Casp9 expression between testes and ovaries although higher expression in testes was also observed.…”

Endocrine disrupting effects of tebuconazole on different life stages of zebrafish (Danio rerio)

“…As known, zebrafish is considered as a class of undifferentiated gonochoristic species (Hoar and Randall, 1969). In recent years, evidences have been found that some synthetic chemicals in environment could affect the sexual differentiation of zebrafish (Chen et al, 2016;Hua et al, 2016;Lee et al, 2017;Santos et al, 2017;Delomas and Dabrowski, 2018;Shi et al, 2018;Yang et al, 2018), playing roles as environmental endocrine disruptors. Delomas and Dabrowski (2018) reported that down-regulation of E2 in juvenile zebrafish induced a male-biased development.…”