Estrogen-Induced Alterations in amh and dmrt1 Expression Signal for Disruption in Male Sexual Development in the Zebrafish

Abstract

Dmrt1 and amh are genes involved in vertebrate sex differentiation. In this study, we cloned dmrt1 and amh cDNAs in zebrafish (Danio rerio) and investigated the effects of exposure to 17a-ethinylestradiol (EE2), during early life on their patterns of expression and impact on the subsequent gonadal phenotype. Expression of both amh and dmrt1 in embryos was detected as early as at 1 day post fertilization (dpf) and enhanced expression of amh from 25 dpf was associated with the period of early gonadal differentiation. Sex-dependent differences in enhanced green fluorescent protein transgene expression driven by the promoter of the germ cell-specific vas gene were exploited to show that at 28dpf and 56dpf both amh and dmrt1 mRNA were overexpressed in males compared with females. Exposure during early life to environmentally relevant concentrations of EE2 had a suppressive effect on the expression of both amh and dmrt1 mRNAs and this was associated with a cessation/retardation in male gonadal sex development. Our findings indicate that estrogen-induced suppression in expression of dmrt1 and amh during early life correlate with subsequent disruptive effects on the sexual phenotype in males.

The progestin levonorgestrel affects sex differentiation in zebrafish at environmentally relevant concentrations

“…dmrt1, foxl2, nr5a1b) was also examined, because they are also important and related to sex differentiation in fish, usually acting as upstream regulators of the cyp19a1a gene (Kanda et al, 2006;Watanabe et al, 1999). In zebrafish, dmrt1 mRNA is expressed in both testes and ovaries, but at markedly higher levels in testes; it plays an important role in early gonadal sex differentiation of male zebrafish (Jørgensen et al, 2008;Schulz et al, 2007). Foxl2 is one of the very few conserved ovarian differentiation genes across vertebrate evolution, with female-specific expression in the differentiating ovaries of mammals (Baron et al, 2005), birds (Govoroun et al, 2004), and fish (Baron et al, 2005;Wang et al, 2007).…”

Histological observation of doublesex-mab 3-related transcription factor 1 (DMRT1) localization in the adult testis of three-spot wrasse

“…In contrast, suppression of DMRT1 transcripts in the gonads was observed in estrogen (E2)-treated male embryos of zebrafish (Schulz et al 2007) and tilapia ). In addition, changes were noticed in DMRT1 expression in concordance with the phases of testicular differentiation in several fishes that change their sexes naturally (Alam et al 2008;He et al 2003;Liarte et al 2007).…”

“…Furthermore, exposure of female embryos to androgen or AI during early stages of gonadal sex differentiation resulted in the sex-reversal of the adults accompanied by DMRT1 up-regulation in tilapia , catfish (Raghuveer and Senthilkumaran 2009) and rainbow trout (Le Gac et al 2008;Schulz et al 2007). In contrast, suppression of DMRT1 transcripts in the gonads was observed in estrogen (E2)-treated male embryos of zebrafish (Schulz et al 2007) and tilapia ).…”

Progesterone and norgestrel alter transcriptional expression of genes along the hypothalamic–pituitary–thyroid axis in zebrafish embryos-larvae

“…However, most of the published studies focused on the effects caused by estrogens (Muncke et al, 2007;Schulz et al, 2007) and androgens (Morthorst et al, 2010;Brockmeier et al, 2013), less on the biological effects by progestins (progestogens) (Huang et al, 2012(Huang et al, , 2013Zucchi et al, 2014). Natural and synthetic progestins in the aquatic environment are mainly originated from domestic sewage wastewater and animal wastewater due to excretion of human and animals (Liu et al, 2011b.…”