Identification and Characterization of Androgen-Responsive Genes in Zebrafish Embryos

Abstract

Responsive genes for fish embryos have been identified so far for some endocrine pathways but not for androgens. Using transcriptome analysis and multiple concentration-response modeling, we identified putative androgen-responsive genes in zebrafish embryos exposed to 0.05-5000 nM 11-ketotestosterone for 24 h. Four selected genes with sigmoidal concentration-dependent expression profiles (EC50 = 6.5-30.0 nM) were characterized in detail. The expression of cyp2k22 and slco1f4 was demonstrated in the pronephros; lipca was detected in the liver, and sult2st3 was found in the olfactory organs and choroid plexus. Their expression domains, the function of human orthologs, and a pathway analysis suggested a role of these genes in the metabolism of hormones. Hence, it was hypothesized that they were induced to compensate for elevated hormone levels. The induction of sult2st3 and cyp2k22 by 11-ketotestosterone was repressed by co-exposure to the androgen receptor antagonist nilutamide supporting a potential androgen receptor mediated regulation. Sensitivity (expressed as EC50 values) of sult2st3 and cyp2k22 gene expression induction after exposure to other steroidal hormones (11-ketotestosterone ∼ testosterone > progesterone > cortisol > ethinylestradiol) correlated with their known binding affinities to zebrafish androgen receptor. Hence, these genes might represent potential markers for screening of androgenic compounds in the zebrafish embryo.

Cortisol Directly Stimulates Spermatogonial Differentiation, Meiosis, and Spermiogenesis in Zebrafish (Danio rerio) Testicular Explants

“…Treatment with cortisol was without effect on 11-KT release from the zebrafish testes. This is in agreement with the expression of cyp2k22, a well-established androgen-responsive gene in zebrafish [52,53], that remained below control levels in the presence of cortisol (0.1 and 1000 ng/mL). In this study, unfortunately, we did not measure steroids considered precursors of the steroidogenic pathway, such as 17α-hydroxyprogesterone, 11β-hydroxyandrostenedione, and 11β-hydroxytestosterone.…”

Histological and Transcriptomic Changes in Male Zebrafish Testes Due to Early Life Exposure to Low Level 2,3,7,8-Tetrachlorodibenzo-p-Dioxin

“…Induction of cyp2k22 is known to occur in response to androgens, possibly through cross talk with other nuclear receptors, and is a potential biomarker for the presence of androgens. 41 This lends further evidence that the hormonal microenvironment within the testes of TCDDtreated zebrafish is altered.…”

“…3 From microarray analysis and qRT-PCR validation, we found significant changes in other genes related to testes development, steroidogenesis, spermatogenesis, and hormone metabolism, namely ca2, cyp2k22, hsp70, lyz, nr5a1b, sox9b, and vasa (Figure 3). 28,[39][40][41][42][43][44][45] Notably, cyp2k22 had a greater than 19-fold increase in TCDD-treated zebrafish compared to controls. Induction of cyp2k22 is known to occur in response to androgens, possibly through cross talk with other nuclear receptors, and is a potential biomarker for the presence of androgens.…”

Transcriptional profiling of cytochrome P450 genes in the liver of adult zebrafish, <i>Danio rerio</i>

“…CYP2K22 was found to be highly specific for males in the RNA-seq data. Zebrafish CYP2K22 was shown to be greatly induced by 17α-methyldihydrotestosterone in the female liver (Hoffmann et al, 2008) and by androgenic compounds in embryos (Fetter et al, 2015). Thus, constitutive expression of CYP2K22 in the male liver and the androgen-induced expression in the female liver both suggest potential roles of this gene in androgen metabolism and homeostasis in this species.…”