Augmentation of progestin signaling rescues testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling

Abstract

Disruption of androgen signaling is known to cause testicular malformation and defective spermatogenesis in zebrafish. However, knockout of cyp17a1, a key enzyme responsible for the androgen synthesis, in ar-/- male zebrafish paradoxically causes testicular hypertrophy and enhanced spermatogenesis. Because Cyp17a1 plays key roles in hydroxylation of pregnenolone and progesterone (P4), and convert of 17α-hydroxypregnenolone to dehydroepiandrosterone and 17α-hydroxyprogesterone to androstenedione, we hypothesize that the unexpected phenotype in cyp17a1-/-;androgen receptor (ar)-/- zebrafish may be mediated through an augmentation of progestin/nuclear progestin receptor (nPgr) signaling. In support of this hypothesis, we show that knockout of cyp17a1 leads to accumulation of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and P4. Further, administration of progestin, a synthetic DHP mimetic, is sufficient to rescue testicular development and spermatogenesis in ar-/- zebrafish, whereas knockout of npgr abolishes the rescue effect of cyp17a1-/- in the cyp17a1-/-;ar-/- double mutant. Analyses of the transcriptomes among the mutants with defective testicular organization and spermatogenesis (ar-/-, ar-/-;npgr-/- and cyp17a-/-;ar-/-;npgr-/-), those with normal phenotype (Control and cyp17a1-/-), and rescued phenotype (cyp17a1-/-;ar-/-) reveal a common link between a down-regulated expression of insl3 and its related downstream genes in cyp17a-/-;ar-/-;npgr-/- zebrafish. Taken together, our data suggest that genetic or pharmacological augmentation of the progestin/nPgr pathway is sufficient to restore testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.

Identification of an Epigenetically Marked Locus within the Sex Determination Region of Channel Catfish

“…In our previous study of male channel catfish, hydin gene was observed with male-biased expression in the testis transcriptome [ 62 ]. In zebrafish, abnormal downregulated expression of hydin gene was observed in androgen signaling-depleted individuals with defective testicular organization and spermatogenesis [ 63 ]. In a similar situation as hydin-1, but to a lesser extent, the other five genes in SDR that were expressed higher in males than in females, including LOC108264027, gtf2ird2b, kcnj1, LOC108264687, and actrt3.…”

Knockout of cyclin dependent kinases 8 and 19 leads to depletion of cyclin C and suppresses spermatogenesis and male fertility in mice

“…An intriguing possibility is activation of a compensatory AR-independent pathway that was recently shown in a zebrafish model (Zhai et al 2022). Such signaling involves increased progestin signaling, and upregulation of 17α,20β-Dihydroxy-4-pregnen-3-one.…”

Use of All-Male cyp17a1-Deficient Zebrafish (Danio rerio) for Evaluation of Environmental Estrogens

“…Total RNA was isolated from the liver or heart of zebrafish using TRIzol reagent (15596018; Ambion), as previously described (Zhai et al, 2022). Real-time quantitative polymerase chain reaction (qPCR) was performed using a Bio-Rad Real-Time System.…”

“…After administration, the dissected gonads were fixed in 4% paraformaldehyde for 24 h, followed by dehydration and infiltration. Staining was performed as previously described (Zhai et al, 2022). Briefly, each fixed sample was dehydrated in gradient ethanol solutions (50%, 75%, 85%, 95%, and 100%), cleared in xylene, and embedded in paraffin wax using an RM2235 microtome (Leica Biosystems).…”

“…The estrogenic impact and feminization effect of EEs have been revealed by a series of ecotoxicological tests using in vivo and in vitro model systems. Several studies have demonstrated that fish are affected by EEs in multiple ways, including steroid levels, gonadal development, vitellogenin (vtg) protein production, gametogenesis, and fertility (Baumann et al, 2013; Chen et al, 2015; Fang et al, 2016; Kidd et al, 2007; Madsen et al, 2013; Molina et al, 2018; Rose et al, 2013; Santangeli et al, 2016; Zhai et al, 2022). Low concentrations of EE2 (5–6 ng/L) led to feminization of males and impacted gonadal development, as evidenced by intersex in males and altered oogenesis in female fathead minnow (Kidd et al, 2007).…”