Blocking of progestin action disrupts spermatogenesis in Nile tilapia (Oreochromis niloticus)

Abstract

In vitro studies have indicated that the maturation-inducing hormone 17a,20b-dihydroxy-4-pregnen-3-one (17a,20b-DP, DHP), probably through nuclear progestin receptor (Pgr), might be involved in the proliferation of spermatogonial cells and the initiation of meiosis in several fish species. However, further in vivo evidence is required to elucidate the role of DHP in spermatogenesis during sexual differentiation in teleosts. In this study, we cloned pgr and analyzed its expression in Nile tilapia (Oreochromis niloticus) and treated XY fish with RU486 (a synthetic Pgr antagonist) from 5 days after hatching (dah) to determine the role of DHP in spermatogenesis. Sequence and phylogenetic analyses revealed that the Pgr identified in tilapia is a genuine Pgr. Pgr was found to be expressed in the Sertoli cells surrounding spermatogonia and spermatids in the testis of tilapia. Real-time PCR analysis revealed that the expression of pgr in the testis was significantly upregulated from 10 dah, further increased at 50 dah, and persisted until adulthood in fish. In the testis of RU486-treated fish, the transcript levels of germ cell markers and a meiotic marker were substantially reduced. However, the expression of markers in Sertoli cells remained unchanged. Moreover, the production of 11-ketotestosterone and the expression of genes encoding various steroidogenic enzymes were also not altered. In contrast, the expression of cyp17a2, encoding one of the critical steroidogenic enzymes involved in DHP biosynthesis, declined significantly, possibly indicating the inhibition of DHP production by RU486. RU486 treatment given for 2 months did not affect spermatogenesis; however, treatment given for more than 3 months resulted in a decrease in spermatogonial cell numbers and depletion of later-phase spermatogenic cells. Simultaneous excessive DHP supplementation restored spermatogenesis in RU486-treated XY fish. Taken together, our data further indicated that DHP, possibly through Pgr, might be essential for spermatogonial cell proliferation and spermatogenesis in fish.

Integrative testis transcriptome analysis reveals differentially expressed miRNAs and their mRNA targets during early puberty in Atlantic salmon

“…As these miRNAs displayed a sharp decrease in expression past the immature stage they are, however, more likely to target a subset of mRNAs that are released from miRNA-mediated inhibition earlier than those targeted by cluster I. The mRNAs enriched in the progesterone-mediated oocyte maturation pathway might be relevant in this respect, since signaling by the progestin 17α,20β-dihydroxy-4-pregnen-3-one (DHP) through this pathway is an important step in stimulating the spermatogonial phase in fish spermatogenesis [ 55 , 56 ]. In adult zebrafish, DHP treatment doubled the testis weight, increased spermatogonial proliferation/differentiation and affected expression of several growth factor genes [ 57 ].…”

Figla Favors Ovarian Differentiation by Antagonizing Spermatogenesis in a Teleosts, Nile Tilapia (Oreochromis niloticus)

“…The gonads were dissected from monosex (XX and XY) fish at 90 and 150 dah, Figla -transgene and control XY fish at 90 dah, then Bouin-fixed, paraffin-embedded, and cut into 5μm sections. These sections were deparaffinized, hydrated and processed according to the previous reports [ 28 , 29 ]. The tissues sections were then treated in a blocking solution (Roche, Germany), incubated with hrGFP (Stratagene, Canada), Figla, Dmrt1, Sycp3, Cyp17a1 and StAR polyclonal antibody (1:1000) overnight at 4°C, respectively, and rinsed with 0.01 M PBS three times for 5 min per wash.…”

Retinoic acid homeostasis through aldh1a2 and cyp26a1 mediates meiotic entry in Nile tilapia (Oreochromis niloticus)

“…The Sycp3 (synaptonemal complex protein 3), a component of meiosis-specific synaptonemal complex, is expressed predominantly at the nuclear envelope at the leptotene stage of meiotic prophase I, and expanded along their entire length at the pachytene stage 18 . As in mice and chickens, sycp3 has been employed as a meiotic maker molecule associated with the timing of gonadal differentiation in tilapia 2 19 20 . Germ cells in XX and XY gonads that were to enter meiotic prophase were recognized by condensed meiotic nuclei and the expression of sycp3 20 .…”

“…As in mice and chickens, sycp3 has been employed as a meiotic maker molecule associated with the timing of gonadal differentiation in tilapia 2 19 20 . Germ cells in XX and XY gonads that were to enter meiotic prophase were recognized by condensed meiotic nuclei and the expression of sycp3 20 . To elucidate the roles of RA in the meiotic initiation of teleosts, we studied the genes encoding the RA metabolic enzymes ( aldh1a2 and cyp26a1 ) in tilapia.…”