Characterization of estrogen receptor beta2 and expression of the estrogen receptor subtypes alpha, beta1, and beta2 in the protandrous black porgy (Acanthopagrus schlegeli) during the sex change process

Molecular characterisation of oestrogen receptor ERα and the effects of bisphenol A on its expression during sexual development in the Chinese giant salamander (Andrias davidianus)

The aim of this study was to characterise the molecular structure of the oestrogen receptor ERα and to evaluate the effect of bisphenol A (BPA) on ERα expression during sexual development of the Chinese giant salamander (Andrias davidianus). The ERα cDNA of A. davidianus includes an open reading frame of 1755bp (encoding 584 amino acids), a 219-bp 5' untranslated region (UTR) and a 611-bp 3'UTR. A polyadenylation signal was not found in the 3'UTR. Amino acid sequence analysis showed high homology between ERα of A. davidianus and that of other amphibians, such as Andrias japonicas (99.66% identity) and Rana rugose (81.06% identity). In 3-year-old A. davidianus, highest ERα expression was observed in the liver and gonads. During different developmental stages in A. davidianus (from 1 to 3 years of age), ERα expression in the testes increased gradually. ERα was localised in the epithelial cells of seminiferous lobules and in interstitial cells. ERα-positive cells were more abundant in the interstitial tissue during testicular development. ERα was located in the nucleus of oocytes during ovary development. We found that the sex of 6-month-old A. davidianus larvae could not be distinguished anatomically. The sex ratio did not change after larvae were treated with 10μM BPA for 1 month. However, BPA treatment reduced bodyweight and ERα expression in the gonads in male larvae.

Impact of environmental estrogens on Yfish considering the diversity of estrogen signaling

Research on endocrine disruption in fish has been dominated by studies on estrogen-active compounds which act as mimics of the natural estrogen, 17β-estradiol (E2), and generally exert their biological actions by binding to and activation of estrogen receptors (ERs). Estrogens play central roles in reproductive physiology and regulate (female) sexual differentiation. In line with this, most adverse effects reported for fish exposed to environmental estrogens relate to sexual differentiation and reproduction. E2, however, utilizes a variety of signaling mechanisms, has multifaceted functions and targets, and therefore the toxicological and ecological effects of environmental estrogens in fish will extend beyond those associated with the reproduction. This review first describes the diversity of estrogen receptor signaling in fish, including both genomic and non-genomic mechanisms, and receptor crosstalk. It then considers the range of non-reproductive physiological processes in fish that are known to be responsive to estrogens, including sensory systems, the brain, the immune system, growth, specifically through the growth hormone/insulin-like growth factor system, and osmoregulation. The diversity in estrogen responses between fish species is then addressed, framed within evolutionary and ecological contexts, and we make assessments on their relevance for toxicological sensitivity as well as ecological vulnerability. The diversity of estrogen actions raises questions whether current risk assessment strategies, which focus on reproductive endpoints, and a few model fish species only, are protective of the wider potential health effects of estrogens. Available - although limited - evidence nevertheless suggests that quantitative environmental threshold concentrations for environmental protection derived from reproductive tests with model fish species are protective for non-reproductive effects as well. The diversity of actions of estrogens across divergent physiological systems, however, may lead to and underestimation of impacts on fish populations as their effects are generally considered on one functional process only and this may underrepresent the impact on the different physiological processes collectively.

The physiology functions of estrogen receptor α (ERα) in reproduction cycle of ovoviviparous black rockfish, Sebastes schlegeli Hilgendorf

This paper revealed the expression pattern of ERα in the ovoviviparous teleost, Sebastes schlegeli. In this paper, we isolated the cDNA encoding for estrogen receptor alpha of black rockfish (S. schlegeli) from its ovary, named as black rockfish ERα (brfERα). The cDNA sequence of brfERα consists of 2972bp with an open reading frame encoding a 624 amino acid putative protein which exhibits high identities with other teleosts'. The tissue distribution of brfERα mRNA was examined using RT-PCR. BrfERα showed generally expressions in most tissues of female black rockfish, besides, the higher degree of expressions were seen in ovary, liver, duodenum and fat, whereas it had a more restricted distribution in male fish. In ovary, the expression level of brfERα was as similar as the serum levels of E2 and P in female. However, it was a different situation in male, where the serum concentration of E2 showed higher levels after spermiation and Serum concentration of P did not show any significant changes during a year. Based on the present study, it is supposed that brfERα plays an important role in ovary and other target organs during the reproductive cycle, Further studies will focus on the transcriptional regulation and localization of brfERα in gonad in order to get a better understand of the physiological function of brfERα in ovoviviparous teleost. This study indicates that the black rockfish may be a good candidate for understanding the mechanism of estrogen in ovoviviparous fish.

Molecular cloning, characterization and expression profiles of three estrogen receptors in protogynous hermaphroditic orange-spotted grouper (Epinephelus coioides)

Estrogen plays key roles in vertebrate reproductive system via estrogen receptors (ERs) as mediating pathways. In the present study, three full-length ERs cDNA sequences were isolated from a protogynous teleost, the orange-spotted grouper (Epinephelus coioides), and were 2235bp for gERα, 1967bp for gERβ1 and 2158bp for gERβ2, respectively. Phylogenetic and amino acid alignment analyses showed that each gER was clustered in the corresponding taxonomic groups of the perciformes and exhibited high evolutional conservation in functional domains. RT-PCR revealed that gERs expressed at different levels in all the obtained tissues. gERα highly expressed in mature ovaries, gERβ1 mainly expressed in immature ovaries and gERβ2 varied greatly during ovarian development. During female to male sex reversal induced by 17α-methyltestosterone (MT) implantation, gERα decreased gradually, gERβ1 increased gradually, and gERβ2 decreased firstly and recovered subsequently in male stage. The present study speculated the potential roles of gERs during female maturation and female to male sex reversal induced by MT in the protogynous grouper E. coioides.

Immunolocalization of estrogen receptor alpha, estrogen receptor beta and androgen receptor in the pre-, peri- and post-pubertal stallion testis

In various species, androgens and estrogens regulate the function of testicular Leydig, Sertoli, peritubular myoid, and germ cells by binding to their respective receptors and eliciting a cellular response. Androgen receptor (AR) is expressed in Sertoli cells, peritubular myoid cells, Leydig cells and perivascular smooth muscle cells in the testis depending on the species, but its presence in germ cells remains controversial. Two different estrogen receptors have been identified, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), and their localization and function in testicular cells varies depending on the species, developmental stage of the cell and type of receptor. The localization of AR in an immature and mature stallion has been reported but estrogen receptors have only been reported for the mature stallion. In the present study, the localizations of AR and ERα/ERβ were investigated in pre-pubertal, peri-pubertal and post-pubertal stallions. Testes were collected by routine castration from 21 horses, of light horse breeds (3 months-27 years). Animals were divided into the following age groups: pre-pubertal (3-11 months; n=7), peri-pubertal (12-23 months; n=7) and post-pubertal (2-27 years; n=7). Testicular tissue samples were fixed and embedded, and the presence of AR, ERα and ERβ was investigated by immunohistochemistry (IHC) using procedures previously validated for the horse. Primary antibodies used were rabbit anti-human AR, mouse anti-human ERβ and rabbit anti-mouse ERα. Sections of each region were incubated with normal rabbit serum (NRS; AR and ERα) or mouse IgG (ERβ) instead of primary antibody to generate negative controls. Androgen receptors were localized in Leydig, Sertoli and peritubular myoid cells of all ages. Estrogen receptor alpha was localized in Leydig and germ cells of all ages but only in pre- and peri-pubertal Sertoli cells and post-pubertal peritubular myoid cells. Estrogen receptor beta was localized in Leydig and Sertoli cells of all ages but in only pre-pubertal germ cells and absent in peritubular myoid cells of all ages. Taken together, the data suggest that estrogen regulates steroidogenesis by acting through ERα and ERβ in the Leydig cells and promotes gametogenesis by acting through ERβ in the Sertoli cells and ERα in the germ cells. In contrast androgen receptors are not found in germ cells throughout development and thus are likely to support spermatogenesis by way of a paracrine/autocrine pathway via its receptors in Leydig, Sertoli and peritubular myoid cells.

Upregulation of estrogen receptor subtypes and vitellogenin mRNA in cinnamon clownfish Amphiprion melanopus during the sex change process: profiles on effects of 17beta-estradiol

In the present study, we investigated the expression pattern of estrogen receptors (esr) and vitellogenin (vtg) mRNA in the gonads and liver during sex change in cinnamon clownfish by using quantitative polymerase chain reaction. We divided gonadal development during the sex change from male to female into 3 stages (mature male, male at 90days after removing female, and mature female) and investigated esr and vtg mRNA expressions during the sex change. With female, the esr and vtg mRNA expressions increased. In western blot analysis, Esr1 protein was detected only in the ovaries of female cinnamon clownfish. Also, to understand the effect of 17beta-estradiol (E(2)), we investigated the esr and vtg mRNA expression patterns in the gonads and liver, and the changes in plasma E(2) level after E(2) injection. E(2) treatment increased both mRNA expression levels of esr and vtg and plasma E(2) levels. The present study describes the molecular characterization of esr subtypes and the interactions between esr and vtg after E(2) treatment in cinnamon clownfish.

Expression of three gonadotropin subunits and gonadotropin receptor mRNA during male-to-female sex change in the cinnamon clownfish, Amphiprion melanopus

To quantify the sex-change progression from male to female in the cinnamon clownfish, Amphiprion melanopus, we divided gonadal development into three stages (I, mature male; II, male at 90 days after removal of the female; and III, mature female), and the expression of GTH subunits and GTH receptors during each of these stages was investigated. The mRNA of the three GTH subunits and their receptors increased with progression from male to female. To understand the effect of gonadotropin-releasing hormone (GnRH) on this progression, we examined expression of genes encoding the GTH subunit mRNA in the pituitary and the GTH-receptor mRNA in the gonads in addition to investigating changes in plasma E(2) levels after GnRH analogue (GnRHa) injection. GnRHa treatment increased mRNA expression levels of these genes, as well as plasma E(2) levels, indicating that GnRH plays an important regulatory role in the brain-pituitary-gonad axis of immature cinnamon clownfish.

Gender-related expression of TRalpha and TRbeta in the protandrous black porgy, Acanthopagrus schlegeli, during sex change processes

We cloned the thyroid hormone receptor alpha (TRalpha) and beta (TRbeta) cDNAs from the ovaries of the protandrous black porgy and compared the expression levels of TRalpha and TRbeta mRNA during the sex change in black porgy. We observed that the TRalpha mRNA by quantitative real-time PCR and protein levels by Western blot were highest in the mature ovaries. Additionally, TRbeta mRNA levels were only expressed highly in the mature ovaries when compared to any other gonadal stages. Then, we injected gonadotropin-releasing hormone analogue (GnRHa) to know the effects on TRs mRNA in immature black porgy. Injection with GnRHa resulted in a significant increase in TRalpha level while significantly reducing TRbeta level after 12h. We concluded that TRalpha was related in testicular development as well as ovarian development and TRbeta was only affect to ovarian development in black porgy. These results will provide a framework for better understanding of the role of TRs during sex change processes in this fish.

Quantitative mRNA expression of sox3 and DMRT1 during sex reversal, and expression profiles after GnRHa administration in black porgy, Acanthopagrus schlegeli

We cloned full-length sox3 cDNA from testis of black porgy, Acanthopagrus schlegeli. Black porgy sox3 cDNA consists of 897 base pairs (bp) and encodes a protein of 298 amino acids. We have investigated the expression pattern of sox3 and DMRT1 mRNA during the sex-reverse process from male to female (immature testis, mature testis, testicular portion of mostly testis, ovarian portion of mostly testis, testicular portion of mostly ovary, ovarian portion of mostly ovary and ovary). The expression of sox3 and DMRT1 mRNA was high in mature testis of black porgy during sex-reverse process. In a histological analysis, testicular portion of gonad was degenerated and the ovary portion was increased during sex reversal from male to female, and then oocytes were increased in ovary. Also we examined the expression of sox3 and DMRT1 mRNA after gonadotropin-releasing hormone analogue (GnRHa) treatment in immature black porgy. The expression of sox3 and DMRT1 mRNA was increased after GnRHa treatment (in vivo and in vitro experiment) in immature black porgy. Therefore, we concluded that sox3 and DMRT1 were involved in the development of testis than ovary in black porgy.