Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)

Regulation of cortisol production during chronic social stress in rainbow trout

Chronic stress resulting from social interactions impacts the endocrine stress response in many vertebrates, including teleost fishes. Juvenile rainbow trout held in pairs form a dominance hierarchy with the subordinate individual exhibiting chronic elevation of plasma cortisol and an attenuated cortisol response to an additional acute stressor. The current study investigated the mechanisms underlying this apparent dichotomy in cortisol production at the level of the head kidney (adrenal homolog). Following four days of chronic social stress, subordinate rainbow trout exhibited elevated plasma cortisol levels that correlated with basal cortisol production by the head kidney in vitro. Subordinate trout had higher transcript abundances of steroidogenic acute regulatory protein and cytochrome p450 side chain cleavage enzyme, which facilitate key steps in steroidogenesis, as well as two paralogs of steroidogenic factor 1. Despite elevation of basal steroidogenesis, acute cortisol production in response to ACTH (in vivo and in vitro) was lower in subordinate trout. Transcript abundances of the ACTH receptor accessory proteins were elevated in subordinate fish, but head kidney cortisol production in response to a cAMP analogue was lower than in dominant fish. Together, the data suggest that the attenuated acute cortisol response of subordinate trout reflects limitations on cortisol production downstream of cAMP signalling in steroidogenic cells of the head kidney, despite the increased basal abundance of key components of the steroidogenic pathway.

Low-dose bisphenol A disrupts gonad development and steroidogenic genes expression in adult female rare minnow Gobiocypris rarus

Bisphenol A (BPA), an estrogenic monomer, has attracted many researchers to study its adverse effects in animal reproduction, especially in fish. To explore the effects of low dose BPA on adult female rare minnow Gobiocypris rarus, we exposed the fish to BPA at nominal concentrations of 5, 15, and 50 μg L(-1) for 14 and 35 d. The 35-d BPA exposure at 50 μg L(-1) had obviously suppressive effects on oocyte development, and BPA at all the three concentrations in both exposure durations of 14 and 35 d had stimulative effects on hepatic vitellogenin (vtg) transcription. BPA at lower concentrations (5 and 15 μg L(-1)) exhibited stimulative effects on the expressions of ovarian steroidogenic genes while at higher concentration (50 μg L(-1)) displayed inhibitive effects. Analysis of ovarian steroidogenic genes 5'-flanking regions and mRNA expressions of their potential regulatory factors revealed that the BPA-mediated actions on steroidogenesis in G. rarus ovary probably involve estrogen receptor (Esr) and androgen receptor (Ar) signaling, nuclear receptor subfamily 5, group A, number 1 (Nr5a1) pathway, and epigenetic regulation.

Molecular identification of genes involved in testicular steroid synthesis and characterization of the responses to hormones stimulation in testis of Japanese sea bass (Lateolabrax japonicas)

Testicular steroids are critical hormones for the regulation of spermatogenesis in male teleosts and their productions have been reported to be regulated by gonadotropins and gonadotropin-releasing hormone. In the Japanese sea bass (Lateolabrax japonicas), the reproductive endocrine, particularly regarding the production and regulation of testicular steroids, are not well understood. For this reason, we first cloned and characterized the response of several key genes regulating the production of testicular steroids and, second, we analyzed the changes of mRNA profiles of these genes during testicular development cycle and in the administration of hCG and GnRHa with corresponding testosterone level in serum, GSI and histological analyses. We succeeded in cloning the full-length cDNAs for the fushi tarazu factor-1 (FTZ-F1) homologues (FTZ-F1a and FTZ-F1b), steroidogenic acute regulatory protein (StAR) and anti-Müllerian hormone (AMH) in Japanese sea bass. Multiple sequence alignment and phylogenetic analysis of these proteins clearly showed that these genes in Japanese sea bass were homologous to those of other piscine species. During the testicular development cycle and hCG/GnRHa administration, quantification of jsbStAR transcripts revealed a trend similar to their serum testosterone levels, while a reciprocal relationship was founded between the serum concentrations of testosterone and jsbAMH and the links between gonadal expression of jsbStAR, jsbAMH and jsbFTZ-F1 were also observed. Our results have identified for the first time several key genes involved in the regulation of steroid production and spermatogenesis in the Japanese sea bass testis and these genes are all detected under gonadotropic hormone and gonadotropin-releasing hormone control.

Characterization of four nr5a genes and gene expression profiling for testicular steroidogenesis-related genes and their regulatory factors in response to bisphenol A in rare minnow Gobiocypris rarus

Bisphenol A (BPA) widely used in the manufacture of numerous products is ubiquitous in aquatic environment. To explore the mechanisms of BPA-mediated actions, male rare minnow Gobiocypris rarus were exposed to BPA at concentrations of 5, 15, and 50 μg/L for 14 and 35 days in the present study. Four subtypes of nr5a gene encoding important transcription factors for steroidogenesis were characterized, and tissue distribution analysis demonstrated distinct expression profiling of the four genes in G. rarus. BPA at environmentally relevant concentration (5 μg/L) caused increase of gonadosomatic index (GSI) of male fish. In response to BPA, no obvious changes on the testis development were observed. Modulation of vtg mRNA expression by BPA suggests estrogenic and/or anti-estrogenic effects of BPA were dependent on exposed duration (14 or 35 days). Gene expression profiling for testicular steroidogenesis-related genes, sexual steroid receptors, gonadotropin receptors, and transcription factors indicates differential regulation was dependent on exposure duration and dose of BPA. The correlation analysis at mRNA level demonstrates that the BPA-mediated actions on testicular steroidogenesis might involve sex steroid hormone receptor signaling, gonadotropin/gonadotropin receptor pathway, and transcription factors such as nuclear receptor subfamily 5, group A (Nr5a), fork head box protein L2 (Foxl2).

Molecular cloning and expression analysis of fushi tarazu factor 1 in the brain of air-breathing catfish, Clarias gariepinus

Background

Fushi tarazu factor 1 (FTZ-F1) encodes an orphan nuclear receptor belonging to the nuclear receptor family 5A (NR5A) which includes adrenal 4-binding protein or steroidogenic factor-1 (Ad4BP/SF-1) and liver receptor homologue 1 (LRH-1) and plays a pivotal role in the regulation of aromatases.

Methodology/Principal Findings

Present study was aimed to understand the importance of FTZ-F1 in relation to brain aromatase (cyp19a1b) during development, recrudescence and after human chorionic gonadotropin (hCG) induction. Initially, we cloned FTZ-F1 from the brain of air-breathing catfish, Clarias gariepinus through degenerate primer RT-PCR and RACE. Its sequence analysis revealed high homology with other NR5A1 group members Ad4BP/SF-1 and LRH-1, and also analogous to the spatial expression pattern of the latter. In order to draw functional correlation of cyp19a1b and FTZ-F1, we analyzed the expression pattern of the latter in brain during gonadal ontogeny, which revealed early expression during gonadal differentiation. The tissue distribution both at transcript and protein levels revealed its prominent expression in brain along with liver, kidney and testis. The expression pattern of brain FTZ-F1 during reproductive cycle and after hCG induction, in vivo was analogous to that of cyp19a1b shown in our earlier study indicating its involvement in recrudescence.

Conclusions/Significance

Based on our previous results on cyp19a1b and the present data, it is plausible to implicate potential roles for brain FTZ-F1 in ovarian differentiation and recrudescence process probably through regulation of cyp19a1b in teleosts. Nevertheless, these interactions would require primary coordinated response from ovarian aromatase and its related transcription factors.

Zebrafish sex determination and differentiation: involvement of FTZ-F1 genes

Sex determination is the process deciding the sex of a developing embryo. This is usually determined genetically; however it is a delicate process, which in many cases can be influenced by environmental factors. The mechanisms controlling zebrafish sex determination and differentiation are not known. To date no sex linked genes have been identified in zebrafish and no sex chromosomes have been identified. However, a number of genes, as presented here, have been linked to the process of sex determination or differentiation in zebrafish. The zebrafish FTZ-F1 genes are of central interest as they are involved in regulating interrenal development and thereby steroid biosynthesis, as well as that they show expression patterns congruent with reproductive tissue differentiation and function. Zebrafish can be sex reversed by exposure to estrogens, suggesting that the estrogen levels are crucial during sex differentiation. The Cyp19 gene product aromatase converts testosterone into 17 beta-estradiol, and when inhibited leads to male to female sex reversal. FTZ-F1 genes are strongly linked to steroid biosynthesis and the regulatory region of Cyp19 contains binding sites for FTZ-F1 genes, further linking FTZ-F1 to this process. The role of FTZ-F1 and other candidates for zebrafish sex determination and differentiation is in focus of this review.

Novel steroidogenic factor-1 homolog (ff1d) is coexpressed with anti-Mullerian hormone (AMH) in zebrafish

ff1d is a novel zebrafish FTZ-F1 gene with sequence characteristics indicating similar basic regulatory mechanisms as the previously characterized ff1 based on the presence of an FTZ-F1 box in the DNA binding domain and an interactive domain (I-Box) and an AF-2 in the ligand binding domain. The highest sequence similarity was found between ff1d and ff1b (NR5A4), a gene previously shown to be a functional homolog to the steroidogenic factor 1 (SF-1). The expression pattern of ff1d was comparable to ff1b both in brain and gonads in adults and in the pituitary and interrenal cells in embryos. SF-1 is crucial in mammalian steroidogenesis and in sex determination by regulating the anti-Mullerian hormone (AMH). In fish, AMH has not been described previously. In this study, we cloned a partial zebrafish AMH. AMH was detected in growing oocytes, the ovarian follicular layer and testicular Sertoli cells, similar to the mammalian pattern, suggesting a conserved role between zebrafish and mammalian AMH. Teleosts lack a gene homolog to SRY, which constitute the universal testis-determining factor in mammalian sex determination. Comparison of sequences and expression patterns indicate that ff1d is a new candidate for sex determination and differentiation in a way similar to SF-1, possibly involving AMH.

cDNA cloning and mRNA expression of a FTZ-F1 homologue from the pituitary of the orange-spotted grouper, epinephelus coioides

A FTZ-F1 homologue was cloned from the pituitary cDNA library of the orange-spotted grouper. The full-length cDNA of the orange-spotted grouper FTZ-F1 spanned 1735 bp including a poly (A) tail. The open reading frame encodes a protein of 468 amino acids. Sequence analysis indicated that it had a structure typical of the orphan nuclear receptor superfamily, and the FTZ-F1 box, a characteristic of the FTZ-F1 family. Phylogenetic analysis indicated that the orange-spotted grouper FTZ-F1 was closely related to medaka FTZ-F1 and did not belong to either the SF-1/Ad4BP group or the LRH-1/FTF group. Virtual Northern Blot detected a major transcript of about 1.7 kb and a minor transcript of 2.2 kb of FTZ-F1 in the orange-spotted grouper pituitary gland. The expression of FTZ-F1 homologue gene in different tissues and during embryonic development of the orange-spotted grouper was determined using one-step RT-PCR coupled with Southern blot analysis. In addition to the pituitary gland, the orange-spotted grouper FTZ-F1 was also expressed in the hypothalamus, forebrain, heart, liver, kidney, and ovary. The stronger signal from the gel image indicated that the expression level of FTZ-F1 homologue gene was higher in the ovary of stage 3 than stage 2. During embryonic development, mRNA for the orange-spotted grouper FTZ-F1 homologue was present in newly fertilized eggs, but disappeared in embryos at 50 min post fertilization. The orange-spotted grouper FTZ-F1 homologue mRNA reappeared in embryos at 1.5 hr post fertilization. Its expression level was increased from late blastula to neurula stages. Taken together, results of the current study suggest that the orange-spotted grouper FTZ-F1 homologue exhibits characteristics indicative of both the LRH-1/FTF- and the SF-1/Ad4BP-like genes, and may also play important roles in the hypothalamus-pituitary-gonadal axis, cholesterol metabolism, and embryogenesis.

Sequence and expression of cytochrome P450 aromatase and FTZ-F1 genes in the protandrous black porgy (Acanthopagrus schlegeli)

In this study, a cDNA encoding cytochrome P450 aromatase (P450arom) was cloned from black porgy Acanthopagrus schlegeli ovary. The deduced amino acid sequence had high homology with ovarian P450arom of other teleost fish. Moreover, we partially cloned two FTZ-F1 homologues (asff1a and asff1b) from black porgy. Comparative sequence analysis grouped asff1a and asff1b in NR5A2 and NR5A4 clades, respectively. Among the various tissues tested, P450arom mRNA was highly expressed in the ovary and weakly in the brain and testis, asff1a was expressed in brain, liver, intestine, kidney, testis, and ovary, asff1b was expressed in brain, kidney, testis, and ovary. The transcript levels of P450arom, asff1a, and asff1b were measured in the ovary and testis of 1+ -year-old, 2+ -year-old, and 5+ -year-old black porgy. The transcript level of P450arom in the ovary of 2+ -year-old fish was significantly higher than those of 1+ -year-old and 5+ -year-old fish. The results suggest that P450arom gene may be involved in the mechanism of natural sex change of protandrous black porgy. No change in ovarian expression of asff1a or asff1b was observed among different ages. These results suggest that up-regulation of the transcript levels of P450arom during the course of natural sex change of black porgy was not regulated via FTZ-F1.

The fetoprotein transcription factor (FTF) gene is essential to embryogenesis and cholesterol homeostasis and is regulated by a DR4 element

The fetoprotein transcription factor (FTF) gene was inactivated in the mouse, with a lacZ gene inserted inframe into exon 4. LacZ staining of FTF+/- embryos shows that the mFTF gene is activated at initial stages of zygotic transcription. FTF gene activity is ubiquitous at the morula and blastocyst stages and then follows expression patterns indicative of multiple FTF functions in fetal development. FTF-/- embryos die at E6.5-7.5, with features typical of visceral endoderm dysfunction. Adult FTF+/- mice are hypocholesterolemic, and express liver FTF at about 40% of the normal level. Overexpression of liver FTF in transgenic mice indicates in vivo that FTF is an activator of CYP7A1. However, CYP7A1 expression is increased in FTF+/- liver. Gene expression profiles indicate that higher CYP7A1 expression is caused by attenuated liver cell stress signaling. Diet experiments support a model where FTF is quenched both by activated c-Jun, and by SHP as a stronger feedback mechanism to repress CYP7A1. A DR4 element is conserved in the FTF gene promoter and activated by LXR-RXR and TR-RXR, qualifying the FTF gene as a direct metabolic sensor. Liver FTF increases in rats treated with thyroid hormone or a high cholesterol diet. The FTF DR4 element tightens functional links between FTF and LXRalpha in cholesterol homeostasis and can explain transient surges of FTF gene activities during development and FTF levels lower than predicted in FTF+/- liver. The FTF-lacZ mouse establishes a central role for FTF in developmental, nutritive, and metabolic functions from early embryogenesis through adulthood.