Protandrous black porgy fish, Acanthopagrus schlegeli, have a striking life cycle, with a mono-male sex differentiation at the juvenile stage and male-to-female sex change at 3 yr of age. We report for the first time integrative molecular data on these interesting phenomena. Sex differentiation occurred between 4 and 5 mo of age. Testicular nr5a4 transcripts increased to high levels during sex differentiation (5 mo old), whereas nr0b1 (Dax-1) did not increase until the age of 8 mo. High nr5a4 and nr0b1 expression in testicular tissue, in contrast to low nr5a4 and high nr0b1 expression in ovarian tissue, were found in the male phase of 0 - to 2-yr-old fish (before sex change). Increased nr5a4, decreased nr0b1, and increased cyp19a1a were found in the ovarian tissues undergoing development from primary oocytes to vitellogenic oocytes during the natural sex change in 2 -yr-old fish. Removal of testicular tissue in 1 -yr-old fish resulted in both increased ovarian nr5a4 and genes in the steroidogenic pathway and decreased nr0b1 together with the appearance of vitellogenic oocytes. Ovary developed into the active stage with the increased expression of star and steroidogenic enzymes, including aromatase, in concordance with the decreased expression of nr0b1 in the testis-excised fish. Long-term estradiol (E2) administration resulted in early sex change, but the ovaries were mainly with primary oocytes. Low nr5a4, high nr0b1, and low steroidogenic enzymes, including cyp19a1a expression, were also observed in these E2-fed ovarian tissues. Thus, nr5a4 but not nr0b1 was associated with male sex differentiation. Testicular development required cooperative functions of both nr5a4 and nr0b1. The present study suggests that nr5a4 and nr0b1 have an antagonistic interaction for the oocyte development. Testicular tissue exerted inhibitory effects on ovarian development. It is probable that nr0b1 regulates the timing of vitellogenic development and sex change in black porgy.

There have been many trials describing the effects of polyunsaturated fatty acids (PUFA) on fecundity, neonatal development, and maternal behavior in humans, but few controlled studies in rodents. We examined the effects of a maternal diet high in omega 3 (N-3) or omega 6 (N-6) PUFA on NIH Swiss mice. Female mice were ad libitum fed one of three complete and balanced diets (N-3, enriched in menhaden oil; N-6, enriched in corn oil; C, control diet, Purina 5015) from age 4 wk until the end of the study. Mice were bred at ∼19 wk and 27 wk of age, providing a total of 838 pups from 129 litters in two experiments. After weaning their pups from parity 1, behavior of dams was assessed on elevated-plus and open-field mazes. Although the fraction of male pups from the N-3 and C groups was not different from 0.5, dams on the N-6 diet birthed more daughters than sons (213 vs. 133; P < 0.001). Although maternal stress has been reported to favor birth of daughters, the behavior of N-6 dams was not different from controls. By contrast, the N-3 dams displayed greater anxiety, spending less time in the open arms and more time in the closed arms of the elevated maze and traveling less distance and exhibiting less exploratory behavior in the open field (P < 0.05). N-3 dams tended to produce smaller litters than C dams, and N-3-suckled pups gained less weight (P < 0.05). In conclusion, the N-3 diet had negative effects on murine fecundity and maternal behavior, whereas the N-6 diet favored birth of daughters.

Maturation of immature bovine oocytes requires cytoplasmic polyadenylation and synthesis of a number of proteins involved in meiotic progression and metaphase-II arrest. Aurora serine-threonine kinases—localized in centrosomes, chromosomes, and midbody—regulate chromosome segregation and cytokinesis in somatic cells. In frog and mouse oocytes, Aurora A regulates polyadenylation-dependent translation of several mRNAs such as MOS and CCNB1, presumably by phosphorylating CPEB, and Aurora B phosphorylates histone H3 during meiosis. We analyzed the expression of three Aurora kinase genes—AURKA, AURKB, and AURKC—in bovine oocytes during meiosis by reverse transcription followed by quantitative real-time PCR and immunodetection. Aurora A was the most abundant form in oocytes, both at mRNA and protein levels. AURKA protein progressively accumulated in the oocyte cytoplasm during antral follicle growth and in vitro maturation. AURKB associated with metaphase chromosomes. AURKB, AURKC, and Thr-phosphorylated AURKA were detected at a contractile ring/midbody during the first polar body extrusion. CPEB, localized in oocyte cytoplasm, was hyperphosphorylated during prophase/metaphase-I transition. Most CPEB degraded in metaphase-II oocytes and remnants remained localized in a contractile ring. Roscovitine, U0126, and metformin inhibited meiotic divisions; they all induced a decrease of CCNB1 and phospho-MAPK3/1 levels and prevented CPEB degradation. However, only metformin depleted AURKA. The Aurora kinase inhibitor VX680 at 100 nmol/L did not inhibit meiosis but led to multinuclear oocytes due to the failure of the polar body extrusion. Thus, in bovine oocyte meiosis, massive destruction of CPEB accompanies metaphase-I/II transition, and Aurora kinases participate in regulating segregation of the chromosomes, maintenance of metaphase-II, and formation of the first polar body.

The testis is regarded as an immunologically privileged site because it tolerates either autoantigenic germ cells or allografts. Because the blood testis barrier represents an incomplete immunological barrier, we have explored whether Sertoli cells, the somatic cells of the seminiferous epithelium, might play an active role in immune evasion. We report data indicating that B7-H1(officially known as CD274)-mediated co-inhibition, an immunomodulatory mechanism based on cell-cell interaction, can be activated in Sertoli cell-lymphocyte cocultures. We have found that, in response to interferon gamma (IFNG), mouse Sertoli cells strongly up-regulate the negative co-stimulatory ligand B7-H1 but remain devoid of positive co-stimulatory molecules. Blockade of B7-H1 on the Sertoli cell surface resulted in enhanced proliferation of CD8 T cells cocultured with Sertoli cells. Moreover, IFNG-stimulated Sertoli cells were found to express, concurrent with B7-H1, MHC class II. Therefore, we have hypothesized that Sertoli cells could function as nonprofessional tolerogenic antigen-presenting cells by inducing enrichment in regulatory T cells (Tregs) in a mixed T lymphocyte population. Interestingly, we found that coculturing T cells with Sertoli cells can indeed induce an increase in CD4 CD25 (officially known as IL2RA)FOXP3 Tregs and a decrease in CD4 CD25⁻ T cells, suggesting Sertoli cell-mediated Treg conversion; this process was found to be B7-H1-independent. Altogether these data show that Sertoli cells are potentially capable of down-regulating the local immune response, on one hand by directly inhibiting CD8 T cell proliferation through B7-H1 and, on the other hand, by inducing an increase in Tregs that might suppress other bystander T cells.

Ovarian follicular development is controlled by numerous paracrine and endocrine regulators, including oocyte-derived growth differentiation factor 9 (GDF9), and a localized increase in bioavailable insulin-like growth factor 1 (IGF1). The effects of GDF9 on function of theca cells collected from small (3–6 mm) and large (8–22 mm) ovarian follicles were investigated. In small-follicle theca cells cultured in the presence of both LH and IGF1, GDF9 increased cell numbers and DNA synthesis, as measured by a ³H-thymidine incorporation assay, and dose-dependently decreased both progesterone and androstenedione production. Theca cells from large follicles had little or no response to GDF9 in terms of cell proliferation or steroid production induced by IGF1. Small-follicle theca cell studies indicated that GDF9 decreased the abundance of LHR and CYP11A1 mRNA in theca cells, but had no effect on IGF1R, STAR, or CYP17A1 mRNA abundance or the percentage of cells staining for CYP17A1 proteins. GDF9 activated similar to mothers against decapentaplegics (SMAD) 2/3-induced CAGA promoter activity in transfected theca cells. Small-follicle theca cells had more ALK5 mRNA than large-follicle theca cells. Small-follicle granulosa cells appeared to have greater GDF9 mRNA abundance than large-follicle granulosa cells, but theca cells had no detectable GDF9 mRNA. We conclude that theca cells from small follicles are more responsive to GDF9 than those from large follicles and that GDF9 mRNA may be produced by granulosa cells in cattle. Because GDF9 increased theca cell proliferation and decreased theca cell steroidogenesis, oocyte- and granulosa cell-derived GDF9 may simultaneously promote theca cell proliferation and prevent premature differentiation of the theca interna during early follicle development.

Correct cell cycle regulation is especially challenging at the start of life. Ovulated oocytes must maintain meiotic arrest until fertilization, and then complete meiosis and initiate a series of modified cell divisions without growth. Moreover, myriad key developmental events, such as chromatin remodeling and transcriptional activation of the genome, are coordinated with each other via the cell cycle, particularly passage through the DNA synthesis phase (S Phase). We examined here the expression of more than 30 mRNAs related to cell cycle regulation in rhesus monkey oocytes and embryos and compared the expression of these mRNAs between oocytes and embryos of different developmental potentials. We find that the maternally inherited stores of cell cycle regulatory mRNAs are especially susceptible to disruption in cases of diminished oocyte and embryo quality in the rhesus monkey. In comparison to published mouse array data, we also observed striking species differences in the temporal expression patterns of many of these genes, suggesting that mechanisms of cell cycle control may differ and that the responses of oocytes and embryos to external insults may likewise differ.

The expression of the steroidogenic acute regulatory protein (STAR) is regulated by PKA in response to trophic hormone stimulation through the second messenger cAMP. However, in steroidogenic cells, the concentrations of hormone necessary to maximally induce cAMP synthesis and PKA activity are often significantly higher than is necessary to achieve maximum steroidogenesis. One general mechanism believed to make PKA signaling more effective is the use of A-kinase anchoring proteins (AKAPs) to recruit PKA to discrete subcellular compartments, which coordinates and focuses PKA action with respect to its substrates. The characterization of AKAP121 has suggested that it enhances the posttranscriptional regulation of STAR by recruiting both Star mRNA and PKA to the mitochondria, thereby permitting more effective translation and phosphorylation of STAR. Testing this hypothesis revealed that cAMP-induced STAR expression and steroidogenesis closely followed AKAP121 abundance when this AKAP was silenced or overexpressed in MA-10 cells but that these changes were effected posttranscriptionally. Moreover, silencing AKAP121 expression in these cells specifically altered the localization of type II PKA regulatory subunit alpha (PKAR2A) at the mitochondria but did not affect its relative expression within the cell. Affinity purification experiments showed that PKAR2A preferentially associated with AKAP121, and cAMP analogs that activate type II PKA induced STAR phosphorylation more efficiently than analogs stimulating type I PKA. This suggests that AKAP121 and PKAR2A serve to enhance steroidogenesis by directing the synthesis and activation of STAR at the mitochondria in response to cAMP.

The mechanisms underlying the initiation of puberty in fish are poorly understood, and whether the Kiss1 receptor (Kiss1r; previously designated G protein-coupled receptor 54; GPR54) and its ligands, kisspeptins, play a significant role, as has been established in mammals, is not yet known. We determined (via real-time PCR) temporal patterns of expression in the brain of kiss1r, gnrh2, and gnrh3 and a suite of related genes in the hypothalamo-pituitary-gonadal (HPG) axis and analyzed them against the timing of gonadal germ cell development in male and female fathead minnow (Pimephales promelas). Full- or partial-length cDNAs for kiss1r (736 bp), gnrh2 (698 bp), and gnrh3 (804 bp) cloned from fathead minnow were found to be expressed only in the brain, testis, and ovary of adult fish. Localization of kiss1r, gnrh2, and gnrh3 within the brain provided evidence for their physiological roles and a likely hypophysiotropic role for GnRH3 in this species (which, like other cyprinids, does not appear to express gnrh1). In both sexes, kiss1r expression in the brain increased at the onset of puberty and reached maximal expression in males when spermatagonia type B appeared in the testis and in females when cortical alveolus-stage oocytes first appeared in the ovary, the timings of which differed for the two sexes. However, kiss1r expression was considerably lower during more advanced stages of spermatogenesis and oogenesis. The expression of kiss1r closely aligned with that of the gnrh genes (gnrh3 in particular), suggesting the Kiss1r/kisspeptin system in fish has a similar role in puberty to that occurring in mammals, and this hypothesis was supported by the induction of gnrh3 (2.25-fold) and kiss1r (1.5-fold) in early-mid pubertal fish injected with mammalian kisspeptin-10 (2 nmol/g wet weight). An intriguing finding, and contrasting that in mammals, was an elevated expression of esr1, ar, and cyp19a2 (genes involved in sex steroid signaling) in the brain at the onset of puberty, and in females slightly in advance of the elevation in the expression of kiss1r.

MUC1, a type I transmembrane glycoprotein expressed on most epithelia and many cancer cells, is involved in embryo implantation and tumor progression. A series of antibodies directed against the MUC1 ectodomain have been used to study MUC1 expression in the female reproductive tract, sometimes with apparently contradictory results. In the current study, we used two monoclonal MUC1 antibodies, 214D4 and HMFG1, to study the relationship between these MUC1 glycoforms in the human uterine epithelial cell line, HES, and human endometrial extracts. In response to tumor necrosis factor stimulation, accumulation of the HMFG1-reactive forms preceded that of the 214D4-reactive forms. Following inhibition of protein synthesis by cycloheximide, HMFG1-reactive species were lost rapidly (metabolic half-life [T_1/2] = 20 min), while there was no change in the level of the 214D4-reactive forms even after 80 min. HMFG1-reactive forms had smaller oligosaccharide chains than the 214D4-reactive forms, and could not be detected on the cell surface of intact cells or in the shed (media) fraction, although they were readily detected in permeabilized cells. Both 214D4- and HMFG1-reactive species were detected in human endometrial extracts throughout the cycle; however, consistent with the HES cell studies, the HMFG1-reactive species were both smaller and less abundant than the 214D4-reactive species. Consistent with this observation, we found that HMFG1-reactive species were difficult to detect in tissue sections unless predigested with neuraminidase, indicating that these structures are rapidly sialylated during synthesis. In contrast, 214D4-reactive species were robustly detected in both proliferative and secretory stages. Collectively, these studies indicate that the HMFG1-reactive glycoform is a precursor of the 214D4-reactive glycoform in HES cells and normal uterine epithelia. Therefore, discrepancies in patterns of MUC1 expression in other studies may be due to failure to account for these glycoform relationships.

Poor maternal nutrition during pregnancy can alter postnatal phenotype and increase susceptibility to adult cardiovascular and metabolic diseases. However, underlying mechanisms are largely unknown. Here, we show that maternal low protein diet (LPD), fed exclusively during mouse preimplantation development, leads to offspring with increased weight from birth, sustained hypertension, and abnormal anxiety-related behavior, especially in females. These adverse outcomes were interrelated with increased perinatal weight being predictive of later adult overweight and hypertension. Embryo transfer experiments revealed that the increase in perinatal weight was induced within blastocysts responding to preimplantation LPD, independent of subsequent maternal environment during later pregnancy. We further identified the embryo-derived visceral yolk sac endoderm (VYSE) as one mediator of this response. VYSE contributes to fetal growth through endocytosis of maternal proteins, mainly via the multiligand megalin (LRP2) receptor and supply of liberated amino acids. Thus, LPD maintained throughout gestation stimulated VYSE nutrient transport capacity and megalin expression in late pregnancy, with enhanced megalin expression evident even when LPD was limited to the preimplantation period. Our results demonstrate that in a nutrient-restricted environment, the preimplantation embryo activates physiological mechanisms of developmental plasticity to stablize conceptus growth and enhance postnatal fitness. However, activation of such responses may also lead to adult excess growth and cardiovascular and behavioral diseases.

Calcium signaling is a cellular event that plays a key role at many steps of fertilization and early development. However, little is known regarding the contribution of extracellular Ca² influx into the cell to this signaling in gametes and early embryos. To better know the significance of calcium entry on oocyte physiology, we have evaluated the mechanism of store-operated calcium entry (SOCE) in human metaphase II (MII) oocytes and its sensitivity to oxidative stress, one of the major factors implicated in the outcome of in vitro fertilization (IVF) techniques. We show that depletion of intracellular Ca² stores through inhibition of sarco(endo)plasmic Ca² -ATPase with thapsigargin triggers Ca² entry in resting human oocytes. Ba² and Mn² influx was also stimulated following inhibition, and Ca² entry was sensitive to pharmacological inhibition because the SOCE blocker 2-aminoethoxydiphenylborate (2-APB) reduced calcium and barium entry. These results support the conclusion that there is a plasma membrane mechanism responsible for the capacitative divalent cation entry in human oocytes. Moreover, the Ca² entry mechanism described in MII oocytes was found to be highly sensitive to oxidative stress. Hydrogen peroxide, at micromolar concentrations that could mimic culture conditions in IVF, elicited an increase of [Ca² ]_i that was dependent on the presence of extracellular Ca² . This rise was preventable by 2-APB, indicating that it was mainly due to the enhanced influx through store-operated calcium channels. In sum, our results demonstrate the occurrence of SOCE in human MII oocytes and the modification of this pathway due to oxidative stress, with possible consequences in IVF.

Implantation is a complex process involving interactions between the embryo and the uterus. Adhesion, remodeling of the maternal vasculature, and decidualization are crucial events necessary for successful implantation to occur. Heparanase (HPSE), an endo-β-d-glucuronidase, cleaves heparan sulfate at specific sites, leading to release of growth factors that may be involved in decidualization and remodeling of the maternal vasculature. HPSE also can function as a cell adhesion molecule. The aim of this study was to determine the expression of HPSE in the uteri of nonpregnant and pregnant baboons as well as in human stromal fibroblasts decidualized in vitro. We examined the localization and expression of HPSE using immunohistochemistry, Western blotting, RT-PCR, and activity assays. In nonpregnant baboon uteri, HPSE expression was localized to the apical surface of the glandular epithelia and in glandular secretions. However, in pregnant baboon uteri, HPSE was localized primarily in decidua. Uteri obtained at midpregnancy had higher heparanase activity compared with the nonpregnant uteri. A slight increase in HPSE expression was observed in human stromal fibroblasts decidualized in vitro. HPSE and HPSE2 mRNA transcripts were present in both decidualized tissue and cells. Increases in heparanase activity in the decidua from pregnant baboon uteri compared with tissue from nonpregnant animals and in human stromal fibroblasts decidualized in vitro suggest that HPSE plays a role in extracellular matrix remodeling and in increasing heparin-binding growth factor release during embryo implantation.

A precise packaging of the paternal genome during spermiogenesis is essential for fertilization and embryogenesis. Most of the nucleosomal DNA supercoiling must be eliminated in elongating spermatids (ES), and transient DNA strand breaks are observed that facilitate the process. Topoisomerases have been considered as ideal candidates for the removal of DNA supercoiling, but their catalytic activity, in the context of such a major chromatin remodeling, entails genetic risks. Using immunofluorescence, we confirmed that topoisomerase II beta (TOP2B) is the type II topoisomerase present in ES between steps 9 and 13. Interestingly, the detection of TOP2B was found coincident with detection of tyrosyl-DNA phosphodiesterase 1 (TDP1), an enzyme known to resolve topoisomerase-mediated DNA damage. The presence of gamma-H2AX (also known as H2AFX) coincident with DNA strand breakage was also confirmed at these steps and indicates that a DNA damage response is triggered. Active DNA repair in ES was demonstrated using a fluorescent in situ DNA polymerase activity assay on squash preparations of staged tubules. In the context of haploid spermatids, any unresolved double-strand breaks, resulting from a failure in the rejoining process of TOP2B, must likely rely on the error-prone nonhomologous end joining, because homologous recombination cannot proceed in the absence of a sister chromatid. Because this process is part of the normal developmental program of the spermatids, dramatic consequences for the genomic integrity of the developing male gamete may arise should any alteration in the process occur.

The Nile tilapia, a gonochoristic teleost fish with an XX/XY sex-determining system, provides an excellent model for studying gonadal sex differentiation because genetic all-females and all-males are available. In this study, we used quantitative real-time RT-PCR to determine the precise timing of the gonadal expression of 17 genes thought to be associated with gonadal sex differentiation in vertebrates. Gonads were isolated from all-female and all-male tilapia before (5–15 days after hatching [dah]) and after (25–70 dah) morphological sex differentiation. The transcript of aromatase (cyp19a1a), an enzyme responsible for producing estradiol-17beta, was expressed only in XX gonads at 5 dah, with a marked elevation in expression thereafter. In contrast, mRNA expression of steroid 11beta-hydroxylase (cyp11b2), an enzyme responsible for the synthesis of 11-ketotestosterone (11-KT, a potent androgen in fish), was found in XY gonads from 35 dah only. These results, combined with the presence of transcripts for other steroidogenic enzymes and estrogen receptors in XX gonads at 5–7 dah, are consistent with our earlier suggestion that estradiol-17beta plays a critical role in ovarian differentiation in tilapia, whereas a role for 11-KT in testicular differentiation is questionable. A close relationship between the expression of foxl2, but not nr5a1 (Ad4BP/SF-1), and that of cyp19a1a in XX gonads suggests an important role for Foxl2 in the transcriptional regulation of cyp19a1a. Dmrt1 exhibited a male-specific expression in XY gonads from 6 dah onward, suggesting an important role for Dmrt1 in testicular differentiation. Sox9 and amh (anti-Mullerian hormone) showed a testis-specific expression, being evident only in the later stages of testicular differentiation. It is concluded that the sex-specific expression of foxl2 and cyp19a1a in XX gonads and dmrt1 in XY gonads during early gonadal differentiation (5–6 dah) is critical for undifferentiated gonads to differentiate into either the ovary or testis in the Nile tilapia.

Spermatozoal maturation in the epididymis is dependent on proteins secreted by the epithelium and those that create the proper ionic composition and pH of the lumen as well as the blood-epididymal barrier. For the human epididymis, little information exists about the regulation of these proteins in male infertility. Our objectives were to assess gene expression profiles in the caput epididymidis from men with normal spermatogenesis and men with nonobstructive azoospermia. With microarrays, we identified 414 genes in the caput epididymidis that were differentially regulated in infertile men by at least 2-fold compared with the fertile men. They were mostly involved in transcription, intracellular signaling, immunity, and fertility. Although the expression of genes encoding tight junctional proteins was not affected, the localization of CLDN10 and TJP1, but not CLDNs 1, 3, and 8, was altered in infertile patients, suggesting that there are changes in the paracellular functions of the blood-epididymal barrier. Differentially regulated genes included several encoding proteins involved in spermatozoal maturation, water and ion channels, and beta-defensins: CRISP1, SPINLW1, FAM12B, and DEFB129 were upregulated, whereas CFTR, AQP5, KCNK4, KCNK17, SLC6A20, SLC13A3, DEFB126, and DEFB106A were downregulated. Furthermore, the immunolocalization of AQP5, but not of CFTR or CRISP1, varied in infertile and fertile patients. The observation that the expression of genes involved in water and ion transport were repressed in infertile patients suggests that these genes are regulated by the presence of testicular products or spermatozoa in the epididymal lumen or are part of a broader syndrome associated with nonobstructive azoospermia.

Pregnancy exposure to di(n-butyl) phthalate (DBP) in rats induces a testicular dysgenesislike syndrome (TDS) in male offspring. Earlier studies suggested altered Sertoli cell development/maturation may result, especially in testes that become cryptorchid. This study quantitatively assessed Sertoli cell numerical and functional development in DBP-exposed rats and compared (unilaterally) cryptorchid and scrotal testes. Pregnant rats were gavaged with 500 mg/kg/day DBP or corn oil from embryonic (E) Days 13.5 to 21.5. Male offspring were sampled on E21.5 or Postnatal Day 6, 10, 15, 25, or 90. Sertoli cell number in DBP-exposed males was reduced by ∼50% at E21.5 but recovered to normal by Days 25–90, accompanied by significant changes in plasma inhibin B and testosterone levels. Sertoli cell maturational development in DBP-exposed males, assessed using five protein markers (anti-müllerian hormone, cytokeratin, androgen receptor, CDKN1B, and Nestin), was largely normal, with some evidence of delayed maturation. However, in adulthood, Sertoli cells (SC) in areas lacking germ cells (Sertoli cell-only [SCO] tubules) often exhibited immature features, especially in cryptorchid testes. Sertoli cells in DBP-exposed animals supported fewer germ cells during puberty, but this normalized in scrotal testes by adulthood. Scrotal and especially cryptorchid testes from DBP-exposed animals exhibited abnormalities (SCO tubules, focal dysgenetic areas) at all postnatal ages. Cryptorchid testes from DBP-exposed animals exhibited more Sertoli cell abnormalities at Day 25 compared with scrotal testes, perhaps indicating more severe underlying Sertoli cell malfunction in these testes. Our findings support the concept of altered Sertoli cell development in TDS, especially in cryptorchid testes, but show that maturational defects in Sertoli cells in adulthood most commonly reflect secondary dedifferentiation in absence of germ cells.

Androgens play an important role in male sexual differentiation and development. They exert their function by binding to and activating the androgen receptor (Ar), a member of the steroid hormone receptor superfamily. Here, we report on the isolation and characterization of zebrafish Ar. The complete transcript of zebrafish ar is 5.3 kb long encoding a putative polypeptide of 868 amino acids. Our experimental and bioinformatic analysis has found a single ar locus in zebrafish. Phylogenetic analysis using the ligand-binding domain showed that the zebrafish Ar clustered with its cyprinid orthologs to form a separate group, which was closer to the beta clade than to the alpha clade. Tissue-specific expression analysis revealed that the ar mRNA was expressed ubiquitously in all adult tissues tested, with sexually dimorphic expression in the gonad and muscle. While the ar transcript was maternally deposited into the embryo, signs of zygotic expression could be detected as early as 24 h after fertilization, and the expression level increased substantially afterwards. When analyzed during gonad development, the expression level of ar mRNA at 4 wk after fertilization was similar in both developing gonads but later became higher in the transforming testis, suggesting a potential role during male gonad differentiation. We also combined theoretical modeling with in vitro experiments to show that the zebrafish Ar is preferentially activated by 11-ketotestosterone.

Previous studies have provided evidence for a paracrine interaction between pituitary gonadotrophs and lactotrophs. Here, we show that GnRH is able to stimulate prolactin (PRL) release in ovine primary pituitary cultures. This effect was observed during the breeding season (BS), but not during the nonbreeding season (NBS), and was abolished by the application of bromocriptine, a specific dopamine agonist. Interestingly, GnRH gained the ability to stimulate PRL release in NBS cultures following treatment with bromocriptine. In contrast, thyrotropin-releasing hormone, a potent secretagogue of PRL, stimulated PRL release during both the BS and NBS and significantly enhanced the PRL response to GnRH during the BS. These results provide evidence for a photoperiodically modulated functional interaction between the GnRH/gonadotropic and prolactin axes in the pituitary gland of a short day breeder. Moreover, the stimulation of PRL release by GnRH was shown not to be mediated by the gonadotropins, since immunocytochemical, Western blotting, and PCR studies failed to detect pituitary LH or FSH receptor protein and mRNA expressions. Similarly, no gonadotropin receptor expression was observed in the pituitary gland of the horse, a long day breeder. In contrast, S100 protein, a marker of folliculostellate cells, which are known to participate in paracrine mechanisms within this tissue, was detected throughout the pituitaries of both these seasonal breeders. Therefore, an alternative gonadotroph secretory product, a direct effect of GnRH on the lactotroph, or another cell type, such as the folliculostellate cell, may be involved in the PRL response to GnRH in these species.