Differential regulation of gonadotropins as revealed by transcriptomes of distinct LH and FSH cells of fish pituitary
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ABSTRACT: From mammals to fish, gametogenesis and sexual maturation are driven by luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the gonadotropic hormones temporally secreted from the pituitary. Teleost fish are an excellent model for addressing the unique regulation and function of each gonadotropin cell because, unlike mammals, they synthesize and secrete LH and FSH from distinct cells. Only two very distant vertebrate classes (fish and birds), demonstrate the mono-hormonal strategy suggesting a potential convergent evolution. By performing cell specific transcriptome analysis of double-labelled transgenic Nile tilapia (Oreochromis niloticus) expressing GFP and RFP in LH or FSH cells, respectively, we identified genes specifically enriched in each cell type, revealing differences in hormone regulation, receptors expression, cell signaling, and electrical properties. We found that each LH and FSH cell in fish express unique GPCR signature that reveals the direct regulation of metabolic and homeostatic hormones. Comparing these novel transcriptomes to that of rat gonadotrophs revealed conserved genes that might specifically contribute to each gonadotropin activity in mammals, suggesting conserved mechanisms controlling the differential regulation of gonadotropins in vertebrates.
Project description:Fertility critically depends on the gonadotropin-releasing hormone (GnRH) pulse generator, a neural construct comprised of hypothalamic neurons coexpressing kisspeptin, neurokoinin-B and dynorphin. Here, using mathematical modeling and in vivo optogenetics we reveal for the first time how this neural construct initiates and sustains the appropriate ultradian frequency essential for reproduction. Prompted by mathematical modeling, we show experimentally using female estrous mice that robust pulsatile release of luteinizing hormone, a proxy for GnRH, emerges abruptly as we increase the basal activity of the neuronal network using continuous low-frequency optogenetic stimulation. Further increase in basal activity markedly increases pulse frequency and eventually leads to pulse termination. Additional model predictions that pulsatile dynamics emerge from nonlinear positive and negative feedback interactions mediated through neurokinin-B and dynorphin signaling respectively are confirmed neuropharmacologically. Our results shed light on the long-elusive GnRH pulse generator offering new horizons for reproductive health and wellbeing.SIGNIFICANCE STATEMENT The gonadotropin-releasing hormone (GnRH) pulse generator controls the pulsatile secretion of the gonadotropic hormones LH and FSH and is critical for fertility. The hypothalamic arcuate kisspeptin neurons are thought to represent the GnRH pulse generator, since their oscillatory activity is coincident with LH pulses in the blood; a proxy for GnRH pulses. However, the mechanisms underlying GnRH pulse generation remain elusive. We developed a mathematical model of the kisspeptin neuronal network and confirmed its predictions experimentally, showing how LH secretion is frequency-modulated as we increase the basal activity of the arcuate kisspeptin neurons in vivo using continuous optogenetic stimulation. Our model provides a quantitative framework for understanding the reproductive neuroendocrine system and opens new horizons for fertility regulation
Model is encoded by Johannes and submitted to BioModels by Ahmad Zyoud.
Project description:In all vertebrates, the dual function of testis (production of sexual steroids and production of gametes) is mainly regulated by two gonadotropic pituitary hormones, FSH and LH. However, in fish the biological activities of the two hormones are not still clearly delineated and moreover, their molecular mechanisms are yet poorly understood. In this study we investigated the effects of FSH and LH on testicular gene expression, in the rainbow trout, at two developmental stages I-II and III (I: spermatogonia only, II: active spermatogonia proliferation, III: meiosis onset with the appearance of spermatocytes and round spermatids). Testes were collected from all-male population rainbow trout and incubated in six replicates for 96 hours, at 12°C, in the absence or presence of purified salmonid gonadotropins, FSH and LH (500 ng/mL).
Project description:Gonadotropin-releasing hormone (GnRH) governs reproduction in vertebrates by regulating pituitary gonadotropins. Zebrafish, however, is an exception as gnrh3–/– fish, which lack the hypophysiotropic GnRH3, are fertile, suggesting that zebrafish utilizes a Gnrh-independent mechanism to regulate reproduction. To elucidate the role of Gnrh3 and the Gnrh-independent mechanisms that regulate the pituitary gonadotropes, we profiled the gene expression in individual pituitary cells of wild-type and gnrh–/– adult female zebrafish and identified transcriptionally defined cell types. The classical Lh and Fsh gonadotropes expressed both gonadotropin beta subunits with a ratio of 13:1 (lhb:fshb) and 40:1 (fshb:lhb), respectively. We discovered that Lh gonadotropes predominantly express genes encoding receptors for Gnrh (gnrhr2), thyroid hormone, estrogen, dopamine, and steroidogenic factor 1 (SF1). No Gnrh receptor expression was enriched in Fsh gonadotropes, instead, the expression of cholecystokinin receptor (cckrb) and galanin receptor (gal1rb) were enriched in these cells. The hereditary loss of Gnrh3 gene resulted in downregulation of fshb in Lh gonadotropes. Likewise, targeted chemogenetic ablation of Gnrh3 neurons led to a decrease in the number of fshb+/lhb+ cells. Our studies suggest that Gnrh3 directly acts on Lh gonadotropes through Gnrhr2, but the outcome of this interaction is still unknown. Gnrh3 also regulates fshb expression, probably via a non-Gnrh receptor route. Altogether, while Lh secretion and synthesis are likely regulated by multiple factors in a Gnrh-independent manner, Gnrh3 seems to play a role in the cellular organization of the pituitary in zebrafish.
Project description:In all vertebrates, the dual function of testis (production of sexual steroids and production of gametes) is mainly regulated by two gonadotropic pituitary hormones, FSH and LH. However, in fish the biological activities of the two hormones are not still clearly delineated and moreover, their molecular mechanisms are yet poorly understood. In this study we investigated the effects of FSH and LH on testicular gene expression, in the rainbow trout, at two developmental stages I-II and III (I: spermatogonia only, II: active spermatogonia proliferation, III: meiosis onset with the appearance of spermatocytes and round spermatids).
Project description:Goal of the experiment: To examine differential gene expression in granulosa cells of women undergoing ovarian stimulation with either recombinant human follicle stimulating hormone or purified human menopausal gonadotropin for in vitro fertilization. Brief description of the experiment: The study was designed to test the hypothesis that human granulosa cell (GC) gene expression response differs between pure recombinant FSH and human menopausal gonadotropin (hMG) stimulation regimens. Women < 35 years-old undergoing in vitro fertilization for tubal or male factor infertility were prospectively randomized to one of two stimulation protocols, Gonadotropin releasing hormone (GnRH) agonist long protocol plus individualized dosages of (1) recombinant follicle stimulating hormone (rFSH) (Gonal-F®) (n=4) or (2) purified human menopausal gonadotropin (hMG; Menopur®; 75 IU FSH/75 IU LH per vial) (n=3). Follicle development was monitored by ultrasound and serum estradiol levels. When two follicles were ≥ 17mm, human chorionic gonadotropin (hCG) (10,000 IU; Novarel®) was administered. Oocytes were retrieved 35 h post-hCG. Following oocyte recovery, GC were immediately collected in RNALater®. Pooled GC from individual patients were washed, centrifuged over 40% Percoll®, resuspended in RNALater, and snap-frozen in LN. Total RNA was extracted and stored at -70C. Biotinylated cRNA was synthesized from total RNA and each sample was run individually on CodeLink Whole Human Genome Bioarrays (Applied Microarrays). Unnamed genes and genes with <2-fold difference in expression were excluded from further analysis. After exclusions, 1736 genes exhibited differential expression between groups. Over 400 were categorized as signal transduction genes, ~180 as transcriptional regulators, and ~175 as enzymes/metabolic genes. Expression of selected genes was confirmed by RT-PCR. Differentially expressed genes included A kinase anchor protein 11 (AKAP11), bone morphogenic protein receptor II (BMPR2), epidermal growth factor (EGF), insulin-like growth factor binding protein (IGFBP)-4, IGFBP-5, basigin, and hypoxia-inducible factor (HIF)-1 alpha. The results suggest that major differences exist in the mechanism by which pure FSH alone versus FSH/LH regulate gene expression in preovulatory GC that could impact oocyte maturity and developmental competence.
Project description:Inter-organ communication is a major hallmark of health and is often orchestrated by hormones released by the anterior pituitary gland. Pituitary gonadotropes secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to regulate gonadal function and control fertility. Whether FSH and LH also act on organs other than the gonads is debated. Here, we found that gonadotrope depletion in adult female mice triggers profound hypogonadism, obesity, glucose intolerance, fatty liver, and bone loss. The absence of sex steroids precipitates these phenotypes, with the notable exception of fatty liver, which results from ovary-independent actions of FSH. We uncover paracrine FSH action on pituitary corticotropes as a novel mechanism to restrain the production of corticosterone and prevent hepatic steatosis. Our data demonstrate that functional communication of two distinct hormone-secreting cell populations in the pituitary regulates hepatic lipid metabolism.
Project description:Roblitz2013 - Menstrual Cycle following GnRH analogue administration
The model describes the menstrual cycle feedback mechanisms. GnRH, FSH, LH, E2, P4, inbibins A and B, and follicular development are modelled. The model predicts hormonal changes following GnRH analogue administration. Simulation results agree with measurements of hormone blood concentrations. The model gives insight into mechanisms underlying gonadotropin supression.
This model is described in the article:
A mathematical model of the human menstrual cycle for the administration of GnRH analogues.
Röblitz S, Stötzel C, Deuflhard P, Jones HM, Azulay DO, van der Graaf PH, Martin SW.
J. Theor. Biol. 2013 Mar; 321: 8-27
Abstract:
The paper presents a differential equation model for the feedback mechanisms between gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), development of follicles and corpus luteum, and the production of estradiol (E2), progesterone (P4), inhibin A (IhA), and inhibin B (IhB) during the female menstrual cycle. Compared to earlier human cycle models, there are three important differences: The model presented here (a) does not involve any delay equations, (b) is based on a deterministic modeling of the GnRH pulse pattern, and (c) contains less differential equations and less parameters. These differences allow for a faster simulation and parameter identification. The focus is on modeling GnRH-receptor binding, in particular, by inclusion of a pharmacokinetic/pharmacodynamic (PK/PD) model for a GnRH agonist, Nafarelin, and a GnRH antagonist, Cetrorelix, into the menstrual cycle model. The final mathematical model describes the hormone profiles (LH, FSH, P4, E2) throughout the menstrual cycle of 12 healthy women. It correctly predicts hormonal changes following single and multiple dose administration of Nafarelin or Cetrorelix at different stages in the cycle.
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Project description:Inhibin α knockout (Inha-/-) female mice develop sex cord-stromal ovarian cancer with complete penetrance and previous studies demonstrate that the pituitary gonadotropins [follicle stimulating hormone (FSH) and luteinizing hormone (LH)] are influential modifiers of granulosa cell tumor development and progression in inhibin-deficient females. Recent studies have demonstrated that Inha-/- ovarian follicles develop precociously to the early antral stage in prepubertal mice without any increase in serum FSH and these studies suggested that in the absence of inhibins, granulosa cells differentiate abnormally, and thus at sexual maturity may undergo an abnormal response to gonadotropin signaling. To test this hypothesis, we stimulated immature WT and Inha-/- female mice prior to gross tumor formation with gonadotropin analogs, and subsequently examined post-gonadotropin induced ovarian follicle development, as well as preovulatory and hCG-induced gene expression changes in granulosa cells. We find that at three weeks of age, inhibin-deficient ovaries do not show further antral development nor undergo cumulus expansion. Widespread alterations in the transcriptome of gonadotropin-treated Inha-/- granulosa cells suggest that gonadotropins initiate an improper program of cell differentiation in Inha-/- cells. Overall, our experiments reveal that inhibins are essential for the normal gonadotropin-dependent response of granulosa cells. (2) Genotypes (WT, Inh KO) collected from 2 preovulatory granulosa cells with and without hCG, in triplicate independent samples
Project description:Effects of the absence of a functional LH receptor and/or expression of a constitutively active FSH receptor on gene expression in the gonads of male mice were studied. The results provide insights into the roles of the hormones LH and FSH in male reproduction. The main conclusion is that constant strong FSH stimulation is able to rescue the impaired spermatogenesis and fertility of male mice in the absence of LH signalling.