The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Allan E Herbison - One of the best experts on this subject based on the ideXlab platform.
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highly redundant neuropeptide volume co transmission underlying episodic activation of the GnRH Neuron dendron
eLife, 2021Co-Authors: Xinhuai Liu, Allan E Herbison, Shelhwa Yeo, James H Mcquillan, Michel K Herde, Sabine Hessler, Isaiah Cheong, Robert PorteousAbstract:The necessity and functional significance of neurotransmitter co-transmission remains unclear. The glutamatergic 'KNDy' Neurons co-express kisspeptin, neurokinin B (NKB), and dynorphin and exhibit a highly stereotyped synchronized behavior that reads out to the gonadotropin-releasing hormone (GnRH) Neuron dendrons to drive episodic hormone secretion. Using expansion microscopy, we show that KNDy Neurons make abundant close, non-synaptic appositions with the GnRH Neuron dendron. Electrophysiology and confocal GCaMP6 imaging demonstrated that, despite all three neuropeptides being released from KNDy terminals, only kisspeptin was able to activate the GnRH Neuron dendron. Mice with a selective deletion of kisspeptin from KNDy Neurons failed to exhibit pulsatile hormone secretion but maintained synchronized episodic KNDy Neuron behavior that is thought to depend on recurrent NKB and dynorphin transmission. This indicates that KNDy Neurons drive episodic hormone secretion through highly redundant neuropeptide co-transmission orchestrated by differential post-synaptic neuropeptide receptor expression at the GnRH Neuron dendron and KNDy Neuron.
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Innervation of GnRH Neuron Distal Projections and Activation by Kisspeptin in a New GnRH-Cre Rat Model
Endocrinology, 2020Co-Authors: Siew Hoong Yip, Xinhuai Liu, Robert Porteous, Pauline Campos, Allan E HerbisonAbstract:The neural mechanisms generating pulsatile GnRH release from the median eminence (ME) remain unclear. Studies undertaken in the mouse demonstrate that GnRH Neurons extend projections to the ME that have properties of both dendrites and axons, termed "dendrons," and that the kisspeptin Neuron pulse generator targets these distal dendrons to drive pulsatile GnRH secretion. It presently remains unknown whether the GnRH Neuron dendron exists in other species. We report here the generation of a knock-in GnRH1-Ires-Cre rat line with near-perfect targeting of Cre recombinase to the GnRH Neuronal phenotype. More than 90% of adult male and female GnRH Neurons express Cre with no ectopic expression. Adeno-associated viruses were used in adult female GnRH1-Ires-Cre rats to target mCherry or GCAMP6 to rostral preoptic area GnRH Neurons. The mCherry tracer revealed the known unipolar and bipolar morphology of GnRH Neurons and their principal projection pathways to the external zone of the ME. Synaptophysin-labeling of presynaptic nerve terminals revealed that GnRH Neuron distal projections received numerous close appositions as they passed through the arcuate nucleus and into the median eminence. Confocal GCaMP6 imaging in acute horizontal brain slices demonstrated that GnRH Neuron distal projections lateral to the median eminence were activated by kisspeptin. These studies indicate the presence of a dendron-like arrangement in the rat with GnRH Neuron distal projections receiving synaptic input and responding to kisspeptin.
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highly redundant neuropeptide volume cotransmission underlying episodic activation of the GnRH Neuron dendron
bioRxiv, 2020Co-Authors: Xinhuai Liu, Shelhwa Yeo, Michel K Herde, Sabine Hessler, Isaiah Cheong, Robert Porteous, Henry J Mcquillan, Allan E HerbisonAbstract:The necessity and functional significance of neurotransmitter co-transmission remains unclear. The glutamatergic KNDy Neurons co-express kisspeptin, neurokinin B (NKB) and dynorphin and exhibit a highly stereotyped synchronized behavior that reads out to the gonadotropin-releasing hormone (GnRH) Neuron dendrons to drive episodic hormone secretion. Using expansion microscopy, we show that KNDy Neurons make abundant close but non-synaptic appositions with the GnRH Neuron dendron. Confocal GCaMP6 calcium imaging demonstrated that, of the neurotransmitters co-expressed by KNDy Neurons, only kisspeptin was able to activate the GnRH Neuron dendron. The selective deletion of kisspeptin from KNDy Neurons resulted in mice in which the synchronized behavior of the KNDy Neurons was maintained but their ability to drive episodic hormone secretion was abolished. This indicates that KNDy Neurons drive episodic hormone secretion through converse modes of highly redundant neuropeptide co-transmission orchestrated by differential postsynaptic neuropeptide receptor expression at their two target sites.
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Different dendritic domains of the GnRH Neuron underlie the pulse and surge modes of GnRH secretion in female mice
eLife, 2020Co-Authors: Li Wang, Allan E Herbison, Wenya Guo, Xi Shen, Shel Yeo, Hui Long, Zhexuan Wang, Qifeng Lyu, Yanping KuangAbstract:The gonadotropin-releasing hormone (GnRH) Neurons exhibit pulse and surge modes of activity to control fertility. They also exhibit an unusual bipolar morphology comprised of a classical soma-proximal dendritic zone and an elongated secretory process that can operate as both a dendrite and an axon, termed a 'dendron'. We show using expansion microscopy that the highest density of synaptic inputs to a GnRH Neuron exists at its distal dendron. In vivo, selective chemogenetic inhibition of the GnRH Neuron distal dendron abolishes the luteinizing hormone (LH) surge and markedly dampens LH pulses. In contrast, inhibitory chemogenetic and optogenetic strategies targeting the GnRH Neuron soma-proximal dendritic zone abolish the LH surge but have no effect upon LH pulsatility. These observations indicate that electrical activity at the soma-proximal dendrites of the GnRH Neuron is only essential for the LH surge while the distal dendron represents an autonomous zone where synaptic integration drives pulsatile GnRH secretion.
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a simple model of estrous cycle negative and positive feedback regulation of GnRH secretion
Frontiers in Neuroendocrinology, 2020Co-Authors: Allan E HerbisonAbstract:The gonadal steroids estradiol and progesterone exert critical suppressive and stimulatory actions upon the brain to control gonadotropin-releasing hormone (GnRH) release that drives the estrous/menstrual cycle. A simple model for understanding these interactions is proposed in which the activity of the "GnRH pulse generator" is restrained by post-ovulation progesterone secretion to bring about the estrus/luteal phase slowing of pulsatile gonadotropin release, while the activity of the "GnRH surge generator" is primed by the rising follicular phase levels of estradiol to generate the pre-ovulatory surge. The physiological fluctuations in estradiol levels across the cycle are considered to clamp the GnRH pulse generator output at a constant level. Independent pulse and surge generator circuitries regulate the excitability of different compartments of the GnRH Neuron. As such, GnRH secretion through the cycle is determined simply by the summed influence of the estradiol-clamped, progesterone-regulated pulse and estradiol-regulated surge generators on the GnRH Neuron.
Suzanne M. Moenter - One of the best experts on this subject based on the ideXlab platform.
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a crh receptor type 1 agonist increases gaba transmission to GnRH Neurons in a circulating estradiol dependent manner
Endocrinology, 2020Co-Authors: Chayarndorn Phumsatitpong, Rose M De Guzman, Damian G Zuloaga, Suzanne M. MoenterAbstract:GnRH Neurons are central regulators of reproduction and respond to factors affecting fertility, such as stress. Corticotropin-releasing hormone (CRH) is released during stress response. In brain slices from unstressed controls, CRH has opposite, estradiol-dependent effects on GnRH Neuron firing depending on the CRH receptor activated; activating CRHR-1 stimulates whereas activating CRHR-2 suppresses activity. We investigated possible direct and indirect mechanisms. Mice were ovariectomized and either not treated further (OVX) or given a capsule producing high positive feedback (OVX + E) or low negative feedback (OVX + low E) physiologic circulating estradiol levels. We tested possible direct effects on GnRH Neurons by altering voltage-gated potassium currents. Two types of voltage-gated potassium currents (transient IA and sustained IK) were measured; neither CRHR-1 nor CRHR-2 agonists altered potassium current density in GnRH Neurons from OVX + E mice. Further, neither CRH nor receptor-specific agonists altered action potential generation in response to current injection in GnRH Neurons from OVX + E mice. To test the possible indirect actions, GABAergic postsynaptic currents were monitored. A CRHR-1 agonist increased GABAergic transmission frequency to GnRH Neurons from OVX + E, but not OVX, mice, whereas a CRHR-2 agonist had no effect. Finally, we tested if CRH alters the firing rate of arcuate kisspeptin Neurons, which provide an important excitatory neuromodulatory input to GnRH Neurons. CRH did not acutely alter firing activity of these Neurons from OVX, OVX + E or OVX + low E mice. These results suggest CRH increases GnRH Neuron activity in an estradiol-dependent manner in part by activating GABAergic afferents. Mechanisms underlying inhibitory effects of CRH remain unknown.
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prenatal androgenization alters the development of GnRH Neuron and preoptic area rna transcripts in female mice
Endocrinology, 2020Co-Authors: Laura L. Burger, Elizabeth R Wagenmaker, Chayarndorn Phumsatitpong, David P Olson, Suzanne M. MoenterAbstract:Polycystic ovary syndrome (PCOS) is the most common form of infertility in women. The causes of PCOS are not yet understood and both genetics and early-life exposure have been considered as candidates. With regard to the latter, circulating androgens are elevated in mid-late gestation in women with PCOS, potentially exposing offspring to elevated androgens in utero; daughters of women with PCOS are at increased risk for developing this disorder. Consistent with these clinical observations, prenatal androgenization (PNA) of several species recapitulates many phenotypes observed in PCOS. There is increasing evidence that symptoms associated with PCOS, including elevated luteinizing hormone (LH) (and presumably gonadotropin-releasing hormone [GnRH]) pulse frequency emerge during the pubertal transition. We utilized translating ribosome affinity purification coupled with ribonucleic acid (RNA) sequencing to examine GnRH Neuron messenger RNAs from prepubertal (3 weeks) and adult female control and PNA mice. Prominent in GnRH Neurons were transcripts associated with protein synthesis and cellular energetics, in particular oxidative phosphorylation. The GnRH Neuron transcript profile was affected more by the transition from prepuberty to adulthood than by PNA treatment; however, PNA did change the developmental trajectory of GnRH Neurons. This included families of transcripts related to both protein synthesis and oxidative phosphorylation, which were more prevalent in adults than in prepubertal mice but were blunted in PNA adults. These findings suggest that prenatal androgen exposure can program alterations in the translatome of GnRH Neurons, providing a mechanism independent of changes in the genetic code for altered expression.
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Chemogenetic Suppression of GnRH Neurons during Pubertal Development Can Alter Adult GnRH Neuron Firing Rate and Reproductive Parameters in Female Mice.
eNeuro, 2020Co-Authors: Eden A. Dulka, R. Anthony Defazio, Suzanne M. MoenterAbstract:Abstract Gonadotropin-releasing hormone (GnRH) Neurons control anterior pituitary, and thereby gonadal, function. GnRH Neurons are active before outward indicators of puberty appear. Prenatal androgen (PNA) exposure mimics reproductive dysfunction of the common fertility disorder polycystic ovary syndrome (PCOS) and reduces prepubertal GnRH Neuron activity. Early Neuron activity can play a critical role in establishing circuitry and adult function. We tested the hypothesis that changing prepubertal GnRH Neuron activity programs adult GnRH Neuron activity and reproduction independent of androgen exposure in female mice. Activating (3Dq) or inhibitory (4Di) designer receptors exclusively activated by designer drugs (DREADDs) were targeted to GnRH Neurons using Cre-lox technology. In control studies, the DREADD ligand clozapine n-oxide (CNO) produced the expected changes in GnRH Neuron activity in vitro and luteinizing hormone (LH) release in vivo. CNO was administered to control or PNA mice between two and three weeks of age, when GnRH Neuron firing rate is reduced in PNA mice. In controls, reducing prepubertal GnRH Neuron activity with 4Di increased adult GnRH Neuron firing rate and days in diestrus but did not change puberty onset or GABA transmission to these cells. In contrast, activating GnRH Neurons had no effect on reproductive parameters or firing rate and did not rescue reproductive phenotypes in PNA mice. These studies support the hypothesis that prepubertal Neuronal activity sculpts elements of the adult reproductive neuroendocrine axis and cyclicity but indicate that other PNA-induced programming actions are required for full reproductive phenotypes and/or that compensatory mechanisms overcome activity-mediated changes to mitigate reproductive changes in adults.
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Ovarian Androgens Maintain High GnRH Neuron Firing Rate in Adult Prenatally-Androgenized Female Mice.
Endocrinology, 2019Co-Authors: Eden A. Dulka, Laura L. Burger, Suzanne M. MoenterAbstract:Changes in gonadotropin-releasing hormone (GnRH) release frequency from the brain help drive reproductive cycles. In polycystic ovary syndrome (PCOS), persistent high GnRH/luteinizing hormone (LH) frequency disrupts cycles and exacerbates hyperandrogenemia. Adult prenatally-androgenized (PNA) mice exhibit increased GnRH Neuron firing rate, elevated ovarian androgens, and disrupted cycles, but before puberty, GnRH Neuron activity is reduced in PNA mice compared with controls. We hypothesized that ovarian feedback mediates the age-dependent change in GnRH Neuron firing rate in PNA vs control mice. Extracellular recordings of green fluorescent protein (GFP)-identified GnRH Neurons were made 5 to 7 days after sham-surgery, ovariectomy (OVX), or, in adults, after OVX plus replacement of sub-male androgen levels with dihydrotestosterone implants (OVX + DHT). In 3-week-old mice, OVX did not affect GnRH Neuron firing rate in either group. In adult controls, OVX increased GnRH Neuron firing rate, which was further enhanced by DHT. In adult PNA mice, however, OVX decreased GnRH Neuron firing rate, and DHT restored firing rate to sham-operated levels. In contrast to the differential effects of ovarian feedback on GnRH Neuron firing rate, serum LH increased after OVX in both control and PNA mice and was not altered by DHT. Pituitary gene expression largely reflected changes expected with OVX, although in PNA but not control mice, DHT treatment increased Lhb expression. These results suggest prenatal androgen exposure programs marked changes in GnRH Neuron regulation by homeostatic steroid feedback. PNA lowers GnRH Neuron activity in low-steroid states (before puberty, OVX), and renders activity in adulthood dependent upon ongoing exposure to elevated ovarian androgens.
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changes in both Neuron intrinsic properties and neurotransmission are needed to drive the increase in GnRH Neuron firing rate during estradiol positive feedback
The Journal of Neuroscience, 2019Co-Authors: Caroline Adams, Anthony R Defazio, Santiago Schnell, Catherine A Christian, Lorin S Milescu, Suzanne M. MoenterAbstract:Central output of gonadotropin-releasing hormone (GnRH) Neurons controls fertility and is sculpted by sex-steroid feedback. A switch of estradiol action from negative to positive feedback initiates a surge of GnRH release, culminating in ovulation. In ovariectomized mice bearing constant-release estradiol implants (OVX+E), GnRH Neuron firing is suppressed in the morning (AM) by negative feedback and activated in the afternoon (PM) by positive feedback; no time-of-day-dependent changes occur in OVX mice. In this daily surge model, GnRH Neuron intrinsic properties are shifted to favor increased firing during positive feedback. It is unclear whether this shift and the observed concomitant increase in GABAergic transmission, which typically excites GnRH Neurons, are independently sufficient for increasing GnRH Neuron firing rate during positive feedback or whether both are needed. To test this, we used dynamic clamp to inject selected previously recorded trains of GABAergic postsynaptic conductances (PSgs) collected during the different feedback states of the daily surge model into GnRH Neurons from OVX, OVX+E AM, and OVX+E PM mice. PSg trains mimicking positive feedback initiated more action potentials in cells from OVX+E PM mice than negative feedback or OVX (open feedback loop) trains in all three animal models, but the positive-feedback train was most effective when applied to cells during positive feedback. In silico studies of model GnRH Neurons in which >1000 PSg trains were tested exhibited the same results. These observations support the hypothesis that GnRH Neurons integrate fast-synaptic and intrinsic changes to increase firing rates during positive feedback. SIGNIFICANCE STATEMENT Infertility affects 15%–20% of couples; failure to ovulate is a common cause. Understanding how the brain controls ovulation is critical for new developments in both infertility treatment and contraception. Ovarian estradiol alters both the intrinsic properties of gonadotropin-releasing hormone (GnRH) Neurons and synaptic inputs to these cells coincident with production of sustained GnRH release that ultimately triggers ovulation. We demonstrate here using dynamic clamp and mathematical modeling that estradiol-induced shifts in synaptic transmission alone can increase firing output, but that the intrinsic properties of GnRH Neurons during positive feedback further poise these cells for increased response to higher frequency synaptic transmission. These data suggest that GnRH Neurons integrate fast-synaptic and intrinsic changes to increase firing rates during the preovulatory GnRH surge.
Pamela L Mellon - One of the best experts on this subject based on the ideXlab platform.
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deletion of the homeodomain protein six6 from GnRH Neurons decreases GnRH gene expression resulting in infertility
Endocrinology, 2019Co-Authors: Erica C. Pandolfi, Hanne M Hoffmann, Karen J Tonsfeldt, Pamela L MellonAbstract:Hypothalamic GnRH (luteinizing hormone-releasing hormone) Neurons are crucial for the hypothalamic-pituitary-gonadal (HPG) axis, which regulates mammalian fertility. Insufficient GnRH disrupts the HPG axis and is often associated with the genetic condition idiopathic hypogonadotropic hypogonadism (IHH). The homeodomain protein sine oculis-related homeobox 6 (Six6) is required for the development of GnRH Neurons. Although it is known that Six6 is specifically expressed within a more mature GnRH Neuronal cell line and that overexpression of Six6 induces GnRH transcription in these cells, the direct role of Six6 within the GnRH Neuron in vivo is unknown. Here we find that global Six6 knockout (KO) embryos show apoptosis of GnRH Neurons beginning at embryonic day 14.5 with 90% loss of GnRH Neurons by postnatal day 1. We sought to determine whether the hypogonadism and infertility reported in the Six6KO mice are generated via actions within the GnRH Neuron in vivo by creating a Six6-flox mouse and crossing it with the LHRHcre mouse. Loss of Six6 specifically within the GnRH Neuron abolished GnRH expression in ∼0% of GnRH Neurons. We further demonstrated that deletion of Six6 only within the GnRH Neuron leads to infertility, hypogonadism, hypogonadotropism, and delayed puberty. We conclude that Six6 plays distinct roles in maintaining fertility in the GnRH Neuron vs in the migratory environment of the GnRH Neuron by maintaining expression of GnRH and survival of GnRH Neurons, respectively. These results increase knowledge of the role of Six6 in the brain and may offer insight into the mechanism of IHH.
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Haploinsufficiency of SIX3 Abolishes Male Reproductive Behavior Through Disrupted Olfactory Development, and Impairs Female Fertility Through Disrupted GnRH Neuron Migration.
Molecular Neurobiology, 2018Co-Authors: Erica C. Pandolfi, Erica L Schoeller, Hanne M Hoffmann, Michael R Gorman, Pamela L MellonAbstract:Mating behavior in males and females is dependent on olfactory cues processed through both the main olfactory epithelium (MOE) and the vomeronasal organ (VNO). Signaling through the MOE is critical for the initiation of male mating behavior, and the loss of MOE signaling severely compromises this comportment. Here, we demonstrate that dosage of the homeodomain gene Six3 affects the degree of development of MOE but not the VNO. Anomalous MOE development in Six3 heterozygote mice leads to hyposmia, specifically disrupting male mounting behavior by impairing detection of volatile female estrus pheromones. Six3 is highly expressed in the MOE, main olfactory bulb (MOB), and hypothalamus; all regions essential in the proper migration of the gonadotropin-releasing hormone (GnRH) Neurons, a key reproductive Neuronal population that migrates along olfactory axons from the developing nose into the brain. Interestingly, we find that the reduction in Six3 expression in Six3 heterozygote mice compromises development of the MOE and MOB, resulting in mis-migration of GnRH Neurons due to improper olfactory axon targeting. This reduction in the hypothalamic GnRH Neuron population, by 45% in adulthood, leads to female subfertility, but does not impact male hormone levels, suggesting that male infertility is not related to GnRH Neuron numbers, but exclusively linked to abnormal olfaction. We here determine that Six3 is haploinsufficient for MOE development, GnRH Neuron migration, and fertility, and represents a novel candidate gene for Kallmann syndrome, a form of inherited infertility.
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transcriptional interaction between cfos and the homeodomain binding transcription factor vax1 on the GnRH promoter controls GnRH1 expression levels in a GnRH Neuron maturation specific manner
Molecular and Cellular Endocrinology, 2018Co-Authors: Hanne M Hoffmann, Ping Gong, Anika Tamrazian, Pamela L MellonAbstract:Gonadotropin-releasing hormone (GnRH) is required for pubertal onset and reproduction, thus the control of GnRH transcription is tightly regulated during development and adulthood. GnRH Neuron development depends on transcription factors of the homeodomain family. For example, Ventral anterior homeobox 1 (Vax1) is necessary to maintain GnRH expression after embryonic day 13 in the mouse. To further our understanding of the mechanisms by which VAX1 regulates GnRH gene expression, we asked whether VAX1 interacts with other transcription factors to modify GnRH expression levels. Using the GnRH cell lines, GN11 and GT1-7, we found that activation of PKC enhances expression of the immediate early gene cFos in both GN11, and GT1-7, and represses expression of Vax1 in GT1-7. Further, VAX1 interacts with cFOS while bound to the GnRH promoter. In immature GN11 cells, VAX1 and cFOS enhance GnRH expression, whereas VAX1 and cFOS have a repressive role in the mature GT1-7 cells.
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A small population of hypothalamic Neurons govern fertility: the critical role of VAX1 in GnRH Neuron development and fertility maintenance.
Neuroscience communications, 2016Co-Authors: Hanne M Hoffmann, Pamela L MellonAbstract:Fertility depends on the correct maturation and function of approximately 800 gonadotropin-releasing hormone (GnRH) Neurons in the brain. GnRH Neurons are at the apex of the hypothalamic-pituitary-gonadal axis that regulates fertility. In adulthood, GnRH Neurons are scattered throughout the anterior hypothalamic area and project to the median eminence, where GnRH is released into the portal vasculature to stimulate release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary. LH and FSH then regulate gonadal steroidogenesis and gametogenesis. Absence of GnRH Neurons or inappropriate GnRH release leads to infertility. Despite the critical role of GnRH Neurons in fertility, we still have a limited understanding of the genes responsible for proper GnRH Neuron development and function in adulthood. GnRH Neurons originate in the olfactory placode then migrate into the brain. Homeodomain transcription factors expressed within GnRH Neurons or along their migratory path are candidate genes for inherited infertility. Using a combined in vitro and in vivo approach, we have identified Ventral Anterior Homeobox 1 (Vax1) as a novel homeodomain transcription factor responsible for GnRH Neuron maturation and fertility. GnRH Neuron counts in Vax1 knock-out embryos revealed Vax1 to be required for the presence of GnRH-expressing cells at embryonic day 17.5 (E17.5), but not at E13.5. To localize the effects of Vax1 on fertility, we generated Vax1flox mice and crossed them with GnRHcre mice to specifically delete Vax1 within GnRH Neurons. GnRH staining in Vax1flox/flox:GnRHcre mice show a total absence of GnRH expression in the adult. We performed lineage tracing in Vax1flox/flox:GnRHcre:RosaLacZ mice which proved GnRH Neurons to be alive, but incapable of expressing GnRH. The absence of GnRH leads to delayed puberty, hypogonadism and complete infertility in both sexes. Finally, using the immortalized model GnRH Neuron cell lines, GN11 and GT1-7, we show that VAX1 is a direct regulator of GnRH1 transcription by binding key ATTA sites within the GnRH1 promoter. This study identifies VAX1 as a key transcription factor regulating GnRH expression and establishes VAX1 as a novel candidate gene implicated in heritable infertility.
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neurokinin b induces c fos transcription via protein kinase c and activation of serum response factor and elk 1 in immortalized GnRH Neurons
Endocrinology, 2014Co-Authors: Christine A Glidewellkenney, Crystal Trang, Paul P Shao, Navarre Gutierrezreed, Adaku M Uzookereke, Djurdjica Coss, Pamela L MellonAbstract:Mutations in neurokinin B (NKB) and its receptor, NK3R, were identified in human patients with hypogonadotropic hypogonadism, a disorder characterized by lack of puberty and infertility. Further studies have suggested that NKB acts at the level of the hypothalamus to control GnRH Neuron activity, either directly or indirectly. We recently reported that treatment with senktide, a NK3R agonist, induced GnRH secretion and expression of c-fos mRNA in GT1-7 cells. Here, we map the responsive region in the murine c-fos promoter to between −400 and −200 bp, identify the signal transducer and activator of transcription (STAT) (−345) and serum response element (−310) sites as required for induction, a modulatory role for the Ets site (−318), and show that induction is protein kinase C dependent. Using gel shift and Gal4 assays, we further show that phosphorylation of Elk-1 leads to binding to DNA in complex with serum response factor at serum response element and Ets sites within the c-fos promoter. Thus, we determine molecular mechanisms involved in NKB regulation of c-fos induction, which may play a role in modulation of GnRH Neuron activation.
Hanne M Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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deletion of the homeodomain protein six6 from GnRH Neurons decreases GnRH gene expression resulting in infertility
Endocrinology, 2019Co-Authors: Erica C. Pandolfi, Hanne M Hoffmann, Karen J Tonsfeldt, Pamela L MellonAbstract:Hypothalamic GnRH (luteinizing hormone-releasing hormone) Neurons are crucial for the hypothalamic-pituitary-gonadal (HPG) axis, which regulates mammalian fertility. Insufficient GnRH disrupts the HPG axis and is often associated with the genetic condition idiopathic hypogonadotropic hypogonadism (IHH). The homeodomain protein sine oculis-related homeobox 6 (Six6) is required for the development of GnRH Neurons. Although it is known that Six6 is specifically expressed within a more mature GnRH Neuronal cell line and that overexpression of Six6 induces GnRH transcription in these cells, the direct role of Six6 within the GnRH Neuron in vivo is unknown. Here we find that global Six6 knockout (KO) embryos show apoptosis of GnRH Neurons beginning at embryonic day 14.5 with 90% loss of GnRH Neurons by postnatal day 1. We sought to determine whether the hypogonadism and infertility reported in the Six6KO mice are generated via actions within the GnRH Neuron in vivo by creating a Six6-flox mouse and crossing it with the LHRHcre mouse. Loss of Six6 specifically within the GnRH Neuron abolished GnRH expression in ∼0% of GnRH Neurons. We further demonstrated that deletion of Six6 only within the GnRH Neuron leads to infertility, hypogonadism, hypogonadotropism, and delayed puberty. We conclude that Six6 plays distinct roles in maintaining fertility in the GnRH Neuron vs in the migratory environment of the GnRH Neuron by maintaining expression of GnRH and survival of GnRH Neurons, respectively. These results increase knowledge of the role of Six6 in the brain and may offer insight into the mechanism of IHH.
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Haploinsufficiency of SIX3 Abolishes Male Reproductive Behavior Through Disrupted Olfactory Development, and Impairs Female Fertility Through Disrupted GnRH Neuron Migration.
Molecular Neurobiology, 2018Co-Authors: Erica C. Pandolfi, Erica L Schoeller, Hanne M Hoffmann, Michael R Gorman, Pamela L MellonAbstract:Mating behavior in males and females is dependent on olfactory cues processed through both the main olfactory epithelium (MOE) and the vomeronasal organ (VNO). Signaling through the MOE is critical for the initiation of male mating behavior, and the loss of MOE signaling severely compromises this comportment. Here, we demonstrate that dosage of the homeodomain gene Six3 affects the degree of development of MOE but not the VNO. Anomalous MOE development in Six3 heterozygote mice leads to hyposmia, specifically disrupting male mounting behavior by impairing detection of volatile female estrus pheromones. Six3 is highly expressed in the MOE, main olfactory bulb (MOB), and hypothalamus; all regions essential in the proper migration of the gonadotropin-releasing hormone (GnRH) Neurons, a key reproductive Neuronal population that migrates along olfactory axons from the developing nose into the brain. Interestingly, we find that the reduction in Six3 expression in Six3 heterozygote mice compromises development of the MOE and MOB, resulting in mis-migration of GnRH Neurons due to improper olfactory axon targeting. This reduction in the hypothalamic GnRH Neuron population, by 45% in adulthood, leads to female subfertility, but does not impact male hormone levels, suggesting that male infertility is not related to GnRH Neuron numbers, but exclusively linked to abnormal olfaction. We here determine that Six3 is haploinsufficient for MOE development, GnRH Neuron migration, and fertility, and represents a novel candidate gene for Kallmann syndrome, a form of inherited infertility.
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transcriptional interaction between cfos and the homeodomain binding transcription factor vax1 on the GnRH promoter controls GnRH1 expression levels in a GnRH Neuron maturation specific manner
Molecular and Cellular Endocrinology, 2018Co-Authors: Hanne M Hoffmann, Ping Gong, Anika Tamrazian, Pamela L MellonAbstract:Gonadotropin-releasing hormone (GnRH) is required for pubertal onset and reproduction, thus the control of GnRH transcription is tightly regulated during development and adulthood. GnRH Neuron development depends on transcription factors of the homeodomain family. For example, Ventral anterior homeobox 1 (Vax1) is necessary to maintain GnRH expression after embryonic day 13 in the mouse. To further our understanding of the mechanisms by which VAX1 regulates GnRH gene expression, we asked whether VAX1 interacts with other transcription factors to modify GnRH expression levels. Using the GnRH cell lines, GN11 and GT1-7, we found that activation of PKC enhances expression of the immediate early gene cFos in both GN11, and GT1-7, and represses expression of Vax1 in GT1-7. Further, VAX1 interacts with cFOS while bound to the GnRH promoter. In immature GN11 cells, VAX1 and cFOS enhance GnRH expression, whereas VAX1 and cFOS have a repressive role in the mature GT1-7 cells.
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A small population of hypothalamic Neurons govern fertility: the critical role of VAX1 in GnRH Neuron development and fertility maintenance.
Neuroscience communications, 2016Co-Authors: Hanne M Hoffmann, Pamela L MellonAbstract:Fertility depends on the correct maturation and function of approximately 800 gonadotropin-releasing hormone (GnRH) Neurons in the brain. GnRH Neurons are at the apex of the hypothalamic-pituitary-gonadal axis that regulates fertility. In adulthood, GnRH Neurons are scattered throughout the anterior hypothalamic area and project to the median eminence, where GnRH is released into the portal vasculature to stimulate release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary. LH and FSH then regulate gonadal steroidogenesis and gametogenesis. Absence of GnRH Neurons or inappropriate GnRH release leads to infertility. Despite the critical role of GnRH Neurons in fertility, we still have a limited understanding of the genes responsible for proper GnRH Neuron development and function in adulthood. GnRH Neurons originate in the olfactory placode then migrate into the brain. Homeodomain transcription factors expressed within GnRH Neurons or along their migratory path are candidate genes for inherited infertility. Using a combined in vitro and in vivo approach, we have identified Ventral Anterior Homeobox 1 (Vax1) as a novel homeodomain transcription factor responsible for GnRH Neuron maturation and fertility. GnRH Neuron counts in Vax1 knock-out embryos revealed Vax1 to be required for the presence of GnRH-expressing cells at embryonic day 17.5 (E17.5), but not at E13.5. To localize the effects of Vax1 on fertility, we generated Vax1flox mice and crossed them with GnRHcre mice to specifically delete Vax1 within GnRH Neurons. GnRH staining in Vax1flox/flox:GnRHcre mice show a total absence of GnRH expression in the adult. We performed lineage tracing in Vax1flox/flox:GnRHcre:RosaLacZ mice which proved GnRH Neurons to be alive, but incapable of expressing GnRH. The absence of GnRH leads to delayed puberty, hypogonadism and complete infertility in both sexes. Finally, using the immortalized model GnRH Neuron cell lines, GN11 and GT1-7, we show that VAX1 is a direct regulator of GnRH1 transcription by binding key ATTA sites within the GnRH1 promoter. This study identifies VAX1 as a key transcription factor regulating GnRH expression and establishes VAX1 as a novel candidate gene implicated in heritable infertility.
Rebecca E Campbell - One of the best experts on this subject based on the ideXlab platform.
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investigating the npy agrp gaba to GnRH Neuron circuit in prenatally androgenized pcos like mice
Journal of the Endocrine Society, 2020Co-Authors: Christopher J Marshall, Melanie Prescott, Rebecca E CampbellAbstract:Polycystic ovary syndrome (PCOS), the most common form of anovulatory infertility, is associated with altered signaling within the hormone-sensitive Neuronal network that regulates gonadotropin-releasing hormone (GnRH) Neurons, leading to a pathological increase in GnRH secretion. Circuit remodeling is evident between GABAergic Neurons in the arcuate nucleus (ARN) and GnRH Neurons in a murine model of PCOS. One-third of ARN GABA Neurons co-express neuropeptide Y (NPY), which has a known yet complex role in regulating GnRH Neurons and reproductive function. Here, we investigated whether the NPY-expressing subpopulation (NPYARN) of ARN GABA Neurons (GABAARN) is also affected in prenatally androgenized (PNA) PCOS-like NPYARN reporter mice [Agouti-related protein (AgRP)-Cre;τGFP]. PCOS-like mice and controls were generated by exposure to di-hydrotestosterone or vehicle (VEH) in late gestation. τGFP-expressing NPYARN Neuron fiber appositions with GnRH Neurons and gonadal steroid hormone receptor expression in τGFP-expressing NPYARN Neurons were assessed using confocal microscopy. Although GnRH Neurons received abundant close contacts from τGFP-expressing NPYARN Neuron fibers, the number and density of putative inputs was not affected by prenatal androgen excess. NPYARN Neurons did not co-express progesterone receptor or estrogen receptor α in either PNA or VEH mice. However, the proportion of NPYARN Neurons co-expressing the androgen receptor was significantly elevated in PNA mice. Therefore, NPYARN Neurons are not remodeled by prenatal androgen excess like the wider GABAARN population, indicating GABA-to-GnRH Neuron circuit remodeling occurs in a presently unidentified non-NPY/AgRP population of GABAARN Neurons. NPYARN Neurons do, however, show independent changes in the form of elevated androgen sensitivity.
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Synaptic Innervation of the GnRH Neuron Distal Dendron in Female Mice.
Endocrinology, 2018Co-Authors: Aleisha M. Moore, Rebecca E Campbell, Siew Hoong Yip, Mel Prescott, Katja Czieselsky, Elodie Desroziers, Allan E HerbisonAbstract:GnRH Neuron cell bodies are scattered throughout the basal forebrain but funnel their projections to the median eminence to release GnRH into the pituitary portal system to control fertility. Prior studies have shown that GnRH Neurons located in the anterior hypothalamus send projections to the median eminence that have characteristics of both dendrites and axons. These unusual structures have been termed "dendrons." To address whether the dendron is unique to anterior hypothalamic GnRH Neurons or is also a characteristic of more rostral GnRH Neurons, we used viral vector‒mediated GnRH Neuron‒specific tract-tracing coupled with CLARITY optical clearing. Individual rostral preoptic area GnRH Neurons in female mice were identified to elaborate processes up to 4 mm in length that exhibited spines and projected all the way to the median eminence before branching into multiple short axons. The synaptic innervation patterns of distal GnRH Neuron dendrons and their short axons in the vicinity of the median eminence were examined using electron microscopy. This revealed the presence of a high density of synaptic inputs to distal dendrons at the border of the median eminence. In contrast, no synapses were detected on any GnRH Neuron axons. These studies demonstrate that GnRH Neurons in the rostral preoptic area project dendrons to the edge of the median eminence, whereupon they branch into multiple short axons responsible for GnRH secretion. The dense synaptic innervation of these distal dendrons likely represents an efficient mechanism for controlling GnRH secretion required for fertility.
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conditional viral tract tracing delineates the projections of the distinct kisspeptin Neuron populations to gonadotropin releasing hormone GnRH Neurons in the mouse
Endocrinology, 2015Co-Authors: Ulrich Boehm, Rebecca E Campbell, Allan E HerbisonAbstract:Kisspeptin Neurons play an essential role in the regulation of fertility through direct regulation of the GnRH Neurons. However, the relative contributions of the two functionally distinct kisspeptin Neuron subpopulations to this critical regulation are not fully understood. Here we analyzed the specific projection patterns of kisspeptin Neurons originating from either the rostral periventricular nucleus of the third ventricle (RP3V) or the arcuate nucleus (ARN) using a cell-specific, viral-mediated tract-tracing approach. We stereotaxically injected a Cre-dependent recombinant adenovirus encoding farnesylated enhanced green fluorescent protein into the ARN or RP3V of adult male and female mice expressing Cre recombinase in kisspeptin Neurons. Fibers from ARN kisspeptin Neurons projected widely; however, we did not find any evidence for direct contact with GnRH Neuron somata or proximal dendrites in either sex. In contrast, we identified RP3V kisspeptin fibers in close contact with GnRH Neuron somata and ...
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conditional viral tract tracing delineates the projections of the distinct kisspeptin Neuron populations to gonadotropin releasing hormone GnRH Neurons in the mouse
Endocrinology, 2015Co-Authors: Siew Hoong Yip, Allan E Herbison, Ulrich Boehm, Rebecca E CampbellAbstract:Kisspeptin Neurons play an essential role in the regulation of fertility through direct regulation of the GnRH Neurons. However, the relative contributions of the two functionally distinct kisspeptin Neuron subpopulations to this critical regulation are not fully understood. Here we analyzed the specific projection patterns of kisspeptin Neurons originating from either the rostral periventricular nucleus of the third ventricle (RP3V) or the arcuate nucleus (ARN) using a cell-specific, viral-mediated tract-tracing approach. We stereotaxically injected a Cre-dependent recombinant adenovirus encoding farnesylated enhanced green fluorescent protein into the ARN or RP3V of adult male and female mice expressing Cre recombinase in kisspeptin Neurons. Fibers from ARN kisspeptin Neurons projected widely; however, we did not find any evidence for direct contact with GnRH Neuron somata or proximal dendrites in either sex. In contrast, we identified RP3V kisspeptin fibers in close contact with GnRH Neuron somata and dendrites in both sexes. Fibers originating from both the RP3V and ARN were observed in close contact with distal GnRH Neuron processes in the ARN and in the lateral and internal aspects of the median eminence. Furthermore, GnRH nerve terminals were found in close contact with the proximal dendrites of ARN kisspeptin Neurons in the ARN, and ARN kisspeptin fibers were found contacting RP3V kisspeptin Neurons in both sexes. Together these data delineate selective zones of kisspeptin Neuron inputs to GnRH Neurons and demonstrate complex interconnections between the distinct kisspeptin populations and GnRH Neurons.
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Ion channels and information processing in GnRH Neuron dendrites.
Channels (Austin Tex.), 2013Co-Authors: Rachael Norberg, Rebecca E Campbell, Kelly J. SuterAbstract:Recent findings indicate that a majority of action potentials originate from dendrites of GnRH Neurons. This localization of the dendrite as the principle site of action potential initiation has sparked considerable interest in the nature of ionic channels throughout GnRH Neurons. This paper will review the ionic conductances described within GnRH Neurons and their implications for physiological output, such as sensitivity to steroids and diurnal state. To date, a majority of information regarding ionic conductances in GnRH Neurons pertains to somata and the first 50–100 µm of dendrite length. Thus, unraveling the tapestry created by the nature and distribution of dendritic conductances in GnRH Neurons lies at the forefront of understanding the control of reproductive hormone secretion.