1
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Grant AD, Kriegsfeld LJ. Neural substrates underlying rhythmic coupling of female reproductive and thermoregulatory circuits. Front Physiol 2023; 14:1254287. [PMID: 37753455 PMCID: PMC10518419 DOI: 10.3389/fphys.2023.1254287] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 08/30/2023] [Indexed: 09/28/2023] Open
Abstract
Coordinated fluctuations in female reproductive physiology and thermoregulatory output have been reported for over a century. These changes occur rhythmically at the hourly (ultradian), daily (circadian), and multi-day (ovulatory) timescales, are critical for reproductive function, and have led to the use of temperature patterns as a proxy for female reproductive state. The mechanisms underlying coupling between reproductive and thermoregulatory systems are not fully established, hindering the expansion of inferences that body temperature can provide about female reproductive status. At present, numerous digital tools rely on temperature to infer the timing of ovulation and additional applications (e.g., monitoring ovulatory irregularities and progression of puberty, pregnancy, and menopause are developed based on the assumption that reproductive-thermoregulatory coupling occurs across timescales and life stages. However, without clear understanding of the mechanisms and degree of coupling among the neural substrates regulating temperature and the reproductive axis, whether such approaches will bear fruit in particular domains is uncertain. In this overview, we present evidence supporting broad coupling among the central circuits governing reproduction, thermoregulation, and broader systemic physiology, focusing on timing at ultradian frequencies. Future work characterizing the dynamics of reproductive-thermoregulatory coupling across the lifespan, and of conditions that may decouple these circuits (e.g., circadian disruption, metabolic disease) and compromise female reproductive health, will aid in the development of strategies for early detection of reproductive irregularities and monitoring the efficacy of fertility treatments.
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Affiliation(s)
| | - Lance J. Kriegsfeld
- Department of Psychology, University of California, Berkeley, CA, United States
- The Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States
- Department of Integrative Biology, University of California, Berkeley, CA, United States
- Graduate Group in Endocrinology, University of California, Berkeley, CA, United States
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2
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Constantin S. Targeting KNDy neurons to control GnRH pulses. Curr Opin Pharmacol 2022; 67:102316. [PMID: 36347163 PMCID: PMC9772270 DOI: 10.1016/j.coph.2022.102316] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/03/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is the final output of the central nervous system that drives fertility. A characteristic of GnRH secretion is its pulsatility, which is driven by a pulse generator. Each GnRH pulse triggers a luteinizing hormone (LH) pulse. However, the puzzle has been to reconcile the synchronicity of GnRH neurons with the scattered hypothalamic distribution of their cell bodies. A leap toward understanding GnRH pulses was the discovery of kisspeptin neurons near the distal processes of GnRH neurons, which secrete kisspeptins, potent excitatory neuropeptides on GnRH neurons, and equipped with dual, but opposite, self-modulatory neuropeptides, neurokinin B and dynorphin. Over the last decade, this cell-to-cell communication has been dissected in animal models. Today the 50-year quest for the basic mechanism of GnRH pulse generation may be over, but questions about its physiological tuning remain. Here is an overview of recent basic research that frames translational research.
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Affiliation(s)
- Stephanie Constantin
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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3
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Terasawa E. The mechanism underlying the pubertal increase in pulsatile GnRH release in primates. J Neuroendocrinol 2022; 34:e13119. [PMID: 35491543 PMCID: PMC9232993 DOI: 10.1111/jne.13119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 02/17/2022] [Accepted: 03/01/2022] [Indexed: 11/29/2022]
Abstract
In primates, the gonatotropin-releasing hormone (GnRH) neurosecretory system, consisting of GnRH, kisspeptin, and neurokinin B neurons, is active during the neonatal/early infantile period. During the late infantile period, however, activity of the GnRH neurosecretory system becomes minimal as a result of gonadal steroid independent central inhibition, and this suppressed GnRH neurosecretory state continues throughout the prepubertal period. At the initiation of puberty, the GnRH neurosecretory system becomes active again because of the decrease in central inhibition. During the progress of puberty, kisspeptin and neurokinin B signaling to GnRH neurons further increases, resulting in the release of gonadotropins and subsequent gonadal maturation, and hence puberty. This review further discusses potential substrates of central inhibition and subsequent pubertal modification of the GnRH neurosecretory system by the pubertal increase in steroid hormones, which ensures the regulation of adult reproductive function.
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Affiliation(s)
- Ei Terasawa
- Department of Pediatrics and Wisconsin National Primate Research CenterUniversity of Wisconsin‐MadisonMadisonWIUSA
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4
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Constantin S, Moenter SM, Piet R. The electrophysiologic properties of gonadotropin-releasing hormone neurons. J Neuroendocrinol 2022; 34:e13073. [PMID: 34939256 PMCID: PMC9163209 DOI: 10.1111/jne.13073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 11/10/2021] [Accepted: 11/18/2021] [Indexed: 11/26/2022]
Abstract
For about two decades, recordings of identified gonadotropin-releasing hormone (GnRH) neurons have provided a wealth of information on their properties. We describe areas of consensus and debate the intrinsic electrophysiologic properties of these cells, their response to fast synaptic and neuromodulatory input, Ca2+ imaging correlates of action potential firing, and signaling pathways regulating these aspects. How steroid feedback and development change these properties, functions of GnRH neuron subcompartments and local networks, as revealed by chemo- and optogenetic approaches, are also considered.
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Affiliation(s)
- Stephanie Constantin
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892-3703, USA
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Suzanne M Moenter
- Departments of Molecular & Integrative Physiology, Internal Medicine, Obstetrics & Gynecology, and the Reproductive Sciences Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Richard Piet
- Brain Health Research Institute & Department of Biological Sciences, Kent State University, Kent, OH, 44242, USA
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5
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Keen KL, Petersen AJ, Figueroa AG, Fordyce BI, Shin J, Yadav R, Erdin S, Pearce RA, Talkowski ME, Bhattacharyya A, Terasawa E. Physiological Characterization and Transcriptomic Properties of GnRH Neurons Derived From Human Stem Cells. Endocrinology 2021; 162:6298609. [PMID: 34125902 PMCID: PMC8294693 DOI: 10.1210/endocr/bqab120] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Indexed: 12/23/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus play a key role in the regulation of reproductive function. In this study, we sought an efficient method for generating GnRH neurons from human embryonic and induced pluripotent stem cells (hESC and hiPSC, respectively). First, we found that exposure of primitive neuroepithelial cells, rather than neuroprogenitor cells, to fibroblast growth factor 8 (FGF8), was more effective in generating GnRH neurons. Second, addition of kisspeptin to FGF8 further increased the efficiency rates of GnRH neurogeneration. Third, we generated a fluorescent marker mCherry labeled human embryonic GnRH cell line (mCh-hESC) using a CRISPR-Cas9 targeting approach. Fourth, we examined physiological characteristics of GnRH (mCh-hESC) neurons: similar to GnRH neurons in vivo, they released the GnRH peptide in a pulsatile manner at ~60 min intervals; GnRH release increased in response to high potassium, kisspeptin, estradiol, and neurokinin B challenges; and injection of depolarizing current induced action potentials. Finally, we characterized developmental changes in transcriptomes of GnRH neurons using hESC, hiPSC, and mCh-hESC. The developmental pattern of transcriptomes was remarkably similar among the 3 cell lines. Collectively, human stem cell-derived GnRH neurons will be an important tool for establishing disease models to understand diseases, such as idiopathic hypothalamic hypogonadism, and testing contraceptive drugs.
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Affiliation(s)
- Kim L Keen
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI, USA
| | - Andrew J Petersen
- Waisman Center, Graduate School, University of Wisconsin, Madison, WI, USA
| | - Alexander G Figueroa
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Benjamin I Fordyce
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI, USA
| | - Jaeweon Shin
- Center for Genomic Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Rachita Yadav
- Center for Genomic Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute, Cambridge, MA, USA
| | - Serkan Erdin
- Center for Genomic Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute, Cambridge, MA, USA
| | - Robert A Pearce
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Michael E Talkowski
- Center for Genomic Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute, Cambridge, MA, USA
| | - Anita Bhattacharyya
- Waisman Center, Graduate School, University of Wisconsin, Madison, WI, USA
- Department of Cell and Regenerative Medicine, University of Wisconsin, Madison, WI, USA
| | - Ei Terasawa
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI, USA
- Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
- Correspondence: Ei Terasawa, PhD, Wisconsin National Primate Research Center, University of Wisconsin, 1223 Capitol Court, Madison, WI 53715-1299, USA.
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6
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Delli V, Silva MSB, Prévot V, Chachlaki K. The KiNG of reproduction: Kisspeptin/ nNOS interactions shaping hypothalamic GnRH release. Mol Cell Endocrinol 2021; 532:111302. [PMID: 33964320 DOI: 10.1016/j.mce.2021.111302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 04/20/2021] [Accepted: 04/23/2021] [Indexed: 12/21/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is the master regulator of the hypothalamic-pituitary-gonadal (HPG) axis, and therefore of fertility and reproduction. The release pattern of GnRH by the hypothalamus includes both pulses and surges. However, despite a considerable body of evidence in support of a determinant role for kisspeptin, the mechanisms regulating a GnRH pulse and surge remain a topic of debate. In this review we challenge the view of kisspeptin as an absolute "monarch", and instead present the idea of a Kisspeptin-nNOS-GnRH or "KiNG" network that is responsible for generating the "GnRH pulse" and "GnRH surge". In particular, the neuromodulator nitric oxide (NO) has opposite effects to kisspeptin on GnRH secretion in many respects, acting as the Yin to kisspeptin's Yang and creating a dynamic system in which kisspeptin provides the "ON" signal, promoting GnRH release, while NO mediates the "OFF" signal, acting as a tonic brake on GnRH secretion. This interplay between an activator and an inhibitor, which is in turn fine-tuned by the gonadal steroid environment, thus leads to the generation of GnRH pulses and surges and is crucial for the proper development and function of the reproductive axis.
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Affiliation(s)
- Virginia Delli
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Mauro S B Silva
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Vincent Prévot
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Konstantina Chachlaki
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France; University Research Institute of Child Health and Precision Medicine, National and Kapodistrian University of Athens, "Aghia Sophia" Children's Hospital, Athens, Greece.
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7
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Baykara M, Ozcan M, Bilgen M, Kelestimur H. Interference of gadolinium dechelated from MR contrast agents by calcium signaling in neuronal cells of GnRH. J Cell Physiol 2020; 236:2139-2143. [PMID: 32740939 DOI: 10.1002/jcp.30000] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 07/21/2020] [Accepted: 07/24/2020] [Indexed: 11/07/2022]
Abstract
Contrast agents (CAs) used in magnetic resonance imaging (MRI) are produced by chelating the metal gadolinium (Gd) with organic ligand molecules to form stable complexes. But, Gd3+ may dissociate from the CAs and subsequently might become toxic to its environment. Besides toxicity, it might inhibit calcium channels on cell membranes and this action could be detrimental to the cells governing biological development. The aim of this study was to investigate the interference of Gd3+ dechelated from the CAs by calcium signaling in the neuronal cells of gonadotropin-releasing hormone (GnRH), regulating puberty, and sexual development. The study used the mouse GT1-7 cell line as a model system, and Fura-2 based calcium imaging for detecting the interruption of intracellular calcium transport by the extracellular presence of Gd3+ as released from the CAs; gadodiamide and gadoterate meglumine, when the cells were stimulated in vitro culture by exposure to melatonin.The CA gadoterate meglumine interfered minimally with the calcium signaling, and thus its use is preferable in standard MRI exams. The release of Gd3+ from gadodiamide was significant and becomes of great concern as it may impact the neurophysiology of the neuronal cells in general, and gonadotropin production in particular, even in normal patients without nephrogenic systemic fibrosis. The toxicity induced by the influx of dechelated Gd3+ in the neurons of GnRH would have significant implications for puberty and reproductive functions.
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Affiliation(s)
- Murat Baykara
- Radiology Department, Faculty of Medicine, Firat University, Elazig, Turkey.,Physiology Department, Faculty of Medicine, Firat University, Elazig, Turkey
| | - Mete Ozcan
- Biophysics Department, Faculty of Medicine, Firat University, Aydin, Turkey
| | - Mehmet Bilgen
- Biophysics Department, Faculty of Medicine, Adnan Menderes University, Aydin, Turkey
| | - Haluk Kelestimur
- Physiology Department, Faculty of Medicine, Firat University, Elazig, Turkey
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8
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Terasawa E. Mechanism of pulsatile GnRH release in primates: Unresolved questions. Mol Cell Endocrinol 2019; 498:110578. [PMID: 31518609 PMCID: PMC6944307 DOI: 10.1016/j.mce.2019.110578] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 12/18/2022]
Abstract
The pulsatility of GnRH release is essential for reproductive function. The key events in reproductive function, such as puberty onset and ovulatory cycles, are regulated by the frequency and amplitude modulation of pulsatile GnRH release. Abnormal patterns of GnRH pulsatility are seen in association with disease states, such as polycystic ovarian syndrome and anorexia nervosa. Recent studies with physiological, track-tracing, optogenetic and electrophysiological recording experiments indicate that a group of kisspeptin neurons in the arcuate nucleus (ARC) of the hypothalamus are responsible for pulsatile GnRH release. Thus, the kisspeptin neuron in the ARC has been called the "GnRH pulse-generator." However, a few pieces of evidence do not quite fit into this concept. This article reviews some old works and discusses unresolved issues on the mechanism of GnRH pulse generation.
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Affiliation(s)
- Ei Terasawa
- AWisconsin National Primate Research Center, University of Wisconsin, Madison, WI, 53715, USA; Department of Pediatrics, University of Wisconsin, Madison, WI, 53706, USA.
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9
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Bhattacharya I, Sen Sharma S, Majumdar SS. Pubertal orchestration of hormones and testis in primates. Mol Reprod Dev 2019; 86:1505-1530. [DOI: 10.1002/mrd.23246] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Accepted: 07/15/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Indrashis Bhattacharya
- Department of Zoology & BiotechnologyHNB Garhwal University, Srinagar CampusSrinagar India
- Cellular Endocrinology LabNational Institute of ImmunologyNew Delhi India
| | - Souvik Sen Sharma
- Cellular Endocrinology LabNational Institute of ImmunologyNew Delhi India
| | - Subeer S. Majumdar
- Cellular Endocrinology LabNational Institute of ImmunologyNew Delhi India
- Gene and Protein Engineering LabNational Institute of Animal BiotechnologyHyderabad India
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Lehnert J, Khadra A. How Pulsatile Kisspeptin Stimulation and GnRH Autocrine Feedback Can Drive GnRH Secretion: A Modeling Investigation. Endocrinology 2019; 160:1289-1306. [PMID: 30874725 DOI: 10.1210/en.2018-00947] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Accepted: 03/09/2019] [Indexed: 02/03/2023]
Abstract
Pulsatile secretion of GnRH from hypothalamic GnRH neurons tightly regulates the release of mammalian reproductive hormones. Although key factors such as electrical activity and stimulation by kisspeptin have been extensively studied, the underlying mechanisms that regulate GnRH release are still not fully understood. Previously developed mathematical models studied hormonal release and electrical properties of GnRH neurons separately, but they never integrated both components. Herein, we present a more complete biophysical model to investigate how electrical activity and hormonal release interact. The model consists of two components: an electrical submodel comprised of a modified Izhikevich formalism incorporating several key ionic currents to reproduce GnRH neuronal bursting behavior, and a hormonal submodel that incorporates pulsatile kisspeptin stimulation and a GnRH autocrine feedback mechanism. Using the model, we examine the electrical activity of GnRH neurons and how kisspeptin affects GnRH pulsatility. The model reproduces the noise-driven bursting behavior of GnRH neurons as well as the experimentally observed electrophysiological effects induced by GnRH and kisspeptin. Specifically, the model reveals that external application of GnRH causes a transient hyperpolarization followed by an increase in firing frequency, whereas administration of kisspeptin leads to long-lasting depolarization of the neuron. The model also shows that GnRH release follows a pulsatile profile similar to that observed experimentally and that kisspeptin and GnRH exhibit ∼7-1 locking in their pulsatility. These results suggest that external kisspeptin stimulation with a period of ∼8 minutes drives the autocrine mechanism beyond a threshold to generate pronounced GnRH pulses every hour.
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Affiliation(s)
- Jonas Lehnert
- Department of Quantitative Life Sciences, McGill University, Montreal, Quebec, Canada
| | - Anmar Khadra
- Department of Quantitative Life Sciences, McGill University, Montreal, Quebec, Canada
- Department of Physiology, McGill University, Montreal, Quebec, Canada
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11
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Vail G, Roepke TA. Membrane-initiated estrogen signaling via Gq-coupled GPCR in the central nervous system. Steroids 2019; 142:77-83. [PMID: 29378226 PMCID: PMC6064680 DOI: 10.1016/j.steroids.2018.01.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 12/08/2017] [Accepted: 01/19/2018] [Indexed: 01/21/2023]
Abstract
The last few decades have revealed increasing complexity and depth to our knowledge of receptor-mediated estrogen signaling. Nuclear estrogen receptors (ERs) ERα and ERβ remain the fundamental dogma, but recent research targeting membrane-bound ERs urges for a more expanded view on ER signaling. ERα and ERβ are also involved in membrane-delineated signaling alongside membrane-specific G protein-coupled estrogen receptor 1 (GPER1), ER-X, and the Gq-coupled membrane ER (Gq-mER). Membrane ERs are responsible for eliciting rapid responses to estrogen signaling, and their importance has been increasingly indicated in central nervous system (CNS) regulation of such functions as reproduction, energy homeostasis, and stress. While the Gq-mER signaling pathway is well characterized, the receptor structure and gene remains uncharacterized, although it is not similar to the nuclear ERα/β. This review will describe the current knowledge of this putative membrane ER and its selective ligand, STX, from its initial characterization in hypothalamic melanocortin circuitry to recent research exploring its role in the CNS outside of the hypothalamus.
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Affiliation(s)
- Gwyndolin Vail
- Department of Animal Sciences, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States; Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States
| | - Troy A Roepke
- Department of Animal Sciences, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States; Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States.
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12
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Herbison AE. The Gonadotropin-Releasing Hormone Pulse Generator. Endocrinology 2018; 159:3723-3736. [PMID: 30272161 DOI: 10.1210/en.2018-00653] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 08/20/2018] [Indexed: 12/18/2022]
Abstract
The pulsatile release of GnRH and LH secretion is essential for fertility in all mammals. Pulses of LH occur approximately every hour in follicular-phase females and every 2 to 3 hours in luteal-phase females and males. Many studies over the last 50 years have sought to identify the nature and mechanism of the "GnRH pulse generator" responsible for pulsatile LH release. This review examines the characteristics of pulsatile hormone release and summarizes investigations that have led to our present understanding of the GnRH pulse generator. There is presently little compelling evidence for an intrinsic mechanism of pulse generation involving interactions between GnRH neuron cell bodies. Rather, data support the presence of an extrinsic pulse generator located within the arcuate nucleus, and attention has focused on the kisspeptin neurons and their projections to GnRH neuron dendrons concentrated around the median eminence. Sufficient evidence has been gathered in rodents to conclude that a subpopulation of arcuate kisspeptin neurons is, indeed, the GnRH pulse generator. Findings in other species are generally compatible with this view and suggest that arcuate/infundibular kisspeptin neurons represent the mammalian GnRH pulse generator. With hindsight, it is likely that past arcuate nucleus multiunit activity recordings have been from kisspeptin neurons. Despite advances in identifying the cells forming the pulse generator, almost nothing is known about their mechanisms of synchronicity and the afferent hormonal and transmitter modulation required to establish the normal patterns of LH pulsatility in mammals.
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Affiliation(s)
- Allan E Herbison
- Centre for Neuroendocrinology and Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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13
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Clarke IJ, Li Q, Henry BA, Millar RP. Continuous Kisspeptin Restores Luteinizing Hormone Pulsatility Following Cessation by a Neurokinin B Antagonist in Female Sheep. Endocrinology 2018; 159:639-646. [PMID: 29126131 DOI: 10.1210/en.2017-00737] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 10/27/2017] [Indexed: 11/19/2022]
Abstract
Pulsatile secretion of the gonadotropin-releasing hormone (GnRH) drives pulsatile secretion of the luteinizing hormone (LH), with evidence that this depends on kisspeptin (Kiss) input to GnRH neurons. Kiss administration causes acute GnRH/LH secretion, and electrophysiological data suggest that Kiss neurons may act in a phasic manner to drive GnRH secretion, but there is not definitive evidence for this. The product of the Kiss-1 gene is proteolytically cleaved to smaller products, and the 10 amino acid C-terminal product (Kiss-10) displays full bioactivity. We have shown previously that continuous delivery of Kiss-10 to anestrous ewes can cause a surge in GnRH secretion and ovulation and increases LH pulse frequency in humans. Here, we tested the hypothesis that continuous Kiss-10 delivery can support pulsatile GnRH/LH secretion in the sheep. Neurokinin B (NKB) provides positive drive to Kiss neurons, so we therefore infused an NKB antagonist (ANT-08) intracerebroventricularly to induce cessation of pulsatile GnRH/LH secretion, with or without concomitant continuous Kiss-10 infusion. ANT-08 suppressed GnRH/LH pulsatility, which was immediately restored with continuous Kiss-10 infusion. These data support the notion that Kiss-10 action is downstream of NKB signaling and that continuous Kiss-10 stimulation of GnRH neurons is sufficient to support a pulsatile pattern of GnRH/LH secretion. This offers further support to the theory that GnRH pulse generation is intrinsic to GnRH neurons and that pulsatile GnRH release can be affected with continuous stimulation by Kiss-10.
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Affiliation(s)
- Iain J Clarke
- Neuroscience Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Qun Li
- Neuroscience Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Belinda A Henry
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
- Metabolic Disease and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Robert P Millar
- Division of Medical Biochemistry, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- Department of Physiology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
- Department of Immunology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
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14
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Abbott DH, Vepraskas SH, Horton TH, Terasawa E, Levine JE. Accelerated Episodic Luteinizing Hormone Release Accompanies Blunted Progesterone Regulation in PCOS-like Female Rhesus Monkeys (Macaca Mulatta) Exposed to Testosterone during Early-to-Mid Gestation. Neuroendocrinology 2018; 107:133-146. [PMID: 29949806 PMCID: PMC7363207 DOI: 10.1159/000490570] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 06/04/2018] [Indexed: 12/25/2022]
Abstract
BACKGROUND/AIMS Ovarian theca cell hyperandrogenism in women with polycystic ovary syndrome (PCOS) is compounded by androgen receptor-mediated impairment of estradiol and progesterone negative feedback regulation of episodic luteinizing hormone (LH) release. The resultant LH hypersecretion, likely the product of accelerated episodic release of gonadotropin-releasing hormone (GnRH) from the median eminence of the hypothalamus, hyperstimulates ovarian theca cell steroidogenesis, enabling testosterone (T) and androstenedione excess. Prenatally androgenized (PA) female monkeys exposed to fetal male levels of T during early-to-mid gestation, when adult, demonstrate PCOS-like traits, including high T and LH levels. This study tests the hypothesis that progesterone resistance-associated acceleration in episodic LH release contributes to PA monkey LH excess. METHODS A total of 4 PA and 3 regularly cycling, healthy control adult female rhesus monkeys of comparable age and body mass index underwent (1) a 10 h, frequent intravenous sampling assessment for LH episodic release, immediately followed by (2) IV infusion of exogenous GnRH to quantify continuing pituitary LH responsiveness, and subsequently (3) an SC injection of a progesterone receptor antagonist, mifepristone, to examine LH responses to blockade of progesterone-mediated action. RESULTS Compared to controls, the relatively hyperandrogenic PA females exhibited ~100% increase (p = 0.037) in LH pulse frequency, positive correlation of LH pulse amplitude (p = 0.017) with androstenedione, ~100% greater increase (p = 0.034) in acute (0-10 min) LH responses to exogenous GnRH, and an absence (p = 0.008) of modest LH elevation following acute progesterone receptor blockade suggestive of diminished progesterone negative feedback. CONCLUSION Such dysregulation of LH release in PCOS-like monkeys implicates impaired feedback control of episodic release of hypothalamic GnRH reminiscent of PCOS neuroendocrinopathy.
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Affiliation(s)
- David H Abbott
- Department of Obstetrics and Gynecology, University of Wisconsin, Madison, Wisconsin, USA
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, Wisconsin, USA
| | - Sarah H Vepraskas
- Department of Obstetrics and Gynecology, University of Wisconsin, Madison, Wisconsin, USA
| | - Teresa H Horton
- Department of Neurobiology and Physiology, Institute for Neuroscience, Center for Reproductive Science, Northwestern University, Evanston, Illinois, USA
| | - Ei Terasawa
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, USA
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, Wisconsin, USA
| | - Jon E Levine
- Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, Wisconsin, USA
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15
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Constantin S. Progress and Challenges in the Search for the Mechanisms of Pulsatile Gonadotropin-Releasing Hormone Secretion. Front Endocrinol (Lausanne) 2017; 8:180. [PMID: 28790978 PMCID: PMC5523686 DOI: 10.3389/fendo.2017.00180] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/10/2017] [Indexed: 12/05/2022] Open
Abstract
Fertility relies on the proper functioning of the hypothalamic-pituitary-gonadal axis. The hormonal cascade begins with hypothalamic neurons secreting gonadotropin-releasing hormone (GnRH) into the hypophyseal portal system. In turn, the GnRH-activated gonadotrophs in the anterior pituitary release gonadotropins, which then act on the gonads to regulate gametogenesis and sex steroidogenesis. Finally, sex steroids close this axis by feeding back to the hypothalamus. Despite this seeming straightforwardness, the axis is orchestrated by a complex neuronal network in the central nervous system. For reproductive success, GnRH neurons, the final output of this network, must integrate and translate a wide range of cues, both environmental and physiological, to the gonadotrophs via pulsatile GnRH secretion. This secretory profile is critical for gonadotropic function, yet the mechanisms underlying these pulses remain unknown. Literature supports both intrinsically and extrinsically driven GnRH neuronal activity. However, the caveat of the techniques supporting either one of the two hypotheses is the gap between events recorded at a single-cell level and GnRH secretion measured at the population level. This review aims to compile data about GnRH neuronal activity focusing on the physiological output, GnRH secretion.
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Affiliation(s)
- Stephanie Constantin
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Stephanie Constantin,
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16
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Woller MJ, Meyer S, Ada-Nguema A, Waechter-Brulla D. Dissecting Autocrine Effects on Pulsatile Release of Gonadotropin-Releasing Hormone in Cultured Rat Hypothalamic Tissue. Exp Biol Med (Maywood) 2016; 229:56-64. [PMID: 14709777 DOI: 10.1177/153537020422900107] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The control of reproductive function is manifested centrally through the control of hypothalamic release of gonadotropin-releasing hormone (GnRH) in episodic events or pulses. For GnRH release to occur in pulses, GnRH neurons must coordinate release events periodically to elicit a bolus of GnRH. We used a perifusion culture system to examine the release of GnRH from both intact hypothalami and enzymatically dispersed hypothalamic cells after challenge with GnRH analogs to evaluate the role of anatomical neuronal connections on autocrine/paracrine signals by GnRH on GnRH neurons. The potent GnRH agonist des-Gly10-D-Ala6-GnRH N-ethylamide, potent GnRH antagonists D-Phe2-D-Ala6-GnRH and D-Phe2,6-Pro3-GnRH or vehicle were infused, whereas GnRH release from hypothalamic tissue and cells were measured. PULSAR analysis of GnRH release profiles was conducted to evaluate parameters of pulsatile GnRH release. Infusion of the GnRH agonist resulted in a decrease in mean GnRH (P < 0.001), pulse nadir (P < 0.01), and pulse frequency (P < 0.05) but no effect on pulse amplitude. Infusion of GnRH antagonists resulted in an increase in mean GnRH (P < 0.001), pulse nadir (P < 0.05), and pulse frequency (P < 0.05) and in GnRH pulse amplitude only in dispersed cells (P < 0.05). These results are consistent with the hypothesis that GnRH inhibits endogenous GnRH release by an ultrashort-loop feedback mechanism and that treatment of hypothalamic tissue or cells with GnRH agonist inhibits ultrashort-loop feedback, whereas treatment with antagonists disrupts normal feedback to GnRH neurons and elicits an increased GnRH signal.
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Affiliation(s)
- Michael J Woller
- Biological Sciences, University of Wisconsin-Whitewater, Whitewater, Wisconsin 53190, USA.
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17
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Kurian JR, Louis S, Keen KL, Wolfe A, Terasawa E, Levine JE. The Methylcytosine Dioxygenase Ten-Eleven Translocase-2 (tet2) Enables Elevated GnRH Gene Expression and Maintenance of Male Reproductive Function. Endocrinology 2016; 157:3588-603. [PMID: 27384303 PMCID: PMC5007894 DOI: 10.1210/en.2016-1087] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Reproduction depends on the establishment and maintenance of elevated GnRH neurosecretion. The elevation of primate GnRH release is accompanied by epigenetic changes. Specifically, cytosine residues within the GnRH gene promoter are actively demethylated, whereas GnRH mRNA levels and peptide release rise. Whether active DNA demethylation has an impact on GnRH neuron development and consequently reproductive function remains unknown. In this study, we investigated whether ten-eleven translocation (tet) enzymes, which initiate the process of active DNA demethylation, influence neuronal function and reproduction. We found that tet2 expression increases with age in the developing mouse preoptic area-hypothalamus and is substantially higher in a mature (GT1-7) than an immature (GN11) GnRH cell line. GnRH mRNA levels and mean GnRH peptide release elevated after overexpression of tet2 in GN11 cells, whereas CRISPR/cas9-mediated knockdown of tet2 in GT1-7 cells led to a significant decline in GnRH expression. Manipulations of tet2 expression altered tet2 genome binding and histone 3 lysine 4 trimethylation abundance at the GnRH promoter. Mice with selective disruption of tet2 in GnRH neurons (GnRH-specific tet2 knockout mice) exhibited no sign of altered pubertal timing in either sex, although plasma LH levels were significantly lower, and fecundity was altered specifically in adult male GnRH-specific tet2 knockout animals, indicating that tet2 may participate in the maintenance GnRH neuronal function. Exposure to bisphenol A, an environmental contaminant that alters GnRH neuron activity, caused a shift in tet2 subcellular localization and a decrease in histone 3 lysine 4 trimethylation abundance at the GnRH promoter. Finally, evaluation of tet2 protein interactions in GT1-7 cells suggests that the influence of tet2 on neuronal function are not limited to nuclear mechanisms but could depend on mitochondrial function, and RNA metabolism. Together, these studies implicate tet2 in the maintenance of GnRH neuronal function and neuroendocrine control of male reproduction.
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Affiliation(s)
- Joseph R Kurian
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Somaja Louis
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Kim L Keen
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Andrew Wolfe
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Ei Terasawa
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Jon E Levine
- Department of Obstetrics and Gynecology (J.R.K., S.L.), Southern Illinois University School of Medicine, Springfield, Illinois 62794; St. John's Hospital Carol Jo Vecchie Women and Children's Center (J.R.K.), Springfield, Illinois 62769; Wisconsin National Primate Research Center (K.L.K., E.T., J.E.L.), Madison, Wisconsin 53705; Department of Pediatrics and Physiology (A.W.), The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Departments of Pediatrics (E.T.) and Neuroscience (J.E.L.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
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18
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Abstract
The gonadotropin-releasing hormone (GnRH) neuronal network generates pulse and surge modes of gonadotropin secretion critical for puberty and fertility. The arcuate nucleus kisspeptin neurons that innervate the projections of GnRH neurons in and around their neurosecretory zone are key components of the pulse generator in all mammals. By contrast, kisspeptin neurons located in the preoptic area project to GnRH neuron cell bodies and proximal dendrites and are involved in surge generation in female rodents (and possibly other species). The hypothalamic-pituitary-gonadal axis develops embryonically but, apart from short periods of activation immediately after birth, remains suppressed through a combination of gonadal and non-gonadal mechanisms. At puberty onset, the pulse generator reactivates, probably owing to progressive stimulatory influences on GnRH neurons from glial and neurotransmitter signalling, and the re-emergence of stimulatory arcuate kisspeptin input. In females, the development of pulsatile gonadotropin secretion enables final maturation of the surge generator that ultimately triggers the first ovulation. Representation of the GnRH neuronal network as a series of interlocking functional modules could help conceptualization of its functioning in different species. Insights into pulse and surge generation are expected to aid development of therapeutic strategies ameliorating pubertal disorders and infertility in the clinic.
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Affiliation(s)
- Allan E Herbison
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Medical Sciences, Dunedin 9054, New Zealand
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19
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Abreu AP, Kaiser UB. Pubertal development and regulation. Lancet Diabetes Endocrinol 2016; 4:254-264. [PMID: 26852256 PMCID: PMC5192018 DOI: 10.1016/s2213-8587(15)00418-0] [Citation(s) in RCA: 273] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/22/2015] [Accepted: 10/22/2015] [Indexed: 12/12/2022]
Abstract
Puberty marks the end of childhood and is a period when individuals undergo physiological and psychological changes to achieve sexual maturation and fertility. The hypothalamic-pituitary-gonadal axis controls puberty and reproduction and is tightly regulated by a complex network of excitatory and inhibitory factors. This axis is active in the embryonic and early postnatal stages of life and is subsequently restrained during childhood, and its reactivation culminates in puberty initiation. The mechanisms underlying this reactivation are not completely known. The age of puberty onset varies between individuals and the timing of puberty initiation is associated with several health outcomes in adult life. In this Series paper, we discuss pubertal markers, epidemiological trends of puberty initiation over time, and the mechanisms whereby genetic, metabolic, and other factors control secretion of gonadotropin-releasing hormone to determine initiation of puberty.
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Affiliation(s)
- Ana Paula Abreu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Ursula B Kaiser
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
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20
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Abstract
The endocrine hypothalamus constitutes those cells which project to the median eminence and secrete neurohormones into the hypophysial portal blood to act on cells of the anterior pituitary gland. The entire endocrine system is controlled by these peptides. In turn, the hypothalamic neuroendocrine cells are regulated by feedback signals from the endocrine glands and other circulating factors. The neuroendocrine cells are found in specific regions of the hypothalamus and are regulated by afferents from higher brain centers. Integrated function is clearly complex and the networks between and amongst the neuroendocrine cells allows fine control to achieve homeostasis. The entry of hormones and other factors into the brain, either via the cerebrospinal fluid or through fenestrated capillaries (in the basal hypothalamus) is important because it influences the extent to which feedback regulation may be imposed. Recent evidence of the passage of factors from the pars tuberalis and the median eminence casts a new layer in our understanding of neuroendocrine regulation. The function of neuroendocrine cells and the means by which pulsatile secretion is achieved is best understood for the close relationship between gonadotropin releasing hormone and luteinizing hormone, which is reviewed in detail. The secretion of other neurohormones is less rigid, so the relationship between hypothalamic secretion and the relevant pituitary hormones is more complex.
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Affiliation(s)
- I J Clarke
- Monash University, Department of Physiology, Clayton, Australia
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21
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Ezzat A, Pereira A, Clarke IJ. Kisspeptin is a component of the pulse generator for GnRH secretion in female sheep but not the pulse generator. Endocrinology 2015; 156:1828-37. [PMID: 25710282 DOI: 10.1210/en.2014-1756] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We tested the hypothesis that kisspeptin cells constitute the "pulse generator" for GnRH secretion. In ewes, we determined whether iv administered kisspeptin elicits a secretory pulse of LH in anaesthetized, sex-steroid suppressed ovariectomized ewes. A response was seen in both anaesthetized and conscious animals, which was not associated with induction of c-Fos labeling in GnRH cells, supporting the notion that kisspeptin acts on the neurosecretory GnRH terminals. Response was lower in the anaesthetized animals, suggesting that some nonkisspeptin elements may be involved in GnRH responses. Microinjection of kisspeptin (100 nmol) into the median eminence of conscious ewes elicited a pulse of LH, indicating that kisspeptin acts at this level to cause GnRH secretion. To determine which cells are activated at the time of GnRH secretion, we blood sampled 18 ewes during the luteal phase of the estrous cycle and harvested brains after 3 hours. Three of these ewes displayed a pulse of LH within 30 minutes of euthanasia. An increase in c-Fos labeling was seen in kisspeptin and glutamate cells of the arcuate nucleus but not in GnRH neurons, preoptic kisspeptin neurons, or preoptic glutamate neurons. Immunohistochemistry in 4 hypothalami showed that 72% of arcuate kisspeptin cells receive glutamatergic input. These data support the concept that the kisspeptin cells of the arcuate nucleus drive pulsatile secretion of GnRH at the level of the median eminence, but this may involve "upstream" input from glutamate cells. We conclude that the pulse generator for GnRH secretion involves more than 1 element.
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Affiliation(s)
- Ahmed Ezzat
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
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22
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Ren X, Wang S, Rong P, Zhu B. Activation of hypothalamic gono-like neurons in female rats during estrus. Neural Regen Res 2014; 7:2413-23. [PMID: 25337091 PMCID: PMC4200715 DOI: 10.3969/j.issn.1673-5374.2012.31.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 10/08/2012] [Indexed: 11/18/2022] Open
Abstract
In mammals, gonadal function is controlled by the activity of hypothalamic gonadotropin-releasing hormone neurons, which control the secretion of adenohypophyseal and gonadal hormones. However, there are a number of unanswered questions in relation to gonadal function. It is currently unknown how erotogenic stimulation of the genitals influences the subpopulation of hypothalamic medial preoptic area neurons, antidromically identified as projecting to the median eminence at different periods of the estrous cycle. Additionally, the distinctiveness of hypothalamic medial preoptic area neurons, with respect to methods of feedback control by exogenous hormones, is also unknown. In this study, spontaneous discharges from individual neurons encountered within the medial preoptic area, gono-like neurons, were recorded extracellularly using glass microelectrodes. To confirm the cellular and histochemical properties of the recording units, antidromic stimulation was performed using a side-by-side bipolar stimulating electrode placed into the median eminence, alongside microiontophoretic injections of the conventional tracer, horseradish peroxidase. In addition, further immunohistochemical analyses were performed. Results showed that elevated gono-neuron activity was accompanied by increased background activity and greater responses to erotogenic stimuli during estrus. Application of clitoral traction stimulation resulted in increased activation of the gono-like neurons. This neuronal activity was noticeably inhibited by β-estradiol administration. Immunohistochemical analyses revealed the presence of gonadotropin-releasing hormone-reactive protein in hypothalamic cells in which electrophysiological recordings were taken. Thus, medial preoptic area neurons represent the subset of hypothalamic gonadotropin-releasing hormone neurons described from brain slices in vitro, and might serve as a useful physiological model to form the basis of future in vivo studies.
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Affiliation(s)
- Xiaoxuan Ren
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China ; School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing 100029, China
| | - Shaojun Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China
| | - Peijing Rong
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China
| | - Bing Zhu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China
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23
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Nunemaker CS, Satin LS. Episodic hormone secretion: a comparison of the basis of pulsatile secretion of insulin and GnRH. Endocrine 2014; 47:49-63. [PMID: 24610206 PMCID: PMC4382805 DOI: 10.1007/s12020-014-0212-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 02/13/2014] [Indexed: 01/01/2023]
Abstract
Rhythms govern many endocrine functions. Examples of such rhythmic systems include the insulin-secreting pancreatic beta-cell, which regulates blood glucose, and the gonadotropin-releasing hormone (GnRH) neuron, which governs reproductive function. Although serving very different functions within the body, these cell types share many important features. Both GnRH neurons and beta-cells, for instance, are hypothesized to generate at least two rhythms endogenously: (1) a burst firing electrical rhythm and (2) a slower rhythm involving metabolic or other intracellular processes. This review discusses the importance of hormone rhythms to both physiology and disease and compares and contrasts the rhythms generated by each system.
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Affiliation(s)
- Craig S. Nunemaker
- Division of Endocrinology and Metabolism, Department of, Medicine, University of Virginia, P.O. Box 801413, Charlottesville, VA 22901, USA,
| | - Leslie S. Satin
- Pharmacology Department, University of Michigan Medical School, 5128 Brehm Tower, Ann Arbor, MI 48105, USA
- Brehm Diabetes Research Center, University of Michigan, Medical School, 5128 Brehm Tower, Ann Arbor, MI 48105, USA
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24
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Yamamura T, Wakabayashi Y, Sakamoto K, Matsui H, Kusaka M, Tanaka T, Ohkura S, Okamura H. The effects of chronic subcutaneous administration of an investigational kisspeptin analog, TAK-683, on gonadotropin-releasing hormone pulse generator activity in goats. Neuroendocrinology 2014; 100:250-64. [PMID: 25428554 DOI: 10.1159/000369819] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 11/07/2014] [Indexed: 11/19/2022]
Abstract
The continuous activation of the kisspeptin receptor by its agonists causes the abrogation of kisspeptin signaling, leading to decreased pulsatile luteinizing hormone (LH) secretion. Employing this phenomenon as a tool for probing kisspeptin action, this study aimed to clarify the role of kisspeptin in gonadotropin-releasing hormone (GnRH) pulse generation in goats. We examined the effects of chronic administration of TAK-683, an investigational kisspeptin analog, on LH secretion, GnRH immunostaining, pituitary responses to exogenous GnRH, and GnRH pulse generator activity, reflected by a characteristic increase in multiple-unit activity (MUA volley). An osmotic pump containing TAK-683 was subcutaneously implanted on day 0. TAK-683 treatment dose-dependently suppressed pulsatile LH secretion on day 1. Higher doses of chronic TAK-683 profoundly suppressed pulsatile LH secretion but had little effect on GnRH immunostaining patterns and pituitary responses to GnRH on day 5. In ovariectomized goats, MUA volleys occurred at approximately every 30 min on day -1. On day 5 of chronic TAK-683 administration, pulsatile LH secretion was markedly suppressed, whereas MUA volleys were similar to those observed on day -1. Male pheromones and senktide (neurokinin B receptor agonist) induced an MUA volley but had no effect on LH secretion during chronic TAK-683 administration. The results indicate that the chronic administration of a kisspeptin analog profoundly suppresses pulsatile LH secretion without affecting GnRH content, pituitary function or GnRH pulse generator activity, and they suggest an indispensable role for kisspeptin signaling in the cascade driving GnRH/LH pulses by the GnRH pulse generator.
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Affiliation(s)
- Takashi Yamamura
- Animal Physiology Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Japan
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25
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Nestor CC, Coolen LM, Nesselrod GL, Valent M, Connors JM, Hileman SM, Cheng G, Lehman MN, Goodman RL. Evidence that orphanin FQ mediates progesterone negative feedback in the ewe. Endocrinology 2013; 154:4249-58. [PMID: 23928375 PMCID: PMC3800756 DOI: 10.1210/en.2013-1274] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 07/30/2013] [Indexed: 11/19/2022]
Abstract
Orphanin FQ (OFQ), a member of the opioid family, is found in many areas of the hypothalamus and, when given centrally OFQ inhibits episodic LH secretion in rodents and sheep. Because GnRH neurons are devoid of the appropriate receptors to mediate steroid negative feedback directly, neurons that release OFQ may be involved. Using immunocytochemistry, we first determined that most OFQ neurons in the arcuate nucleus (ARC) and other hypothalamic regions of luteal phase ewes contained both estrogen receptor α and progesterone (P) receptor. Given a similar high degree of steroid receptor colocalization in other ARC subpopulations, we examined whether OFQ neurons of the ARC contained those other neuropeptides and neurotransmitters. OFQ did not colocalize with kisspeptin, tyrosine hydroxylase, or agouti-related peptide, but all ARC OFQ neurons coexpressed proopiomelanocortin. To test for a role for endogenous OFQ, we examined the effects of an OFQ receptor antagonist, [Nphe1,Arg14,Lys15]Nociceptin-NH2 (UFP-101) (30 nmol intracerebroventricular/h), on LH secretion in steroid-treated ewes in the breeding season and ovary-intact ewes in anestrus. Ovariectomized ewes with luteal phase concentrations of P and estradiol showed a significant increase in LH pulse frequency during infusion of UFP-101 (4.5 ± 0.5 pulses/6 h) compared with saline infusion (2.6 ± 0.4 pulses/6 h), whereas ewes implanted with only estradiol did not. Ovary-intact anestrous ewes displayed no significant differences in LH pulse amplitude or frequency during infusion of UFP-101. Therefore, we conclude that OFQ mediates, at least in part, the negative feedback action of P on GnRH/LH pulse frequency in sheep.
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Affiliation(s)
- Casey C Nestor
- Department of Physiology and Pharmacology, PO Box 9229, West Virginia University, Morgantown, West Virginia 26506.
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26
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Choe HK, Kim HD, Park SH, Lee HW, Park JY, Seong JY, Lightman SL, Son GH, Kim K. Synchronous activation of gonadotropin-releasing hormone gene transcription and secretion by pulsatile kisspeptin stimulation. Proc Natl Acad Sci U S A 2013; 110:5677-82. [PMID: 23509283 PMCID: PMC3619287 DOI: 10.1073/pnas.1213594110] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH) is essential for pituitary gonadotrope function. Although the importance of pulsatile GnRH secretion has been recognized for several decades, the mechanisms underlying GnRH pulse generation in hypothalamic neural networks remain elusive. Here, we demonstrate the ultradian rhythm of GnRH gene transcription in single GnRH neurons using cultured hypothalamic slices prepared from transgenic mice expressing a GnRH promoter-driven destabilized luciferase reporter. Although GnRH promoter activity in each GnRH neuron exhibited an ultradian pattern of oscillations with a period of ∼10 h, GnRH neuronal cultures exhibited partially synchronized bursts of GnRH transcriptional activity at ∼2-h intervals. Surprisingly, pulsatile administration of kisspeptin, a potent GnRH secretagogue, evoked dramatic synchronous activation of GnRH gene transcription with robust stimulation of pulsatile GnRH secretion. We also addressed the issue of hierarchical interaction between the circadian and ultradian rhythms by using Bmal1-deficient mice with defective circadian clocks. The circadian molecular oscillator barely affected basal ultradian oscillation of GnRH transcription but was heavily involved in kisspeptin-evoked responses of GnRH neurons. In conclusion, we have clearly shown synchronous bursts of GnRH gene transcription in the hypothalamic GnRH neuronal population in association with episodic neurohormone secretion, thereby providing insight into GnRH pulse generation.
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Affiliation(s)
- Han Kyoung Choe
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
- Brain Research Center for the 21st Frontier Program in Neuroscience, Seoul 151-742, Korea
| | - Hee-Dae Kim
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
- Brain Research Center for the 21st Frontier Program in Neuroscience, Seoul 151-742, Korea
| | - Sung Ho Park
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
- Brain Research Center for the 21st Frontier Program in Neuroscience, Seoul 151-742, Korea
| | - Han-Woong Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Jae-Yong Park
- Department of Physiology, Institute of Health Science and Medical Research Center for Neural Dysfunction, Biomedical Center (BK21), Gyeongsang National University School of Medicine, Jinju 660-751, Korea
| | | | - Stafford L. Lightman
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol BS1 3NY, United Kingdom
| | - Gi Hoon Son
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
- Brain Research Center for the 21st Frontier Program in Neuroscience, Seoul 151-742, Korea
- Department of Legal Medicine, College of Medicine, Korea University, Seoul 136-705, Korea; and
| | - Kyungjin Kim
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
- Brain Research Center for the 21st Frontier Program in Neuroscience, Seoul 151-742, Korea
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Park MK, Kanaho YI, Enomoto M. Regulation of the cell proliferation and migration as extra-pituitary functions of GnRH. Gen Comp Endocrinol 2013; 181:259-64. [PMID: 23032076 DOI: 10.1016/j.ygcen.2012.09.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 09/21/2012] [Indexed: 11/16/2022]
Abstract
GnRH was originally identified as a hypothalamic factor which promotes gonadotropin release from the pituitary and was named gonadotropin-releasing hormone (GnRH). However, broad tissue distributions of GnRH and the GnRH receptor in various extrapituitary tissues and organs have been revealed and it has been suggested that GnRH has extrapituitary effects such as neuromodulation, immunomodulation, and regulation of follicular atresia and ovulation. Although a number of studies have been performed on these effects, little is known about the molecular mechanisms and physiological settings in which GnRH exerts its activities in extrapituitary organs or tissues. Our recent studies had demonstrated that GnRH is able to regulate both cell proliferation and cell migration at much lower concentration than that in the peripheral circulation by using human carcinoma cell lines. Moreover, stimulating activity of GnRH on the developing chick embryonic GnRH neurons was also demonstrated and strongly suggests possible involvement of GnRH in some of extrapituitary functions. This mini-review intends to provide solid evidence of GnRH activity in the regulation of cell proliferation and migration and its physiological relevance in extra-pituitary functions. Recent other research, including that in various invertebrates, provides new insight into the evolutionary scenarios of GnRH signaling systems, and GnRH functions. Both proliferating and migrating activities are important fundamental cellular activities and could provide an important clue into understanding what the driving force behind the evolution of the GnRH signaling system was.
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Affiliation(s)
- Min Kyun Park
- Department of Biological Sciences, School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan.
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Young J, George JT, Tello JA, Francou B, Bouligand J, Guiochon-Mantel A, Brailly-Tabard S, Anderson RA, Millar RP. Kisspeptin restores pulsatile LH secretion in patients with neurokinin B signaling deficiencies: physiological, pathophysiological and therapeutic implications. Neuroendocrinology 2013; 97:193-202. [PMID: 22377698 PMCID: PMC3902960 DOI: 10.1159/000336376] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 01/05/2012] [Indexed: 11/19/2022]
Abstract
Pulsatile gonadotropin-releasing hormone (GnRH) is crucial to normal reproductive function and abnormalities in pulse frequency give rise to reproductive dysfunction. Kisspeptin and neurokinin B (NKB), neuropeptides secreted by the same neuronal population in the ventral hypothalamus, have emerged recently as critical central regulators of GnRH and thus gonadotropin secretion. Patients with mutations resulting in loss of signaling by either of these neuroendocrine peptides fail to advance through puberty but the mechanisms mediating this remain unresolved. We report here that continuous kisspeptin infusion restores gonadotropin pulsatility in patients with loss-of-function mutations in NKB (TAC3) or its receptor (TAC3R), indicating that kisspeptin on its own is sufficient to stimulate pulsatile GnRH secretion. Moreover, our findings suggest that NKB action is proximal to kisspeptin in the reproductive neuroendocrine cascade regulating GnRH secretion, and may act as an autocrine modulator of kisspeptin secretion. The ability of continuous kisspeptin infusion to induce pulsatile gonadotropin secretion further indicates that GnRH neurons are able to set up pulsatile secretion in the absence of pulsatile exogenous kisspeptin.
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Affiliation(s)
- Jacques Young
- Faculté de Médecine Paris-Sud UMR-S693, Université Paris-Sud, France
- INSERM U693, IFR93, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
- Service d'Endocrinologie et des Maladies de la Reproduction, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Jyothis T. George
- MRC Human Reproductive Sciences Unit, University of Edinburgh, Edinburgh, UK
| | - Javier A. Tello
- MRC Human Reproductive Sciences Unit, University of Edinburgh, Edinburgh, UK
- Centre for Integrative Physiology, University of Edinburgh, School of Biomedical Sciences, Edinburgh, UK
| | - Bruno Francou
- Faculté de Médecine Paris-Sud UMR-S693, Université Paris-Sud, France
- INSERM U693, IFR93, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
- Service de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Jerome Bouligand
- Faculté de Médecine Paris-Sud UMR-S693, Université Paris-Sud, France
- INSERM U693, IFR93, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
- Service de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Anne Guiochon-Mantel
- Faculté de Médecine Paris-Sud UMR-S693, Université Paris-Sud, France
- INSERM U693, IFR93, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
- Service de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Sylvie Brailly-Tabard
- Faculté de Médecine Paris-Sud UMR-S693, Université Paris-Sud, France
- INSERM U693, IFR93, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
- Service de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Richard A. Anderson
- MRC Human Reproductive Sciences Unit, University of Edinburgh, Edinburgh, UK
| | - Robert P. Millar
- MRC Human Reproductive Sciences Unit, University of Edinburgh, Edinburgh, UK
- Centre for Integrative Physiology, University of Edinburgh, School of Biomedical Sciences, Edinburgh, UK
- Mammal Research Institute, University of Pretoria, Pretoria, and UCT/MRC Receptor Biology Unit, University of Cape Town, Cape Town, South Africa
- *Robert P. Millar, Mammal Research Institute, University of Pretoria, Pretoria 0028 (South Africa), Tel. +27 420 3776, E-Mail
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Kurian JR, Terasawa E. Epigenetic control of gonadotropin releasing hormone neurons. Front Endocrinol (Lausanne) 2013; 4:61. [PMID: 23750154 PMCID: PMC3664328 DOI: 10.3389/fendo.2013.00061] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 05/13/2013] [Indexed: 12/27/2022] Open
Abstract
Epigenetic modifications to the genome, including DNA methylation and histone modifications, occur in response to external stimuli. Reproductive function is highly sensitive to environmental conditions including season, diet, hormonal changes, and exposure to chemical contaminants. GnRH neurons, which play a key role in reproduction, are particularly sensitive to various environmental stimuli. We recently reported that the rhesus monkey GnRH gene exhibits distinct epigenetic changes during embryonic development. More recently, we further found that a similar epigenetic phenomenon occurs across puberty. In this article we highlight recent findings, including those of afferent inputs, to describe the epigenetic control of GnRH circuit development as a link between the environment and reproductive function.
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Affiliation(s)
- Joseph R. Kurian
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI, USA
- *Correspondence: Joseph R. Kurian, Wisconsin National Primate Research Center, University of Wisconsin-Madison, 1220 Capitol Ct, Madison, WI 53705, USA. e-mail:
| | - Ei Terasawa
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
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30
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Bashour NM, Wray S. Progesterone directly and rapidly inhibits GnRH neuronal activity via progesterone receptor membrane component 1. Endocrinology 2012; 153:4457-69. [PMID: 22822163 PMCID: PMC3423625 DOI: 10.1210/en.2012-1122] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 07/03/2012] [Indexed: 01/03/2023]
Abstract
GnRH neurons are essential for reproduction, being an integral component of the hypothalamic-pituitary-gonadal axis. Progesterone (P4), a steroid hormone, modulates reproductive behavior and is associated with rapid changes in GnRH secretion. However, a direct action of P4 on GnRH neurons has not been previously described. Receptors in the progestin/adipoQ receptor family (PAQR), as well as progesterone receptor membrane component 1 (PgRMC1) and its partner serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1) mRNA binding protein 1 (SERBP1), have been shown to mediate rapid progestin actions in various tissues, including the brain. This study shows that PgRMC1 and SERBP1, but not PAQR, are expressed in prenatal GnRH neurons. Expression of PgRMC1 and SERBP1 was verified in adult mouse GnRH neurons. To investigate the effect of P4 on GnRH neuronal activity, calcium imaging was used on primary GnRH neurons maintained in explants. Application of P4 significantly decreased the activity of GnRH neurons, independent of secretion of gamma-aminobutyric acidergic and glutamatergic input, suggesting a direct action of P4 on GnRH neurons. Inhibition was not blocked by RU486, an antagonist of the classic nuclear P4 receptor. Inhibition was also maintained after uncoupling of the inhibitory regulative G protein (G(i/o)), the signal transduction pathway used by PAQR. However, AG-205, a PgRMC1 ligand and inhibitor, blocked the rapid P4-mediated inhibition, and inhibition of protein kinase G, thought to be activated downstream of PgRMC1, also blocked the inhibitory activity of P4. These data show for the first time that P4 can act directly on GnRH neurons through PgRMC1 to inhibit neuronal activity.
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Affiliation(s)
- Nicholas Michael Bashour
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke/National Institutes of Health, Bethesda, Maryland 20892, USA
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31
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Kenealy BP, Terasawa E. Rapid direct action of estradiol in GnRH neurons: findings and implications. Front Endocrinol (Lausanne) 2012; 2:106. [PMID: 22654841 PMCID: PMC3356072 DOI: 10.3389/fendo.2011.00106] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 12/06/2011] [Indexed: 12/27/2022] Open
Abstract
Estradiol plays a pivotal role in the control of gonadotropin-releasing hormone (GnRH) neuronal function and female reproduction. While positive and negative feedback actions of estradiol that enhance and suppress release of GnRH and LH are primarily mediated through estrogen receptor alpha located in interneurons, a series of recent studies in our laboratory indicate that rapid excitatory actions of estradiol also directly modify GnRH neuronal activity. We observed this phenomenon in cultured primate GnRH neurons, but similar rapid direct actions of estradiol are also described in cultured GnRH neurons and green fluorescent protein-labeled GnRH neurons of mice. Importantly, rapid direct action of estradiol in GnRH neurons is mediated through membrane or membrane associated receptors, such as GPR30, STX-sensitive receptors, and ERβ. In this review, possible implications of this rapid estradiol action in GnRH neurons are discussed.
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Affiliation(s)
- Brian P. Kenealy
- Wisconsin National Primate Research Center, University of WisconsinMadison, WI, USA
| | - E. Terasawa
- Wisconsin National Primate Research Center, University of WisconsinMadison, WI, USA
- Department of Pediatrics, University of WisconsinMadison, WI, USA
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32
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Maghsoodi M, Hemati E, Qadermazi B, Yari Z. Hollow microspheres for gastroretentive floating- pulsatile drug delivery: preparation and in vitro evaluation. Adv Pharm Bull 2011; 1:55-61. [PMID: 24312757 DOI: 10.5681/apb.2011.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 11/05/2011] [Indexed: 11/17/2022] Open
Abstract
PURPOSE A multiparticular floating-pulsatile drug delivery system was developed for time and site specific drug release of piroxicam. A blend of floating and pulsatile principles of drug delivery system would have the advantage that a drug can be released in the upper GI tract after a definite time period. METHODS Hollow microspheres were prepared by the emulsion solvent diffusion method using Eudragit S as an enteric acrylic polymer with piroxicam at various polymer/drug ratios in a mixture of dichloromethane and ethanol. Developed formulations were evaluated for yield, encapsulation efficiency, particle size, shape, apparent density, buoyancy studies and dissolution studies. RESULTS The obtained microballoons were spherical with no major surface irregularity and mean particle size ranging from 250 to 380 for different batches. Formulations show a slight amount of relaese ranging from 0.7 to 11% in acidic medium (SGF) with complete release of drug in simulated intestinal fluid (SIF) in less than 3 h. Encapsulation efficiency of different formulations varied from 90 to 98%. The optimum loading amount of drug in the particles was found to impart suitable floatable properties to the microballoons. With increasing polymer/drug ratio, buancy of the microballoons increases accompanied by simultaneous reduction of apparent particle density. CONCLUSION A pulsatile release of piroxicam was demonstrated by a simple drug delivery system which could be useful in chronopharmacotherapy of rheumatoid arthritis.
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Affiliation(s)
- Maryam Maghsoodi
- Drug applied Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
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33
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Constantin S, Jasoni C, Romanò N, Lee K, Herbison AE. Understanding calcium homeostasis in postnatal gonadotropin-releasing hormone neurons using cell-specific Pericam transgenics. Cell Calcium 2011; 51:267-76. [PMID: 22177387 DOI: 10.1016/j.ceca.2011.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 11/07/2011] [Accepted: 11/17/2011] [Indexed: 12/11/2022]
Abstract
The gonadotropin-releasing hormone (GnRH) neurons are the key output cells of a complex neuronal network controlling fertility in mammals. To examine calcium homeostasis in postnatal GnRH neurons, we generated a transgenic mouse line in which the genetically encodable calcium indicator ratiometric Pericam (rPericam) was targeted to the GnRH neurons. This mouse model enabled real-time imaging of calcium concentrations in GnRH neurons in the acute brain slice preparation. Investigations in GnRH-rPericam mice revealed that GnRH neurons exhibited spontaneous, long-duration (~8s) calcium transients. Dual electrical-calcium recordings revealed that the calcium transients were correlated perfectly with burst firing in GnRH neurons and that calcium transients in GnRH neurons regulated two calcium-activated potassium channels that, in turn, determined burst firing dynamics in these cells. Curiously, the occurrence of calcium transients in GnRH neurons across puberty or through the estrous cycle did not correlate well with the assumption that GnRH neuron burst firing was contributory to changing patterns of pulsatile GnRH release at these times. The GnRH-rPericam mouse was also valuable in determining differential mechanisms of GABA and glutamate control of calcium levels in GnRH neurons as well as effects of G-protein-coupled receptors for GnRH and kisspeptin. The simultaneous measurement of calcium levels in multiple GnRH neurons was hampered by variable rPericam fluorescence in different GnRH neurons. Nevertheless, in the multiple recordings that were achieved no evidence was found for synchronous calcium transients. Together, these observations show the great utility of transgenic targeting strategies for investigating the roles of calcium with specified neuronal cell types.
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Affiliation(s)
- Stéphanie Constantin
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin 9054, New Zealand
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34
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Fuenzalida LC, Keen KL, Terasawa E. Colocalization of FM1-43, Bassoon, and GnRH-1: GnRH-1 release from cell bodies and their neuroprocesses. Endocrinology 2011; 152:4310-21. [PMID: 21896672 PMCID: PMC3199012 DOI: 10.1210/en.2011-1416] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pulsatile release of GnRH-1 is critical for reproductive function. However, the cellular mechanism of GnRH-1 neurosecretion is still elusive. In this study, we examined the neurosecretory process of GnRH-1 neurons using time-lapse image acquisition followed by immunocytochemistry with confocal microscopy. To monitor exocytotic processes, cultured GnRH-1 neurons derived from monkey embryos were labeled with the lipophilic dye, FM1-43, or its fixable form FM1-43Fx, in the presence or absence of depolarization signals, and changes in vesicles labeled with FM1-43 were analyzed. The results show FM1-43 was taken up into the cell and labeled puncta in the soma and neuroprocesses in the absence of depolarization signals, indicating that GnRH-1 neurons were spontaneously active. Depolarization of GnRH-1 neurons with high K+ or veratridine challenge increased the intensity and size of puncta in both soma and neuroprocesses, and the veratridine-induced changes in puncta were blocked by tetrodotoxin, indicating that changes in the puncta intensity and size reflect neurosecretory activity. Subsequent double immunocytochemistry for GnRH-1 and the synaptic vesicle marker, vesicle-associated membrane protein, demonstrated that the FM1-43Fx-labeled puncta were synaptic vesicles with the GnRH-1 peptide. Additional double immunocytochemistry for GnRH-1 and the marker of the neurosecretory active zone, Bassoon, indicated that the FM1-43Fx-labeled puncta were located at the sites of neurosecretory active zones in GnRH-1 neurons. These results suggest that GnRH-1 neurons have the capacity to release the peptide from the soma and dendrites. Collectively, we hypothesize that soma-dendritic release of the peptide may be a mechanism of synchronized activity among GnRH-1 neurons.
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Affiliation(s)
- Lidia C Fuenzalida
- Department of Pediatrics and Wisconsin National Primate Research Center, 1223 Capitol Court, Madison, Wisconsin 53715-1299, USA
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35
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Moenter SM. Scene of the crime: where is GnRH released, and what might this tell us? Endocrinology 2011; 152:4014-5. [PMID: 22021199 PMCID: PMC3858666 DOI: 10.1210/en.2011-1721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Suzanne M Moenter
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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36
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Kenealy BP, Keen KL, Rønnekleiv OK, Terasawa E. STX, a novel nonsteroidal estrogenic compound, induces rapid action in primate GnRH neuronal calcium dynamics and peptide release. Endocrinology 2011; 152:3182-91. [PMID: 21628385 PMCID: PMC3138232 DOI: 10.1210/en.2011-0097] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Previously, we reported that 1 nM 17ß-estradiol (E(2)) induces a rapid action, which is, in part, mediated through the G protein-coupled receptor GPR30 in primate GnRH neurons. Because it has been reported that the diphenylacrylamide compound, STX, causes estrogenic action in the mouse and guinea pig hypothalamus, the present study examined effects of STX in primate GnRH neurons and whether there is an action independent of GPR30. Results are summarized as follows. STX (10 nM) exposure increased 1) the oscillation frequency of intracellular calcium concentration ([Ca(2+)](i)), 2) the percentage of cells stimulated, and 3) the synchronization frequency of [Ca(2+)](i) oscillations. STX (10-100 nM) also stimulated GnRH release. The effects of STX on both [Ca(2+)](i) oscillations and GnRH release were similar to those caused by E(2) (1 nM), although with less magnitude. STX (10 nM)-induced changes in [Ca(2+)](i) oscillations were not altered by GPR30 small interfering RNA transfection, indicating that STX-sensitive receptors differ from GPR30. Finally, a higher dose of E(2) (10 nM) induced a larger change in [Ca(2+)](i) oscillations than that with a smaller dose of E(2) (1 nM), and the effects of 10 nM E(2) were reduced but not completely blocked by GPR30 small interfering RNA transfection, indicating that the effects of 10 nM E(2) in primate GnRH neurons are mediated by multiple membrane receptors, including GPR30 and STX-sensitive receptors. Collectively, the rapid action of E(2) mediated through GPR30 differs from that mediated through STX-sensitive receptors. The molecular structure of the STX-sensitive receptor remains to be identified.
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Affiliation(s)
- B P Kenealy
- Wisconsin National Primate Research Center, University of Wisconsin, 1223 Capitol Court, Madison, Wisconsin 53715-1299, USA
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37
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Kenealy BP, Keen KL, Terasawa E. Rapid action of estradiol in primate GnRH neurons: the role of estrogen receptor alpha and estrogen receptor beta. Steroids 2011; 76:861-6. [PMID: 21354432 PMCID: PMC3183999 DOI: 10.1016/j.steroids.2011.02.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 02/07/2011] [Accepted: 02/16/2011] [Indexed: 01/08/2023]
Abstract
Estrogens play a pivotal role in the control of female reproductive function. Recent studies using primate GnRH neurons derived from embryonic nasal placode indicate that 17β-estradiol (E(2)) causes a rapid stimulatory action. E(2) (1nM) stimulates firing activity and intracellular calcium ([Ca(2+)](i)) oscillations of primate GnRH neurons within a few min. E(2) also stimulates GnRH release within 10min. However, the classical estrogen receptors, ERα and ERβ, do not appear to play a role in E(2)-induced [Ca(2+)](i) oscillations or GnRH release, as the estrogen receptor antagonist, ICI 182,780, failed to block these responses. Rather, this rapid E(2) action is, at least in part, mediated by a G-protein coupled receptor GPR30. In the present study we further investigate the role of ERα and ERβ in the rapid action of E(2) by knocking down cellular ERα and ERβ by transfection of GnRH neurons with specific siRNA for rhesus monkey ERα and ERβ. Results indicate that cellular knockdown of ERα and ERβ failed to block the E(2)-induced changes in [Ca(2+)](i) oscillations. It is concluded that neither ERα nor ERβ is required for the rapid action of E(2) in primate GnRH neurons.
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Affiliation(s)
- B P Kenealy
- Wisconsin National Primate Research Center, Madison, WI 53715, USA
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38
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Control of GnRH secretion: one step back. Front Neuroendocrinol 2011; 32:367-75. [PMID: 21216259 DOI: 10.1016/j.yfrne.2011.01.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 11/17/2010] [Accepted: 01/03/2011] [Indexed: 01/09/2023]
Abstract
The reproductive system is controlled by gonadotropin releasing hormone (GnRH) secretion from the brain, which is finely modulated by a number of factors including gonadal sex steroids. GnRH cells do not express estrogen receptor α, but feedback is transmitted by neurons that are at least 'one step back' from the GnRH cells. Modulation by season, stress and nutrition are effected by neuronal pathways that converge on the GnRH cells. Kisspeptin and gonadotropin inhibitory hormone (GnIH) neurons are regulators of GnRH secretion, the former being a major conduit for transmission of sex steroid feedback. GnIH cells project to GnRH cells and may play a role in the seasonal changes in reproductive activity in sheep. GnIH also modulates the action of GnRH at the level of the pituitary gonadotrope. This review focuses on the role that kisspeptin and GnIH neurons play, as modulators that are 'one step back' from GnRH neurons.
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Abstract
Gonadotrophin-releasing hormone (GnRH)-secreting neurones are the final output of the central nervous system driving fertility in all mammals. Although it has been known for decades that the efficiency of communication between the hypothalamus and the pituitary depends on the pulsatile profile of GnRH secretion, how GnRH neuronal activity is patterned to generate pulses at the median eminence is unknown. To date, the scattered distribution of the GnRH cell bodies remains the main limitation to assessing the cellular events that could lead to pulsatile GnRH secretion. Taking advantage of the unique developmental feature of GnRH neurones, the nasal explant model allows primary GnRH neurones to be maintained within a micro-network where pulsatile secretion is preserved and where individual cellular activity can be monitored simultaneously across the cell population. This review summarises the data obtained from work using this in vitro model, and brings some insights into GnRH cellular physiology.
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Affiliation(s)
- S Constantin
- Department of Physiology, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand.
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Roepke TA, Ronnekleiv OK, Kelly MJ. Physiological consequences of membrane-initiated estrogen signaling in the brain. Front Biosci (Landmark Ed) 2011; 16:1560-73. [PMID: 21196248 DOI: 10.2741/3805] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Many of the actions of 17beta-estradiol (E2) in the central nervous system (CNS) are mediated via the classical nuclear steroid receptors, ER(alpha) and ERbeta, which interact with the estrogen response element to modulate gene expression. In addition to the nuclear-initiated estrogen signaling, E2 signaling in the brain can occur rapidly within minutes prior to any sufficient effects on transcription of relevant genes. These rapid, membrane-initiated E2 signaling mechanisms have now been characterized in many brain regions, most importantly in neurons of the hypothalamus and hippocampus. Furthermore, our understanding of the physiological effects of membrane-initiated pathways is now a major field of interest in the hypothalamic control of reproduction, energy balance, thermoregulation and other homeostatic functions as well as the effects of E2 on physiological and pathophysiological functions of the hippocampus. Membrane signaling pathways impact neuronal excitability, signal transduction, cell death, neurotransmitter release and gene expression. This review will summarize recent findings on membrane-initiated E2 signaling in the hypothalamus and hippocampus and its contribution to the control of physiological and behavioral functions.
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Affiliation(s)
- Troy A Roepke
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR 97239, USA
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Maeda KI, Ohkura S, Uenoyama Y, Wakabayashi Y, Oka Y, Tsukamura H, Okamura H. Neurobiological mechanisms underlying GnRH pulse generation by the hypothalamus. Brain Res 2010; 1364:103-15. [DOI: 10.1016/j.brainres.2010.10.026] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 10/03/2010] [Accepted: 10/08/2010] [Indexed: 10/18/2022]
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Vidal A, Clément F. A dynamical model for the control of the gonadotrophin-releasing hormone neurosecretory system. J Neuroendocrinol 2010; 22:1251-66. [PMID: 20722979 DOI: 10.1111/j.1365-2826.2010.02055.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The gonadotrophin-releasing hormone (GnRH) neurosecretory system involves both endocrine neurones and associated brain cells responsible for the control of GnRH release into the pituitary portal blood. Alternation between a pulsatile regime and the pre-ovulatory surge is the hallmark of GnRH secretion in ovarian cycles of female mammals. In previous studies, we have introduced a mathematical model of the pulse and surge GnRH generator and derived appropriate dynamics-based constraints on the model parameters, both to reproduce the right sequence of secretion events and to fulfil quantitative specifications on GnRH release. In the present study, we explain how these constraints amount to embedding time- and dose-dependent steroid control within the model. We further examine under which conditions the oestradiol-driven surge may be withdrawn by pre-surge progesterone administration and simulate both oestradiol and progesterone challenges in the pulsatile regime.
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Affiliation(s)
- A Vidal
- Département de Mathématiques, Université d'Evry-Val-d'Essonne (UEVE), Laboratoire Analyse et Probabilités, Evry, France.
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Abstract
Cellular and molecular mechanisms underlying pulsatile GnRH release are not well understood. In the present study, we examined the developmental changes in intracellular calcium dynamics, peptide release, gene expression, and DNA methylation in cultured GnRH neurons derived from the nasal placode of rhesus monkeys. We found that GnRH neurons were functionally immature, exhibiting little fluctuation in intracellular calcium ([Ca(2+)](i)) and sparse pulses of GnRH peptide release in the first 12 d in vitro (div). By 14-18 div, GnRH neurons exhibited periodic [Ca(2+)](i) oscillations, synchronizing at approximately 60-min intervals and GnRH pulses occurred at approximately 60-min intervals. Interestingly, the total GnRH peptide release further increased after 18 div. Measurement of GnRH mRNA and gene CpG methylation status at 0, 14, and 20 div indicated that mRNA levels significantly (P < 0.05) increased between 14 and 20 div, just as maximal decapeptide release was observed. By bisulfite sequencing across a 5' CpG island of the GnRH gene, we further found that methylation at eight of 14 CpG sites significantly (P < 0.05) decreased between 0 and 20 div. These data indicate that epigenetic differentiation occurs during GnRH neuronal development and suggest that increased GnRH gene expression and decreased CpG methylation status are molecular phenotypes of mature GnRH neurons. To our knowledge, this is the first report that developmental DNA demethylation occurs in postmitotic neurons toward a stable neuronal phenotype.
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Affiliation(s)
- Joseph R Kurian
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, 1223 Capitol Court, Madison, Wisconsin 53715, USA
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Rance NE, Krajewski SJ, Smith MA, Cholanian M, Dacks PA. Neurokinin B and the hypothalamic regulation of reproduction. Brain Res 2010; 1364:116-28. [PMID: 20800582 DOI: 10.1016/j.brainres.2010.08.059] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Revised: 08/17/2010] [Accepted: 08/19/2010] [Indexed: 10/19/2022]
Abstract
Loss-of-function mutations in the genes encoding either neurokinin B (NKB) or its receptor, NK3 (NK3R), result in hypogonadotropic hypogonadism, characterized by an absence of pubertal development and low circulating levels of LH and gonadal steroids. These studies implicate NKB and NK3R as essential elements of the human reproductive axis. Studies over the last two decades provide evidence that a group of neurons in the hypothalamic infundibular/arcuate nucleus form an important component of this regulatory circuit. These neurons are steroid-responsive and coexpress NKB, kisspeptin, dynorphin, NK3R, and estrogen receptor α (ERα) in a variety of mammalian species. Compelling evidence in the human indicates these neurons function in the hypothalamic circuitry regulating estrogen negative feedback on gonadotropin-releasing hormone (GnRH) secretion. Moreover, in the rat, they form a bilateral, interconnected network that projects to NK3R-expressing GnRH terminals in the median eminence. This network provides an anatomical framework to explain how coordination among NKB/kisspeptin/dynorphin/NK3R/ERα neurons could mediate feedback information from the gonads to modulate pulsatile GnRH secretion. There is substantial (but indirect) evidence that this network may be part of the neural circuitry known as the "GnRH pulse generator," with NK3R signaling as an important component. This theory provides a compelling explanation for the occurrence of hypogonadotropic hypogonadism in patients with inactivating mutations in the TAC3 or TACR3 genes. Future studies will be needed to determine whether NKB signaling plays a permissive role in the onset of puberty or is part of the driving force initiating the maturation of reproductive function.
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Affiliation(s)
- Naomi E Rance
- Department of Pathology, and the Evelyn F. McNight Brain Research Institute, University of Arizona College of Medicine, Tucson, AZ 85724, USA.
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Lehman MN, Coolen LM, Goodman RL. Minireview: kisspeptin/neurokinin B/dynorphin (KNDy) cells of the arcuate nucleus: a central node in the control of gonadotropin-releasing hormone secretion. Endocrinology 2010; 151:3479-89. [PMID: 20501670 PMCID: PMC2940527 DOI: 10.1210/en.2010-0022] [Citation(s) in RCA: 527] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recently, a subset of neurons was identified in the arcuate nucleus of the hypothalamus that colocalize three neuropeptides, kisspeptin, neurokinin B, and dynorphin, each of which has been shown to play a critical role in the central control of reproduction. Growing evidence suggests that these neurons, abbreviated as the KNDy subpopulation, are strongly conserved across a range of species from rodents to humans and play a key role in the physiological regulation of GnRH neurons. KNDy cells are a major target for steroid hormones, form a reciprocally interconnected network, and have direct projections to GnRH cell bodies and terminals, features that position them well to convey steroid feedback control to GnRH neurons and potentially serve as a component of the GnRH pulse generator. In addition, recent work suggests that alterations in KNDy cell peptides may underlie neuroendocrine defects seen in clinical reproductive disorders such as polycystic ovarian syndrome. Taken together, this evidence suggests a key role for the KNDy subpopulation as a focal point in the control of reproductive function in health and disease.
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Affiliation(s)
- Michael N Lehman
- Department of Anatomy and Cell Biology, Medical Sciences Building, University of Western Ontario, London, Ontario, Canada.
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Abstract
Oscillations in intracellular calcium levels have been described in GnRH-1 neurons in both prenatal and adult cells. However, differences have been reported in the mechanisms underlying these [Ca(2+)](i) oscillations, dependent on the model used. The goal of this study was to address whether these changes depend on the maturation status of GnRH-1 neurons by assaying prenatal GnRH-1 cells maintained in explants, at two different developmental stages. This report documents an increase in the frequency of [Ca(2+)](i) oscillations between 1 and 3 wk of in vitro maturation. During the early stage, [Ca(2+)](i) oscillations are blocked by tetrodotoxin and are mainly triggered by excitatory neurotransmitters, gamma-aminobutyric acid (GABA), and glutamate. In contrast, in the later stage, some cells exhibit residual tetrodotoxin-insensitive [Ca(2+)](i) oscillations, which are sustained by action potential-independent GABA and glutamate release. The strength of these two excitatory inputs remained relatively constant during the maturation process, and the increase in frequency of [Ca(2+)](i) oscillations observed at the later stage is due to a novel excitatory input carried by cholecystokinin. Together, these data indicate developmentally regulated release and interactions of neurotransmitters (known regulators of GnRH-1 cells in adults) and point to extrinsic factors regulating GnRH-1 cellular physiology.
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Affiliation(s)
- Stephanie Constantin
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke/National Institutes of Health, Bethesda, Maryland 20892-3703, USA
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Jasoni CL, Romanò N, Constantin S, Lee K, Herbison AE. Calcium dynamics in gonadotropin-releasing hormone neurons. Front Neuroendocrinol 2010; 31:259-69. [PMID: 20594958 DOI: 10.1016/j.yfrne.2010.05.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 05/25/2010] [Accepted: 05/27/2010] [Indexed: 02/04/2023]
Abstract
The gonadotropin-releasing hormone (GnRH) neurons represent the key output cells of the neuronal network controlling fertility. Intracellular calcium ion concentration ([Ca(2+)](i)) is likely to be a key signaling tool used by GnRH neurons to regulate and co-ordinate multiple cell processes. This review examines the dynamics and control of [Ca(2+)](i) in GT1 cells, embryonic GnRH neurons in the nasal placode culture, and adult GnRH neurons in the acute brain slice preparation. GnRH neurons at all stages of development display spontaneous [Ca(2+)](i) transients driven, primarily, by their burst firing. However, the intracellular mechanisms generating [Ca(2+)](i) transients, and the control of [Ca(2+)](i) by neurotransmitters, varies markedly across the different developmental stages. The functional roles of [Ca(2+)](i) transients are beginning to be unraveled with one key action being that of regulating the dynamics of GnRH neuron burst firing.
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Affiliation(s)
- Christine L Jasoni
- Centre for Neuroendocrinology, Departments of Physiology, University of Otago, Dunedin 9054, New Zealand
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Terasawa E, Kurian JR, Guerriero KA, Kenealy BP, Hutz ED, Keen KL. Recent discoveries on the control of gonadotrophin-releasing hormone neurones in nonhuman primates. J Neuroendocrinol 2010; 22:630-8. [PMID: 20456608 PMCID: PMC2908205 DOI: 10.1111/j.1365-2826.2010.02027.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Since Ernst Knobil proposed the concept of the gonadotrophin-releasing hormone (GnRH) pulse-generator in the monkey hypothalamus three decades ago, we have made significant progress in this research area with cellular and molecular approaches. First, an increase in pulsatile GnRH release triggers the onset of puberty. However, the question of what triggers the pubertal increase in GnRH is still unclear. GnRH neurones are already mature before puberty but GnRH release is suppressed by a tonic GABA inhibition. Our recent work indicates that blocking endogenous GABA inhibition with the GABA(A) receptor blocker, bicuculline, dramatically increases kisspeptin release, which plays an important role in the pubertal increase in GnRH release. Thus, an interplay between the GABA, kisspeptin, and GnRH neuronal systems appears to trigger puberty. Second, cultured GnRH neurones derived from the olfactory placode of monkey embryos exhibit synchronised intracellular calcium, [Ca(2+)](i), oscillations and release GnRH in pulses at approximately 60-min intervals after 14 days in vitro (div). During the first 14 div, GnRH neurones undergo maturational changes from no [Ca(2+)](i) oscillations and little GnRH release to the fully functional state. Recent work also shows GnRH mRNA expression increases during in vitro maturation. This mRNA increase coincides with significant demethylation of a CpG island in the GnRH 5'-promoter region. This suggests that epigenetic differentiation occurs during GnRH neuronal maturation. Third, oestradiol causes rapid, direct, excitatory action in GnRH neurones and this action of oestradiol appears to be mediated through a membrane receptor, such as G-protein coupled receptor 30.
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Affiliation(s)
- E Terasawa
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715-1299, USA.
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Klenke U, Constantin S, Wray S. Neuropeptide Y directly inhibits neuronal activity in a subpopulation of gonadotropin-releasing hormone-1 neurons via Y1 receptors. Endocrinology 2010; 151:2736-46. [PMID: 20351316 PMCID: PMC2875836 DOI: 10.1210/en.2009-1198] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Neuropeptide Y (NPY), a member of the pancreatic polypeptide family, is an orexigenic hormone. GnRH-1 neurons express NPY receptors. This suggests a direct link between metabolic function and reproduction. However, the effect of NPY on GnRH-1 cells has been variable, dependent on metabolic and reproductive status of the animal. This study circumvents these issues by examining the role of NPY on GnRH-1 neuronal activity in an explant model that is based on the extra-central nervous system origin of GnRH-1 neurons. These prenatal GnRH-1 neurons express many receptors found in GnRH-1 neurons in the brain and use similar transduction pathways. In addition, these GnRH-1 cells exhibit spontaneous and ligand-induced oscillations in intracellular calcium as well as pulsatile calcium-controlled GnRH-1 release. Single-cell PCR determined that prenatal GnRH-1 neurons express the G protein-coupled Y1 receptor (Y1R). To address the influence of NPY on GnRH-1 neuronal activity, calcium imaging was used to monitor individual and population dynamics. NPY treatment, mimicked with Y1R agonist, significantly decreased the number of calcium peaks per minute in GnRH-1 neurons and was prevented by a Y1R antagonist. Pertussis toxin blocked the effect of NPY on GnRH-1 neuronal activity, indicating the coupling of Y1R to inhibitory G protein. The NPY-induced inhibition was independent of the adenylate cyclase pathway but mediated by the activation of G protein-coupled inwardly rectifying potassium channels. These results indicate that at an early developmental stage, GnRH-1 neuronal activity can be directly inhibited by NPY via its Y1R.
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Affiliation(s)
- Ulrike Klenke
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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Chen Q, Weiner RI, Blackman BE. Decreased expression of A-kinase anchoring protein 150 in GT1 neurons decreases neuron excitability and frequency of intrinsic gonadotropin-releasing hormone pulses. Endocrinology 2010; 151:281-90. [PMID: 19887564 PMCID: PMC2803148 DOI: 10.1210/en.2009-0894] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The frequency of intrinsic pulsatile GnRH secretion from endogenous GnRH neurons and GT1 GnRH cell lines is stimulated by increased intracellular cAMP levels. The downstream molecules comprising the cAMP signaling pathway are organized in microdomains by a family of scaffolding proteins, A-kinase anchoring proteins (AKAPs). These molecules tether protein kinase A, cAMP-specific phosphodiesterases, phosphatases to known substrates. In neurons AKAP150 organizes many of the signaling molecules known to regulate the excitability and intrinsic pulsatile activity of GnRH neurons. AKAP150 was expressed in both the GT1-1 and GT1-7 cells. We determined the role of AKAP150 in coordinating GT1-1 cell excitability and intrinsic GnRH pulsatile secretion by lowering AKAP150 levels with a small interfering RNA (siRNA) adenovirus construct to AKAP150 (Ad-AKAP150-siRNA). Infection with Ad-AKAP150-siRNA specifically decreased AKAP150 mRNA levels by 74% and protein levels by 53% relative to uninfected cells or cells infected with a luciferase control adenovirus siRNA vector. In GT1 cells, spontaneous Ca(2+) oscillations, an index of neuron excitability, are stimulated by increased levels of intracellular cAMP and lowered by decreased levels. The frequency of spontaneous Ca(2+) oscillations in Ad-AKAP150-siRNA-treated GT1-1 cells decreased by 47.2% relative to controls. A dramatic decrease in the number of spontaneous GnRH pulses was also observed after infection with Ad-AKAP150-siRNA. The interpulse interval increased to 143 +/- 20.25 min in Ad-AKAP150-siRNA infected cells from 32.2 +/- 7.3 min in luciferase control adenovirus siRNA vector-infected cells. These data demonstrate an important role of AKAP150 in coordinating signaling events regulating the frequency of intrinsic pulsatile GnRH secretion.
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Affiliation(s)
- Qiumei Chen
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California 94143, USA
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