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Perrin F, Anderson LC, Mitchell SPC, Sinha P, Turchyna Y, Maesako M, Houser MCQ, Zhang C, Wagner SL, Tanzi RE, Berezovska O. PS1/gamma-secretase acts as rogue chaperone of glutamate transporter EAAT2/GLT-1 in Alzheimer's disease. RESEARCH SQUARE 2023:rs.3.rs-3495211. [PMID: 37986905 PMCID: PMC10659539 DOI: 10.21203/rs.3.rs-3495211/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The recently discovered interaction between presenilin 1 (PS1), a catalytic subunit of γ-secretase responsible for the generation of amyloid-β(Aβ) peptides, and GLT-1, the major glutamate transporter in the brain (EAAT2 in the human) may provide a mechanistic link between two important pathological aspects of Alzheimer's disease (AD): abnormal Aβoccurrence and neuronal network hyperactivity. In the current study, we employed a FRET-based approach, fluorescence lifetime imaging microscopy (FLIM), to characterize the PS1/GLT-1 interaction in its native environment in the brain tissue of sporadic AD (sAD) patients. There was significantly less interaction between PS1 and GLT-1 in sAD brains, compared to tissue from patients with frontotemporal lobar degeneration (FTLD), or non-demented age-matched controls. Since PS1 has been shown to adopt pathogenic "closed" conformation in sAD but not in FTLD, we assessed the impact of changes in PS1 conformation on the interaction. Familial AD (fAD) PS1 mutations which induce a "closed" PS1 conformation similar to that in sAD brain and gamma-secretase modulators (GSMs) which induce a "relaxed" conformation, reduced and increased the interaction, respectively. This indicates that PS1 conformation seems to have a direct effect on the interaction with GLT-1. Furthermore, using biotinylation/streptavidin pull-down, western blotting, and cycloheximide chase assays, we determined that the presence of PS1 increased GLT-1 cell surface expression and GLT-1 homomultimer formation, but did not impact GLT-1 protein stability. Together, the current findings suggest that the newly described PS1/GLT-1 interaction endows PS1 with chaperone activity, modulating GLT-1 transport to the cell surface and stabilizing the dimeric-trimeric states of the protein. The diminished PS1/GLT-1 interaction suggests that these functions of the interaction may not work properly in AD.
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Analysis of a cell niche with proliferative potential at the roof of the aqueduct of Sylvius. Neurosci Res 2023; 188:28-38. [PMID: 36375656 DOI: 10.1016/j.neures.2022.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 11/08/2022] [Indexed: 11/13/2022]
Abstract
The aqueduct of Sylvius connects the third with the fourth ventricle and is surrounded by the Periaqueductal Grey. Here, we report a novel niche of cells in the dorsal section of the aqueduct, hereby named dorsal aqueduct niche or DAN, by applying a battery of selective markers and transgenic mouse lines. The somata of DAN cells are located toward the lumen of the ventricle forming multiple layers in close association with the cerebrospinal fluid (CSF). A single process emerges from the soma and run with the blood vessels. Cells of the DAN express radial glia/stem cell markers such as GFAP, vimentin and nestin, and the glutamate transporter GLAST or the oligodendrocyte precursor/pericyte marker NG2, thereby suggesting their potential for the generation of new cells. Morphologically, DAN cells resemble tanycytes of the third ventricle, which transfer biochemical signals from the CSF to the central nervous system and display proliferative capacity. The aqueduct ependymal lining can proliferate as observed by the integration of BrdU and expression of Ki67. Thus, the dorsal section of the aqueduct of Sylvius possesses cells that may act a niche of new glial cells in the adult mouse brain.
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Coutteau-Robles A, Prevot V, Sharif A. Cell proliferation and glial cell marker expression in the wall of the third ventricle in the tuberal region of the male mouse hypothalamus during postnatal development. J Neuroendocrinol 2023; 35:e13239. [PMID: 36863859 DOI: 10.1111/jne.13239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/18/2023] [Accepted: 02/03/2023] [Indexed: 02/10/2023]
Abstract
The third ventricle (3 V) wall of the tuberal hypothalamus is composed of two types of cells; specialized ependymoglial cells called tanycytes located ventrally and ependymocytes dorsally, which control the exchanges between the cerebrospinal fluid and the hypothalamic parenchyma. By regulating the dialogue between the brain and the periphery, tanycytes are now recognized as central players in the control of major hypothalamic functions such as energy metabolism and reproduction. While our knowledge of the biology of adult tanycytes is progressing rapidly, our understanding of their development remains very incomplete. To gain insight into the postnatal maturation of the 3 V ependymal lining, we conducted a comprehensive immunofluorescent study of the mouse tuberal region at four postnatal ages (postnatal day (P) 0, P4, P10, and P20). We analyzed the expression profile of a panel of tanycyte and ependymocyte markers (vimentin, S100, connexin-43 [Cx43], and glial fibrillary acidic protein [GFAP]) and characterized cell proliferation in the 3 V wall using the thymidine analog bromodeoxyuridine. Our results show that most changes in marker expression occur between P4 and P10, with a switch from a 3 V mostly lined by radial cells to the emergence of a tanycytic domain ventrally and an ependymocytic domain dorsally, a drop in cell proliferation and increased expression of S100, Cx43, and GFAP that acquire a mature profile at P20. Our study thus identifies the transition between the first and the second postnatal week as a critical time window for the postnatal maturation of the 3 V wall ependymal lining.
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Affiliation(s)
- Adrian Coutteau-Robles
- CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, University of Lille, Inserm, Lille, France
| | - Vincent Prevot
- CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, University of Lille, Inserm, Lille, France
| | - Ariane Sharif
- CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, University of Lille, Inserm, Lille, France
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4
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Lopez-Rodriguez D, Rohrbach A, Lanzillo M, Gervais M, Croizier S, Langlet F. Ontogeny of ependymoglial cells lining the third ventricle in mice. Front Endocrinol (Lausanne) 2023; 13:1073759. [PMID: 36686420 PMCID: PMC9849764 DOI: 10.3389/fendo.2022.1073759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 12/02/2022] [Indexed: 01/07/2023] Open
Abstract
Introduction During hypothalamic development, the germinative neuroepithelium gives birth to diverse neural cells that regulate numerous physiological functions in adulthood. Methods Here, we studied the ontogeny of ependymal cells in the mouse mediobasal hypothalamus using the BrdU approach and publicly available single-cell RNAseq datasets. Results We observed that while typical ependymal cells are mainly produced at E13, tanycyte birth depends on time and subtypes and lasts up to P8. Typical ependymocytes and β tanycytes are the first to arise at the top and bottom of the dorsoventral axis around E13, whereas α tanycytes emerge later in development, generating an outside-in dorsoventral gradient along the third ventricle. Additionally, α tanycyte generation displayed a rostral-to-caudal pattern. Finally, tanycytes mature progressively until they reach transcriptional maturity between P4 and P14. Discussion Altogether, this data shows that ependyma generation differs in time and distribution, highlighting the heterogeneity of the third ventricle.
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Affiliation(s)
- David Lopez-Rodriguez
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Antoine Rohrbach
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Marc Lanzillo
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Manon Gervais
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Sophie Croizier
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Fanny Langlet
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
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5
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Rodríguez-Campuzano AG, Ortega A. Glutamate transporters: Critical components of glutamatergic transmission. Neuropharmacology 2021; 192:108602. [PMID: 33991564 DOI: 10.1016/j.neuropharm.2021.108602] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/09/2021] [Accepted: 04/27/2021] [Indexed: 02/06/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the vertebrate central nervous system. Once released, it binds to specific membrane receptors and transporters activating a wide variety of signal transduction cascades, as well as its removal from the synaptic cleft in order to avoid its extracellular accumulation and the overstimulation of extra-synaptic receptors that might result in neuronal death through a process known as excitotoxicity. Although neurodegenerative diseases are heterogenous in clinical phenotypes and genetic etiologies, a fundamental mechanism involved in neuronal degeneration is excitotoxicity. Glutamate homeostasis is critical for brain physiology and Glutamate transporters are key players in maintaining low extracellular Glutamate levels. Therefore, the characterization of Glutamate transporters has been an active area of glutamatergic research for the last 40 years. Transporter activity its regulated at different levels: transcriptional and translational control, transporter protein trafficking and membrane mobility, and through extensive post-translational modifications. The elucidation of these mechanisms has emerged as an important piece to shape our current understanding of glutamate actions in the nervous system.
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Affiliation(s)
- Ada G Rodríguez-Campuzano
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico
| | - Arturo Ortega
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico.
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6
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Kostin A, Alam MA, McGinty D, Alam MN. Adult hypothalamic neurogenesis and sleep-wake dysfunction in aging. Sleep 2021; 44:5986548. [PMID: 33202015 DOI: 10.1093/sleep/zsaa173] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 07/22/2020] [Indexed: 12/21/2022] Open
Abstract
In the mammalian brain, adult neurogenesis has been extensively studied in the hippocampal sub-granular zone and the sub-ventricular zone of the anterolateral ventricles. However, growing evidence suggests that new cells are not only "born" constitutively in the adult hypothalamus, but many of these cells also differentiate into neurons and glia and serve specific functions. The preoptic-hypothalamic area plays a central role in the regulation of many critical functions, including sleep-wakefulness and circadian rhythms. While a role for adult hippocampal neurogenesis in regulating hippocampus-dependent functions, including cognition, has been extensively studied, adult hypothalamic neurogenic process and its contributions to various hypothalamic functions, including sleep-wake regulation are just beginning to unravel. This review is aimed at providing the current understanding of the hypothalamic adult neurogenic processes and the extent to which it affects hypothalamic functions, including sleep-wake regulation. We propose that hypothalamic neurogenic processes are vital for maintaining the proper functioning of the hypothalamic sleep-wake and circadian systems in the face of regulatory challenges. Sleep-wake disturbance is a frequent and challenging problem of aging and age-related neurodegenerative diseases. Aging is also associated with a decline in the neurogenic process. We discuss a hypothesis that a decrease in the hypothalamic neurogenic process underlies the aging of its sleep-wake and circadian systems and associated sleep-wake disturbance. We further discuss whether neuro-regenerative approaches, including pharmacological and non-pharmacological stimulation of endogenous neural stem and progenitor cells in hypothalamic neurogenic niches, can be used for mitigating sleep-wake and other hypothalamic dysfunctions in aging.
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Affiliation(s)
- Andrey Kostin
- Research Service (151A3), Veterans Affairs Greater Los Angeles Healthcare System, Sepulveda, CA
| | - Md Aftab Alam
- Research Service (151A3), Veterans Affairs Greater Los Angeles Healthcare System, Sepulveda, CA.,Department of Psychiatry, University of California, Los Angeles, CA
| | - Dennis McGinty
- Research Service (151A3), Veterans Affairs Greater Los Angeles Healthcare System, Sepulveda, CA.,Department of Psychology, University of California, Los Angeles, CA
| | - Md Noor Alam
- Research Service (151A3), Veterans Affairs Greater Los Angeles Healthcare System, Sepulveda, CA.,Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
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7
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Zhou Y, Eid T, Hassel B, Danbolt NC. Novel aspects of glutamine synthetase in ammonia homeostasis. Neurochem Int 2020; 140:104809. [DOI: 10.1016/j.neuint.2020.104809] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 02/07/2023]
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8
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Pasquettaz R, Kolotuev I, Rohrbach A, Gouelle C, Pellerin L, Langlet F. Peculiar protrusions along tanycyte processes face diverse neural and nonneural cell types in the hypothalamic parenchyma. J Comp Neurol 2020; 529:553-575. [PMID: 32515035 PMCID: PMC7818493 DOI: 10.1002/cne.24965] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/22/2020] [Accepted: 05/27/2020] [Indexed: 12/15/2022]
Abstract
Tanycytes are highly specialized ependymal cells that line the bottom and the lateral walls of the third ventricle. In contact with the cerebrospinal fluid through their cell bodies, they send processes into the arcuate nucleus, the ventromedial nucleus, and the dorsomedial nucleus of the hypothalamus. In the present work, we combined transgenic and immunohistochemical approaches to investigate the neuroanatomical associations between tanycytes and neural cells present in the hypothalamic parenchyma, in particular in the arcuate nucleus. The specific expression of tdTomato in tanycytes first allowed the observation of peculiar subcellular protrusions along tanycyte processes and at their endfeet such as spines, swelling, en passant boutons, boutons, or claws. Interestingly, these protrusions contact different neural cells in the brain parenchyma including blood vessels and neurons, and in particular NPY and POMC neurons in the arcuate nucleus. Using both fluorescent and electron microscopy, we finally observed that these tanycyte protrusions contain ribosomes, mitochondria, diverse vesicles, and transporters, suggesting dense tanycyte/neuron and tanycyte/blood vessel communications. Altogether, our results lay the neuroanatomical basis for tanycyte/neural cell interactions, which will be useful to further understand cell-to-cell communications involved in the regulation of neuroendocrine functions.
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Affiliation(s)
- Roxane Pasquettaz
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Irina Kolotuev
- Electron Microscopy Facility, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Antoine Rohrbach
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Cathy Gouelle
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Luc Pellerin
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.,Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536 CNRS, LabEx TRAIL-IBIO, Université de Bordeaux, Bordeaux Cedex, France.,Inserm U1082, Universite de Poitiers, Poitiers Cedex, France
| | - Fanny Langlet
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
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9
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Langlet F. Targeting Tanycytes: Balance between Efficiency and Specificity. Neuroendocrinology 2020; 110:574-581. [PMID: 31986518 DOI: 10.1159/000505549] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 12/18/2019] [Indexed: 11/19/2022]
Abstract
Tanycytes are peculiar ependymoglial cells lining the bottom and the lateral wall of the third ventricle. For a decade, the utilization of molecular genetic approaches allowed us to make important discoveries about their diverse physiological functions. Here, I review the current methods used to target tanycytes, focusing on their specificity, their efficiency, their limitations, as well as their potential future improvements.
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Affiliation(s)
- Fanny Langlet
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland,
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10
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Müller-Fielitz H, Schwaninger M. The Role of Tanycytes in the Hypothalamus-Pituitary-Thyroid Axis and
the Possibilities for Their Genetic Manipulation. Exp Clin Endocrinol Diabetes 2019; 128:388-394. [DOI: 10.1055/a-1065-1855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
AbstractThyroid hormone (TH) regulation is important for development, energy homeostasis,
heart function, and bone formation. To control the effects of TH in target
organs, the hypothalamus-pituitary-thyroid (HPT) axis and the tissue-specific
availability of TH are highly regulated by negative feedback. To exert a central
feedback, TH must enter the brain via specific transport mechanisms and cross
the blood-brain barrier. Here, tanycytes, which are located in the ventral walls
of the 3rd ventricle in the mediobasal hypothalamus (MBH), function as
gatekeepers. Tanycytes are able to transport, sense, and modify the release of
hormones of the HPT axis and are involved in feedback regulation. In this
review, we focus on the relevance of tanycytes in thyrotropin-releasing hormone
(TRH) release and review available genetic tools to investigate the
physiological functions of these cells.
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Affiliation(s)
- Helge Müller-Fielitz
- Institute for Experimental and Clinical Pharmacology and Toxicology,
Lübeck, University of Lübeck, Germany
| | - Markus Schwaninger
- Institute for Experimental and Clinical Pharmacology and Toxicology,
Lübeck, University of Lübeck, Germany
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11
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Langlet F. Tanycyte Gene Expression Dynamics in the Regulation of Energy Homeostasis. Front Endocrinol (Lausanne) 2019; 10:286. [PMID: 31133987 PMCID: PMC6514105 DOI: 10.3389/fendo.2019.00286] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/18/2019] [Indexed: 01/01/2023] Open
Abstract
Animal survival relies on a constant balance between energy supply and energy expenditure, which is controlled by several neuroendocrine functions that integrate metabolic information and adapt the response of the organism to physiological demands. Polarized ependymoglial cells lining the floor of the third ventricle and sending a single process within metabolic hypothalamic parenchyma, tanycytes are henceforth described as key components of the hypothalamic neural network controlling energy balance. Their strategic position and peculiar properties convey them diverse physiological functions ranging from blood/brain traffic controllers, metabolic modulators, and neural stem/progenitor cells. At the molecular level, these functions rely on an accurate regulation of gene expression. Indeed, tanycytes are characterized by their own molecular signature which is mostly associated to their diverse physiological functions, and the detection of variations in nutrient/hormone levels leads to an adequate modulation of genetic profile in order to ensure energy homeostasis. The aim of this review is to summarize recent knowledge on the nutritional control of tanycyte gene expression.
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12
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Prevot V, Dehouck B, Sharif A, Ciofi P, Giacobini P, Clasadonte J. The Versatile Tanycyte: A Hypothalamic Integrator of Reproduction and Energy Metabolism. Endocr Rev 2018; 39:333-368. [PMID: 29351662 DOI: 10.1210/er.2017-00235] [Citation(s) in RCA: 147] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/12/2018] [Indexed: 12/16/2022]
Abstract
The fertility and survival of an individual rely on the ability of the periphery to promptly, effectively, and reproducibly communicate with brain neural networks that control reproduction, food intake, and energy homeostasis. Tanycytes, a specialized glial cell type lining the wall of the third ventricle in the median eminence of the hypothalamus, appear to act as the linchpin of these processes by dynamically controlling the secretion of neuropeptides into the portal vasculature by hypothalamic neurons and regulating blood-brain and blood-cerebrospinal fluid exchanges, both processes that depend on the ability of these cells to adapt their morphology to the physiological state of the individual. In addition to their barrier properties, tanycytes possess the ability to sense blood glucose levels, and play a fundamental and active role in shuttling circulating metabolic signals to hypothalamic neurons that control food intake. Moreover, accumulating data suggest that, in keeping with their putative descent from radial glial cells, tanycytes are endowed with neural stem cell properties and may respond to dietary or reproductive cues by modulating hypothalamic neurogenesis. Tanycytes could thus constitute the missing link in the loop connecting behavior, hormonal changes, signal transduction, central neuronal activation and, finally, behavior again. In this article, we will examine these recent advances in the understanding of tanycytic plasticity and function in the hypothalamus and the underlying molecular mechanisms. We will also discuss the putative involvement and therapeutic potential of hypothalamic tanycytes in metabolic and fertility disorders.
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Affiliation(s)
- Vincent Prevot
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Bénédicte Dehouck
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Ariane Sharif
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Philippe Ciofi
- Inserm, Neurocentre Magendie, Bordeaux, France.,Université de Bordeaux, Bordeaux, France
| | - Paolo Giacobini
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Jerome Clasadonte
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
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13
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Axon-terminals expressing EAAT2 (GLT-1; Slc1a2) are common in the forebrain and not limited to the hippocampus. Neurochem Int 2018. [PMID: 29530756 DOI: 10.1016/j.neuint.2018.03.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The excitatory amino acid transporter type 2 (EAAT2) represents the major mechanism for removal of extracellular glutamate. In the hippocampus, there is some EAAT2 in axon-terminals, whereas most of the protein is found in astroglia. The functional importance of the neuronal EAAT2 is unknown, and it is debated whether EAAT2-expressing nerve terminals are present in other parts of the brain. Here we selectively deleted the EAAT2 gene in neurons (by crossing EAAT2-flox mice with synapsin 1-Cre mice in the C57B6 background). To reduce interference from astroglial EAAT2, we measured glutamate accumulation in crude tissue homogenates. EAAT2 proteins levels were measured by immunoblotting. Although synapsin 1-Cre mediated gene deletion only reduced the forebrain tissue content of EAAT2 protein to 95.5 ± 3.4% of wild-type (littermate) controls, the glutamate accumulation in homogenates of neocortex, hippocampus, striatum and thalamus were nevertheless diminished to, respectively, 54 ± 4, 46 ± 3, 46 ± 2 and 65 ± 7% of controls (average ± SEM, n = 3 pairs of littermates). GABA uptake was unaffected. After injection of U-13C-glucose, lack of neuronal EAAT2 resulted in higher 13C-labeling of glutamine and GABA in the hippocampus suggesting that neuronal EAAT2 is partly short-circuiting the glutamate-glutamine cycle in wild-type mice. Crossing synapsin 1-Cre mice with Ai9 reporter mice revealed that Cre-mediated excision occurred efficiently in hippocampus CA3, but less efficiently in other regions and hardly at all in the cerebellum. Conclusions: (1) EAAT2 is expressed in nerve terminals in multiple brain regions. (2) The uptake catalyzed by neuronal EAAT2 plays a role in glutamate metabolism, at least in the hippocampus. (3) Synapsin 1-Cre does not delete floxed genes in all neurons, and the contribution of neuronal EAAT2 is therefore likely to be larger than revealed in the present study.
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14
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Ottestad-Hansen S, Hu QX, Follin-Arbelet VV, Bentea E, Sato H, Massie A, Zhou Y, Danbolt NC. The cystine-glutamate exchanger (xCT, Slc7a11) is expressed in significant concentrations in a subpopulation of astrocytes in the mouse brain. Glia 2018; 66:951-970. [DOI: 10.1002/glia.23294] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 12/28/2017] [Accepted: 01/02/2018] [Indexed: 01/09/2023]
Affiliation(s)
- Sigrid Ottestad-Hansen
- The Neurotransporter Group, Section of Anatomy, Department of Molecular Medicine; Institute of Basic Medical Sciences, University of Oslo; Oslo 0317 Norway
| | - Qiu Xiang Hu
- The Neurotransporter Group, Section of Anatomy, Department of Molecular Medicine; Institute of Basic Medical Sciences, University of Oslo; Oslo 0317 Norway
| | - Virgine Veronique Follin-Arbelet
- The Neurotransporter Group, Section of Anatomy, Department of Molecular Medicine; Institute of Basic Medical Sciences, University of Oslo; Oslo 0317 Norway
| | - Eduard Bentea
- Department of Pharmaceutical Biotechnology and Molecular Biology; Center for Neurosciences, Vrije Universiteit Brussel; Brussels 1090 Belgium
| | - Hideyo Sato
- Laboratory of Biochemistry and Molecular Biology, Department of Medical Technology; Niigata University; Niigata Niigata Prefecture 950-2181 Japan
| | - Ann Massie
- Department of Pharmaceutical Biotechnology and Molecular Biology; Center for Neurosciences, Vrije Universiteit Brussel; Brussels 1090 Belgium
| | - Yun Zhou
- The Neurotransporter Group, Section of Anatomy, Department of Molecular Medicine; Institute of Basic Medical Sciences, University of Oslo; Oslo 0317 Norway
| | - Niels Christian Danbolt
- The Neurotransporter Group, Section of Anatomy, Department of Molecular Medicine; Institute of Basic Medical Sciences, University of Oslo; Oslo 0317 Norway
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15
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Tanycytes control the hormonal output of the hypothalamic-pituitary-thyroid axis. Nat Commun 2017; 8:484. [PMID: 28883467 PMCID: PMC5589884 DOI: 10.1038/s41467-017-00604-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 07/13/2017] [Indexed: 12/29/2022] Open
Abstract
The hypothalamic–pituitary–thyroid (HPT) axis maintains circulating thyroid hormone levels in a narrow physiological range. As axons containing thyrotropin-releasing hormone (TRH) terminate on hypothalamic tanycytes, these specialized glial cells have been suggested to influence the activity of the HPT axis, but their exact role remained enigmatic. Here, we demonstrate that stimulation of the TRH receptor 1 increases intracellular calcium in tanycytes of the median eminence via Gαq/11 proteins. Activation of Gαq/11 pathways increases the size of tanycyte endfeet that shield pituitary vessels and induces the activity of the TRH-degrading ectoenzyme. Both mechanisms may limit the TRH release to the pituitary. Indeed, blocking TRH signaling in tanycytes by deleting Gαq/11 proteins in vivo enhances the response of the HPT axis to the chemogenetic activation of TRH neurons. In conclusion, we identify new TRH- and Gαq/11-dependent mechanisms in the median eminence by which tanycytes control the activity of the HPT axis. The hypothalamic-pituitary-thyroid (HPT) axis regulates a wide range of physiological processes. Here the authors show that hypothalamic tanycytes play a role in the homeostatic regulation of the HPT axis; activation of TRH signaling in tanycytes elevates their intracellular Ca2+ via Gαq/11 pathway, ultimately resulting in reduced TRH release into the pituitary vessels.
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Szilvásy-Szabó A, Varga E, Beliczai Z, Lechan RM, Fekete C. Localization of connexin 43 gap junctions and hemichannels in tanycytes of adult mice. Brain Res 2017; 1673:64-71. [PMID: 28803831 DOI: 10.1016/j.brainres.2017.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 06/22/2017] [Accepted: 08/09/2017] [Indexed: 12/22/2022]
Abstract
Tanycytes are specialized glial cells lining the lateral walls and the floor of the third ventricle behind the optic chiasm. In addition to functioning as barrier cells, they also have an important role in the regulation of neuroendocrine axes and energy homeostasis. To determine whether tanycytes communicate with each other via Connexin 43 (Cx43) gap junctions, individual tanycytes were loaded with Lucifer yellow (LY) through a patch pipette. In all cases, LY filled a larger group of tanycytes as well as blood vessels adjacent to tanycyte processes. The Cx43-blocker, carbenoxolone, inhibited spreading of LY. The greatest density of Cx43-immunoreactive spots was observed in the cell membrane of α-tanycyte cell bodies. Cx43-immunoreactivity was also present in the membrane of β-tanycyte cell bodies, but in lower density. Processes of both types of tanycytes also contained Cx43-immunoreactivity. At the ultrastructural level, Cx43-immunoreactivity was present in the cell membrane of all types of tanycytes including their ventricular surface, but gap junctions were more frequent among α-tanycytes. Cx43-immunoreactivity was also observed in the cell membrane between contacting tanycyte endfeet processes, and between tanycyte endfeet process and axon varicosities in the external zone of the median eminence and capillaries in the arcuate nucleus and median eminence. These results suggest that gap junctions are present not only among tanycytes, but also between tanycytes and the axons of hypophysiotropic neurons. Cx43 hemichannels may also facilitate the transport between tanycytes and extracellular fluids, including the cerebrospinal fluid, extracellular space of the median eminence and bloodstream.
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Affiliation(s)
- Anett Szilvásy-Szabó
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary; Semmelweis University Neurosciences Doctoral School, Neuroendocrinology Program, Budapest, Hungary
| | - Edina Varga
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsuzsa Beliczai
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ronald M Lechan
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, MA, USA; Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Csaba Fekete
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, MA, USA.
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Chowdhury GMI, Wang P, Ciardi A, Mamillapalli R, Johnson J, Zhu W, Eid T, Behar K, Chan O. Impaired Glutamatergic Neurotransmission in the Ventromedial Hypothalamus May Contribute to Defective Counterregulation in Recurrently Hypoglycemic Rats. Diabetes 2017; 66:1979-1989. [PMID: 28416628 PMCID: PMC5482086 DOI: 10.2337/db16-1589] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Accepted: 04/10/2017] [Indexed: 12/11/2022]
Abstract
The objectives of this study were to understand the role of glutamatergic neurotransmission in the ventromedial hypothalamus (VMH) in response to hypoglycemia and to elucidate the effects of recurrent hypoglycemia (RH) on this neurotransmitter. We 1) measured changes in interstitial VMH glutamate levels by using microdialysis and biosensors, 2) identified the receptors that mediate glutamate's stimulatory effects on the counterregulatory responses, 3) quantified glutamate metabolic enzyme levels in the VMH, 4) examined astrocytic glutamate reuptake mechanisms, and 5) used 1H-[13C]-nuclear magnetic resonance (NMR) spectroscopy to evaluate the effects of RH on neuronal glutamate metabolism. We demonstrated that glutamate acts through kainic acid receptors in the VMH to augment counterregulatory responses. Biosensors showed that the normal transient rise in glutamate levels in response to hypoglycemia is absent in RH animals. More importantly, RH reduced extracellular glutamate concentrations partly as a result of decreased glutaminase expression. Decreased glutamate was also associated with reduced astrocytic glutamate transport in the VMH. NMR analysis revealed a decrease in [4-13C]glutamate but unaltered [4-13C]glutamine concentrations in the VMH of RH animals. The data suggest that glutamate release is important for proper activation of the counterregulatory response to hypoglycemia and that impairment of glutamate metabolic and resynthetic pathways with RH may contribute to counterregulatory failure.
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Affiliation(s)
- Golam M I Chowdhury
- Department of Psychiatry, Yale School of Medicine, New Haven, CT
- Magnetic Resonance Research Center, Yale School of Medicine, New Haven, CT
| | - Peili Wang
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
| | - Alisha Ciardi
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
| | - Ramanaiah Mamillapalli
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
| | - Justin Johnson
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
| | - Wanling Zhu
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
| | - Tore Eid
- Departments of Neurosurgery and Laboratory Medicine, Yale School of Medicine, New Haven, CT
| | - Kevin Behar
- Department of Psychiatry, Yale School of Medicine, New Haven, CT
- Magnetic Resonance Research Center, Yale School of Medicine, New Haven, CT
| | - Owen Chan
- Section of Endocrinology, Department of Internal Medicine, Yale School of Medicine, New Haven, CT
- Division of Endocrinology, Metabolism, and Diabetes, Department of Internal Medicine, University of Utah, Salt Lake City, UT
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Hofmann K, Lamberz C, Piotrowitz K, Offermann N, But D, Scheller A, Al-Amoudi A, Kuerschner L. Tanycytes and a differential fatty acid metabolism in the hypothalamus. Glia 2016; 65:231-249. [PMID: 27726181 DOI: 10.1002/glia.23088] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 08/31/2016] [Accepted: 09/28/2016] [Indexed: 11/12/2022]
Abstract
Although the brain controls all main metabolic pathways in the whole organism, its lipid metabolism is partially separated from the rest of the body. Circulating lipids and other metabolites are taken up into brain areas like the hypothalamus and are locally metabolized and sensed involving several hypothalamic cell types. In this study we show that saturated and unsaturated fatty acids are differentially processed in the murine hypothalamus. The observed differences involve both lipid distribution and metabolism. Key findings were: (i) hypothalamic astrocytes are targeted by unsaturated, but not saturated lipids in lean mice; (ii) in obese mice labeling of these astrocytes by unsaturated oleic acid cannot be detected unless β-oxidation or ketogenesis is inhibited; (iii) the hypothalamus of obese animals increases ketone body and neutral lipid synthesis while tanycytes, hypothalamic cells facing the ventricle, increase their lipid droplet content; and (iv) tanycytes show different labeling for saturated or unsaturated lipids. Our data support a metabolic connection between tanycytes and astrocytes likely to impact hypothalamic lipid sensing. GLIA 2017;65:231-249.
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Affiliation(s)
- Kristina Hofmann
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, D-53115, Germany
| | - Christian Lamberz
- German Center for Neurodegenerative Diseases (DZNE), Bonn, D-53175, Germany
| | - Kira Piotrowitz
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, D-53115, Germany
| | - Nina Offermann
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, D-53115, Germany
| | - Diana But
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, D-53115, Germany
| | - Anja Scheller
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, D-66421, Germany
| | - Ashraf Al-Amoudi
- German Center for Neurodegenerative Diseases (DZNE), Bonn, D-53175, Germany
| | - Lars Kuerschner
- Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn, D-53115, Germany
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Danbolt NC, Furness DN, Zhou Y. Neuronal vs glial glutamate uptake: Resolving the conundrum. Neurochem Int 2016; 98:29-45. [PMID: 27235987 DOI: 10.1016/j.neuint.2016.05.009] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/03/2016] [Accepted: 05/17/2016] [Indexed: 12/30/2022]
Abstract
Neither normal brain function nor the pathological processes involved in neurological diseases can be adequately understood without knowledge of the release, uptake and metabolism of glutamate. The reason for this is that glutamate (a) is the most abundant amino acid in the brain, (b) is at the cross-roads between several metabolic pathways, and (c) serves as the major excitatory neurotransmitter. In fact most brain cells express glutamate receptors and are thereby influenced by extracellular glutamate. In agreement, brain cells have powerful uptake systems that constantly remove glutamate from the extracellular fluid and thereby limit receptor activation. It has been clear since the 1970s that both astrocytes and neurons express glutamate transporters. However the relative contribution of neuronal and glial transporters to the total glutamate uptake activity, however, as well as their functional importance, has been hotly debated ever since. The present short review provides (a) an overview of what we know about neuronal glutamate uptake as well as an historical description of how we got there, and (b) a hypothesis reconciling apparently contradicting observations thereby possibly resolving the paradox.
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Affiliation(s)
- N C Danbolt
- The Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
| | - D N Furness
- School of Life Sciences, Keele University, Keele, Staffs. ST5 5BG, UK
| | - Y Zhou
- The Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Reductions in hypothalamic Gfap expression, glial cells and α-tanycytes in lean and hypermetabolic Gnasxl-deficient mice. Mol Brain 2016; 9:39. [PMID: 27080240 PMCID: PMC4832494 DOI: 10.1186/s13041-016-0219-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 04/08/2016] [Indexed: 01/31/2023] Open
Abstract
Background Neuronal and glial differentiation in the murine hypothalamus is not complete at birth, but continues over the first two weeks postnatally. Nutritional status and Leptin deficiency can influence the maturation of neuronal projections and glial patterns, and hypothalamic gliosis occurs in mouse models of obesity. Gnasxl constitutes an alternative transcript of the genomically imprinted Gnas locus and encodes a variant of the signalling protein Gαs, termed XLαs, which is expressed in defined areas of the hypothalamus. Gnasxl-deficient mice show postnatal growth retardation and undernutrition, while surviving adults remain lean and hypermetabolic with increased sympathetic nervous system (SNS) activity. Effects of this knock-out on the hypothalamic neural network have not yet been investigated. Results RNAseq analysis for gene expression changes in hypothalami of Gnasxl-deficient mice indicated Glial fibrillary acid protein (Gfap) expression to be significantly down-regulated in adult samples. Histological analysis confirmed a reduction in Gfap-positive glial cell numbers specifically in the hypothalamus. This reduction was observed in adult tissue samples, whereas no difference was found in hypothalami of postnatal stages, indicating an adaptation in adult Gnasxl-deficient mice to their earlier growth phenotype and hypermetabolism. Especially noticeable was a loss of many Gfap-positive α-tanycytes and their processes, which form part of the ependymal layer that lines the medial and dorsal regions of the 3rd ventricle, while β-tanycytes along the median eminence (ME) and infundibular recesses appeared unaffected. This was accompanied by local reductions in Vimentin and Nestin expression. Hypothalamic RNA levels of glial solute transporters were unchanged, indicating a potential compensatory up-regulation in the remaining astrocytes and tanycytes. Conclusion Gnasxl deficiency does not directly affect glial development in the hypothalamus, since it is expressed in neurons, and Gfap-positive astrocytes and tanycytes appear normal during early postnatal stages. The loss of Gfap-expressing cells in adult hypothalami appears to be a consequence of the postnatal undernutrition, hypoglycaemia and continued hypermetabolism and leanness of Gnasxl-deficient mice, which contrasts with gliosis observed in obese mouse models. Since α-tanycytes also function as adult neural progenitor cells, these findings might indicate further developmental abnormalities in hypothalamic formations of Gnasxl-deficient mice, potentially including neuronal composition and projections. Electronic supplementary material The online version of this article (doi:10.1186/s13041-016-0219-1) contains supplementary material, which is available to authorized users.
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Goodman T, Hajihosseini MK. Hypothalamic tanycytes-masters and servants of metabolic, neuroendocrine, and neurogenic functions. Front Neurosci 2015; 9:387. [PMID: 26578855 PMCID: PMC4624852 DOI: 10.3389/fnins.2015.00387] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 10/05/2015] [Indexed: 11/13/2022] Open
Abstract
There is a resurgent interest in tanycytes, a radial glial-like cell population occupying the floor and ventro-lateral walls of the third ventricle (3V). Tanycytes reside in close proximity to hypothalamic neuronal nuclei that regulate appetite and energy expenditure, with a subset sending projections into these nuclei. Moreover, tanycytes are exposed to 3V cerebrospinal fluid and have privileged access to plasma metabolites and hormones, through fenestrated capillaries. Indeed, some tanycytes act as conduits for trafficking of these molecules into the brain parenchyma. Tanycytes can also act as neural stem/progenitor cells, supplying the postnatal and adult hypothalamus with new neurons. Collectively, these findings suggest that tanycytes regulate and integrate important trophic and metabolic processes and possibly endow functional malleability to neuronal circuits of the hypothalamus. Hence, manipulation of tanycyte biology could provide a valuable tool for modulating hypothalamic functions such as energy uptake and expenditure in order to tackle prevalent eating disorders such as obesity and anorexia.
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Affiliation(s)
- Timothy Goodman
- School of Biological Sciences, University of East Anglia Norwich, UK
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Yin W, Sun Z, Mendenhall JM, Walker DM, Riha PD, Bezner KS, Gore AC. Expression of Vesicular Glutamate Transporter 2 (vGluT2) on Large Dense-Core Vesicles within GnRH Neuroterminals of Aging Female Rats. PLoS One 2015; 10:e0129633. [PMID: 26053743 PMCID: PMC4459826 DOI: 10.1371/journal.pone.0129633] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/10/2015] [Indexed: 11/20/2022] Open
Abstract
The pulsatile release of GnRH is crucial for normal reproductive physiology across the life cycle, a process that is regulated by hypothalamic neurotransmitters. GnRH terminals co-express the vesicular glutamate transporter 2 (vGluT2) as a marker of a glutamatergic phenotype. The current study sought to elucidate the relationship between glutamate and GnRH nerve terminals in the median eminence—the site of GnRH release into the portal capillary vasculature. We also determined whether this co-expression may change during reproductive senescence, and if steroid hormones, which affect responsiveness of GnRH neurons to glutamate, may alter the co-expression pattern. Female Sprague-Dawley rats were ovariectomized at young adult, middle-aged and old ages (~4, 11, and 22 months, respectively) and treated four weeks later with sequential vehicle + vehicle (VEH + VEH), estradiol + vehicle (E2 + VEH), or estradiol + progesterone (E2+P4). Rats were perfused 24 hours after the second hormone treatment. Confocal microscopy was used to determine colocalization of GnRH and vGluT2 immunofluorescence in the median eminence. Post-embedding immunogold labeling of GnRH and vGluT2, and a serial electron microscopy (EM) technique were used to determine the cellular interaction between GnRH terminals and glutamate signaling. Confocal analysis showed that GnRH and vGluT2 immunofluorescent puncta were extensively colocalized in the median eminence and that their density declined with age but was unaffected by short-term hormone treatment. EM results showed that vGluT2 immunoreactivity was extensively associated with large dense-core vesicles, suggesting a unique glutamatergic signaling pathway in GnRH terminals. Our results provide novel subcellular information about the intimate relationship between GnRH terminals and glutamate in the median eminence.
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Affiliation(s)
- Weiling Yin
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Zengrong Sun
- School of Public Health, Tianjin Medical University, Tianjin, China
| | - John M. Mendenhall
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
| | - Deena M. Walker
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
| | - Penny D. Riha
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Kelsey S. Bezner
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Andrea C. Gore
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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Zhou Y, Danbolt NC. Glutamate as a neurotransmitter in the healthy brain. J Neural Transm (Vienna) 2014; 121:799-817. [PMID: 24578174 PMCID: PMC4133642 DOI: 10.1007/s00702-014-1180-8] [Citation(s) in RCA: 519] [Impact Index Per Article: 51.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 02/11/2014] [Indexed: 12/13/2022]
Abstract
Glutamate is the most abundant free amino acid in the brain and is at the crossroad between multiple metabolic pathways. Considering this, it was a surprise to discover that glutamate has excitatory effects on nerve cells, and that it can excite cells to their death in a process now referred to as "excitotoxicity". This effect is due to glutamate receptors present on the surface of brain cells. Powerful uptake systems (glutamate transporters) prevent excessive activation of these receptors by continuously removing glutamate from the extracellular fluid in the brain. Further, the blood-brain barrier shields the brain from glutamate in the blood. The highest concentrations of glutamate are found in synaptic vesicles in nerve terminals from where it can be released by exocytosis. In fact, glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. It took, however, a long time to realize that. The present review provides a brief historical description, gives a short overview of glutamate as a transmitter in the healthy brain, and comments on the so-called glutamate-glutamine cycle. The glutamate transporters responsible for the glutamate removal are described in some detail.
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Affiliation(s)
- Y. Zhou
- The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Blindern, P.O. Box 1105, 0317 Oslo, Norway
| | - N. C. Danbolt
- The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Blindern, P.O. Box 1105, 0317 Oslo, Norway
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Sharif A, Ojeda SR, Prevot V. Neurogenesis and Gliogenesis in the Postnatal Hypothalamus: A New Level of Plasticity for the Regulation of Hypothalamic Function? ENDOGENOUS STEM CELL-BASED BRAIN REMODELING IN MAMMALS 2014. [DOI: 10.1007/978-1-4899-7399-3_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Sauvageau M, Goff LA, Lodato S, Bonev B, Groff AF, Gerhardinger C, Sanchez-Gomez DB, Hacisuleyman E, Li E, Spence M, Liapis SC, Mallard W, Morse M, Swerdel MR, D'Ecclessis MF, Moore JC, Lai V, Gong G, Yancopoulos GD, Frendewey D, Kellis M, Hart RP, Valenzuela DM, Arlotta P, Rinn JL. Multiple knockout mouse models reveal lincRNAs are required for life and brain development. eLife 2013; 2:e01749. [PMID: 24381249 PMCID: PMC3874104 DOI: 10.7554/elife.01749] [Citation(s) in RCA: 534] [Impact Index Per Article: 48.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Many studies are uncovering functional roles for long noncoding RNAs (lncRNAs), yet few have been tested for in vivo relevance through genetic ablation in animal models. To investigate the functional relevance of lncRNAs in various physiological conditions, we have developed a collection of 18 lncRNA knockout strains in which the locus is maintained transcriptionally active. Initial characterization revealed peri- and postnatal lethal phenotypes in three mutant strains (Fendrr, Peril, and Mdgt), the latter two exhibiting incomplete penetrance and growth defects in survivors. We also report growth defects for two additional mutant strains (linc–Brn1b and linc–Pint). Further analysis revealed defects in lung, gastrointestinal tract, and heart in Fendrr−/− neonates, whereas linc–Brn1b−/− mutants displayed distinct abnormalities in the generation of upper layer II–IV neurons in the neocortex. This study demonstrates that lncRNAs play critical roles in vivo and provides a framework and impetus for future larger-scale functional investigation into the roles of lncRNA molecules. DOI:http://dx.doi.org/10.7554/eLife.01749.001 The mammalian genome is comprised of DNA sequences that contain the templates for proteins, and other DNA sequences that do not code for proteins. The coding DNA sequences are transcribed to make messenger RNA molecules, which are then translated to make proteins. Researchers have known for many years that some of the noncoding DNA sequences are also transcribed to make other types of RNA molecules, such as transfer and ribosomal RNA. However, the true breadth and diversity of the roles played by these other RNA molecules have only recently begun to be fully appreciated. Mammalian genomes contain thousands of noncoding DNA sequences that are transcribed. Recent in vitro studies suggest that the resulting long noncoding RNA molecules can act as regulators of transcription, translation, and cell cycle. In vitro studies also suggest that these long noncoding RNA molecules may play a role in mammalian development and disease. Yet few in vivo studies have been performed to support or confirm such hypotheses. Now Sauvageau et al. have developed several lines of knockout mice to investigate a subset of noncoding RNA molecules known as long intergenic noncoding RNAs (lincRNAs). These experiments reveal that lincRNAs have a strong influence on the overall viability of mice, and also on a number of developmental processes, including the development of lungs and the cerebral cortex. Given that the vast majority of the human genome is transcribed, the mouse models developed by Sauvageau et al. represent an important step in determining the physiological relevance, on a genetic level, of the noncoding portion of the genome in vivo. DOI:http://dx.doi.org/10.7554/eLife.01749.002
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Affiliation(s)
- Martin Sauvageau
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, United States
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Fgf10-expressing tanycytes add new neurons to the appetite/energy-balance regulating centers of the postnatal and adult hypothalamus. J Neurosci 2013; 33:6170-80. [PMID: 23554498 DOI: 10.1523/jneurosci.2437-12.2013] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Increasing evidence suggests that neurogenesis occurs in the postnatal and adult mammalian hypothalamus. However, the identity and location of the putative progenitor cells is under much debate, and little is known about the dynamics of neurogenesis in unchallenged brain. Previously, we postulated that Fibroblast growth factor 10-expressing (Fgf10(+)) tanycytes constitute a population of progenitor cells in the mouse hypothalamus. Here, we show that Fgf10(+) tanycytes express markers of neural stem/progenitor cells, divide late into postnatal life, and can generate both neurons and astrocytes in vivo. Stage-specific lineage-tracing of Fgf10(+) tanycytes using Fgf10-creERT2 mice, reveals robust neurogenesis at postnatal day 28 (P28), lasting as late as P60. Furthermore, we present evidence for amplification of Fgf10-lineage traced neural cells within the hypothalamic parenchyma itself. The neuronal descendants of Fgf10(+) tanycytes predominantly populate the arcuate nucleus, a subset of which express the orexigenic neuronal marker, Neuropeptide-Y, and respond to fasting and leptin-induced signaling. These studies provide direct evidence in support of hypothalamic neurogenesis during late postnatal and adult life, and identify Fgf10(+) tanycytes as a source of parenchymal neurons with putative roles in appetite and energy balance.
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García-Cáceres C, Fuente-Martín E, Argente J, Chowen JA. Emerging role of glial cells in the control of body weight. Mol Metab 2012; 1:37-46. [PMID: 24024117 DOI: 10.1016/j.molmet.2012.07.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 12/18/2022] Open
Abstract
Glia are the most abundant cell type in the brain and are indispensible for the normal execution of neuronal actions. They protect neurons from noxious insults and modulate synaptic transmission through affectation of synaptic inputs, release of glial transmitters and uptake of neurotransmitters from the synaptic cleft. They also transport nutrients and other circulating factors into the brain thus controlling the energy sources and signals reaching neurons. Moreover, glia express receptors for metabolic hormones, such as leptin and insulin, and can be activated in response to increased weight gain and dietary challenges. However, chronic glial activation can be detrimental to neurons, with hypothalamic astrocyte activation or gliosis suggested to be involved in the perpetuation of obesity and the onset of secondary complications. It is now accepted that glia may be a very important participant in metabolic control and a possible therapeutical target. Here we briefly review this rapidly advancing field.
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Affiliation(s)
- Cristina García-Cáceres
- Institute of Diabetes and Obesity, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Munich, Germany ; CIBER de Fisiopatología de Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain
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Nehmé B, Henry M, Mouginot D, Drolet G. The Expression Pattern of the Na(+) Sensor, Na(X) in the Hydromineral Homeostatic Network: A Comparative Study between the Rat and Mouse. Front Neuroanat 2012; 6:26. [PMID: 22833716 PMCID: PMC3400090 DOI: 10.3389/fnana.2012.00026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/21/2012] [Indexed: 12/19/2022] Open
Abstract
The Scn7a gene encodes for the specific sodium channel NaX, which is considered a primary determinant of sodium sensing in the brain. Only partial data exist describing the NaX distribution pattern and the cell types that express NaX in both the rat and mouse brain. To generate a global view of the sodium detection mechanisms in the two rodent brains, we combined NaX immunofluorescence with fluorescent cell markers to map and identify the NaX-expressing cell populations throughout the network involved in hydromineral homeostasis. Here, we designed an anti-NaX antibody targeting the interdomain 2–3 region of the NaX channel’s α-subunit. In both the rat and mouse, NaX immunostaining was colocalized with vimentin positive cells in the median eminence and with magnocellular neurons immunopositive for neurophysin associated with oxytocin or vasopressin in both the supraoptic and paraventricular nuclei. NaX immunostaining was also detected in neurons of the area postrema. In addition to this common NaX expression pattern, several differences in NaX immunostaining for certain structures and cell types were found between the rat and mouse. NaX was present in both NeuN and vimentin positive cells in the subfornical organ and the vascular organ of the lamina terminalis of the rat whereas NaX was only colocalized with vimentin positive cells in the mouse circumventricular organs. In addition, NaX immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat. Overall, this study characterized the NaX-expressing cell types in the network controlling hydromineral homeostasis of the rat and mouse. NaX expression pattern was clearly different in the nuclei of the lamina terminalis of the rat and mouse, indicating that the mechanisms involved in systemic and central Na+ sensing are specific to each rodent species.
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Affiliation(s)
- Benjamin Nehmé
- Axe Neurosciences du CRCHUQ (CHUL), Faculté de Médecine, Université Laval Québec, QC, Canada
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Nakahara K, Takata S, Ishii A, Nagao K, Bannai M, Takahashi M, Murakami N. Somatostatin is involved in anorexia in mice fed a valine-deficient diet. Amino Acids 2012; 42:1397-404. [PMID: 21293891 DOI: 10.1007/s00726-011-0836-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 01/14/2011] [Indexed: 10/18/2022]
Abstract
The ingestion of a valine (Val)-deficient diet results in a significant reduction of food intake and body weight within 24 h, and this phenomenon continues throughout the period over which such a diet is supplied. Both microarray and real-time PCR analyses revealed that the expression of somatostatin mRNA was increased in the hypothalamus in anorectic mice that received a Val-deficient diet. On the other hand, when somatostatin was administered intracerebroventricularly to intact animals that were fed a control diet, their 24-h food intake decreased significantly. In addition, Val-deficient but not pair-fed mice or those fasted for 24 h showed a less than 0.5-fold decrease in the hypothalamic mRNA expression levels of Crym, Foxg1, Itpka and two unknown EST clone genes and a more than twofold increase in those of Slc6a3, Bdh1, Ptgr2 and one unknown EST clone gene. These results suggest that hypothalamic somatostatin and genes responsive to Val deficiency may be involved in the central mechanism of anorexia induced by a Val-deficient diet.
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Affiliation(s)
- Keiko Nakahara
- Department of Veterinary Physiology, Faculty of Agriculture, University of Miyazaki, Miyazaki, 889-2192, Japan
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30
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Nilaweera K, Herwig A, Bolborea M, Campbell G, Mayer CD, Morgan PJ, Ebling FJP, Barrett P. Photoperiodic regulation of glycogen metabolism, glycolysis, and glutamine synthesis in tanycytes of the Siberian hamster suggests novel roles of tanycytes in hypothalamic function. Glia 2011; 59:1695-705. [DOI: 10.1002/glia.21216] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 06/16/2011] [Indexed: 12/27/2022]
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Zhou J, Pan J, Eckardt S, Leu NA, McLaughlin KJ, Wang PJ. Nxf3 is expressed in Sertoli cells, but is dispensable for spermatogenesis. Mol Reprod Dev 2011; 78:241-9. [PMID: 21308854 DOI: 10.1002/mrd.21291] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 01/17/2011] [Indexed: 02/03/2023]
Abstract
In eukaryotes, mRNA is actively exported to the cytoplasm by a family of nuclear RNA export factors (NXF). Four Nxf genes have been identified in the mouse: Nxf1, Nxf2, Nxf3, and Nxf7. Inactivation of Nxf2, a germ cell-specific gene, causes defects in spermatogenesis. Here we report that Nxf3 is expressed exclusively in Sertoli cells of the postnatal testis, in a developmentally regulated manner. Expression of Nxf3 coincides with the cessation of Sertoli cell proliferation and the beginning of their differentiation. Continued expression of Nxf3 in mature Sertoli cells of the adult is spermatogenesis stage-independent. Nxf3 is not essential for spermatogenesis, however, suggesting functional redundancy among Nxf family members. With its unique expression pattern in the testis, the promoter of Nxf3 can be used to drive postnatal Sertoli cell-specific expression of other proteins such as Cre recombinase.
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Affiliation(s)
- Jian Zhou
- Department of Animal Biology, Center for Animal Transgenesis and Germ Cell Research, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104, USA
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32
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Pérez-Martín M, Cifuentes M, Grondona JM, López-Avalos MD, Gómez-Pinedo U, García-Verdugo JM, Fernández-Llebrez P. IGF-I stimulates neurogenesis in the hypothalamus of adult rats. Eur J Neurosci 2010; 31:1533-48. [PMID: 20525067 DOI: 10.1111/j.1460-9568.2010.07220.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the brain of adult rats neurogenesis persists in the subventricular zone of the lateral ventricles and in the dentate gyrus of the hippocampus. By contrast, low proliferative activity was observed in the hypothalamus. We report here that, after intracerebroventricular treatment with insulin-like growth factor I (IGF-I), cell proliferation significantly increased in both the periventricular and the parenchymal zones of the whole hypothalamus. Neurons, astrocytes, tanycytes, microglia and endothelial cells of the local vessels were stained with the proliferative marker 5-bromo-2'-deoxyuridine (BrdU) in response to IGF-I. Conversely, we never observed BrdU-positive ciliated cubic ependymal cells. Proliferation was intense in the subventricular area of a distinct zone of the mid third ventricle wall limited dorsally by ciliated cubic ependyma and ventrally by tanycytic ependyma. In this area, we saw a characteristic cluster of proliferating cells. This zone of the ventricular wall displayed three cell layers: ciliated ependyma, subependyma and underlying tanycytes. After IGF-I treatment, proliferating cells were seen in the subependyma and in the layer of tanycytes. In the subependyma, proliferating glial fibrillary acidic protein-positive astrocytes contacted the ventricle by an apical process bearing a single cilium and there were many labyrinthine extensions of the periventricular basement membranes. Both features are typical of neurogenic niches in other brain zones, suggesting that the central overlapping zone of the rat hypothalamic wall could be considered a neurogenic niche in response to IGF-I.
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Affiliation(s)
- M Pérez-Martín
- Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
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Xu B, Yang L, Lye RJ, Hinton BT. p-MAPK1/3 and DUSP6 regulate epididymal cell proliferation and survival in a region-specific manner in mice. Biol Reprod 2010; 83:807-17. [PMID: 20650883 DOI: 10.1095/biolreprod.110.085613] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A fully developed, functional epididymis is important for male fertility. In particular, it is apparent that without the most proximal region, the initial segment (IS), infertility results. Therefore, it is important to understand the development and regulation of this crucial epididymal region. We have previously shown that many functions of the IS are regulated by luminal fluid factors/lumicrine factors from the testis. This study provides evidence that lumicrine factors activated the ERK pathway only in epithelial cells of the IS from Postnatal Day (P) 14 to P19 and sustained this activation into adulthood. The activated ERK pathway promoted cell proliferation and differentiation in the developing IS, although in the adult, its role was switched to maintain cell survival. To understand further the regulation of cell proliferation in the IS, we examined the role of DUSP6, an MAPK1/3 (ERK1/2) preferred phosphatase that is also regulated by lumicrine factors in the IS. Utilizing Dusp6(-/-) mice, our studies, surprisingly, revealed that Dusp6 was a major regulator of cell proliferation in the caput and corpus regions, whereas components of the ERK pathway, together with PTEN and SRC, were the major regulators of cell proliferation in the IS. We hypothesize that region-specific regulation of cell proliferation is caused by differences in the balance of activities between pro- and antiproliferation signaling pathway components for each epididymal region. An understanding of the mechanisms of cell proliferation may provide clues as to why the epididymis rarely succumbs to cancer.
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Affiliation(s)
- Bingfang Xu
- Department of Cell Biology, University of Virginia Health System, Charlottesville, Virginia 22908, USA
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Levin BE. Developmental gene x environment interactions affecting systems regulating energy homeostasis and obesity. Front Neuroendocrinol 2010; 31:270-83. [PMID: 20206200 PMCID: PMC2903638 DOI: 10.1016/j.yfrne.2010.02.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 02/25/2010] [Accepted: 02/25/2010] [Indexed: 11/25/2022]
Abstract
Most human obesity is inherited as a polygenic trait which is largely refractory to medical therapy because obese individuals avidly defend their elevated body weight set-point. This set-point is mediated by an integrated neural network that controls energy homeostasis. Epidemiological studies suggest that perinatal and pre-pubertal environmental factors can promote offspring obesity. Rodent studies demonstrate the important interactions between genetic predisposition and environmental factors in promoting obesity. This review covers issues of development and function of neural systems involved in the regulation of energy homeostasis and the roles of leptin and insulin in these processes, the ways in which interventions at various phases from gestation, lactation and pre-pubertal stages of development can favorably and unfavorably alter the development of obesity n offspring. These studies suggest that early identification of obesity-prone humans and of the factors that can prevent them from becoming obese could provide an effective strategy for preventing the world-wide epidemic of obesity.
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Affiliation(s)
- Barry E Levin
- Neurology Service, VA Medical Center, E. Orange, NJ 07018-1095, USA.
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Lima SS, Lima dos Santos MC, Sinder MP, Moura AS, Barradas PC, Tenório F. Glycogen stores are impaired in hypothalamic nuclei of rats malnourished during early life. Nutr Neurosci 2010; 13:21-8. [PMID: 20132651 DOI: 10.1179/147683010x12611460763805] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Perinatal nutrition has persistent influences on neural development and cognition. In humans and other animals, protein malnutrition during the perinatal period causes permanent changes, inducing to adulthood metabolic syndrome. Feeding is mainly modulated by neural and hormonal inputs to the hypothalamus. Hypothalamic glycogen stores are a source of glucose in high energetic demands, as during development of neural circuits. As some hypothalamic circuits are formed during lactation, we studied the effects of malnutrition, during the first 10 days of lactation, on glycogen stores in hypothalamic nuclei involved in the control of energy metabolism. Female pregnant rats were fed ad libitum with a normal protein diet (22% protein). After delivery, each dam was kept with 6 male pups. During the first 10 days of lactation, dams from the experimental group received a protein-free diet and the control group a normoprotein diet. By post-natal day 10 (P10), glycogen stores were very high in the arcuate nucleus and median eminence of control group. Glycogen stores decreased during development. In P20 control animals, glycogen stores were lower when compared to P10 control animals. Animals submitted to malnutrition presented a staining even lower than control ones. After P45, it was difficult to determine differences between control and diet groups because glycogen stores were reduced. We also showed that tanycytes were the cells presenting glycogen stores. Our data reinforce the concept that maternal nutritional state during lactation may be critical for neurodevelopment since it resulted in a low hypothalamic glycogen store, which may be critical for establishment of neuronal circuitry.
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Affiliation(s)
- S S Lima
- Departamento de Farmacologia e Psicobiologia, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brasil
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36
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Rodríguez EM, Blázquez JL, Guerra M. The design of barriers in the hypothalamus allows the median eminence and the arcuate nucleus to enjoy private milieus: the former opens to the portal blood and the latter to the cerebrospinal fluid. Peptides 2010; 31:757-76. [PMID: 20093161 DOI: 10.1016/j.peptides.2010.01.003] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 01/09/2010] [Accepted: 01/10/2010] [Indexed: 11/20/2022]
Abstract
The blood-brain barrier (BBB) is a single uninterrupted barrier that in the brain capillaries is located at the endothelial cells and in the circumventricular organs, such as the choroid plexuses (CP) and median eminence (ME), is displaced to specialized ependymal cells. How do hypothalamic hormones reach the portal circulation without making the BBB leaky? The ME milieu is open to the portal vessels, while it is closed to the cerebrospinal fluid (CSF) and to the arcuate nucleus. The cell body and most of the axons of neurons projecting to the ME are localized in areas protected by the BBB, while the axon terminals are localized in the BBB-free area of the ME. This design implies a complex organization of the intercellular space of the median basal hypothalamus. The privacy of the ME milieu implies that those neurons projecting to this area would not be under the influence of compounds leaking from the portal capillaries, unless receptors for such compounds are located at the axon terminal. Amazingly, the arcuate nucleus also has its private milieu that is closed to all adjacent neural structures and open to the infundibular recess. The absence of multiciliated cells in this recess should result in a slow CSF flow at this level. This whole arrangement should facilitate the arrival of CSF signal to the arcuate nucleus. This review will show how peripheral hormones can reach hypothalamic targets without making the BBB leaky.
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Affiliation(s)
- Esteban M Rodríguez
- Facultad de Medicina, Instituto de Anatomía, Histología y Patología, Universidad Austral de Chile, Valdivia, Chile.
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37
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Shen J, Gilmore EC, Marshall CA, Haddadin M, Reynolds JJ, Eyaid W, Bodell A, Allen K, Chang BS, Grix A, Hill RS, Topcu M, Caldecott KW, Barkovich AJ, Walsh CA. Mutations in PNKP cause microcephaly, seizures and defects in DNA repair. Nat Genet 2010; 42:245-9. [PMID: 20118933 PMCID: PMC2835984 DOI: 10.1038/ng.526] [Citation(s) in RCA: 211] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Accepted: 12/23/2009] [Indexed: 12/18/2022]
Abstract
Maintenance of DNA integrity is crucial for all cell types, but neurons are particularly sensitive to mutations in DNA repair genes, which lead to both abnormal development and neurodegeneration. We describe a previously unknown autosomal recessive disease characterized by microcephaly, early-onset, intractable seizures and developmental delay (denoted MCSZ). Using genome-wide linkage analysis in consanguineous families, we mapped the disease locus to chromosome 19q13.33 and identified multiple mutations in PNKP (polynucleotide kinase 3'-phosphatase) that result in severe neurological disease; in contrast, a splicing mutation is associated with more moderate symptoms. Unexpectedly, although the cells of individuals carrying this mutation are sensitive to radiation and other DNA-damaging agents, no such individual has yet developed cancer or immunodeficiency. Unlike other DNA repair defects that affect humans, PNKP mutations universally cause severe seizures. The neurological abnormalities in individuals with MCSZ may reflect a role for PNKP in several DNA repair pathways.
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Affiliation(s)
- Jun Shen
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | - Edward C. Gilmore
- Division of Genetics and The Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
- Division of Child Neurology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Christine A. Marshall
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | - Mary Haddadin
- Department of Pathology, Cytogenetics Laboratory, Al-Bashir Hospital, Ministry of Health, Amman, Jordan
| | - John J. Reynolds
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, BN1 9RQ, UK
| | - Wafaa Eyaid
- Genetics & Endocrinology, Department of Pediatrics Mail Code 1510, King Fahad National Guard Hospital, King Abdul Aziz Medical City, Saudi Arabia
| | - Adria Bodell
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
- Division of Genetics and The Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
| | - Kathryn Allen
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | - Bernard S. Chang
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | - Arthur Grix
- Department of Medical Genetics, Kaiser-Permanente Point West Medical Offices, Sacramento, USA
| | - R. Sean Hill
- Division of Genetics and The Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
| | - Meral Topcu
- Hacettepe University, Medical Faculty, Ihsan Dogramaci Children's Hospital, Department of Pediatrics, Section of Pediatric Neurology, Sihhiye 06100, Ankara, Turkey
| | - Keith W. Caldecott
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, BN1 9RQ, UK
| | - A. James Barkovich
- Department of Radiology, Department of Neurology, and Department of Pediatrics, University of California at San Francisco, San Francisco, CA 94143-0628, USA
| | - Christopher A. Walsh
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
- Division of Genetics and The Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA 02142, USA
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38
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Mutations in the formin gene INF2 cause focal segmental glomerulosclerosis. Nat Genet 2009; 42:72-6. [PMID: 20023659 PMCID: PMC2980844 DOI: 10.1038/ng.505] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 11/16/2009] [Indexed: 01/11/2023]
Abstract
Focal segmental glomerulosclerosis (FSGS) is a pattern of kidney injury observed either as an idiopathic finding or as a consequence of underlying systemic conditions. Several genes have been identified which, when mutated, lead to inherited FSGS and/or the nephrotic syndrome. These findings have accelerated the understanding of glomerular podocyte function and disease, motivating our search for additional FSGS genes. Using linkage analysis, we identified a locus for autosomal dominant FSGS on a region of chromosome 14q. By sequencing multiple genes in this region, we detected nine independent non-conservative missense mutations in INF2, which encodes a member of the formin family of actin regulating proteins. These mutations, all within the diaphanous inhibitory domain, segregate with disease in 11 unrelated families and alter highly conserved amino acid residues. The observation that mutations in this podocyte-expressed formin cause FSGS highlights the importance of fine regulation of actin polymerization in podocyte function.
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Goto S, Nagao K, Bannai M, Takahashi M, Nakahara K, Kangawa K, Murakami N. Anorexia in rats caused by a valine-deficient diet is not ameliorated by systemic ghrelin treatment. Neuroscience 2009; 166:333-40. [PMID: 20006681 DOI: 10.1016/j.neuroscience.2009.12.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 11/26/2009] [Accepted: 12/04/2009] [Indexed: 11/28/2022]
Abstract
Rodents exhibit aversive behavior toward a diet that lacks at least one of the essential amino acids. We sought to determine whether the particular form of anorexia caused by such diets could be ameliorated by the administration of orexigenic peptides while simultaneously analyzing the neural mechanisms underlying anorexia. Rats were fed a valine-deficient diet, which induced severe anorexia (reducing food consumption by 80%). The severe anorexia was associated with a significant decrease in the cerebrospinal fluid valine concentration and hyper-ghrelinemia. Between 6 and 12 days after initiation of the valine-deficient diet, we injected rats twice daily with valine and/or an orexigenic peptide (ghrelin, neuropeptide Y, or agouti-related protein) either i.p. or i.c.v.. We then measured dietary intake. An i.c.v. valine injection allowed earlier food intake compared with an i.p valine injection and increased the density of c-Fos-positive ependymal cells lining the third ventricle. Whereas an i.c.v. injection of ghrelin or neuropeptide Y increased consumption of the valine-deficient diet, i.p injection of ghrelin or i.c.v. injection of agouti-related protein did not. Following i.c.v. administration of either valine or ghrelin, we did not observe complete recovery of consumption of the valine-deficient diet. This may be due to the ineffectiveness of peripheral ghrelin and central agouti-related protein and/or to conditioned aversion to the valine-deficient diet. Since ghrelin is known to be involved in food anticipatory activities, whether the hyper-ghrelinemia observed in valine-deficient rats play role in foraging behavior other than food intake is the future study to be investigated.
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Affiliation(s)
- S Goto
- Department of Veterinary Physiology, Miyazaki University, Miyazaki, Miyazaki 889-2192, Japan
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40
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Mochida GH, Mahajnah M, Hill AD, Basel-Vanagaite L, Gleason D, Hill RS, Bodell A, Crosier M, Straussberg R, Walsh CA. A truncating mutation of TRAPPC9 is associated with autosomal-recessive intellectual disability and postnatal microcephaly. Am J Hum Genet 2009; 85:897-902. [PMID: 20004763 PMCID: PMC2790576 DOI: 10.1016/j.ajhg.2009.10.027] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2009] [Revised: 10/22/2009] [Accepted: 10/26/2009] [Indexed: 12/25/2022] Open
Abstract
Although autosomal genes are increasingly recognized as important causes of intellectual disability, very few of them are known. We identified a genetic locus for autosomal-recessive nonsyndromic intellectual disability associated with variable postnatal microcephaly through homozygosity mapping of a consanguineous Israeli Arab family. Sequence analysis of genes in the candidate interval identified a nonsense nucleotide change in the gene that encodes TRAPPC9 (trafficking protein particle complex 9, also known as NIBP), which has been implicated in NF-kappaB activation and possibly in intracellular protein trafficking. TRAPPC9 is highly expressed in the postmitotic neurons of the cerebral cortex, and MRI analysis of affected patients shows defects in axonal connectivity. This suggests essential roles of TRAPPC9 in human brain development, possibly through its effect on NF-kappaB activation and protein trafficking in the postmitotic neurons of the cerebral cortex.
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Affiliation(s)
- Ganeshwaran H. Mochida
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Division of Genetics and Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Boston, MA 02115, USA
- Pediatric Neurology Unit, Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Muhammad Mahajnah
- Pediatric Neurology and Child Developmental Center, Hillel Yaffe Medical Center, Hadera 38100, Israel
- Rappaport Faculty of Medicine, The Technion, Haifa 31096, Israel
| | - Anthony D. Hill
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Lina Basel-Vanagaite
- Department of Medical Genetics, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel
- Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva 49202, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Danielle Gleason
- Division of Genetics and Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Boston, MA 02115, USA
| | - R. Sean Hill
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Adria Bodell
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Moira Crosier
- MRC-Wellcome Trust Human Developmental Biology Resource (Newcastle), Institute of Human Genetics, Newcastle University, International Centre for Life, Newcastle upon Tyne NE1 3BZ, UK
| | - Rachel Straussberg
- Neurogenetic Clinic, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Christopher A. Walsh
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
- Division of Genetics and Manton Center for Orphan Disease Research, Department of Medicine, Children's Hospital Boston, Boston, MA 02115, USA
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Novel subtype-specific genes identify distinct subpopulations of callosal projection neurons. J Neurosci 2009; 29:12343-54. [PMID: 19793993 DOI: 10.1523/jneurosci.6108-08.2009] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Little is known about the molecular development and heterogeneity of callosal projection neurons (CPN), cortical commissural neurons that connect homotopic regions of the two cerebral hemispheres via the corpus callosum and that are critical for bilateral integration of cortical information. Here we report on the identification of a series of genes that individually and in combination define CPN and novel CPN subpopulations during embryonic and postnatal development. We used in situ hybridization analysis, immunocytochemistry, and retrograde labeling to define the layer-specific and neuron-type-specific distribution of these newly identified CPN genes across different stages of maturation. We demonstrate that a subset of these genes (e.g., Hspb3 and Lpl) appear specific to all CPN (in layers II/III and V-VI), whereas others (e.g., Nectin-3, Plexin-D1, and Dkk3) discriminate between CPN of the deep layers and those of the upper layers. Furthermore, the data show that several genes finely subdivide CPN within individual layers and appear to label CPN subpopulations that have not been described previously using anatomical or morphological criteria. The genes identified here likely reflect the existence of distinct programs of gene expression governing the development, maturation, and function of the newly identified subpopulations of CPN. Together, these data define the first set of genes that identify and molecularly subcategorize distinct populations of callosal projection neurons, often located in distinct subdivisions of the canonical cortical laminae.
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Peschansky VJ, Burbridge TJ, Volz AJ, Fiondella C, Wissner-Gross Z, Galaburda AM, Lo Turco JJ, Rosen GD. The effect of variation in expression of the candidate dyslexia susceptibility gene homolog Kiaa0319 on neuronal migration and dendritic morphology in the rat. ACTA ACUST UNITED AC 2009; 20:884-97. [PMID: 19679544 DOI: 10.1093/cercor/bhp154] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We investigated the postnatal effects of embryonic knockdown and overexpression of the candidate dyslexia gene homolog Kiaa0319. We used in utero electroporation to transfect cells in E15/16 rat neocortical ventricular zone with either 1) small hairpin RNA (shRNA) vectors targeting Kiaa0319, 2) a KIAA0319 expression construct, 3) Kiaa0319 shRNA along with KIAA0319 expression construct ("rescue"), or 4) a scrambled version of Kiaa0319 shRNA. Knockdown, but not overexpression, of Kiaa0319 resulted in periventricular heterotopias that contained large numbers of both transfected and non-transfected neurons. This suggested that Kiaa0319 shRNA disrupts neuronal migration by cell autonomous as well as non-cell autonomous mechanisms. Of the Kiaa0319 shRNA-transfected neurons that migrated into the cortical plate, most migrated to their appropriate lamina. In contrast, neurons transfected with the KIAA0319 expression vector attained laminar positions subjacent to their expected positions. Neurons transfected with Kiaa0319 shRNA exhibited apical, but not basal, dendrite hypertrophy, which was rescued by overexpression of KIAA0319. The results provide additional supportive evidence linking candidate dyslexia susceptibility genes to migrational disturbances during brain development, and extends the role of Kiaa0319 to include growth and differentiation of dendrites.
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Affiliation(s)
- Veronica J Peschansky
- The Dyslexia Research Laboratory, Division of Behavioral Neurology, Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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Massie A, Cnops L, Smolders I, McCullumsmith R, Kooijman R, Kwak S, Arckens L, Michotte Y. High-affinity Na+/K+-dependent glutamate transporter EAAT4 is expressed throughout the rat fore- and midbrain. J Comp Neurol 2008; 511:155-72. [DOI: 10.1002/cne.21823] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Yano K, Okada Y, Beldi G, Shih SC, Bodyak N, Okada H, Kang PM, Luscinskas W, Robson SC, Carmeliet P, Karumanchi SA, Aird WC. Elevated levels of placental growth factor represent an adaptive host response in sepsis. ACTA ACUST UNITED AC 2008; 205:2623-31. [PMID: 18852292 PMCID: PMC2571936 DOI: 10.1084/jem.20080398] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recently, we demonstrated that circulating levels of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are increased in sepsis (Yano, K., P.C. Liaw, J.M. Mullington, S.C. Shih, H. Okada, N. Bodyak, P.M. Kang, L. Toltl, B. Belikoff, J. Buras, et al. 2006. J. Exp. Med. 203:1447–1458). Moreover, enhanced VEGF/Flk-1 signaling was shown to contribute to sepsis morbidity and mortality. We tested the hypothesis that PlGF also contributes to sepsis outcome. In mouse models of endotoxemia and cecal ligation puncture, the genetic absence of PlGF or the systemic administration of neutralizing anti-PlGF antibodies resulted in higher mortality compared with wild-type or immunoglobulin G–injected controls, respectively. The increased mortality associated with genetic deficiency of PlGF was reversed by adenovirus (Ad)-mediated overexpression of PlGF. In the endotoxemia model, PlGF deficiency was associated with elevated circulating levels of VEGF, induction of VEGF expression in the liver, impaired cardiac function, and organ-specific accentuation of barrier dysfunction and inflammation. Mortality of endotoxemic PlGF-deficient mice was increased by Ad-mediated overexpression of VEGF and was blocked by expression of soluble Flt-1. Collectively, these data suggest that up-regulation of PlGF in sepsis is an adaptive host response that exerts its benefit, at least in part, by attenuating VEGF signaling.
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Affiliation(s)
- Kiichiro Yano
- The Center for Vascular Biology Research and Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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Majumdar D, Maunsbach AB, Shacka JJ, Williams JB, Berger UV, Schultz KP, Harkins LE, Boron WF, Roth KA, Bevensee MO. Localization of electrogenic Na/bicarbonate cotransporter NBCe1 variants in rat brain. Neuroscience 2008; 155:818-32. [PMID: 18582537 DOI: 10.1016/j.neuroscience.2008.05.037] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 05/16/2008] [Accepted: 05/20/2008] [Indexed: 10/22/2022]
Abstract
The activity of HCO(3)(-) transporters contributes to the acid-base environment of the nervous system. In the present study, we used in situ hybridization, immunoblotting, immunohistochemistry, and immunogold electron microscopy to localize electrogenic Na/bicarbonate cotransporter NBCe1 splice variants (-A, -B, and -C) in rat brain. The in situ hybridization data are consistent with NBCe1-B and -C, but not -A, being the predominant NBCe1 variants in brain, particularly in the cerebellum, hippocampus, piriform cortex, and olfactory bulb. An antisense probe to the B and C variants strongly labeled granule neurons in the dentate gyrus of the hippocampus, and cells in the granule layer and Purkinje layer (e.g. Bergmann glia) of the cerebellum. Weaker labeling was observed in the pyramidal layer of the hippocampus and in astrocytes throughout the brain. Similar, but weaker labeling was obtained with an antisense probe to the A and B variants. In immunoblot studies, antibodies to the A and B variants (alphaA/B) and C variant (alphaC) labeled approximately 130-kDa proteins in various brain regions. From immunohistochemistry data, both alphaA/B and alphaC exhibited diffuse labeling throughout brain, but alphaA/B labeling was more intracellular and punctate. Based on co-localization studies with antibodies to neuronal or astrocytic markers, alphaA/B labeled neurons in the pyramidal layer and dentate gyrus of the hippocampus, as well as cortex. alphaC labeled glia surrounding neurons (and possibly neurons) in the neuropil of the Purkinje cell layer of the cerebellum, the pyramidal cell layer and dentate gyrus of the hippocampus, and the cortex. According to electron microscopy data from the cerebellum, alphaA/B primarily labeled neurons intracellularly and alphaC labeled astrocytes at the plasma membrane. In summary, the B and C variants are the predominant NBCe1 variants in rat brain and exhibit different localization profiles.
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Affiliation(s)
- D Majumdar
- Department of Physiology and Biophysics, University of Alabama at Birmingham, 1918 University Boulevard, 812 MCLM, Birmingham, AL 35294, USA
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Abstract
L-glutamate, the main excitatory neurotransmitter, influences virtually all neurones of the neuroendocrine hypothalamus via synaptic mechanisms. Vesicular glutamate transporters (VGLUT1-3), which selectively accumulate L-glutamate into synaptic vesicles, provide markers with which to visualise glutamatergic neurones in histological preparations; excitatory neurones in the endocrine hypothalamus synthesise the VGLUT2 isoform. Results of recent dual-label in situ hybridisation studies indicate that glutamatergic neurones in the preoptic area and the hypothalamic paraventricular, supraoptic and periventricular nuclei include parvocellular and magnocellular neurosecretory neurones which secrete peptide neurohormones into the bloodstream to regulate endocrine functions. Neurosecretory terminals of GnRH, TRH, CRF-, somatostatin-, oxytocin- and vasopressin-secreting neurones contain VGLUT2 immunoreactivity, suggesting the co-release of glutamate with hypophysiotrophic peptides. The presence of VGLUT2 also indicates glutamate secretion from non-neuronal endocrine cells, including gonadotrophs and thyrotrophs of the anterior pituitary. Results of in vitro studies show that ionotropic glutamate receptor analogues can elicit hormone secretion at neuroendocrine/endocrine release sites. Structural constituents of the median eminence, adenohypophysis and neurohypophysis contain elements of glutamatergic transmission, including glutamate receptors and enzymes of the glutamate/glutamine cycle. The synthesis of VGLUT2 exhibits robust up-regulation in response to certain endocrine challenges, indicating that altered glutamatergic signalling may represent an important adaptive mechanism. This review article discusses the newly emerged non-synaptic role of glutamate in neuroendocrine and endocrine communication.
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Affiliation(s)
- E Hrabovszky
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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Melanin-concentrating hormone (MCH) immunoreactivity in non-neuronal cells within the raphe nuclei and subventricular region of the brainstem of the cat. Brain Res 2008; 1210:163-78. [PMID: 18410908 DOI: 10.1016/j.brainres.2008.02.104] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 01/31/2008] [Accepted: 02/29/2008] [Indexed: 11/22/2022]
Abstract
Neurons that utilize melanin-concentrating hormone (MCH) as a neuromodulator are localized within the postero-lateral hypothalamus and zona incerta. These neurons project diffusely throughout the central nervous system and have been implicated in critical physiological processes such as energy homeostasis and sleep. In the present report, we examined the distribution of MCH immunoreactivity in the brainstem of the cat. In addition to MCH+ axons, we found MCH-immunoreactive cells that have not been previously described either in the midbrain raphe nuclei or in the periaqueductal and periventricular areas. These MCH+ cells constituted: 1. ependymal cells that lined the fourth ventricle and aqueduct, 2. ependymal cells with long basal processes that projected deeply into the subventricular (subaqueductal) parenchyma, and, 3. cells in subventricular regions and the midbrain raphe nuclei. The MCH+ cells in the midbrain raphe nuclei were closely related to neuronal processes of serotonergic neurons. Utilizing Neu-N and GFAP immunohistochemistry we determined that the preceding MCH+ cells were neither neurons nor astrocytes. However, we found that vimentin, an intermediate-filament protein that is used as a marker for tanycytes, was specifically co-localized with MCH in these cells. We conclude that MCH is present in tanycytes whose processes innervate the midbrain raphe nuclei and adjacent subependymal regions. Because tanycytes are specialized cells that transport substances from the cerebrospinal fluid (CSF) to neural parenchyma, we suggest that MCH is absorbed from the CSF by tanycytes and subsequently liberate to act upon neurons of brainstem nuclei.
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Ctip2 controls the differentiation of medium spiny neurons and the establishment of the cellular architecture of the striatum. J Neurosci 2008; 28:622-32. [PMID: 18199763 DOI: 10.1523/jneurosci.2986-07.2008] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Striatal medium spiny neurons (MSN) are critically involved in motor control, and their degeneration is a principal component of Huntington's disease. We find that the transcription factor Ctip2 (also known as Bcl11b) is central to MSN differentiation and striatal development. Within the striatum, it is expressed by all MSN, although it is excluded from essentially all striatal interneurons. In the absence of Ctip2, MSN do not fully differentiate, as demonstrated by dramatically reduced expression of a large number of MSN markers, including DARPP-32, FOXP1, Chrm4, Reelin, MOR1 (mu-opioid receptor 1), glutamate receptor 1, and Plexin-D1. Furthermore, MSN fail to aggregate into patches, resulting in severely disrupted patch-matrix organization within the striatum. Finally, heterotopic cellular aggregates invade the Ctip2-/- striatum, suggesting a failure by MSN to repel these cells in the absence of Ctip2. This is associated with abnormal dopaminergic innervation of the mutant striatum and dramatic changes in gene expression, including dysregulation of molecules involved in cellular repulsion. Together, these data indicate that Ctip2 is a critical regulator of MSN differentiation, striatal patch development, and the establishment of the cellular architecture of the striatum.
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Burbridge TJ, Wang Y, Volz AJ, Peschansky VJ, Lisann L, Galaburda AM, Lo Turco JJ, Rosen GD. Postnatal analysis of the effect of embryonic knockdown and overexpression of candidate dyslexia susceptibility gene homolog Dcdc2 in the rat. Neuroscience 2008; 152:723-33. [PMID: 18313856 DOI: 10.1016/j.neuroscience.2008.01.020] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 01/03/2008] [Accepted: 01/07/2008] [Indexed: 12/13/2022]
Abstract
Embryonic knockdown of candidate dyslexia susceptibility gene (CDSG) homologs in cerebral cortical progenitor cells in the rat results in acute disturbances of neocortical migration. In the current report we investigated the effects of embryonic knockdown and overexpression of the homolog of DCDC2, one of the CDSGs, on the postnatal organization of the cerebral cortex. Using a within-litter design, we transfected cells in rat embryo neocortical ventricular zone around embryonic day (E) 15 with either 1) small hairpin RNA (shRNA) vectors targeting Dcdc2, 2) a DCDC2 overexpression construct, 3) Dcdc2 shRNA along with DCDC2 overexpression construct, 4) an overexpression construct composed of the C terminal domain of DCDC2, or 5) an overexpression construct composed of the DCX terminal domain of DCDC2. RNAi of Dcdc2 resulted in pockets of heterotopic neurons in the periventricular region. Approximately 25% of the transfected brains had hippocampal pyramidal cell migration anomalies. Dcdc2 shRNA-transfected neurons migrated in a bimodal pattern, with approximately 7% of the neurons migrating a short distance from the ventricular zone, and another 30% migrating past their expected lamina. Rats transfected with Dcdc2 shRNA along with the DCDC2 overexpression construct rescued the periventricular heterotopia phenotype, but did not affect the percentage of transfected neurons that migrate past their expected laminar location. There were no malformations associated with any of the overexpression constructs, nor was there a significant laminar disruption of migration. These results support the claim that knockdown of Dcdc2 expression results in neuronal migration disorders similar to those seen in the brains of dyslexics.
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Affiliation(s)
- T J Burbridge
- The Dyslexia Research Laboratory, Division of Behavioral Neurology, Department of Neurology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
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SOX5 Controls the Sequential Generation of Distinct Corticofugal Neuron Subtypes. Neuron 2008; 57:232-47. [DOI: 10.1016/j.neuron.2007.12.023] [Citation(s) in RCA: 247] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Revised: 11/30/2007] [Accepted: 12/19/2007] [Indexed: 12/12/2022]
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