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Vaughen JP, Theisen E, Clandinin TR. From seconds to days: Neural plasticity viewed through a lipid lens. Curr Opin Neurobiol 2023; 80:102702. [PMID: 36965206 DOI: 10.1016/j.conb.2023.102702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 01/31/2023] [Accepted: 02/16/2023] [Indexed: 03/27/2023]
Abstract
Many adult neurons are dynamically remodeled across timescales ranging from the rapid addition and removal of specific synaptic connections, to largescale structural plasticity events that reconfigure circuits over hours, days, and months. Membrane lipids, including brain-enriched sphingolipids, play crucial roles in these processes. In this review, we summarize progress at the intersection of neuronal activity, lipids, and structural remodeling. We highlight how brain activity modulates lipid metabolism to enable adaptive structural plasticity, and showcase glia as key players in membrane remodeling. These studies reveal that lipids act as critical signaling molecules that instruct the dynamic architecture of the brain.
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Affiliation(s)
- John P Vaughen
- Department of Neurobiology, Stanford University, Stanford, CA, 94305, United States; Department of Developmental Biology, Stanford University, Stanford, CA, 94305, United States. https://twitter.com/gliaful
| | - Emma Theisen
- Department of Neurobiology, Stanford University, Stanford, CA, 94305, United States. https://twitter.com/emmaktheisen
| | - Thomas R Clandinin
- Department of Neurobiology, Stanford University, Stanford, CA, 94305, United States.
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2
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Sunkaria A, Bhardwaj S. Sleep Disturbance and Alzheimer's Disease: The Glial Connection. Neurochem Res 2022; 47:1799-1815. [PMID: 35303225 DOI: 10.1007/s11064-022-03578-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/27/2022] [Accepted: 03/09/2022] [Indexed: 12/28/2022]
Abstract
Poor quality and quantity of sleep are very common in elderly people throughout the world. Growing evidence has suggested that sleep disturbances could accelerate the process of neurodegeneration. Recent reports have shown a positive correlation between sleep deprivation and amyloid-β (Aβ)/tau aggregation in the brain of Alzheimer's patients. Glial cells have long been implicated in the progression of Alzheimer's disease (AD) and recent findings have also suggested their role in regulating sleep homeostasis. However, how glial cells control the sleep-wake balance and exactly how disturbed sleep may act as a trigger for Alzheimer's or other neurological disorders have recently gotten attention. In an attempt to connect the dots, the present review has highlighted the role of glia-derived sleep regulatory molecules in AD pathogenesis. Role of glia in sleep disturbance and Alzheimer's progression.
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Affiliation(s)
- Aditya Sunkaria
- Department of Biotechnology, Guru Nanak Dev University, Amritsar, Punjab, 143005, India.
| | - Supriya Bhardwaj
- Department of Dermatology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India
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3
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Zhou J, Wang H, Ouyang Q. Network rewiring and plasticity promotes synchronization of suprachiasmatic nucleus neurons. CHAOS (WOODBURY, N.Y.) 2022; 32:023101. [PMID: 35232040 DOI: 10.1063/5.0073480] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 01/17/2022] [Indexed: 06/14/2023]
Abstract
In mammals, circadian rhythms throughout the body are orchestrated by the master clock in the hypothalamic suprachiasmatic nucleus (SCN), where SCN neurons are coupled with neurotransmitters to generate a uniform circadian rhythm. How the SCN circadian rhythm is so robust and flexible is, however, unclear. In this paper, we propose a temporal SCN network model and investigate the effects of dynamical rewiring and flexible coupling due to synaptic plasticity on the synchronization of the neural network in SCN. In networks consisting of simple Poincaré oscillators and complex circadian clocks, we found that dynamical rewiring and coupling plasticity enhance the synchronization in inhomogeneous networks. We verified the effect of enhanced synchronization in different architectures of random, scale-free, and small-world networks. A simple mean-field analysis for synchronization in plastic networks is proposed. Intuitively, the synchronization is greatly enhanced because both the random rewiring and coupling plasticity in the heterogeneous network have effectively increased the coupling strength in the whole network. Our results suggest that a proper network model for the master SCN circadian rhythm needs to take into account the effects of dynamical changes in topology and plasticity in neuron interactions that could help the brain to generate a robust circadian rhythm for the whole body.
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Affiliation(s)
- Jiaxin Zhou
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Hongli Wang
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Qi Ouyang
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
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4
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Astiz M, Delgado-García LM, López-Mascaraque L. Astrocytes as essential time-keepers of the central pacemaker. Glia 2021; 70:808-819. [PMID: 34816453 DOI: 10.1002/glia.24121] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 11/10/2021] [Accepted: 11/12/2021] [Indexed: 12/13/2022]
Abstract
Since the early observations made by Santiago Ramon y Cajal more than a century ago till now, astrocytes have gradually gained protagonism as essential partners of neurons in building brain circuits that regulate complex behavior. In mammals, processes such as sleep-wake cycle, locomotor activity, cognition and memory consolidation, homeostatic and hedonic appetite and stress response (among others), are synchronized in 24-h rhythms by the circadian system. In such a way, physiology efficiently anticipates and adapts to daily recurring changes in the environment. The hypothalamic suprachiasmatic nucleus (SCN) is considered the central pacemaker, it has been traditionally described as a nucleus of around 10,000 neurons nearly all GABAergic able to be entrained by light and to convey time information through multiple neuronal and hormonal pathways. Only recently, this neuro-centered view was challenged by breakthrough discoveries implicating astrocytes as essential time-keepers. In the present review, we will describe the current view on the SCN circuit and discuss whether astrocytic functions described in other brain regions and state-of-the-art experimental approaches, could help explaining better those well- and not so well-known features of the central pacemaker.
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Affiliation(s)
- Mariana Astiz
- Institute of Neurobiology, Center of Brain, Behavior and Metabolism (CBBM), University of Lübeck, Lübeck, Germany
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5
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Moldavan M, Cravetchi O, Allen CN. Diurnal properties of tonic and synaptic GABA A receptor-mediated currents in suprachiasmatic nucleus neurons. J Neurophysiol 2021; 126:637-652. [PMID: 34259044 DOI: 10.1152/jn.00556.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synaptic and extrasynaptic GABAA receptor (GABAAR)-mediated neurotransmission is a critical component of the suprachiasmatic nucleus (SCN) neuronal network. However, the properties of the GABAA tonic current (Itonic) and its origin remain unexplored. Spontaneous GABAA postsynaptic currents (sGPSCs) and Itonic were recorded from SCN neurons with the whole cell voltage-clamp technique at different times of the day. GABAAR antagonists (bicuculline, gabazine, and picrotoxin) inhibited sGPSC and induced an outward shift of the holding current, which defined the Itonic amplitude. The sGPSC frequency, synaptic charge transfer, and Itonic amplitude all demonstrated significant diurnal rhythms, with peaks in the middle of the day [zeitgeber time (ZT)7-8] and nadirs at night (ZT19-20). The Itonic amplitude increased proportionally with the sGPSC frequency and synaptic charge transfer during the day and required action potential-mediated GABA release, which was confirmed by TTX application. The activation of presynaptic GABAB receptors by baclofen did not significantly alter the Itonic of neurons with low-frequency sGPSC. The equilibrium potential (Eq) for Itonic was similar to the Eq for chloride and GABAA receptor-activated currents. Itonic showed outward rectification at membrane potentials over the range of -70 to -10 mV and then was linear at voltages greater than -10 mV. GABAAR containing α4-, α5-, and δ-subunits were expressed in SCN, and their contribution to Itonic was confirmed by application of the GABAAR agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) and the GABAAR inverse agonist 11,12,13,13a-tetrahydro-7-methoxy-9-oxo-9H-imidazo[1,5-a]pyrrolo[2,1-c][1,4]benzodiazepine-1-carboxylic acid ethyl ester (L655,708). Thus, the Itonic was mediated by extrasynaptic GABAARs activated predominantly by GABA diffusing out of GABAergic synapses.NEW & NOTEWORTHY A tonic current (Itonic) mediated by GABAA receptors (GABAARs) containing α4-, α5- and δ-subunits was observed in the suprachiasmatic nucleus. The Itonic amplitude strongly depended on the action potential-mediated synaptic release of GABA. The equilibrium potential for Itonic corresponds to that for GABAA currents. The frequency of GABAA postsynaptic currents and Itonic amplitude increased during the day, with peak in the middle of the day, and then gradually declined with a nadir at night, thus showing a diurnal rhythm.
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Affiliation(s)
- Michael Moldavan
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon
| | - Olga Cravetchi
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon
| | - Charles N Allen
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon.,Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon
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6
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Moreno CRC, Wright K, Skene DJ, Louzada FM. Phenotypic plasticity of circadian entrainment under a range of light conditions. Neurobiol Sleep Circadian Rhythms 2020; 9:100055. [PMID: 32923743 PMCID: PMC7475273 DOI: 10.1016/j.nbscr.2020.100055] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 11/25/2022] Open
Abstract
The response to a zeitgeber, particularly the light/dark cycle, may vary phenotypically. Phenotypic plasticity can be defined as the ability of one genome to express different phenotypes in response to environmental variation. In this opinion paper, we present some evidence that one of the most prominent effects of the introduction of electric light to the everyday life of humans is a significant increase in phenotypic plasticity and differences in interindividual phases of entrainment. We propose that the healthy limits of phenotypic plasticity have been surpassed in contemporary society. Electric light increased phenotypic plasticity in humans and differences in interindividual phases of entrainment. Healthy limits of phenotypic plasticity have been surpassed in contemporary society. The correlation between biological time (DLMO) and behavioral time (MSFsc) is reduced in the population without access to electrical light.
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Affiliation(s)
- C R C Moreno
- School of Public Health, University of São Paulo, Brazil.,Stress Research Institute, Department of Psychology, Stockholm University, Sweden
| | - K Wright
- Sleep and Chronobiology Laboratory, Department of Integrative Physiology, University of Colorado Boulder, USA
| | - D J Skene
- Chronobiology, Faculty of Health & Medical Sciences, University of Surrey, UK
| | - F M Louzada
- Department of Physiology, Federal University of Paraná, Brazil
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7
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Coupling Neuropeptide Levels to Structural Plasticity in Drosophila Clock Neurons. Curr Biol 2020; 30:3154-3166.e4. [PMID: 32619484 DOI: 10.1016/j.cub.2020.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 05/05/2020] [Accepted: 06/02/2020] [Indexed: 12/24/2022]
Abstract
We have previously reported that pigment dispersing factor (PDF) neurons, which are essential in the control of rest-activity cycles in Drosophila, undergo circadian remodeling of their axonal projections, a phenomenon called circadian structural plasticity. Axonal arborizations display higher complexity during the day and become simpler at night, and this remodeling involves changes in the degree of connectivity. This phenomenon depends on the clock present within the ventrolateral neurons (LNvs) as well as in glia. In this work, we characterize in detail the contribution of the PDF neuropeptide to structural plasticity at different times across the day. Using diverse genetic strategies to temporally restrict its downregulation, we demonstrate that even subtle alterations to PDF cycling at the dorsal protocerebrum correlate with impaired remodeling, underscoring its relevance for the characteristic morning spread; PDF released from the small LNvs (sLNvs) and the large LNvs (lLNvs) contribute to the process. Moreover, forced depolarization recruits activity-dependent mechanisms to mediate growth only at night, overcoming the restriction imposed by the clock on membrane excitability. Interestingly, the active process of terminal remodeling requires PDF receptor (PDFR) signaling acting locally through the cyclic-nucleotide-gated channel ion channel subunit A (CNGA). Thus, clock-dependent PDF signaling shapes the connectivity of these essential clock neurons on daily basis.
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8
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Okada Y, Okada M. Quercetin, caffeic acid and resveratrol regulate circadian clock genes and aging-related genes in young and old human lung fibroblast cells. Mol Biol Rep 2019; 47:1021-1032. [PMID: 31773385 DOI: 10.1007/s11033-019-05194-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 11/12/2019] [Indexed: 02/07/2023]
Abstract
The circadian timing system of mammals is synchronized in concert with a central clock, but is also influenced by additional stimuli, including nutrients. However, little research has been done on polyphenols other than resveratrol and there seem to be no studies on their influence on young and old cells. The purpose of this study was to analyse the potential effects of quercetin, caffeic acid, and resveratrol on young and old fibroblast cells in the expressions of different clock genes and aging-related genes, and further investigate the mechanism. The mRNA expression of different clock genes and aging-related genes was assessed by quantitative real-time PCR. The protein levels of clock genes (BMAL1, PER1 and SIRT1) and glucocorticoid receptor α (GRα) were assessed by ELISA. Quercetin and caffeic acid in old fibroblast cells showed higher clock gene expression than resveratrol, quercetin increased Sirt1 expression, and caffeic acid increased Sirt6 expression indicating the possibility of an anti-aging effect. Also, quercetin and caffeic acid showed higher clock-controlled gene (Sirt1 and NR1D1) expression than resveratrol in young fibroblast cells. It appears that caffeic acid acts on NRF2 expression, and in turn to the actions of GRα, GDF11, Sirt1, and Sirt6. Regarding the increased expression of Per1, the activation effect on NR1D1 was confirmed only for caffeic acid in young fibroblast cells. Our results have confirmed the interplay of the circadian clock genes and cellular aging.
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Affiliation(s)
- Yoshinori Okada
- Laboratory on Ageing & Health Management, Graduate School of Nursing & Health, Aichi Prefectural University, Tohgoku, Kamishidami, Moriyama, Nagoya, 463-8502, Japan.
| | - Mizue Okada
- Nutrition Section, Ageing and Nutrition Research, Yms Laboratory, Gifu, 503, Japan
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9
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Itoi K, Motoike I, Liu Y, Clokie S, Iwasaki Y, Uchida K, Sato T, Aguilera G. Genome-Wide Analysis of Glucocorticoid-Responsive Transcripts in the Hypothalamic Paraventricular Region of Male Rats. Endocrinology 2019; 160:38-54. [PMID: 30364965 PMCID: PMC6302960 DOI: 10.1210/en.2018-00535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 10/19/2018] [Indexed: 11/19/2022]
Abstract
Glucocorticoids (GCs) are essential for stress adaptation, acting centrally and in the periphery. Corticotropin-releasing factor (CRF), a major regulator of adrenal GC synthesis, is produced in the paraventricular nucleus of the hypothalamus (PVH), which contains multiple neuroendocrine and preautonomic neurons. GCs may be involved in diverse regulatory mechanisms in the PVH, but the target genes of GCs are largely unexplored except for the CRF gene (Crh), a well-known target for GC negative feedback. Using a genome-wide RNA-sequencing analysis, we identified transcripts that changed in response to either high-dose corticosterone (Cort) exposure for 12 days (12-day high Cort), corticoid deprivation for 7 days (7-day ADX), or acute Cort administration. Among others, canonical GC target genes were upregulated prominently by 12-day high Cort. Crh was upregulated or downregulated most prominently by either 7-day ADX or 12-day high Cort, emphasizing the recognized feedback effects of GC on the hypothalamic-pituitary-adrenal (HPA) axis. Concomitant changes in vasopressin and apelin receptor gene expression are likely to contribute to HPA repression. In keeping with the pleotropic cellular actions of GCs, 7-day ADX downregulated numerous genes of a broad functional spectrum. The transcriptome response signature differed markedly between acute Cort injection and 12-day high Cort. Remarkably, six immediate early genes were upregulated 1 hour after Cort injection, which was confirmed by quantitative reverse transcription PCR and semiquantitative in situ hybridization. This study may provide a useful database for studying the regulatory mechanisms of GC-dependent gene expression and repression in the PVH.
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Affiliation(s)
- Keiichi Itoi
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
- Department of Neuroendocrinology, Graduate School of Medicine, Tohoku University, Sendai, Japan
- Correspondence: Keiichi Itoi, MD, PhD, Graduate School of Information Biology, Tohoku University, 6-3-09, Aramaki-aza Aoba, Sendai 980-8579, Japan. E-mail:
| | - Ikuko Motoike
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan
| | - Ying Liu
- Section on Endocrine Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Sam Clokie
- Section of Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | | | - Katsuya Uchida
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
| | - Tatsuya Sato
- Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan
| | - Greti Aguilera
- Section on Endocrine Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
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Carmona-Alcocer V, Rohr KE, Joye DAM, Evans JA. Circuit development in the master clock network of mammals. Eur J Neurosci 2018; 51:82-108. [PMID: 30402923 DOI: 10.1111/ejn.14259] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/08/2018] [Accepted: 10/31/2018] [Indexed: 12/24/2022]
Abstract
Daily rhythms are generated by the circadian timekeeping system, which is orchestrated by the master circadian clock in the suprachiasmatic nucleus (SCN) of mammals. Circadian timekeeping is endogenous and does not require exposure to external cues during development. Nevertheless, the circadian system is not fully formed at birth in many mammalian species and it is important to understand how SCN development can affect the function of the circadian system in adulthood. The purpose of the current review is to discuss the ontogeny of cellular and circuit function in the SCN, with a focus on work performed in model rodent species (i.e., mouse, rat, and hamster). Particular emphasis is placed on the spatial and temporal patterns of SCN development that may contribute to the function of the master clock during adulthood. Additional work aimed at decoding the mechanisms that guide circadian development is expected to provide a solid foundation upon which to better understand the sources and factors contributing to aberrant maturation of clock function.
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Affiliation(s)
| | - Kayla E Rohr
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Deborah A M Joye
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Jennifer A Evans
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
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11
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Mansilla A, Jordán-Álvarez S, Santana E, Jarabo P, Casas-Tintó S, Ferrús A. Molecular mechanisms that change synapse number. J Neurogenet 2018; 32:155-170. [DOI: 10.1080/01677063.2018.1506781] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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12
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Cooper JM, Halter KA, Prosser RA. Circadian rhythm and sleep-wake systems share the dynamic extracellular synaptic milieu. Neurobiol Sleep Circadian Rhythms 2018; 5:15-36. [PMID: 31236509 PMCID: PMC6584685 DOI: 10.1016/j.nbscr.2018.04.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/06/2018] [Accepted: 04/10/2018] [Indexed: 01/23/2023] Open
Abstract
The mammalian circadian and sleep-wake systems are closely aligned through their coordinated regulation of daily activity patterns. Although they differ in their anatomical organization and physiological processes, they utilize overlapping regulatory mechanisms that include an assortment of proteins and molecules interacting within the extracellular space. These extracellular factors include proteases that interact with soluble proteins, membrane-attached receptors and the extracellular matrix; and cell adhesion molecules that can form complex scaffolds connecting adjacent neurons, astrocytes and their respective intracellular cytoskeletal elements. Astrocytes also participate in the dynamic regulation of both systems through modulating neuronal appositions, the extracellular space and/or through release of gliotransmitters that can further contribute to the extracellular signaling processes. Together, these extracellular elements create a system that integrates rapid neurotransmitter signaling across longer time scales and thereby adjust neuronal signaling to reflect the daily fluctuations fundamental to both systems. Here we review what is known about these extracellular processes, focusing specifically on areas of overlap between the two systems. We also highlight questions that still need to be addressed. Although we know many of the extracellular players, far more research is needed to understand the mechanisms through which they modulate the circadian and sleep-wake systems.
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Key Words
- ADAM, A disintegrin and metalloproteinase
- AMPAR, AMPA receptor
- Astrocytes
- BDNF, brain-derived neurotrophic factor
- BMAL1, Brain and muscle Arnt-like-1 protein
- Bmal1, Brain and muscle Arnt-like-1 gene
- CAM, cell adhesion molecules
- CRY, cryptochrome protein
- Cell adhesion molecules
- Circadian rhythms
- Cry, cryptochrome gene
- DD, dark-dark
- ECM, extracellular matrix
- ECS, extracellular space
- EEG, electroencephalogram
- Endo N, endoneuraminidase N
- Extracellular proteases
- GFAP, glial fibrillary acidic protein
- IL, interleukin
- Ig, immunoglobulin
- LC, locus coeruleus
- LD, light-dark
- LH, lateral hypothalamus
- LRP-1, low density lipoprotein receptor-related protein 1
- LTP, long-term potentiation
- MMP, matrix metalloproteinases
- NCAM, neural cell adhesion molecule protein
- NMDAR, NMDA receptor
- NO, nitric oxide
- NST, nucleus of the solitary tract
- Ncam, neural cell adhesion molecule gene
- Nrl, neuroligin gene
- Nrx, neurexin gene
- P2, purine type 2 receptor
- PAI-1, plasminogen activator inhibitor-1
- PER, period protein
- PPT, peduculopontine tegmental nucleus
- PSA, polysialic acid
- Per, period gene
- REMS, rapid eye movement sleep
- RSD, REM sleep disruption
- SCN, suprachiasmatic nucleus
- SWS, slow wave sleep
- Sleep-wake system
- Suprachiasmatic nucleus
- TNF, tumor necrosis factor
- TTFL, transcriptional-translational negative feedback loop
- VIP, vasoactive intestinal polypeptide
- VLPO, ventrolateral preoptic
- VP, vasopressin
- VTA, ventral tegmental area
- dNlg4, drosophila neuroligin-4 gene
- nNOS, neuronal nitric oxide synthase gene
- nNOS, neuronal nitric oxide synthase protein
- tPA, tissue-type plasminogen activator
- uPA, urokinase-type plasminogen activator
- uPAR, uPA receptor
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Photoperiod-Induced Neuroplasticity in the Circadian System. Neural Plast 2018; 2018:5147585. [PMID: 29681926 PMCID: PMC5851158 DOI: 10.1155/2018/5147585] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/11/2018] [Indexed: 01/01/2023] Open
Abstract
Seasonal changes in light exposure have profound effects on behavioral and physiological functions in many species, including effects on mood and cognitive function in humans. The mammalian brain's master circadian clock, the suprachiasmatic nucleus (SCN), transmits information about external light conditions to other brain regions, including some implicated in mood and cognition. Although the detailed mechanisms are not yet known, the SCN undergoes highly plastic changes at the cellular and network levels under different light conditions. We therefore propose that the SCN may be an essential mediator of the effects of seasonal changes of day length on mental health. In this review, we explore various forms of neuroplasticity that occur in the SCN and other brain regions to facilitate seasonal adaptation, particularly altered phase distribution of cellular circadian oscillators in the SCN and changes in hypothalamic neurotransmitter expression.
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14
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Belle MDC, Diekman CO. Neuronal oscillations on an ultra-slow timescale: daily rhythms in electrical activity and gene expression in the mammalian master circadian clockwork. Eur J Neurosci 2018; 48:2696-2717. [PMID: 29396876 DOI: 10.1111/ejn.13856] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 01/16/2018] [Accepted: 01/28/2018] [Indexed: 12/17/2022]
Abstract
Neuronal oscillations of the brain, such as those observed in the cortices and hippocampi of behaving animals and humans, span across wide frequency bands, from slow delta waves (0.1 Hz) to ultra-fast ripples (600 Hz). Here, we focus on ultra-slow neuronal oscillators in the hypothalamic suprachiasmatic nuclei (SCN), the master daily clock that operates on interlocking transcription-translation feedback loops to produce circadian rhythms in clock gene expression with a period of near 24 h (< 0.001 Hz). This intracellular molecular clock interacts with the cell's membrane through poorly understood mechanisms to drive the daily pattern in the electrical excitability of SCN neurons, exhibiting an up-state during the day and a down-state at night. In turn, the membrane activity feeds back to regulate the oscillatory activity of clock gene programs. In this review, we emphasise the circadian processes that drive daily electrical oscillations in SCN neurons, and highlight how mathematical modelling contributes to our increasing understanding of circadian rhythm generation, synchronisation and communication within this hypothalamic region and across other brain circuits.
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Affiliation(s)
- Mino D C Belle
- Institute of Clinical and Biomedical Sciences, University of Exeter Medical School, University of Exeter, Exeter, EX4 4PS, UK
| | - Casey O Diekman
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, USA.,Institute for Brain and Neuroscience Research, New Jersey Institute of Technology, Newark, NJ, USA
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15
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The Role of Mammalian Glial Cells in Circadian Rhythm Regulation. Neural Plast 2017; 2017:8140737. [PMID: 29435373 PMCID: PMC5757113 DOI: 10.1155/2017/8140737] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 11/19/2017] [Indexed: 11/23/2022] Open
Abstract
Circadian rhythms are biological oscillations with a period of about 24 hours. These rhythms are maintained by an innate genetically determined time-keeping system called the circadian clock. A large number of the proteins involved in the regulation of this clock are transcription factors controlling rhythmic transcription of so-called clock-controlled genes, which participate in a plethora of physiological functions in the organism. In the brain, several areas, besides the suprachiasmatic nucleus, harbor functional clocks characterized by a well-defined time pattern of clock gene expression. This expression rhythm is not restricted to neurons but is also present in glia, suggesting that these cells are involved in circadian rhythmicity. However, only certain glial cells fulfill the criteria to be called glial clocks, namely, to display molecular oscillators based on the canonical clock protein PERIOD, which depends on the suprachiasmatic nucleus for their synchronization. In this contribution, we summarize the current information about activity of the clock genes in glial cells, their potential role as oscillators as well as clinical implications.
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16
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Herrero A, Duhart JM, Ceriani MF. Neuronal and Glial Clocks Underlying Structural Remodeling of Pacemaker Neurons in Drosophila. Front Physiol 2017; 8:918. [PMID: 29184510 PMCID: PMC5694478 DOI: 10.3389/fphys.2017.00918] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 10/30/2017] [Indexed: 11/24/2022] Open
Abstract
A number of years ago we reported that ventral Lateral Neurons (LNvs), which are essential in the control of rest-activity cycles in Drosophila, undergo circadian remodeling of their axonal projections. This structural plasticity gives rise to changes in the degree of connectivity, which could provide a means of transmitting time of day information. Thus far, work from different laboratories has shown that circadian remodeling of adult projections relies on activity-dependent and -independent mechanisms. In terms of clock- dependent mechanisms, several neuronal types undergoing circadian remodeling hinted to a differential effect of clock genes; while per mutants exhibited poorly developed axonal terminals giving rise to low complexity arbors, tim mutants displayed a characteristic hyper branching phenotype, suggesting these genes could be playing additional roles to those ascribed to core clock function. To shed light onto this possibility we altered clock gene levels through RNAi- mediated downregulation and expression of a dominant negative form exclusively in the adult LNvs. These experiments confirmed that the LNv clock is necessary to drive the remodeling process. We next explored the contribution of glia to the structural plasticity of the small LNvs through acute disruption of their internal clock. Interestingly, impaired glial clocks also abolished circadian structural remodeling, without affecting other clock-controlled outputs. Taken together our data shows that both neuronal and glial clocks are recruited to define the architecture of the LNv projections along the day, thus enabling a precise reconfiguration of the circadian network.
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Affiliation(s)
| | | | - Maria F. Ceriani
- Laboratorio de Genética del Comportamiento, Fundación Instituto Leloir, IIB-BA CONICET, Buenos Aires, Argentina
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17
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Duhart JM, Brocardo L, Caldart CS, Marpegan L, Golombek DA. Circadian Alterations in a Murine Model of Hypothalamic Glioma. Front Physiol 2017; 8:864. [PMID: 29163208 PMCID: PMC5670357 DOI: 10.3389/fphys.2017.00864] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/16/2017] [Indexed: 01/09/2023] Open
Abstract
The mammalian circadian system is controlled by a central oscillator located in the suprachiasmatic nuclei (SCN) of the hypothalamus, in which glia appears to play a prominent role. Gliomas originate from glial cells and are the primary brain tumors with the highest incidence and mortality. Optic pathway/hypothalamic gliomas account for 4–7% of all pediatric intracranial tumors. Given the anatomical location, which compromises both the circadian pacemaker and its photic input pathway, we decided to study whether the presence of gliomas in the hypothalamic region could alter circadian behavioral outputs. Athymic nude mice implanted with LN229 human glioma cells showed an increase in the endogenous period of the circadian clock, which was also less robust in terms of sustaining the free running period throughout 2 weeks of screening. We also found that implanted mice showed a slower resynchronization rate after an abrupt 6 h advance of the light-dark (LD) cycle, advanced phase angle, and a decreased direct effect of light in general activity (masking), indicating that hypothalamic tumors could also affect photic sensitivity of the circadian clock. Our work suggests that hypothalamic gliomas have a clear impact both on the endogenous pacemaking of the circadian system, as well as on the photic synchronization of the clock. These findings strongly suggest that the observation of altered circadian parameters in patients might be of relevance for glioma diagnosis.
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Affiliation(s)
- José M Duhart
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Lucila Brocardo
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Carlos S Caldart
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Luciano Marpegan
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Diego A Golombek
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina
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18
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Albers HE, Walton JC, Gamble KL, McNeill JK, Hummer DL. The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus. Front Neuroendocrinol 2017; 44:35-82. [PMID: 27894927 PMCID: PMC5225159 DOI: 10.1016/j.yfrne.2016.11.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 10/16/2016] [Accepted: 11/22/2016] [Indexed: 12/31/2022]
Abstract
Virtually every neuron within the suprachiasmatic nucleus (SCN) communicates via GABAergic signaling. The extracellular levels of GABA within the SCN are determined by a complex interaction of synthesis and transport, as well as synaptic and non-synaptic release. The response to GABA is mediated by GABAA receptors that respond to both phasic and tonic GABA release and that can produce excitatory as well as inhibitory cellular responses. GABA also influences circadian control through the exclusively inhibitory effects of GABAB receptors. Both GABA and neuropeptide signaling occur within the SCN, although the functional consequences of the interactions of these signals are not well understood. This review considers the role of GABA in the circadian pacemaker, in the mechanisms responsible for the generation of circadian rhythms, in the ability of non-photic stimuli to reset the phase of the pacemaker, and in the ability of the day-night cycle to entrain the pacemaker.
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Affiliation(s)
- H Elliott Albers
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States.
| | - James C Walton
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Karen L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - John K McNeill
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Daniel L Hummer
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Department of Psychology, Morehouse College, Atlanta, GA 30314, United States
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19
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Evans JA. Collective timekeeping among cells of the master circadian clock. J Endocrinol 2016; 230:R27-49. [PMID: 27154335 PMCID: PMC4938744 DOI: 10.1530/joe-16-0054] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 05/06/2016] [Indexed: 01/09/2023]
Abstract
The suprachiasmatic nucleus (SCN) of the anterior hypothalamus is the master circadian clock that coordinates daily rhythms in behavior and physiology in mammals. Like other hypothalamic nuclei, the SCN displays an impressive array of distinct cell types characterized by differences in neurotransmitter and neuropeptide expression. Individual SCN neurons and glia are able to display self-sustained circadian rhythms in cellular function that are regulated at the molecular level by a 24h transcriptional-translational feedback loop. Remarkably, SCN cells are able to harmonize with one another to sustain coherent rhythms at the tissue level. Mechanisms of cellular communication in the SCN network are not completely understood, but recent progress has provided insight into the functional roles of several SCN signaling factors. This review discusses SCN organization, how intercellular communication is critical for maintaining network function, and the signaling mechanisms that play a role in this process. Despite recent progress, our understanding of SCN circuitry and coupling is far from complete. Further work is needed to map SCN circuitry fully and define the signaling mechanisms that allow for collective timekeeping in the SCN network.
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Affiliation(s)
- Jennifer A Evans
- Department of Biomedical SciencesMarquette University, Milwaukee, WI, USA
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20
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Jones KA, Han JE, DeBruyne JP, Philpot BD. Persistent neuronal Ube3a expression in the suprachiasmatic nucleus of Angelman syndrome model mice. Sci Rep 2016; 6:28238. [PMID: 27306933 PMCID: PMC4910164 DOI: 10.1038/srep28238] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/31/2016] [Indexed: 01/31/2023] Open
Abstract
Mutations or deletions of the maternal allele of the UBE3A gene cause Angelman syndrome (AS), a severe neurodevelopmental disorder. The paternal UBE3A/Ube3a allele becomes epigenetically silenced in most neurons during postnatal development in humans and mice; hence, loss of the maternal allele largely eliminates neuronal expression of UBE3A protein. However, recent studies suggest that paternal Ube3a may escape silencing in certain neuron populations, allowing for persistent expression of paternal UBE3A protein. Here we extend evidence in AS model mice (Ube3a(m-/p+)) of paternal UBE3A expression within the suprachiasmatic nucleus (SCN), the master circadian pacemaker. Paternal UBE3A-positive cells in the SCN show partial colocalization with the neuropeptide arginine vasopressin (AVP) and clock proteins (PER2 and BMAL1), supporting that paternal UBE3A expression in the SCN is often of neuronal origin. Paternal UBE3A also partially colocalizes with a marker of neural progenitors, SOX2, implying that relaxed or incomplete imprinting of paternal Ube3a reflects an overall immature molecular phenotype. Our findings highlight the complexity of Ube3a imprinting in the brain and illuminate a subpopulation of SCN neurons as a focal point for future studies aimed at understanding the mechanisms of Ube3a imprinting.
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Affiliation(s)
- Kelly A. Jones
- Department of Cell Biology & Physiology, UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
- Carolina Institute for Developmental Disabilities, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Ji Eun Han
- Department of Cell Biology & Physiology, UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Jason P. DeBruyne
- Department of Pharmacology & Toxicology, Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA
| | - Benjamin D. Philpot
- Department of Cell Biology & Physiology, UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
- Carolina Institute for Developmental Disabilities, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
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21
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Moldavan M, Cravetchi O, Williams M, Irwin RP, Aicher SA, Allen CN. Localization and expression of GABA transporters in the suprachiasmatic nucleus. Eur J Neurosci 2015; 42:3018-32. [PMID: 26390912 DOI: 10.1111/ejn.13083] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/12/2015] [Accepted: 09/17/2015] [Indexed: 01/25/2023]
Abstract
GABA is a principal neurotransmitter in the suprachiasmatic hypothalamic nucleus (SCN), the master circadian clock. Despite the importance of GABA and GABA uptake for functioning of the circadian pacemaker, the localization and expression of GABA transporters (GATs) in the SCN has not been investigated. The present studies used Western blot analysis, immunohistochemistry and electron microscopy to demonstrate the presence of GABA transporter 1 (GAT1) and GAT3 in the SCN. By using light microscopy, GAT1 and GAT3 were co-localized throughout the SCN, but were not expressed in the perikarya of arginine vasopressin- or vasoactive intestinal peptide-immunoreactive (-ir) neurons of adult rats, nor in the neuronal processes labelled with the neurofilament heavy chain. Using electron microscopy, GAT1- and GAT3-ir was found in glial processes surrounding unlabelled neuronal perikarya, axons, dendrites, and enveloped symmetric and asymmetric axo-dendritic synapses. Glial fibrillary acidic protein-ir astrocytes grown in cell culture were immunopositive for GAT1 and GAT3 and both GATs could be observed in the same glial cell. These data demonstrate that synapses in the SCN function as 'tripartite' synapses consisting of presynaptic axon terminals, postsynaptic membranes and astrocytes that contain GABA transporters. This model suggests that astrocytes expressing both GATs may regulate the extracellular GABA, and thereby modulate the activity of neuronal networks in the SCN.
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Affiliation(s)
- Michael Moldavan
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Olga Cravetchi
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Melissa Williams
- Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA
| | - Robert P Irwin
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA
| | - Sue A Aicher
- Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA
| | - Charles N Allen
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA.,Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, USA
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22
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Jasinska M, Grzegorczyk A, Woznicka O, Jasek E, Kossut M, Barbacka-Surowiak G, Litwin JA, Pyza E. Circadian rhythmicity of synapses in mouse somatosensory cortex. Eur J Neurosci 2015; 42:2585-94. [PMID: 26274013 DOI: 10.1111/ejn.13045] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 08/07/2015] [Accepted: 08/12/2015] [Indexed: 11/29/2022]
Abstract
The circadian rhythmicity displayed by motor behavior of mice: activity at night and rest during the day; and the associated changes in the sensory input are reflected by cyclic synaptic plasticity in the whisker representations located in the somatosensory (barrel) cortex. It was not clear whether diurnal rhythmic changes in synapse density previously observed in the barrel cortex resulted from changes in the activity of the animals, from daily light/dark (LD) rhythm or are driven by an endogenous clock. These changes were investigated in the barrel cortex of C57BL/6 mouse strain kept under LD 12 : 12 h conditions and in constant darkness (DD). Stereological analysis of serial electron microscopic sections was used to assess numerical density of synapses. In mice kept under LD conditions, the total density of synapses and the density of excitatory synapses located on dendritic spines was higher during the light period (rest phase). In contrast, the density of inhibitory synapses located on dendritic spines increased during the dark period (activity phase). Under DD conditions, the upregulation of the inhibitory synapses during the activity phase was retained, but the cyclic changes in the density of excitatory synapses were not observed. The results show that the circadian plasticity concerns only synapses located on spines (and not those on dendritic shafts), and that excitatory and inhibitory synapses are differently regulated during the 24 h cycle: the excitatory synapses are influenced by light, whilst the inhibitory synapses are driven by the endogenous circadian clock.
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Affiliation(s)
- Malgorzata Jasinska
- Department of Histology, Jagiellonian University Medical College, 31-034, Krakow, Poland
| | - Anna Grzegorczyk
- Department of Animal Products Technology, University of Agriculture, 31-120, Krakow, Poland
| | - Olga Woznicka
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Ewa Jasek
- Department of Histology, Jagiellonian University Medical College, 31-034, Krakow, Poland
| | - Malgorzata Kossut
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, 02-093, Warsaw, Poland.,University of Social Sciences and Humanities, 03-815, Warsaw, Poland
| | - Grazyna Barbacka-Surowiak
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Jan A Litwin
- Department of Histology, Jagiellonian University Medical College, 31-034, Krakow, Poland
| | - Elzbieta Pyza
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
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23
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Koo J, Choe HK, Kim HD, Chun SK, Son GH, Kim K. Effect of Mefloquine, a Gap Junction Blocker, on Circadian Period2 Gene Oscillation in the Mouse Suprachiasmatic Nucleus Ex Vivo. Endocrinol Metab (Seoul) 2015; 30:361-70. [PMID: 25491783 PMCID: PMC4595362 DOI: 10.3803/enm.2015.30.3.361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 07/31/2014] [Accepted: 10/17/2014] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND In mammals, the master circadian pacemaker is localized in an area of the ventral hypothalamus known as the suprachiasmatic nucleus (SCN). Previous studies have shown that pacemaker neurons in the SCN are highly coupled to one another, and this coupling is crucial for intrinsic self-sustainability of the SCN central clock, which is distinguished from peripheral oscillators. One plausible mechanism underlying the intercellular communication may involve direct electrical connections mediated by gap junctions. METHODS We examined the effect of mefloquine, a neuronal gap junction blocker, on circadian Period 2 (Per2) gene oscillation in SCN slice cultures prepared from Per2::luciferase (PER2::LUC) knock-in mice using a real-time bioluminescence measurement system. RESULTS Administration of mefloquine causes instability in the pulse period and a slight reduction of amplitude in cyclic PER2::LUC expression. Blockade of gap junctions uncouples PER2::LUC-expressing cells, in terms of phase transition, which weakens synchrony among individual cellular rhythms. CONCLUSION These findings suggest that neuronal gap junctions play an important role in synchronizing the central pacemaker neurons and contribute to the distinct self-sustainability of the SCN master clock.
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Affiliation(s)
- Jinmi Koo
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Han Kyoung Choe
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Hee Dae Kim
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Sung Kook Chun
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Gi Hoon Son
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Legal Medicine, Korea University College of Medicine, Seoul, Korea
| | - Kyungjin Kim
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
- Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea.
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24
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Ng FS, Jackson FR. The ROP vesicle release factor is required in adult Drosophila glia for normal circadian behavior. Front Cell Neurosci 2015; 9:256. [PMID: 26190976 PMCID: PMC4490253 DOI: 10.3389/fncel.2015.00256] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 06/22/2015] [Indexed: 11/22/2022] Open
Abstract
We previously showed that endocytosis and/or vesicle recycling mechanisms are essential in adult Drosophila glial cells for the neuronal control of circadian locomotor activity. In this study, our goal was to identify specific glial vesicle trafficking, recycling, or release factors that are required for rhythmic behavior. From a glia-specific, RNAi-based genetic screen, we identified eight glial factors that are required for normally robust circadian rhythms in either a light-dark cycle or in constant dark conditions. In particular, we show that conditional knockdown of the ROP vesicle release factor in adult glial cells results in arrhythmic behavior. Immunostaining for ROP reveals reduced protein in glial cell processes and an accumulation of the Par Domain Protein 1ε (PDP1ε) clock output protein in the small lateral clock neurons. These results suggest that glia modulate rhythmic circadian behavior by secretion of factors that act on clock neurons to regulate a clock output factor.
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Affiliation(s)
- Fanny S Ng
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - F Rob Jackson
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
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25
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Bosler O, Girardet C, Franc JL, Becquet D, François-Bellan AM. Structural plasticity of the circadian timing system. An overview from flies to mammals. Front Neuroendocrinol 2015; 38:50-64. [PMID: 25703789 DOI: 10.1016/j.yfrne.2015.02.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 02/10/2015] [Accepted: 02/11/2015] [Indexed: 12/22/2022]
Abstract
The circadian timing system orchestrates daily variations in physiology and behavior through coordination of multioscillatory cell networks that are highly plastic in responding to environmental changes. Over the last decade, it has become clear that this plasticity involves structural changes and that the changes may be observed not only in central brain regions where the master clock cells reside but also in clock-controlled structures. This review considers experimental data in invertebrate and vertebrate model systems, mainly flies and mammals, illustrating various forms of structural circadian plasticity from cellular to circuit-based levels. It highlights the importance of these plastic events in the functional adaptation of the clock to the changing environment.
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Affiliation(s)
- Olivier Bosler
- Aix-Marseille Université, CNRS, CRN2M, UMR 7286, Faculté de médecine, secteur nord, Boulevard Pierre Dramard, CS 80011, F-13344 Marseille cedex 15, France.
| | - Clémence Girardet
- Aix-Marseille Université, CNRS, CRN2M, UMR 7286, Faculté de médecine, secteur nord, Boulevard Pierre Dramard, CS 80011, F-13344 Marseille cedex 15, France.
| | - Jean-Louis Franc
- Aix-Marseille Université, CNRS, CRN2M, UMR 7286, Faculté de médecine, secteur nord, Boulevard Pierre Dramard, CS 80011, F-13344 Marseille cedex 15, France
| | - Denis Becquet
- Aix-Marseille Université, CNRS, CRN2M, UMR 7286, Faculté de médecine, secteur nord, Boulevard Pierre Dramard, CS 80011, F-13344 Marseille cedex 15, France
| | - Anne-Marie François-Bellan
- Aix-Marseille Université, CNRS, CRN2M, UMR 7286, Faculté de médecine, secteur nord, Boulevard Pierre Dramard, CS 80011, F-13344 Marseille cedex 15, France
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26
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Neuronal expression of SOX2 is enriched in specific hypothalamic cell groups. J Chem Neuroanat 2014; 61-62:153-60. [PMID: 25263324 DOI: 10.1016/j.jchemneu.2014.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/16/2014] [Accepted: 09/16/2014] [Indexed: 02/04/2023]
Abstract
The transcription factor SOX2 has many established roles in neural development but is generally considered to have limited activity in the adult brain. As part of a study of neuronal phenotypes in the adult rodent hypothalamus, we have now used immunohistochemical analysis to investigate the expression of SOX2 in the adult rat and mouse hypothalamus. Our analysis has revealed that SOX2 protein is extensively expressed in cells of the suprachiasmatic nucleus (SCN). Co-localization with the nuclear marker proteins NeuN and MeCP2 confirmed SOX2 expression in mature neurons of the rat SCN, and the functional integrity of these SOX2+ neurons was also confirmed by demonstrating co-localization with light-induced EGR1 protein. In addition to the SCN, we have also revealed a population of SOX2+/(NeuN+/MeCP2+) neurons in the rat periventricular nucleus (PeN). However, in other hypothalamic nuclei such as the supraoptic nucleus (SON) SOX2+ cells were rare. In extra-hypothalamic areas, SOX2+ cells were also scarce although we have confirmed populations of non-neuronal SOX2+ cells in both the rat sub-ventricular zone (SVZ) and sub-granular zone (SGZ) of the hippocampus. In addition, we have identified an extensive, novel population of non-neuronal SOX2+ cells in the rat subfornical organ (SFO). Our findings provide further evidence of 'immature' phenotypes in rodent SCN neurons and, given the extensive expression of SOX2 across these hypothalamic neurons, may identify a common regulatory factor that maintains this unusual neuronal phenotype. Conservation of SCN SOX2 expression in both rat and mouse indicates a functional requirement for this transcription factor that may be integral to the role of these SCN neurons in mediating daily physiological rhythms.
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27
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Frank MG, Cantera R. Sleep, clocks, and synaptic plasticity. Trends Neurosci 2014; 37:491-501. [PMID: 25087980 PMCID: PMC4152403 DOI: 10.1016/j.tins.2014.06.005] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/12/2014] [Accepted: 06/30/2014] [Indexed: 01/24/2023]
Abstract
Sleep is widely believed to play an essential role in synaptic plasticity. However, the precise mechanisms governing this presumptive function are largely unknown. There is also evidence for independent circadian oscillations in synaptic strength and morphology. Therefore, synaptic changes observed after sleep reflect interactions between state-dependent (e.g., wake versus sleep) and state-independent (circadian) processes. In this review we consider how sleep and biological clocks influence synaptic plasticity. We discuss these findings in the context of current plasticity-based theories of sleep function and propose a new model that integrates circadian and brain-state influences on synaptic plasticity.
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Affiliation(s)
- Marcos G. Frank
- Department of Neuroscience Perelman School of Medicine University of Pennsylvania Philadelphia, PA 19104
| | - Rafael Cantera
- Zoology Department Stockholm University Stockholm, Sweden Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
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28
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Ruiz S, Ferreiro MJ, Menhert KI, Casanova G, Olivera A, Cantera R. Rhythmic changes in synapse numbers in Drosophila melanogaster motor terminals. PLoS One 2013; 8:e67161. [PMID: 23840613 PMCID: PMC3695982 DOI: 10.1371/journal.pone.0067161] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 05/15/2013] [Indexed: 11/18/2022] Open
Abstract
Previous studies have shown that the morphology of the neuromuscular junction of the flight motor neuron MN5 in Drosophila melanogaster undergoes daily rhythmical changes, with smaller synaptic boutons during the night, when the fly is resting, than during the day, when the fly is active. With electron microscopy and laser confocal microscopy, we searched for a rhythmic change in synapse numbers in this neuron, both under light:darkness (LD) cycles and constant darkness (DD). We expected the number of synapses to increase during the morning, when the fly has an intense phase of locomotion activity under LD and DD. Surprisingly, only our DD data were consistent with this hypothesis. In LD, we found more synapses at midnight than at midday. We propose that under LD conditions, there is a daily rhythm of formation of new synapses in the dark phase, when the fly is resting, and disassembly over the light phase, when the fly is active. Several parameters appeared to be light dependent, since they were affected differently under LD or DD. The great majority of boutons containing synapses had only one and very few had either two or more, with a 70∶25∶5 ratio (one, two and three or more synapses) in LD and 75∶20∶5 in DD. Given the maintenance of this proportion even when both bouton and synapse numbers changed with time, we suggest that there is a homeostatic mechanism regulating synapse distribution among MN5 boutons.
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Affiliation(s)
- Santiago Ruiz
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
| | - Maria Jose Ferreiro
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
| | | | - Gabriela Casanova
- Unidad de Microscopía Electrónica de Transmisión, Facultad de Ciencias, UdelaR, Montevideo, Uruguay
| | - Alvaro Olivera
- Unidad de Microscopía Electrónica de Transmisión, Facultad de Ciencias, UdelaR, Montevideo, Uruguay
| | - Rafael Cantera
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
- Zoology Department, Stockholm University, Stockholm, Sweden
- * E-mail:
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Girardet C, Lebrun B, Cabirol-Pol MJ, Tardivel C, François-Bellan AM, Becquet D, Bosler O. Brain-derived neurotrophic factor/TrkB signaling regulates daily astroglial plasticity in the suprachiasmatic nucleus: electron-microscopic evidence in mouse. Glia 2013; 61:1172-7. [PMID: 23640807 DOI: 10.1002/glia.22509] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 03/20/2013] [Indexed: 11/07/2022]
Abstract
Synchronization of circadian rhythms to the 24-h light/dark (L/D) cycle is associated with daily rearrangements of the neuronal-glial network of the suprachiasmatic nucleus of the hypothalamus (SCN), the central master clock orchestrating biological functions in mammals. These anatomical plastic events involve neurons synthesizing vasoactive intestinal peptide (VIP), known as major integrators of photic signals in the retinorecipient region of the SCN. Using an analog-sensitive kinase allele murine model (TrkB(F616A) ), we presently show that the pharmacological blockade of the tropomyosin-related kinase receptor type B (TrkB), the high-affinity receptor of brain-derived neurotrophic factor (BDNF), abolished day/night changes in the dendrite enwrapping of VIP neurons by astrocytic processes (glial coverage), used as an index of SCN plasticity on electron-microscopic sections. Therefore, the BDNF/TrkB signaling pathway exerts a permissive role on the ultrastructural rearrangements that occur in SCN under L/D alternance, an action that could be a critical determinant of the well-established role played by BDNF in the photic regulation of the SCN. In contrast, the extent of glial coverage of non-VIP neighboring dendrites was not different at daytime and nighttime in TrkB(F616A) mice submitted to TrkB inactivation or not receiving any pharmacological treatment. These data not only show that BDNF regulates SCN structural plasticity across the 24-h cycle but also reinforce the view that the daily changes in SCN architecture subserve the light synchronization process.
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Affiliation(s)
- Clémence Girardet
- Aix Marseille Université, CNRS, CRN2M UMR7286, Faculté de Médecine, 13344 cedex 15, Marseille, France
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Saaltink DJ, Håvik B, Verissimo CS, Lucassen P, Vreugdenhil E. Doublecortin and doublecortin-like are expressed in overlapping and non-overlapping neuronal cell population: Implications for neurogenesis. J Comp Neurol 2012; 520:2805-23. [DOI: 10.1002/cne.23144] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Guillaumond F, Becquet D, Boyer B, Bosler O, Delaunay F, Franc JL, François-Bellan AM. DNA microarray analysis and functional profile of pituitary transcriptome under core-clock protein BMAL1 control. Chronobiol Int 2012; 29:103-30. [PMID: 22324551 DOI: 10.3109/07420528.2011.645707] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Although it is known to contain five cell types that synthesize and release hormones with a circadian pattern, the pituitary gland is poorly characterized as a circadian oscillator. By a differential microarray analysis, 252 genes were found to be differentially expressed in pituitaries from Bmal1(-/-) knockout versus wild-type mice. By integrative analyses of the data set with the Annotation, Visualization, and Integrated Discovery (DAVID) Bioinformatics Resources annotation analysis system, pituitary genes with altered expression in Bmal1(-/-) mice were dispatched among functional categories. Clusters of genes related to signaling and rhythmic processes as well as transcription regulators, in general, were found enriched in the data set, as were pathways such as circadian rhythm, transforming growth factor β (TGFβ) signaling, valine, leucine, and isoleucine degradation, and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Gene Ontology term overrepresentation analyses revealed significant enrichment for genes involved in 10 key biological processes. To determine whether genes with altered expression in Bmal1(-/-) mice were actually circadian genes, we further characterized in the mouse pituitary gland the daily pattern of some of these genes, including core-clock genes. Core-clock genes and genes selected from three identified overrepresented biological processes, namely, hormone metabolic process, regulation of transcription from RNA polymerase II promoter, and cell adhesion, displayed a rhythmic pattern. Given the enrichment in genes dedicated to cell adhesion and their daily changes in the pituitary, it is hypothesized that cell-cell interactions could be involved in the transmission of information between endocrine cells, allowing rhythmic hormone outputs to be controlled in a temporally precise manner.
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Affiliation(s)
- F Guillaumond
- Aix-Marseille University , INSERM-U624, Marseille, France
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Kalsbeek A, van der Spek R, Lei J, Endert E, Buijs RM, Fliers E. Circadian rhythms in the hypothalamo-pituitary-adrenal (HPA) axis. Mol Cell Endocrinol 2012; 349:20-9. [PMID: 21782883 DOI: 10.1016/j.mce.2011.06.042] [Citation(s) in RCA: 248] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 06/29/2011] [Accepted: 06/30/2011] [Indexed: 01/06/2023]
Abstract
The pronounced daily variation in the release of adrenal hormones has been at the heart of the deciphering and understanding of the circadian timing system. Indeed, the first demonstration of an endocrine day/night rhythm was provided by Pincus (1943), by showing a daily pattern of 17-keto-steroid excretion in the urine of 7 healthy males. Twenty years later the adrenal gland was one of the very first organs to show, in vitro, that circadian rhythmicity was maintained. In the seventies, experimental manipulation of the daily corticosterone rhythm served as evidence for the identification of respectively the light- and food-entrainable oscillator. Another 20 years later the hypothalamo-pituitary-adrenal (HPA)-axis was key in furthering our understanding of the way in which rhythmic signals generated by the central pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) are forwarded to the rest of the brain and to the organism as a whole. To date, the adrenal gland is still of prime importance for understanding how the oscillations of clock genes in peripheral tissues result in functional rhythms of these tissues, whereas it has become even more evident that adrenal glucocorticoids are key in the resetting of the circadian system after a phase-shift. The HPA-axis thus still is an excellent model for studying the transmission of circadian information in the body.
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Affiliation(s)
- A Kalsbeek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, The Netherlands.
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Girardet C, Bosler O. [Structural plasticity of the adult central nervous system: insights from the neuroendocrine hypothalamus]. Biol Aujourdhui 2011; 205:179-97. [PMID: 21982406 DOI: 10.1051/jbio/2011018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Indexed: 01/26/2023]
Abstract
Accumulating evidence renders the dogma obsolete according to which the structural organization of the brain would remain essentially stable in adulthood, changing only in response to a need for compensatory processes during increasing age and degeneration. It has indeed become clear from investigations on various models that the adult nervous system can adapt to physiological demands by altering reversibly its synaptic circuits. This potential for structural and functional modifications results not only from the plastic properties of neurons but also from the inherent capacity of the glial cellular components to undergo remodeling as well. This is currently known for astrocytes, the major glial cells in brain which are well-recognized as dynamic partners in the mechanisms of synaptic transmission, and for the tanycytes and pituicytes which contribute to the regulation of neurosecretory processes in neurohemal regions of the hypothalamus. Studies on the neuroendocrine hypothalamus, whose role is central in homeostatic regulations, have gained good insights into the spectacular neuronal-glial rearrangements that may subserve functional plasticity in the adult brain. Following pioneering works on the morphological reorganizations taking place in the hypothalamo-neurohypophyseal system under certain physiological conditions such as dehydration and lactation, studies on the gonadotropic system that orchestrates reproductive functions have re-emphasized the dynamic interplay between neurons and glia in brain structural plasticity processes. This review summarizes the major contributions provided by these researches in the field and also addresses the question of the morphological rearrangements that occur on a 24-h basis in the central component of the circadian clock responsible for the temporal aspects of endocrine regulations. Taken together, the reviewed data highlight the close cooperation between neurons and glia in developing strategies for functional adaptation of the brain to the changing conditions of the internal and external environment.
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Affiliation(s)
- Clémence Girardet
- Centre de Recherche en Neurobiologie-Neurophysiologie de Marseille, France.
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Girardet C, Becquet D, Blanchard MP, François-Bellan AM, Bosler O. Neuroglial and synaptic rearrangements associated with photic entrainment of the circadian clock in the suprachiasmatic nucleus. Eur J Neurosci 2011. [DOI: 10.1111/j.1460-9568.2011.07712.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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