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Placzek M, Chinnaiya K, Kim DW, Blackshaw S. Control of tuberal hypothalamic development and its implications in metabolic disorders. Nat Rev Endocrinol 2025; 21:118-130. [PMID: 39313573 PMCID: PMC11864813 DOI: 10.1038/s41574-024-01036-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/29/2024] [Indexed: 09/25/2024]
Abstract
The tuberal hypothalamus regulates a range of crucial physiological processes, including energy homeostasis and metabolism. In this Review, we explore the intricate molecular mechanisms and signalling pathways that control the development of the tuberal hypothalamus, focusing on aspects that shape metabolic outcomes. Major developmental events are discussed in the context of their effect on the establishment of both functional hypothalamic neuronal circuits and brain-body interfaces that are pivotal to the control of metabolism. Emerging evidence indicates that aberrations in molecular pathways during tuberal hypothalamic development contribute to metabolic dysregulation. Understanding the molecular underpinnings of tuberal hypothalamic development provides a comprehensive view of neurodevelopmental processes and offers a promising avenue for future targeted interventions to prevent and treat metabolic disorders.
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Affiliation(s)
- Marysia Placzek
- School of Biosciences, University of Sheffield, Sheffield, UK.
- Bateson Centre, University of Sheffield, Sheffield, UK.
- Neuroscience Institute, University of Sheffield, Sheffield, UK.
| | | | - Dong Won Kim
- Danish Research Institute of Translational Neuroscience (DANDRITE), Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Aarhus, Denmark
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Seth Blackshaw
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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2
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Ness N, Díaz-Clavero S, Hoekstra MMB, Brancaccio M. Rhythmic astrocytic GABA production synchronizes neuronal circadian timekeeping in the suprachiasmatic nucleus. EMBO J 2025; 44:356-381. [PMID: 39623138 PMCID: PMC11731042 DOI: 10.1038/s44318-024-00324-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 10/18/2024] [Accepted: 11/04/2024] [Indexed: 01/15/2025] Open
Abstract
Astrocytes of the suprachiasmatic nucleus (SCN) can regulate sleep-wake cycles in mammals. However, the nature of the information provided by astrocytes to control circadian patterns of behavior is unclear. Neuronal circadian activity across the SCN is organized into spatiotemporal waves that govern seasonal adaptations and timely engagement of behavioral outputs. Here, we show that astrocytes across the mouse SCN exhibit instead a highly uniform, pulse-like nighttime activity. We find that rhythmic astrocytic GABA production via polyamine degradation provides an inhibitory nighttime tone required for SCN circuit synchrony, thereby acting as an internal astrocyte zeitgeber (or "astrozeit"). We further identify synaptic GABA and astrocytic GABA as two key players underpinning coherent spatiotemporal circadian patterns of SCN neuronal activity. In describing a new mechanism by which astrocytes contribute to circadian timekeeping, our work provides a general blueprint for understanding how astrocytes encode temporal information underlying complex behaviors in mammals.
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Affiliation(s)
- Natalie Ness
- Department of Brain Science, Imperial College London, London, UK
- UK Dementia Research Institute at Imperial College London, London, UK
| | - Sandra Díaz-Clavero
- Department of Brain Science, Imperial College London, London, UK
- UK Dementia Research Institute at Imperial College London, London, UK
| | - Marieke M B Hoekstra
- Department of Brain Science, Imperial College London, London, UK
- UK Dementia Research Institute at Imperial College London, London, UK
| | - Marco Brancaccio
- Department of Brain Science, Imperial College London, London, UK.
- UK Dementia Research Institute at Imperial College London, London, UK.
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3
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Zhang Y, Wang W, Li J, Zhao D, Shu Y, Jia X, Wang Y, Cheng X, Wang L, Cheng J. Dexmedetomidine accelerates photoentrainment and affects sleep structure through the activation of SCN VIP neurons. Commun Biol 2024; 7:1707. [PMID: 39730868 DOI: 10.1038/s42003-024-07430-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 12/19/2024] [Indexed: 12/29/2024] Open
Abstract
Dexmedetomidine (DexM), a highly selective α2-adrenoceptor agonist, significantly reduces postoperative adverse effects, including sleep and circadian rhythm disruptions. Vasoactive intestinal peptide neurons in the suprachiasmatic nucleus (SCNVIP) regulate the synchronization of circadian rhythms with the external environment in mammals. We investigate the effects of DexM on sleep and circadian rhythms, as well as the underlying mechanisms. Using electrophysiological and chemogenetic methods, along with locomotor activity and electroencephalogram/electromyogram recordings, we found that DexM accelerates the rate of re-entrainment following an 8-hour phase advance in the 12-hour light:12-hour dark cycle, increases the amount of non-rapid eye movement sleep, and decreases the mean duration of rapid eye movement sleep. Chemogenetic inhibition of SCNVIP neurons hinders the acceleration of re-entrainment and the changes in the sleep-wakefulness cycle induced by DexM. Electrophysiological results show that DexM increases the firing rate and the frequency of spontaneous glutamatergic postsynaptic currents while decreasing the frequency of spontaneous GABAergic PSCs in SCNVIP neurons through the α2-adrenergic receptor. Additionally, DexM reduces the frequency of miniature GABAergic PSCs in SCNVIP neurons. In conclusion, these findings suggest that DexM promotes sleep and maintains the coordination of circadian rhythms with the external environment by activating SCNVIP neurons through the α2-adrenoceptor.
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Affiliation(s)
- Ying Zhang
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Wei Wang
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Jiaxin Li
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Dongmei Zhao
- Department of Infectious Disease, First Affiliated Hospital of Anhui Medical University, Hefei, 230032, China
| | - Yue Shu
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Xinlu Jia
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Yibo Wang
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China
| | - Xinqi Cheng
- Department of Anesthesiology, First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui, China.
| | - Liecheng Wang
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China.
- College of Stomatology, Anhui Medical University, Hefei, 230032, Anhui, China.
| | - Juan Cheng
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230032, Anhui, China.
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4
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Nikhil K, Singhal B, Granados-Fuentes D, Li JS, Kiss IZ, Herzog ED. The Functional Connectome Mediating Circadian Synchrony in the Suprachiasmatic Nucleus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.12.06.627294. [PMID: 39713450 PMCID: PMC11661124 DOI: 10.1101/2024.12.06.627294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/24/2024]
Abstract
Circadian rhythms in mammals arise from the spatiotemporal synchronization of ~20,000 neuronal clocks in the Suprachiasmatic Nucleus (SCN). While anatomical, molecular, and genetic approaches have revealed diverse cell types and signaling mechanisms, the network wiring that enables SCN cells to communicate and synchronize remains unclear. To overcome the challenges of revealing functional connectivity from fixed tissue, we developed MITE (Mutual Information & Transfer Entropy), an information theory approach that infers directed cell-cell connections with high fidelity. By analyzing 3447 hours of continuously recorded clock gene expression from 9011 cells in 17 mice, we found that the functional connectome of SCN was highly conserved bilaterally and across mice, sparse, and organized into a dorsomedial and a ventrolateral module. While most connections were local, we discovered long-range connections from ventral cells to cells in both the ventral and dorsal SCN. Based on their functional connectivity, SCN cells can be characterized as circadian signal generators, broadcasters, sinks, or bridges. For example, a subset of VIP neurons acts as hubs that generate circadian signals critical to synchronize daily rhythms across the SCN neural network. Simulations of the experimentally inferred SCN networks recapitulated the stereotypical dorsal-to-ventral wave of daily PER2 expression and ability to spontaneously synchronize, revealing that SCN emergent dynamics are sculpted by cell-cell connectivity. We conclude that MITE provides a powerful method to infer functional connectomes, and that the conserved architecture of cell-cell connections mediates circadian synchrony across space and time in the mammalian SCN.
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Affiliation(s)
- K.L. Nikhil
- Department of Biology, Washington University in Saint Louis, USA
| | - Bharat Singhal
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, USA
| | | | - Jr-Shin Li
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, USA
| | | | - Erik D. Herzog
- Department of Biology, Washington University in Saint Louis, USA
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5
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Klett N, Gompf HS, Allen CN, Cravetchi O, Hablitz LM, Gunesch AN, Irwin RP, Todd WD, Saper CB, Fuller PM. GABAergic signalling in the suprachiasmatic nucleus is required for coherent circadian rhythmicity. Eur J Neurosci 2024; 60:6652-6667. [PMID: 39558544 PMCID: PMC11612841 DOI: 10.1111/ejn.16582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 09/11/2024] [Accepted: 10/07/2024] [Indexed: 11/20/2024]
Abstract
The suprachiasmatic nucleus is the circadian pacemaker of the mammalian brain. Suprachiasmatic nucleus neurons display synchronization of their firing frequency on a circadian timescale, which is required for the pacemaker function of the suprachiasmatic nucleus. However, the mechanisms by which suprachiasmatic nucleus neurons remain synchronized in vivo are poorly understood, although synaptic communication is considered indispensable. Suprachiasmatic nucleus neurons contain the neurotransmitter GABA and express GABA receptors. This has inspired the hypothesis that GABA signalling may play a central role in network synchronization, although this remains untested in vivo. Here, using local genetic deletion, we show that disruption of GABA synaptic transmission within the suprachiasmatic nucleus of adult mice results in the eventual deterioration of physiological and behavioural rhythmicity in vivo and concomitant cellular desynchrony in vitro. These findings suggest that intercellular GABA signalling is essential for behavioural rhythmicity and cellular synchrony of the suprachiasmatic nucleus neural network.
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Affiliation(s)
- Nathan Klett
- Oregon Institute for Occupational Health SciencesUSA
- Neuroscience Graduate ProgramUSA
| | - Heinrich S. Gompf
- Department of Neurological SurgeryUniversity of California, DavisDavisCAUSA
| | - Charles N. Allen
- Oregon Institute for Occupational Health SciencesUSA
- Department of Behavioral NeuroscienceOregon Health & Science UniversityPortlandORUSA
| | | | - Lauren M. Hablitz
- Oregon Institute for Occupational Health SciencesUSA
- Department of Behavioral NeuroscienceOregon Health & Science UniversityPortlandORUSA
- Present address:
Center for Translational NeuromedicineUniversity of Rochester Medical CenterRochesterNYUSA
| | | | | | - William D. Todd
- Department of Neurology, Division of Sleep Medicine, and Program in NeuroscienceBeth Israel Deaconess Medical Center, Harvard Medical School BostonMAUSA
- Present address:
Department of Zoology and PhysiologyUniversity of WyomingLaramieWYUSA
| | - Clifford B. Saper
- Department of Neurology, Division of Sleep Medicine, and Program in NeuroscienceBeth Israel Deaconess Medical Center, Harvard Medical School BostonMAUSA
| | - Patrick M. Fuller
- Department of Neurological SurgeryUniversity of California, DavisDavisCAUSA
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6
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Zheng W, Gu C, Yang H, Wang H, Rohling JHT. Adaptive coupling between neurons widens the entrainment range of the suprachiasmatic nucleus. Phys Rev E 2024; 110:034212. [PMID: 39425370 DOI: 10.1103/physreve.110.034212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Accepted: 08/28/2024] [Indexed: 10/21/2024]
Abstract
In many realistic systems, such as neural networks in the brain, the coupling strength between neurons is not fixed, but adaptively adjusts according to their activities. The suprachiasmatic nucleus (SCN), as the main clock in the mammalian brain, has been found to be a plastic neural network, and the coupling strength between neurons is highly dynamical. An important function of the SCN is entrainment, reflecting the ability of the SCN to synchronize with the external light-dark cycle. The entrainment ability is reflected by the entrainment range, which is a period range for the external light-dark cycle to which the SCN can entrain. In this article, we investigated whether the entrainment range of the SCN is affected by the adaptive coupling. We use a modified Kuramoto model with external light-dark cycle. We found that when the light sensitivity is larger than the fixed coupling strength (the coupling strength without adaptive rules), adaptive coupling can widen the entrainment range. Our findings help to understand the impact of the adaptive coupling between oscillatorty neurons on the collective behavior of the SCN, and provides a possible explanation for the plasticity of coupling in the master clock network.
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7
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Osuna-Lopez F, Herrera-Zamora JM, Reyes-Méndez ME, Aguilar-Roblero RA, Sánchez-Pastor EA, Navarro-Polanco RA, Moreno-Galindo EG, Alamilla J. Age-, region-, and day/night-related variation of the chloride reversal potential in the rat suprachiasmatic nucleus. J Neurosci Res 2024; 102:e25373. [PMID: 39101281 DOI: 10.1002/jnr.25373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 06/06/2024] [Accepted: 07/21/2024] [Indexed: 08/06/2024]
Abstract
The master control of mammalian circadian rhythms is the suprachiasmatic nucleus (SCN), which is formed by the ventral and dorsal regions. In SCN neurons, GABA has an important function and even excitatory actions in adulthood. However, the physiological role of this neurotransmitter in the developing SCN is unknown. Here, we recorded GABAergic postsynaptic currents (in the perforated-patch configuration using gramicidin) to determine the chloride reversal potential (ECl) and also assessed the immunological expression of the Na-K-Cl cotransporter 1 (NKCC1) at early ages of the rat (postnatal days (P) 3 to 25), during the day and night, in the two SCN regions. We detected that ECl greatly varied with age and depending on the SCN region and time of day. Broadly speaking, ECl was more hyperpolarized with age, except for the oldest age studied (P20-25) in both day and night in the ventral SCN, where it was less negative. Likewise, ECl was more hyperpolarized in the dorsal SCN both during the day and at night; while ECl was more negative at night both in the ventral and the dorsal SCN. Moreover, the total NKCC1 fluorescent expression was higher during the day than at night. These results imply that NKCC1 regulates the circadian and developmental fluctuations in the [Cl-]i to fine-tune ECl, which is crucial for either excitatory or inhibitory GABAergic actions to occur in the SCN.
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Affiliation(s)
- Fernando Osuna-Lopez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | | | - Miriam E Reyes-Méndez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | - Raúl A Aguilar-Roblero
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | | | | | - Eloy G Moreno-Galindo
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
| | - Javier Alamilla
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico
- Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT)-Universidad de Colima, Colima, Mexico
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8
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Granados-Fuentes D, Lambert P, Simon T, Mennerick S, Herzog ED. GABA A receptor subunit composition regulates circadian rhythms in rest-wake and synchrony among cells in the suprachiasmatic nucleus. Proc Natl Acad Sci U S A 2024; 121:e2400339121. [PMID: 39047036 PMCID: PMC11295074 DOI: 10.1073/pnas.2400339121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 06/24/2024] [Indexed: 07/27/2024] Open
Abstract
The mammalian circadian clock located in the suprachiasmatic nucleus (SCN) produces robust daily rhythms including rest-wake. SCN neurons synthesize and respond to γ-aminobutyric acid (GABA), but its role remains unresolved. We tested the hypothesis that γ2- and δ-subunits of the GABAA receptor in the SCN differ in their regulation of synchrony among circadian cells. We used two approaches: 1) shRNA to knock-down (KD) the expression of either γ2 or δ subunits in the SCN or 2) knock-in mice harboring a point mutation in the M2 domains of the endogenous GABAA γ2 or δ subunits. KD of either γ2 or δ subunits in the SCN increased daytime running and reduced nocturnal running by reducing their circadian amplitude by a third. Similarly, δ subunit knock-in mice showed decreased circadian amplitude, increased duration of daily activity, and decreased total daily activity. Reduction, or mutation of either γ2 or δ subunits halved the synchrony among, and amplitude of, circadian SCN cells as measured by firing rate or expression of the PERIOD2 protein, in vitro. Surprisingly, overexpression of the γ2 subunit rescued these phenotypes following KD or mutation of the δ subunit, and overexpression of the δ subunit rescued deficiencies due to γ2 subunit KD or mutation. We conclude that γ2 and δ GABAA receptor subunits play similar roles in maintaining circadian synchrony in the SCN and amplitude of daily rest-wake rhythms, but that modulation of their relative densities can change the duration and amplitude of daily activities.
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Affiliation(s)
| | - Peter Lambert
- Department of Psychiatry, Washington University in St. Louis, MO63130-4899
| | - Tatiana Simon
- Department of Biology, Washington University in St. Louis, MO63130-4899
| | - Steven Mennerick
- Department of Psychiatry, Washington University in St. Louis, MO63130-4899
| | - Erik D. Herzog
- Department of Biology, Washington University in St. Louis, MO63130-4899
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Wang Z, Yu J, Zhai M, Wang Z, Sheng K, Zhu Y, Wang T, Liu M, Wang L, Yan M, Zhang J, Xu Y, Wang X, Ma L, Hu W, Cheng H. System-level time computation and representation in the suprachiasmatic nucleus revealed by large-scale calcium imaging and machine learning. Cell Res 2024; 34:493-503. [PMID: 38605178 PMCID: PMC11217450 DOI: 10.1038/s41422-024-00956-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 03/28/2024] [Indexed: 04/13/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) is the mammalian central circadian pacemaker with heterogeneous neurons acting in concert while each neuron harbors a self-sustained molecular clockwork. Nevertheless, how system-level SCN signals encode time of the day remains enigmatic. Here we show that population-level Ca2+ signals predict hourly time, via a group decision-making mechanism coupled with a spatially modular time feature representation in the SCN. Specifically, we developed a high-speed dual-view two-photon microscope for volumetric Ca2+ imaging of up to 9000 GABAergic neurons in adult SCN slices, and leveraged machine learning methods to capture emergent properties from multiscale Ca2+ signals as a whole. We achieved hourly time prediction by polling random cohorts of SCN neurons, reaching 99.0% accuracy at a cohort size of 900. Further, we revealed that functional neuron subtypes identified by contrastive learning tend to aggregate separately in the SCN space, giving rise to bilaterally symmetrical ripple-like modular patterns. Individual modules represent distinctive time features, such that a module-specifically learned time predictor can also accurately decode hourly time from random polling of the same module. These findings open a new paradigm in deciphering the design principle of the biological clock at the system level.
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Affiliation(s)
- Zichen Wang
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, Jiangsu, China
| | - Jing Yu
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, Jiangsu, China
| | - Muyue Zhai
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
| | - Zehua Wang
- Wangxuan Institute of Computer Technology, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Kaiwen Sheng
- Beijing Academy of Artificial Intelligence, Beijing, China
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Yu Zhu
- Beijing Academy of Artificial Intelligence, Beijing, China
| | - Tianyu Wang
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
| | - Mianzhi Liu
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
| | - Lu Wang
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
| | - Miao Yan
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
| | - Jue Zhang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- College of Engineering, Peking University, Beijing, China
| | - Ying Xu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Su Genomic Resource Center, Medical School of Soochow University, Suzhou, Jiangsu, China
| | - Xianhua Wang
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, Jiangsu, China
| | - Lei Ma
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China.
- Beijing Academy of Artificial Intelligence, Beijing, China.
| | - Wei Hu
- Wangxuan Institute of Computer Technology, Peking University, Beijing, China.
| | - Heping Cheng
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking University, Beijing, China.
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, Jiangsu, China.
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10
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Schmal C. The seasons within: a theoretical perspective on photoperiodic entrainment and encoding. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:549-564. [PMID: 37659985 PMCID: PMC11226496 DOI: 10.1007/s00359-023-01669-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 08/11/2023] [Accepted: 08/16/2023] [Indexed: 09/04/2023]
Abstract
Circadian clocks are internal timing devices that have evolved as an adaption to the omnipresent natural 24 h rhythmicity of daylight intensity. Properties of the circadian system are photoperiod dependent. The phase of entrainment varies systematically with season. Plastic photoperiod-dependent re-arrangements in the mammalian circadian core pacemaker yield an internal representation of season. Output pathways of the circadian clock regulate photoperiodic responses such as flowering time in plants or hibernation in mammals. Here, we review the concepts of seasonal entrainment and photoperiodic encoding. We introduce conceptual phase oscillator models as their high level of abstraction, but, yet, intuitive interpretation of underlying parameters allows for a straightforward analysis of principles that determine entrainment characteristics. Results from this class of models are related and discussed in the context of more complex conceptual amplitude-phase oscillators as well as contextual molecular models that take into account organism, tissue, and cell-type-specific details.
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Affiliation(s)
- Christoph Schmal
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Philippstr. 13, 10115, Berlin, Germany.
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11
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Czeisler MÉ, Shan Y, Schalek R, Berger DR, Suissa-Peleg A, Takahashi JS, Lichtman JW. Extensive soma-soma plate-like contact sites (ephapses) connect suprachiasmatic nucleus neurons. J Comp Neurol 2024; 532:e25624. [PMID: 38896499 PMCID: PMC11419332 DOI: 10.1002/cne.25624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 03/30/2024] [Accepted: 04/29/2024] [Indexed: 06/21/2024]
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) is the central pacemaker for mammalian circadian rhythms. As such, this ensemble of cell-autonomous neuronal oscillators with divergent periods must maintain coordinated oscillations. To investigate ultrastructural features enabling such synchronization, 805 coronal ultrathin sections of mouse SCN tissue were imaged with electron microscopy and aligned into a volumetric stack, from which selected neurons within the SCN core were reconstructed in silico. We found that clustered SCN core neurons were physically connected to each other via multiple large soma-to-soma plate-like contacts. In some cases, a sliver of a glial process was interleaved. These contacts were large, covering on average ∼21% of apposing neuronal somata. It is possible that contacts may be the electrophysiological substrate for synchronization between SCN neurons. Such plate-like contacts may explain why the synchronization of SCN neurons is maintained even when chemical synaptic transmission or electrical synaptic transmission via gap junctions is blocked. Such ephaptic contact-mediated synchronization among nearby neurons may therefore contribute to the wave-like oscillations of circadian core clock genes and calcium signals observed in the SCN.
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Affiliation(s)
- Mark É. Czeisler
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Yongli Shan
- Department of Neuroscience, Peter O’Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Richard Schalek
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Daniel R. Berger
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Adi Suissa-Peleg
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Joseph S. Takahashi
- Department of Neuroscience, Peter O’Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Jeff W. Lichtman
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
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12
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Rodan AR. Circadian Rhythm Regulation by Pacemaker Neuron Chloride Oscillation in Flies. Physiology (Bethesda) 2024; 39:0. [PMID: 38411570 PMCID: PMC11368518 DOI: 10.1152/physiol.00006.2024] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 02/28/2024] Open
Abstract
Circadian rhythms in physiology and behavior sync organisms to external environmental cycles. Here, circadian oscillation in intracellular chloride in central pacemaker neurons of the fly, Drosophila melanogaster, is reviewed. Intracellular chloride links SLC12 cation-coupled chloride transporter function with kinase signaling and the regulation of inwardly rectifying potassium channels.
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Affiliation(s)
- Aylin R Rodan
- Molecular Medicine Program, University of Utah, Salt Lake City, Utah, United States
- Department of Internal Medicine, Division of Nephrology and Hypertension, University of Utah, Salt Lake City, Utah, United States
- Department of Human Genetics, University of Utah, Salt Lake City, Utah, United States
- Medical Service, Veterans Affairs Salt Lake City Health Care System, Salt Lake City, Utah, United States
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13
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Ono D, Weaver DR, Hastings MH, Honma KI, Honma S, Silver R. The Suprachiasmatic Nucleus at 50: Looking Back, Then Looking Forward. J Biol Rhythms 2024; 39:135-165. [PMID: 38366616 PMCID: PMC7615910 DOI: 10.1177/07487304231225706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
It has been 50 years since the suprachiasmatic nucleus (SCN) was first identified as the central circadian clock and 25 years since the last overview of developments in the field was published in the Journal of Biological Rhythms. Here, we explore new mechanisms and concepts that have emerged in the subsequent 25 years. Since 1997, methodological developments, such as luminescent and fluorescent reporter techniques, have revealed intricate relationships between cellular and network-level mechanisms. In particular, specific neuropeptides such as arginine vasopressin, vasoactive intestinal peptide, and gastrin-releasing peptide have been identified as key players in the synchronization of cellular circadian rhythms within the SCN. The discovery of multiple oscillators governing behavioral and physiological rhythms has significantly advanced our understanding of the circadian clock. The interaction between neurons and glial cells has been found to play a crucial role in regulating these circadian rhythms within the SCN. Furthermore, the properties of the SCN network vary across ontogenetic stages. The application of cell type-specific genetic manipulations has revealed components of the functional input-output system of the SCN and their correlation with physiological functions. This review concludes with the high-risk effort of identifying open questions and challenges that lie ahead.
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Affiliation(s)
- Daisuke Ono
- Stress Recognition and Response, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan
- Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - David R Weaver
- Department of Neurobiology and NeuroNexus Institute, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA
| | - Michael H Hastings
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Ken-Ichi Honma
- Research and Education Center for Brain Science, Hokkaido University, Sapporo, Japan
- Center for Sleep and Circadian Rhythm Disorders, Sapporo Hanazono Hospital, Sapporo, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University, Sapporo, Japan
- Center for Sleep and Circadian Rhythm Disorders, Sapporo Hanazono Hospital, Sapporo, Japan
| | - Rae Silver
- Stress Recognition and Response, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan
- Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Department of Neuroscience & Behavior, Barnard College and Department of Psychology, Columbia University, New York City, New York, USA
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14
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Liao M, Gao X, Chen C, Li Q, Guo Q, Huang H, Zhang E, Ju D. Integrated neural tracing and in-situ barcoded sequencing reveals the logic of SCN efferent circuits in regulating circadian behaviors. SCIENCE CHINA. LIFE SCIENCES 2024; 67:518-528. [PMID: 38057622 DOI: 10.1007/s11427-023-2420-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 06/30/2023] [Indexed: 12/08/2023]
Abstract
The circadian clock coordinates rhythms in numerous physiological processes to maintain organismal homeostasis. Since the suprachiasmatic nucleus (SCN) is widely accepted as the circadian pacemaker, it is critical to understand the neural mechanisms by which rhythmic information is transferred from the SCN to peripheral clocks. Here, we present the first comprehensive map of SCN efferent connections and suggest a molecular logic underlying these projections. The SCN projects broadly to most major regions of the brain, rather than solely to the hypothalamus and thalamus. The efferent projections from different subtypes of SCN neurons vary in distance and intensity, and blocking synaptic transmission of these circuits affects circadian rhythms in locomotion and feeding to different extents. We also developed a barcoding system to integrate retrograde tracing with in-situ sequencing, allowing us to link circuit anatomy and spatial patterns of gene expression. Analyses using this system revealed that brain regions functioning downstream of the SCN receive input from multiple neuropeptidergic cell types within the SCN, and that individual SCN neurons generally project to a single downstream brain region. This map of SCN efferent connections provides a critical foundation for future investigations into the neural circuits underlying SCN-mediated rhythms in physiology. Further, our new barcoded tracing method provides a tool for revealing the molecular logic of neuronal circuits within heterogeneous brain regions.
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Affiliation(s)
- Meimei Liao
- College of Biological Sciences, China Agriculture University, Beijing, 100193, China
- National Institute of Biological Sciences (NIBS), Beijing, 102206, China
| | - Xinwei Gao
- Chinese Institute for Brain Research, Beijing, 102206, China
| | - Chen Chen
- National Institute of Biological Sciences (NIBS), Beijing, 102206, China
| | - Qi Li
- National Institute of Biological Sciences (NIBS), Beijing, 102206, China
- Tsinghua Institute of Multidisciplinar^ Biomedical Research, Tsinghua University, Beijing, 102206, China
| | - Qingchun Guo
- Chinese Institute for Brain Research, Beijing, 102206, China
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China
| | - He Huang
- Department of Anesthesiology, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, 401336, China
| | - Erquan Zhang
- National Institute of Biological Sciences (NIBS), Beijing, 102206, China
- Tsinghua Institute of Multidisciplinar^ Biomedical Research, Tsinghua University, Beijing, 102206, China
| | - Dapeng Ju
- Department of Anesthesiology, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, 401336, China.
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15
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Naveed M, Chao OY, Hill JW, Yang YM, Huston JP, Cao R. Circadian neurogenetics and its implications in neurophysiology, behavior, and chronomedicine. Neurosci Biobehav Rev 2024; 157:105523. [PMID: 38142983 PMCID: PMC10872425 DOI: 10.1016/j.neubiorev.2023.105523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/13/2023] [Accepted: 12/20/2023] [Indexed: 12/26/2023]
Abstract
The circadian rhythm affects multiple physiological processes, and disruption of the circadian system can be involved in a range of disease-related pathways. The genetic underpinnings of the circadian rhythm have been well-studied in model organisms. Significant progress has been made in understanding how clock genes affect the physiological functions of the nervous system. In addition, circadian timing is becoming a key factor in improving drug efficacy and reducing drug toxicity. The circadian biology of the target cell determines how the organ responds to the drug at a specific time of day, thus regulating pharmacodynamics. The current review brings together recent advances that have begun to unravel the molecular mechanisms of how the circadian clock affects neurophysiological and behavioral processes associated with human brain diseases. We start with a brief description of how the ubiquitous circadian rhythms are regulated at the genetic, cellular, and neural circuit levels, based on knowledge derived from extensive research on model organisms. We then summarize the latest findings from genetic studies of human brain disorders, focusing on the role of human clock gene variants in these diseases. Lastly, we discuss the impact of common dietary factors and medications on human circadian rhythms and advocate for a broader application of the concept of chronomedicine.
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Affiliation(s)
- Muhammad Naveed
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, USA; Department of Physiology and Pharmacology, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH 43614, USA
| | - Owen Y Chao
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, USA
| | - Jennifer W Hill
- Department of Physiology and Pharmacology, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH 43614, USA
| | - Yi-Mei Yang
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, USA; Department of Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455, USA
| | - Joseph P Huston
- Center for Behavioral Neuroscience, Institute of Experimental Psychology, Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Ruifeng Cao
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA; Department of Neurology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA.
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16
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Bussi IL, Neitz AF, Sanchez REA, Casiraghi LP, Moldavan M, Kunda D, Allen CN, Evans JA, de la Iglesia HO. Expression of the vesicular GABA transporter within neuromedin S + neurons sustains behavioral circadian rhythms. Proc Natl Acad Sci U S A 2023; 120:e2314857120. [PMID: 38019855 PMCID: PMC10710084 DOI: 10.1073/pnas.2314857120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of a central circadian clock that orchestrates overt rhythms of physiology and behavior. Circadian timekeeping requires intercellular communication among SCN neurons, and multiple signaling pathways contribute to SCN network coupling. Gamma-aminobutyric acid (GABA) is produced by virtually all SCN neurons, and previous work demonstrates that this transmitter regulates coupling in the adult SCN but is not essential for the nucleus to sustain overt circadian rhythms. Here, we show that the deletion of the gene that codes for the GABA vesicular transporter Vgat from neuromedin-S (NMS)+ neurons-a subset of neurons critical for SCN function-causes arrhythmia of locomotor activity and sleep. Further, NMS-Vgat deletion impairs intrinsic clock gene rhythms in SCN explants cultured ex vivo. Although vasoactive intestinal polypeptide (VIP) is critical for SCN function, Vgat deletion from VIP-expressing neurons did not lead to circadian arrhythmia in locomotor activity rhythms. Likewise, adult SCN-specific deletion of Vgat led to mild impairment of behavioral rhythms. Our results suggest that while the removal of GABA release from the adult SCN does not affect the pacemaker's ability to sustain overt circadian rhythms, its removal from a critical subset of neurons within the SCN throughout development removes the nucleus ability to sustain circadian rhythms. Our findings support a model in which SCN GABA release is critical for the developmental establishment of intercellular network properties that define the SCN as a central pacemaker.
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Affiliation(s)
- Ivana L. Bussi
- Department of Biology, University of Washington, Seattle, WA98195-1800
| | - Alexandra F. Neitz
- Department of Biology, University of Washington, Seattle, WA98195-1800
- Molecular and Cellular Biology in Seattle, University of Washington and Fred Hutch, Seattle, WA98195-7275
| | - Raymond E. A. Sanchez
- Department of Biology, University of Washington, Seattle, WA98195-1800
- Graduate Program in Neuroscience, University of Washington, Seattle, WA98195
| | | | - Michael Moldavan
- Oregon Institute for Occupational Health Sciences, Oregon Health & Science University, Portland, OR97239
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR97239
| | - Divya Kunda
- Department of Biology, University of Washington, Seattle, WA98195-1800
| | - Charles N. Allen
- Oregon Institute for Occupational Health Sciences, Oregon Health & Science University, Portland, OR97239
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR97239
| | - Jennifer A. Evans
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI53233
| | - Horacio O. de la Iglesia
- Department of Biology, University of Washington, Seattle, WA98195-1800
- Molecular and Cellular Biology in Seattle, University of Washington and Fred Hutch, Seattle, WA98195-7275
- Graduate Program in Neuroscience, University of Washington, Seattle, WA98195
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17
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Ocampo-Espindola JL, Nikhil KL, Li JS, Herzog ED, Kiss IZ. Synchronization, clustering, and weak chimeras in a densely coupled transcription-based oscillator model for split circadian rhythms. CHAOS (WOODBURY, N.Y.) 2023; 33:083105. [PMID: 37535024 PMCID: PMC10403273 DOI: 10.1063/5.0156135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/08/2023] [Indexed: 08/04/2023]
Abstract
The synchronization dynamics for the circadian gene expression in the suprachiasmatic nucleus is investigated using a transcriptional circadian clock gene oscillator model. With global coupling in constant dark (DD) conditions, the model exhibits a one-cluster phase synchronized state, in dim light (dim LL), bistability between one- and two-cluster states and in bright LL, a two-cluster state. The two-cluster phase synchronized state, where some oscillator pairs synchronize in-phase, and some anti-phase, can explain the splitting of the circadian clock, i.e., generation of two bouts of daily activities with certain species, e.g., with hamsters. The one- and two-cluster states can be reached by transferring the animal from DD or bright LL to dim LL, i.e., the circadian synchrony has a memory effect. The stability of the one- and two-cluster states was interpreted analytically by extracting phase models from the ordinary differential equation models. In a modular network with two strongly coupled oscillator populations with weak intragroup coupling, with appropriate initial conditions, one group is synchronized to the one-cluster state and the other group to the two-cluster state, resulting in a weak-chimera state. Computational modeling suggests that the daily rhythms in sleep-wake depend on light intensity acting on bilateral networks of suprachiasmatic nucleus (SCN) oscillators. Addition of a network heterogeneity (coupling between the left and right SCN) allowed the system to exhibit chimera states. The simulations can guide experiments in the circadian rhythm research to explore the effect of light intensity on the complexities of circadian desynchronization.
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Affiliation(s)
| | - K. L. Nikhil
- Department of Biology, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130-4899, USA
| | - Jr-Shin Li
- Department of Electrical and Systems Engineering, Washington University in St Louis, 1 Brookings Drive, St. Louis, Missouri 63130, USA
| | - Erik D. Herzog
- Department of Biology, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130-4899, USA
| | - István Z. Kiss
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave., St. Louis, Missouri 63103, USA
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18
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Patton AP, Morris EL, McManus D, Wang H, Li Y, Chin JW, Hastings MH. Astrocytic control of extracellular GABA drives circadian timekeeping in the suprachiasmatic nucleus. Proc Natl Acad Sci U S A 2023; 120:e2301330120. [PMID: 37186824 PMCID: PMC10214171 DOI: 10.1073/pnas.2301330120] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 04/12/2023] [Indexed: 05/17/2023] Open
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) is the master mammalian circadian clock. Its cell-autonomous timing mechanism, a transcriptional/translational feedback loop (TTFL), drives daily peaks of neuronal electrical activity, which in turn control circadian behavior. Intercellular signals, mediated by neuropeptides, synchronize and amplify TTFL and electrical rhythms across the circuit. SCN neurons are GABAergic, but the role of GABA in circuit-level timekeeping is unclear. How can a GABAergic circuit sustain circadian cycles of electrical activity, when such increased neuronal firing should become inhibitory to the network? To explore this paradox, we show that SCN slices expressing the GABA sensor iGABASnFR demonstrate a circadian oscillation of extracellular GABA ([GABA]e) that, counterintuitively, runs in antiphase to neuronal activity, with a prolonged peak in circadian night and a pronounced trough in circadian day. Resolving this unexpected relationship, we found that [GABA]e is regulated by GABA transporters (GATs), with uptake peaking during circadian day, hence the daytime trough and nighttime peak. This uptake is mediated by the astrocytically expressed transporter GAT3 (Slc6a11), expression of which is circadian-regulated, being elevated in daytime. Clearance of [GABA]e in circadian day facilitates neuronal firing and is necessary for circadian release of the neuropeptide vasoactive intestinal peptide, a critical regulator of TTFL and circuit-level rhythmicity. Finally, we show that genetic complementation of the astrocytic TTFL alone, in otherwise clockless SCN, is sufficient to drive [GABA]e rhythms and control network timekeeping. Thus, astrocytic clocks maintain the SCN circadian clockwork by temporally controlling GABAergic inhibition of SCN neurons.
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Affiliation(s)
- Andrew P. Patton
- Neurobiology Division, Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - Emma L. Morris
- Neurobiology Division, Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - David McManus
- Neurobiology Division, Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - Huan Wang
- State Key Laboratory of Membrane Biology, Peking University, School of Life Sciences, 100871Beijing, China
| | - Yulong Li
- State Key Laboratory of Membrane Biology, Peking University, School of Life Sciences, 100871Beijing, China
| | - Jason W. Chin
- PNAC Division, Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
| | - Michael H. Hastings
- Neurobiology Division, Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
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19
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Olde Engberink AHO, de Torres Gutiérrez P, Chiosso A, Das A, Meijer JH, Michel S. Aging affects GABAergic function and calcium homeostasis in the mammalian central clock. Front Neurosci 2023; 17:1178457. [PMID: 37260848 PMCID: PMC10229097 DOI: 10.3389/fnins.2023.1178457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 04/24/2023] [Indexed: 06/02/2023] Open
Abstract
Introduction Aging impairs the function of the central circadian clock in mammals, the suprachiasmatic nucleus (SCN), leading to a reduction in the output signal. The weaker timing signal from the SCN results in a decline in rhythm strength in many physiological functions, including sleep-wake patterns. Accumulating evidence suggests that the reduced amplitude of the SCN signal is caused by a decreased synchrony among the SCN neurons. The present study was aimed to investigate the hypothesis that the excitation/inhibition (E/I) balance plays a role in synchronization within the network. Methods Using calcium (Ca2+) imaging, the polarity of Ca2+ transients in response to GABA stimulation in SCN slices of old mice (20-24 months) and young controls was studied. Results We found that the amount of GABAergic excitation was increased, and that concordantly the E/I balance was higher in SCN slices of old mice when compared to young controls. Moreover, we showed an effect of aging on the baseline intracellular Ca2+ concentration, with higher Ca2+ levels in SCN neurons of old mice, indicating an alteration in Ca2+ homeostasis in the aged SCN. We conclude that the change in GABAergic function, and possibly the Ca2+ homeostasis, in SCN neurons may contribute to the altered synchrony within the aged SCN network.
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20
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Giantomasi L, Ribeiro JF, Barca-Mayo O, Malerba M, Miele E, De Pietri Tonelli D, Berdondini L. Astrocytes actively support long-range molecular clock synchronization of segregated neuronal populations. Sci Rep 2023; 13:4815. [PMID: 36964220 PMCID: PMC10038999 DOI: 10.1038/s41598-023-31966-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 03/20/2023] [Indexed: 03/26/2023] Open
Abstract
In mammals, the suprachiasmatic nucleus of the hypothalamus is the master circadian pacemaker that synchronizes the clocks in the central nervous system and periphery, thus orchestrating rhythms throughout the body. However, little is known about how so many cellular clocks within and across brain circuits can be effectively synchronized. In this work, we investigated the implication of two possible pathways: (i) astrocytes-mediated synchronization and (ii) neuronal paracrine factors-mediated synchronization. By taking advantage of a lab-on-a-chip microfluidic device developed in our laboratory, here we report that both pathways are involved. We found the paracrine factors-mediated synchronization of molecular clocks is diffusion-limited and, in our device, effective only in case of a short distance between neuronal populations. Interestingly, interconnecting astrocytes define an active signaling channel that can synchronize molecular clocks of neuronal populations also at longer distances. At mechanism level, we found that astrocytes-mediated synchronization involves both GABA and glutamate, while neuronal paracrine factors-mediated synchronization occurs through GABA signaling. These findings identify a previously unknown role of astrocytes as active cells that might distribute long-range signals to synchronize the brain clocks, thus further strengthening the importance of reciprocal interactions between glial and neuronal cells in the context of circadian circuitry.
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Affiliation(s)
- Lidia Giantomasi
- Microtechnology for Neuroelectronics, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy
| | - João F Ribeiro
- Microtechnology for Neuroelectronics, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy
| | - Olga Barca-Mayo
- Neurobiology of miRNA, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy
- Circadian and Glial Biology Lab, Physiology Department, Molecular Medicine, and Chronic Diseases Research Centre (CiMUS), University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Mario Malerba
- Microtechnology for Neuroelectronics, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy
- Centre de Nanosciences et de Nanotechnologies (C2N), CNRS UMR 9001, Université Paris-Saclay, 91120, Palaiseau, France
| | - Ermanno Miele
- Microtechnology for Neuroelectronics, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | | | - Luca Berdondini
- Microtechnology for Neuroelectronics, Fondazione Istituto Italiano Di Tecnologia (IIT), 16163, Genova, Italy.
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21
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Hitrec T, Petit C, Cryer E, Muir C, Tal N, Fustin JM, Hughes AT, Piggins HD. Timed exercise stabilizes behavioral rhythms but not molecular programs in the brain's suprachiasmatic clock. iScience 2023; 26:106002. [PMID: 36866044 PMCID: PMC9971895 DOI: 10.1016/j.isci.2023.106002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/25/2022] [Accepted: 01/13/2023] [Indexed: 01/20/2023] Open
Abstract
Timed daily access to a running-wheel (scheduled voluntary exercise; SVE) synchronizes rodent circadian rhythms and promotes stable, 24h rhythms in animals with genetically targeted impairment of neuropeptide signaling (Vipr2 -/- mice). Here we used RNA-seq and/or qRT-PCR to assess how this neuropeptide signaling impairment as well as SVE shapes molecular programs in the brain clock (suprachiasmatic nuclei; SCN) and peripheral tissues (liver and lung). Compared to Vipr2 +/+ animals, the SCN transcriptome of Vipr2 -/- mice showed extensive dysregulation which included core clock components, transcription factors, and neurochemicals. Furthermore, although SVE stabilized behavioral rhythms in these animals, the SCN transcriptome remained dysregulated. The molecular programs in the lung and liver of Vipr2 -/- mice were partially intact, although their response to SVE differed to that of these peripheral tissues in the Vipr2 +/+ mice. These findings highlight that SVE can correct behavioral abnormalities in circadian rhythms without causing large scale alterations to the SCN transcriptome.
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Affiliation(s)
- Timna Hitrec
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Cheryl Petit
- School of Medical Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester M13 9PT, UK
| | - Emily Cryer
- School of Biological Sciences, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Charlotte Muir
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Natalie Tal
- School of Medical Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester M13 9PT, UK
| | - Jean-Michel Fustin
- School of Medical Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester M13 9PT, UK
| | - Alun T.L. Hughes
- School of Medical Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester M13 9PT, UK,School of Biological and Environmental Sciences, Faculty of Science, Liverpool John Moores University, Liverpool L3 3AF, UK,Corresponding author
| | - Hugh D. Piggins
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Life Sciences, University of Bristol, Bristol BS8 1TD, UK,School of Medical Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester M13 9PT, UK,Corresponding author
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22
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Zheng Y, Pan L, Wang F, Yan J, Wang T, Xia Y, Yao L, Deng K, Zheng Y, Xia X, Su Z, Chen H, Lin J, Ding Z, Zhang K, Zhang M, Chen Y. Neural function of Bmal1: an overview. Cell Biosci 2023; 13:1. [PMID: 36593479 PMCID: PMC9806909 DOI: 10.1186/s13578-022-00947-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/19/2022] [Indexed: 01/04/2023] Open
Abstract
Bmal1 (Brain and muscle arnt-like, or Arntl) is a bHLH/PAS domain transcription factor central to the transcription/translation feedback loop of the biologic clock. Although Bmal1 is well-established as a major regulator of circadian rhythm, a growing number of studies in recent years have shown that dysfunction of Bmal1 underlies a variety of psychiatric, neurodegenerative-like, and endocrine metabolism-related disorders, as well as potential oncogenic roles. In this review, we systematically summarized Bmal1 expression in different brain regions, its neurological functions related or not to circadian rhythm and biological clock, and pathological phenotypes arising from Bmal1 knockout. This review also discusses oscillation and rhythmicity, especially in the suprachiasmatic nucleus, and provides perspective on future progress in Bmal1 research.
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Affiliation(s)
- Yuanjia Zheng
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China ,grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Lingyun Pan
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Feixue Wang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jinglan Yan
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Taiyi Wang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yucen Xia
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Lin Yao
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Kelin Deng
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yuqi Zheng
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xiaoye Xia
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Zhikai Su
- grid.411866.c0000 0000 8848 7685The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong China
| | - Hongjie Chen
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Jie Lin
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Zhenwei Ding
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Kaitong Zhang
- grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Meng Zhang
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yongjun Chen
- grid.464402.00000 0000 9459 9325Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, China ,grid.411866.c0000 0000 8848 7685South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China ,Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong-Macao Greater Bay Area, Guangzhou, China
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23
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Singla R, Mishra A, Cao R. The trilateral interactions between mammalian target of rapamycin (mTOR) signaling, the circadian clock, and psychiatric disorders: an emerging model. Transl Psychiatry 2022; 12:355. [PMID: 36045116 PMCID: PMC9433414 DOI: 10.1038/s41398-022-02120-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 08/08/2022] [Accepted: 08/12/2022] [Indexed: 02/07/2023] Open
Abstract
Circadian (~24 h) rhythms in physiology and behavior are evolutionarily conserved and found in almost all living organisms. The rhythms are endogenously driven by daily oscillatory activities of so-called "clock genes/proteins", which are widely distributed throughout the mammalian brain. Mammalian (mechanistic) target of rapamycin (mTOR) signaling is a fundamental intracellular signal transduction cascade that controls important neuronal processes including neurodevelopment, synaptic plasticity, metabolism, and aging. Dysregulation of the mTOR pathway is associated with psychiatric disorders including autism spectrum disorders (ASD) and mood disorders (MD), in which patients often exhibit disrupted daily physiological rhythms and abnormal circadian gene expression in the brain. Recent work has found that the activities of mTOR signaling are temporally controlled by the circadian clock and exhibit robust circadian oscillations in multiple systems. In the meantime, mTOR signaling regulates fundamental properties of the central and peripheral circadian clocks, including period length, entrainment, and synchronization. Whereas the underlying mechanisms remain to be fully elucidated, increasing clinical and preclinical evidence support significant crosstalk between mTOR signaling, the circadian clock, and psychiatric disorders. Here, we review recent progress in understanding the trilateral interactions and propose an "interaction triangle" model between mTOR signaling, the circadian clock, and psychiatric disorders (focusing on ASD and MD).
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Affiliation(s)
- Rubal Singla
- grid.17635.360000000419368657Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812 USA
| | - Abhishek Mishra
- grid.17635.360000000419368657Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812 USA
| | - Ruifeng Cao
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN, 55812, USA. .,Department of Neuroscience, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
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24
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Shao YQ, Fan L, Wu WY, Zhu YJ, Xu HT. A developmental switch between electrical and neuropeptide communication in the ventromedial hypothalamus. Curr Biol 2022; 32:3137-3145.e3. [PMID: 35659861 DOI: 10.1016/j.cub.2022.05.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/15/2022] [Accepted: 05/11/2022] [Indexed: 12/29/2022]
Abstract
Dissecting neural connectivity patterns within local brain regions is an essential step to understanding the function of the brain.1 Neural microcircuits in brain regions, such as the neocortex and the hippocampus, have been extensively studied.2 By contrast, the microcircuit in the hypothalamus remains largely uncharacterized. The hypothalamus is crucial for animals' survival and reproduction.3 Knowledge of how different hypothalamic nuclei coordinate with each other and outside brain regions for hypothalamus-related functions has been significantly advanced.4-9 Although there are limited studies on the neural microcircuit in the lateral hypothalamus (LHA)10,11 and the suprachiasmatic nucleus (SCN),12,13 the patterns of neural microcircuits in most of the given hypothalamic nuclei remain largely unknown. This study applied combinatory approaches to address the local neural circuit pattern in the ventromedial hypothalamus (VMH) and other hypothalamic nuclei. We discovered a unique neural circuit design in the VMH. Neurons in the VMH were electrically coupled at the early postnatal stage like ones in the neocortex.14 However, unlike neocortical neurons,14,15 they developed very few chemical synapses after the disappearance of electrical synapses. Instead, VMH neurons communicated with neuropeptides. The similar scarceness of synaptic connectivity found in other hypothalamic nuclei further indicated that the lack of synaptic connections is a unique feature for local neural circuits in most adult hypothalamic nuclei. Thus, our findings provide a solid synaptic basis at the cellular level to understand hypothalamic functions better.
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Affiliation(s)
- Yin-Qi Shao
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liu Fan
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wen-Yan Wu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi-Jun Zhu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hua-Tai Xu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
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25
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Lee R, McGee A, Fernandez FX. Systematic review of drugs that modify the circadian system's phase-shifting responses to light exposure. Neuropsychopharmacology 2022; 47:866-879. [PMID: 34961774 PMCID: PMC8882192 DOI: 10.1038/s41386-021-01251-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/08/2021] [Accepted: 11/30/2021] [Indexed: 11/09/2022]
Abstract
We searched PubMed for primary research quantifying drug modification of light-induced circadian phase-shifting in rodents. This search, conducted for work published between 1960 and 2018, yielded a total of 146 papers reporting results from 901 studies. Relevant articles were those with any extractable data on phase resetting in wildtype (non-trait selected) rodents administered a drug, alongside a vehicle/control group, near or at the time of exposure. Most circadian pharmacology experiments were done using drugs thought to act directly on either the brain's central pacemaker, the suprachiasmatic nucleus (SCN), the SCN's primary relay, the retinohypothalamic tract, secondary pathways originating from the medial/dorsal raphe nuclei and intergeniculate leaflet, or the brain's sleep-arousal centers. While the neurotransmitter systems underlying these circuits were of particular interest, including those involving glutamate, gamma-aminobutyric acid, serotonin, and acetylcholine, other signaling modalities have also been assessed, including agonists and antagonists of receptors linked to dopamine, histamine, endocannabinoids, adenosine, opioids, and second-messenger pathways downstream of glutamate receptor activation. In an effort to identify drugs that unduly influence circadian responses to light, we quantified the net effects of each drug class by ratioing the size of the phase-shift observed after administration to that observed with vehicle in a given experiment. This allowed us to organize data across the literature, compare the relative efficacy of one mechanism versus another, and clarify which drugs might best suppress or potentiate phase resetting. Aggregation of the available data in this manner suggested that several candidates might be clinically relevant as auxiliary treatments to suppress ectopic light responses during shiftwork or amplify the circadian effects of timed bright light therapy. Future empirical research will be necessary to validate these possibilities.
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Affiliation(s)
- Robert Lee
- Department of Psychology, University of Arizona, Tucson, AZ, USA
| | - Austin McGee
- Department of Psychology, University of Arizona, Tucson, AZ, USA
| | - Fabian-Xosé Fernandez
- Department of Psychology, University of Arizona, Tucson, AZ, USA.
- Department of Neurology, University of Arizona, Tucson, AZ, USA.
- BIO5 and McKnight Brain Research Institutes, Tucson, AZ, USA.
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26
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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: 0.3] [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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27
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Klett NJ, Cravetchi O, Allen CN. Long-Term Imaging Reveals a Circadian Rhythm of Intracellular Chloride in Neurons of the Suprachiasmatic Nucleus. J Biol Rhythms 2022; 37:110-123. [PMID: 34994231 PMCID: PMC9203244 DOI: 10.1177/07487304211059770] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Both inhibitory and excitatory GABA transmission exist in the mature suprachiasmatic nucleus (SCN), the master pacemaker of circadian physiology. Whether GABA is inhibitory or excitatory depends on the intracellular chloride concentration ([Cl-]i). Here, using the genetically encoded ratiometric probe Cl-Sensor, we investigated [Cl-]i in AVP and VIP-expressing SCN neurons for several days in culture. The chloride ratio (RCl) demonstrated circadian rhythmicity in AVP + neurons and VIP + neurons, but was not detected in GFAP + astrocytes. RCl peaked between ZT 7 and ZT 8 in both AVP + and VIP + neurons. RCl rhythmicity was not dependent on the activity of several transmembrane chloride carriers, action potential generation, or the L-type voltage-gated calcium channels, but was sensitive to GABA antagonists. We conclude that [Cl-]i is under circadian regulation in both AVP + and VIP + neurons.
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Affiliation(s)
- Nathan J. Klett
- Neuroscience Graduate Program, Oregon Health & Science University, Portland, OR 97239
- Oregon Institute for Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239
| | - Olga Cravetchi
- Oregon Institute for Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239
| | - Charles N. Allen
- Oregon Institute for Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239
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28
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Gu C, Li J, Zhou J, Yang H, Rohling J. Network Structure of the Master Clock Is Important for Its Primary Function. Front Physiol 2021; 12:678391. [PMID: 34483953 PMCID: PMC8415478 DOI: 10.3389/fphys.2021.678391] [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: 03/09/2021] [Accepted: 07/22/2021] [Indexed: 11/13/2022] Open
Abstract
A master clock located in the suprachiasmatic nucleus (SCN) regulates the circadian rhythm of physiological and behavioral activities in mammals. The SCN has two main functions in the regulation: an endogenous clock produces the endogenous rhythmic signal in body rhythms, and a calibrator synchronizes the body rhythms to the external light-dark cycle. These two functions have been determined to depend on either the dynamic behaviors of individual neurons or the whole SCN neuronal network. In this review, we first introduce possible network structures for the SCN, as revealed by time series analysis from real experimental data. It was found that the SCN network is heterogeneous and sparse, that is, the average shortest path length is very short, some nodes are hubs with large node degrees but most nodes have small node degrees, and the average node degree of the network is small. Secondly, the effects of the SCN network structure on the SCN function are reviewed based on mathematical models of the SCN network. It was found that robust rhythms with large amplitudes, a high synchronization between SCN neurons and a large entrainment ability exists mainly in small-world and scale-free type networks, but not other types. We conclude that the SCN most probably is an efficient small-world type or scale-free type network, which drives SCN function.
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Affiliation(s)
- Changgui Gu
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jiahui Li
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jian Zhou
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Huijie Yang
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jos Rohling
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
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29
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Sueviriyapan N, Granados-Fuentes D, Simon T, Herzog ED, Henson MA. Modelling the functional roles of synaptic and extra-synaptic γ-aminobutyric acid receptor dynamics in circadian timekeeping. J R Soc Interface 2021; 18:20210454. [PMID: 34520693 PMCID: PMC8440032 DOI: 10.1098/rsif.2021.0454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/23/2021] [Indexed: 11/12/2022] Open
Abstract
In the suprachiasmatic nucleus (SCN), γ-aminobutyric acid (GABA) is a primary neurotransmitter. GABA can signal through two types of GABAA receptor subunits, often referred to as synaptic GABAA (gamma subunit) and extra-synaptic GABAA (delta subunit). To test the functional roles of these distinct GABAA in regulating circadian rhythms, we developed a multicellular SCN model where we could separately compare the effects of manipulating GABA neurotransmitter or receptor dynamics. Our model predicted that blocking GABA signalling modestly increased synchrony among circadian cells, consistent with published SCN pharmacology. Conversely, the model predicted that lowering GABAA receptor density reduced firing rate, circadian cell fraction, amplitude and synchrony among individual neurons. When we tested these predictions, we found that the knockdown of delta GABAA reduced the amplitude and synchrony of clock gene expression among cells in SCN explants. The model further predicted that increasing gamma GABAA densities could enhance synchrony, as opposed to increasing delta GABAA densities. Overall, our model reveals how blocking GABAA receptors can modestly increase synchrony, while increasing the relative density of gamma over delta subunits can dramatically increase synchrony. We hypothesize that increased gamma GABAA density in the winter could underlie the tighter phase relationships among SCN cells.
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Affiliation(s)
- Natthapong Sueviriyapan
- Department of Chemical Engineering and the Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, USA
| | | | - Tatiana Simon
- Department of Biology, Washington University in St Louis, Saint Louis, MO, USA
| | - Erik D. Herzog
- Department of Biology, Washington University in St Louis, Saint Louis, MO, USA
| | - Michael A. Henson
- Department of Chemical Engineering and the Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, USA
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30
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Hughes ATL, Samuels RE, Baño-Otálora B, Belle MDC, Wegner S, Guilding C, Northeast RC, Loudon ASI, Gigg J, Piggins HD. Timed daily exercise remodels circadian rhythms in mice. Commun Biol 2021; 4:761. [PMID: 34145388 PMCID: PMC8213798 DOI: 10.1038/s42003-021-02239-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 05/18/2021] [Indexed: 01/26/2023] Open
Abstract
Regular exercise is important for physical and mental health. An underexplored and intriguing property of exercise is its actions on the body’s 24 h or circadian rhythms. Molecular clock cells in the brain’s suprachiasmatic nuclei (SCN) use electrical and chemical signals to orchestrate their activity and convey time of day information to the rest of the brain and body. To date, the long-lasting effects of regular physical exercise on SCN clock cell coordination and communication remain unresolved. Utilizing mouse models in which SCN intercellular neuropeptide signaling is impaired as well as those with intact SCN neurochemical signaling, we examined how daily scheduled voluntary exercise (SVE) influenced behavioral rhythms and SCN molecular and neuronal activities. We show that in mice with disrupted neuropeptide signaling, SVE promotes SCN clock cell synchrony and robust 24 h rhythms in behavior. Interestingly, in both intact and neuropeptide signaling deficient animals, SVE reduces SCN neural activity and alters GABAergic signaling. These findings illustrate the potential utility of regular exercise as a long-lasting and effective non-invasive intervention in the elderly or mentally ill where circadian rhythms can be blunted and poorly aligned to the external world. Using mice with disrupted neuropeptide signaling, Hughes et al. show that daily scheduled voluntary exercise (SVE) promotes suprachiasmatic nuclei (SCN) clock cell synchrony and robust 24 h rhythms in behavior. This study suggests the potential utility of regular exercise as a non-invasive intervention for the elderly or mentally ill, where circadian rhythms can be poorly aligned to the external world.
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Affiliation(s)
- Alun Thomas Lloyd Hughes
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Rayna Eve Samuels
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Beatriz Baño-Otálora
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Mino David Charles Belle
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,University of Exeter Medical School, Exeter, UK
| | - Sven Wegner
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Clare Guilding
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,School of Medical Education, Newcastle University, Newcastle, UK
| | | | | | - John Gigg
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Hugh David Piggins
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK. .,School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, UK.
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31
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Ono D, Honma KI, Honma S. Roles of Neuropeptides, VIP and AVP, in the Mammalian Central Circadian Clock. Front Neurosci 2021; 15:650154. [PMID: 33935635 PMCID: PMC8081951 DOI: 10.3389/fnins.2021.650154] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 03/10/2021] [Indexed: 12/14/2022] Open
Abstract
In mammals, the central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Individual SCN cells exhibit intrinsic oscillations, and their circadian period and robustness are different cell by cell in the absence of cellular coupling, indicating that cellular coupling is important for coherent circadian rhythms in the SCN. Several neuropeptides such as arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) are expressed in the SCN, where these neuropeptides function as synchronizers and are important for entrainment to environmental light and for determining the circadian period. These neuropeptides are also related to developmental changes of the circadian system of the SCN. Transcription factors are required for the formation of neuropeptide-related neuronal networks. Although VIP is critical for synchrony of circadian rhythms in the neonatal SCN, it is not required for synchrony in the embryonic SCN. During postnatal development, the clock genes cryptochrome (Cry)1 and Cry2 are involved in the maturation of cellular networks, and AVP is involved in SCN networks. This mini-review focuses on the functional roles of neuropeptides in the SCN based on recent findings in the literature.
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Affiliation(s)
- Daisuke Ono
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.,Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Ken-Ichi Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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32
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Ding G, Li X, Hou X, Zhou W, Gong Y, Liu F, He Y, Song J, Wang J, Basil P, Li W, Qian S, Saha P, Wang J, Cui C, Yang T, Zou K, Han Y, Amos CI, Xu Y, Chen L, Sun Z. REV-ERB in GABAergic neurons controls diurnal hepatic insulin sensitivity. Nature 2021; 592:763-767. [PMID: 33762728 PMCID: PMC8085086 DOI: 10.1038/s41586-021-03358-w] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 02/12/2021] [Indexed: 02/08/2023]
Abstract
Systemic insulin sensitivity shows a diurnal rhythm with a peak upon waking1,2. The molecular mechanism that underlies this temporal pattern is unclear. Here we show that the nuclear receptors REV-ERB-α and REV-ERB-β (referred to here as 'REV-ERB') in the GABAergic (γ-aminobutyric acid-producing) neurons in the suprachiasmatic nucleus (SCN) (SCNGABA neurons) control the diurnal rhythm of insulin-mediated suppression of hepatic glucose production in mice, without affecting diurnal eating or locomotor behaviours during regular light-dark cycles. REV-ERB regulates the rhythmic expression of genes that are involved in neurotransmission in the SCN, and modulates the oscillatory firing activity of SCNGABA neurons. Chemogenetic stimulation of SCNGABA neurons at waking leads to glucose intolerance, whereas restoration of the temporal pattern of either SCNGABA neuron firing or REV-ERB expression rescues the time-dependent glucose metabolic phenotype caused by REV-ERB depletion. In individuals with diabetes, an increased level of blood glucose after waking is a defining feature of the 'extended dawn phenomenon'3,4. Patients with type 2 diabetes with the extended dawn phenomenon exhibit a differential temporal pattern of expression of REV-ERB genes compared to patients with type 2 diabetes who do not have the extended dawn phenomenon. These findings provide mechanistic insights into how the central circadian clock regulates the diurnal rhythm of hepatic insulin sensitivity, with implications for our understanding of the extended dawn phenomenon in type 2 diabetes.
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Affiliation(s)
- Guolian Ding
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai, China
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Xin Li
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Xinguo Hou
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Wenjun Zhou
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Yingyun Gong
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
- Department of Endocrinology and Metabolism, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Fuqiang Liu
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Yanlin He
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
- Laboratory of Brain Glycemia and Metabolism Control, Pennington Biomedical Research Center, Baton Rouge, LA, USA
| | - Jia Song
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Jing Wang
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Paul Basil
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Wenbo Li
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Sichong Qian
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
| | - Pradip Saha
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Jinbang Wang
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Chen Cui
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China
| | - Tingting Yang
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Kexin Zou
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai, China
| | - Younghun Han
- Department of Medicine, Section of Epidemiology and Population Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Christopher I Amos
- Department of Medicine, Section of Epidemiology and Population Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Yong Xu
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Li Chen
- Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, China.
| | - Zheng Sun
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, USA.
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
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Maejima T, Tsuno Y, Miyazaki S, Tsuneoka Y, Hasegawa E, Islam MT, Enoki R, Nakamura TJ, Mieda M. GABA from vasopressin neurons regulates the time at which suprachiasmatic nucleus molecular clocks enable circadian behavior. Proc Natl Acad Sci U S A 2021; 118:e2010168118. [PMID: 33526663 PMCID: PMC8017960 DOI: 10.1073/pnas.2010168118] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals, is a network structure composed of multiple types of γ-aminobutyric acid (GABA)-ergic neurons and glial cells. However, the roles of GABA-mediated signaling in the SCN network remain controversial. Here, we report noticeable impairment of the circadian rhythm in mice with a specific deletion of the vesicular GABA transporter in arginine vasopressin (AVP)-producing neurons. These mice showed disturbed diurnal rhythms of GABAA receptor-mediated synaptic transmission in SCN neurons and marked lengthening of the activity time in circadian behavioral rhythms due to the extended interval between morning and evening locomotor activities. Synchrony of molecular circadian oscillations among SCN neurons did not significantly change, whereas the phase relationships between SCN molecular clocks and circadian morning/evening locomotor activities were altered significantly, as revealed by PER2::LUC imaging of SCN explants and in vivo recording of intracellular Ca2+ in SCN AVP neurons. In contrast, daily neuronal activity in SCN neurons in vivo clearly showed a bimodal pattern that correlated with dissociated morning/evening locomotor activities. Therefore, GABAergic transmission from AVP neurons regulates the timing of SCN neuronal firing to temporally restrict circadian behavior to appropriate time windows in SCN molecular clocks.
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Affiliation(s)
- Takashi Maejima
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, 920-8640 Ishikawa, Japan
| | - Yusuke Tsuno
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, 920-8640 Ishikawa, Japan
| | - Shota Miyazaki
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, 214-8571 Kanagawa, Japan
| | - Yousuke Tsuneoka
- Department of Anatomy, Faculty of Medicine, Toho University, 143-8540 Tokyo, Japan
| | - Emi Hasegawa
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, 920-8640 Ishikawa, Japan
| | - Md Tarikul Islam
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, 920-8640 Ishikawa, Japan
| | - Ryosuke Enoki
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 444-8787 Okazaki, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, 444-8787 Okazaki, Japan
| | - Takahiro J Nakamura
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, 214-8571 Kanagawa, Japan
| | - Michihiro Mieda
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, 920-8640 Ishikawa, Japan;
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34
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Resilience in the suprachiasmatic nucleus: Implications for aging and Alzheimer's disease. Exp Gerontol 2021; 147:111258. [PMID: 33516909 DOI: 10.1016/j.exger.2021.111258] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 12/27/2020] [Accepted: 01/24/2021] [Indexed: 12/13/2022]
Abstract
Many believe that the circadian impairments associated with aging and Alzheimer's disease are, simply enough, a byproduct of tissue degeneration within the central pacemaker, the suprachiasmatic nucleus (SCN). However, the findings that have accumulated to date examining the SCNs obtained postmortem from the brains of older individuals, or those diagnosed with Alzheimer's disease upon autopsy, suggest only limited atrophy. We review this literature as well as a complementary one concerning fetal-donor SCN transplant, which established that many circadian timekeeping functions can be maintained with rudimentary (structurally limited) representations of the SCN. Together, these corpora of data suggest that the SCN is a resilient brain region that cannot be directly (or solely) implicated in the behavioral manifestations of circadian disorganization often witnessed during aging as well as early and late progression of Alzheimer's disease. We complete our review by suggesting future directions of research that may bridge this conceptual divide and briefly discuss the implications of it for improving health outcomes in later adulthood.
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35
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Belle MDC, Baño-Otalora B, Piggins HD. Perforated Multi-Electrode Array Recording in Hypothalamic Brain Slices. Methods Mol Biol 2021; 2130:263-285. [PMID: 33284451 DOI: 10.1007/978-1-0716-0381-9_20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The ability to record ensemble action potential (AP) discharge frequencies from large populations of neurons over extended periods of time in vitro offers clear advantages in neuroscience and circadian biology research. Here, we provide an overview of a step-by-step method to perform multisite extracellular AP activity recordings in suprachiasmatic and mediobasal hypothalamic nuclei brain slices, using a state-of-the-art perforated multielectrode array system. Further, we describe in detail a setup architecture which systematically delivers stable, high-quality recordings with excellent anatomical accuracy and consistency. We also provide some procedural, technical, and methodological troubleshooting notes and examples of good quality recordings.
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Affiliation(s)
- Mino D C Belle
- Faculty of Biology, Medicine, and Health, AV Hill Building, University of Manchester, Manchester, UK.
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, UK.
| | - Beatriz Baño-Otalora
- Faculty of Biology, Medicine, and Health, AV Hill Building, University of Manchester, Manchester, UK
| | - Hugh D Piggins
- Faculty of Biology, Medicine, and Health, AV Hill Building, University of Manchester, Manchester, UK
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, UK
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36
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Seasonality and light phase-resetting in the mammalian circadian rhythm. Sci Rep 2020; 10:19506. [PMID: 33177530 PMCID: PMC7658258 DOI: 10.1038/s41598-020-74002-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/18/2020] [Indexed: 11/13/2022] Open
Abstract
We study the impact of light on the mammalian circadian system using the theory of phase response curves. Using a recently developed ansatz we derive a low-dimensional macroscopic model for the core circadian clock in mammals. Significantly, the variables and parameters in our model have physiological interpretations and may be compared with experimental results. We focus on the effect of four key factors which help shape the mammalian phase response to light: heterogeneity in the population of oscillators, the structure of the typical light phase response curve, the fraction of oscillators which receive direct light input and changes in the coupling strengths associated with seasonal day-lengths. We find these factors can explain several experimental results and provide insight into the processing of light information in the mammalian circadian system. In particular, we find that the sensitivity of the circadian system to light may be modulated by changes in the relative coupling forces between the light sensing and non-sensing populations. Finally, we show how seasonal day-length, after-effects to light entrainment and seasonal variations in light sensitivity in the mammalian circadian clock are interrelated.
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37
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Circadian VIPergic Neurons of the Suprachiasmatic Nuclei Sculpt the Sleep-Wake Cycle. Neuron 2020; 108:486-499.e5. [PMID: 32916091 PMCID: PMC7803671 DOI: 10.1016/j.neuron.2020.08.001] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 10/07/2019] [Accepted: 07/31/2020] [Indexed: 01/08/2023]
Abstract
Although the mammalian rest-activity cycle is controlled by a "master clock" in the suprachiasmatic nucleus (SCN) of the hypothalamus, it is unclear how firing of individual SCN neurons gates individual features of daily activity. Here, we demonstrate that a specific transcriptomically identified population of mouse VIP+ SCN neurons is active at the "wrong" time of day-nighttime-when most SCN neurons are silent. Using chemogenetic and optogenetic strategies, we show that these neurons and their cellular clocks are necessary and sufficient to gate and time nighttime sleep but have no effect upon daytime sleep. We propose that mouse nighttime sleep, analogous to the human siesta, is a "hard-wired" property gated by specific neurons of the master clock to favor subsequent alertness prior to dawn (a circadian "wake maintenance zone"). Thus, the SCN is not simply a 24-h metronome: specific populations sculpt critical features of the sleep-wake cycle.
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38
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Ono D, Honma KI, Honma S. GABAergic mechanisms in the suprachiasmatic nucleus that influence circadian rhythm. J Neurochem 2020; 157:31-41. [PMID: 32198942 DOI: 10.1111/jnc.15012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/06/2020] [Accepted: 03/09/2020] [Indexed: 01/23/2023]
Abstract
The mammalian central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN contains multiple circadian oscillators which synchronize with each other via several neurotransmitters. Importantly, an inhibitory neurotransmitter, γ-amino butyric acid (GABA), is expressed in almost all SCN neurons. In this review, we discuss how GABA influences circadian rhythms in the SCN. Excitatory and inhibitory effects of GABA may depend on intracellular Cl- concentration, in which several factors such as day-length, time of day, development, and region in the SCN may be involved. GABA also mediates oscillatory coupling of the circadian rhythms in the SCN. Recent genetic approaches reveal that GABA refines circadian output rhythms, but not circadian oscillations in the SCN. Since several efferent projections of the SCN have been suggested, GABA might work downstream of neuronal pathways from the SCN which regulate the temporal order of physiology and behavior.
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Affiliation(s)
- Daisuke Ono
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.,Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Ken-Ichi Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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39
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Mieda M. The central circadian clock of the suprachiasmatic nucleus as an ensemble of multiple oscillatory neurons. Neurosci Res 2020; 156:24-31. [DOI: 10.1016/j.neures.2019.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 08/09/2019] [Indexed: 10/26/2022]
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40
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McNeill JK, Walton JC, Ryu V, Albers HE. The Excitatory Effects of GABA within the Suprachiasmatic Nucleus: Regulation of Na-K-2Cl Cotransporters (NKCCs) by Environmental Lighting Conditions. J Biol Rhythms 2020; 35:275-286. [PMID: 32406304 DOI: 10.1177/0748730420924271] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The suprachiasmatic nucleus (SCN) contains a pacemaker that generates circadian rhythms and entrains them with the 24-h light-dark cycle (LD). The SCN is composed of 16,000 to 20,000 heterogeneous neurons in bilaterally paired nuclei. γ-amino butyric acid (GABA) is the primary neurochemical signal within the SCN and plays a key role in regulating circadian function. While GABA is the primary inhibitory neurotransmitter in the brain, there is now evidence that GABA can also exert excitatory effects in the adult brain. Cation chloride cotransporters determine the effects of GABA on chloride equilibrium, thereby determining whether GABA produces hyperpolarizing or depolarizing actions following activation of GABAA receptors. The activity of Na-K-2Cl cotransporter1 (NKCC1), the most prevalent chloride influx cotransporter isoform in the brain, plays a critical role in determining whether GABA has depolarizing effects. In the present study, we tested the hypothesis that NKCC1 protein expression in the SCN is regulated by environmental lighting and displays daily and circadian changes in the intact circadian system of the Syrian hamster. In hamsters housed in constant light (LL), the overall NKCC1 immunoreactivity (NKCC1-ir) in the SCN was significantly greater than in hamsters housed in LD or constant darkness (DD), although NKCC1 protein levels in the SCN were not different between hamsters housed in LD and DD. In hamsters housed in LD cycles, no differences in NKCC1-ir within the SCN were observed over the 24-h cycle. NKCC1 protein in the SCN was found to vary significantly over the circadian cycle in hamsters housed in free-running conditions. Overall, NKCC1 protein was greater in the ventral SCN than in the dorsal SCN, although no significant differences were observed across lighting conditions or time of day in either subregion. These data support the hypothesis that NKCC1 protein expression can be regulated by environmental lighting and circadian mechanisms within the SCN.
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Affiliation(s)
- John K McNeill
- Neuroscience Institute and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia
| | - James C Walton
- Neuroscience Institute and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia
| | - Vitaly Ryu
- Neuroscience Institute and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia
| | - H Elliott Albers
- Neuroscience Institute and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia
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41
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Aberrant mPFC GABAergic synaptic transmission and fear behavior in neuroligin-2 R215H knock-in mice. Brain Res 2020; 1730:146671. [DOI: 10.1016/j.brainres.2020.146671] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 01/10/2020] [Accepted: 01/12/2020] [Indexed: 11/19/2022]
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42
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Hastings MH, Smyllie NJ, Patton AP. Molecular-genetic Manipulation of the Suprachiasmatic Nucleus Circadian Clock. J Mol Biol 2020; 432:3639-3660. [PMID: 31996314 DOI: 10.1016/j.jmb.2020.01.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/10/2020] [Accepted: 01/15/2020] [Indexed: 01/08/2023]
Abstract
Circadian (approximately daily) rhythms of physiology and behaviour adapt organisms to the alternating environments of day and night. The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal circadian timekeeper of mammals. The mammalian cell-autonomous circadian clock is built around a self-sustaining transcriptional-translational negative feedback loop (TTFL) in which the negative regulators Per and Cry suppress their own expression, which is driven by the positive regulators Clock and Bmal1. Importantly, such TTFL-based clocks are present in all major tissues across the organism, and the SCN is their central co-ordinator. First, we analyse SCN timekeeping at the cell-autonomous and the circuit-based levels of organisation. We consider how molecular-genetic manipulations have been used to probe cell-autonomous timing in the SCN, identifying the integral components of the clock. Second, we consider new approaches that enable real-time monitoring of the activity of these clock components and clock-driven cellular outputs. Finally, we review how intersectional genetic manipulations of the cell-autonomous clockwork can be used to determine how SCN cells interact to generate an ensemble circadian signal. Critically, it is these network-level interactions that confer on the SCN its emergent properties of robustness, light-entrained phase and precision- properties that are essential for its role as the central co-ordinator. Remaining gaps in knowledge include an understanding of how the TTFL proteins behave individually and in complexes: whether particular SCN neuronal populations act as pacemakers, and if so, by which signalling mechanisms, and finally the nature of the recently discovered role of astrocytes within the SCN network.
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Affiliation(s)
- Michael H Hastings
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK.
| | - Nicola J Smyllie
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK
| | - Andrew P Patton
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK
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Rohr KE, Pancholi H, Haider S, Karow C, Modert D, Raddatz NJ, Evans J. Seasonal plasticity in GABA A signaling is necessary for restoring phase synchrony in the master circadian clock network. eLife 2019; 8:49578. [PMID: 31746738 PMCID: PMC6867713 DOI: 10.7554/elife.49578] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 10/15/2019] [Indexed: 12/14/2022] Open
Abstract
Annual changes in the environment threaten survival, and numerous biological processes in mammals adjust to this challenge via seasonal encoding by the suprachiasmatic nucleus (SCN). To tune behavior according to day length, SCN neurons display unified rhythms with synchronous phasing when days are short, but will divide into two sub-clusters when days are long. The transition between SCN states is critical for maintaining behavioral responses to seasonal change, but the mechanisms regulating this form of neuroplasticity remain unclear. Here we identify that a switch in chloride transport and GABAA signaling is critical for maintaining state plasticity in the SCN network. Further, we reveal that blocking excitatory GABAA signaling locks the SCN into its long day state. Collectively, these data demonstrate that plasticity in GABAA signaling dictates how clock neurons interact to maintain environmental encoding. Further, this work highlights factors that may influence susceptibility to seasonal disorders in humans. In winter, as the days become shorter, millions of people find that their mood and energy levels start to drop. They crave carbohydrates, struggle with their weight, and find it harder to get out of bed in the mornings. These individuals are suffering from the ‘winter blues’ or seasonal affective disorder (SAD), and most find that their symptoms spontaneously improve in the spring when the days become longer again. Many also benefit from bright light therapy during the winter months, but not everyone responds fully to this treatment, so additional options are needed. The winter blues occur when the brain adjusts to changes in day length with the onset of winter. The brain region responsible for making this adjustment is the suprachiasmatic nucleus (SCN). The SCN is the master clock of the brain that coordinates the body’s circadian rhythms – the daily fluctuations in things like appetite, body temperature, sleep and wakefulness. But as well as being the brain’s clock, the SCN is also the brain’s calendar. In winter, when the days are short, SCN neurons coordinate their activity and fire in synchrony. But in summer, when the days are long, SCN neurons divide into two clusters, which fire at different times. By transitioning between these two states, the SCN helps the body adjust to seasonal changes in day length. Rohr, Pancholi et al. now provide new insight into the mechanism behind this process by showing that light alters the neurochemistry of the SCN. Exposing mice to long days causes a brain chemical called GABA to switch from inhibiting neurons in the SCN to activating them. Blocking this switch from inhibition to activation locks the SCN into its 'summer state'. Rohr, Pancholi et al. propose that this failure to transition to the winter state may be an interesting way to prevent the winter blues. While much remains to be learned about this process, these findings pave the way for better understanding the neurobiology of winter depression and how best to treat it.
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Affiliation(s)
- Kayla E Rohr
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - Harshida Pancholi
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - Shabi Haider
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - Christopher Karow
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - David Modert
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - Nicholas J Raddatz
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
| | - Jennifer Evans
- Department of Biomedical Sciences, Marquette University, Milwaukee, United States
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Kanders K, Stoop N, Stoop R. Universality in the firing of minicolumnar-type neural networks. CHAOS (WOODBURY, N.Y.) 2019; 29:093109. [PMID: 31575124 DOI: 10.1063/1.5111867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/19/2019] [Indexed: 06/10/2023]
Abstract
An open question in biological neural networks is whether changes in firing modalities are mainly an individual network property or whether networks follow a joint pathway. For the early developmental period, our study focusing on a simple network class of excitatory and inhibitory neurons suggests the following answer: Networks with considerable variation of topology and dynamical parameters follow a universal firing paradigm that evolves as the overall connectivity strength and firing level increase, as seen in the process of network maturation. A simple macroscopic model reproduces the main features of the paradigm as a result of the competition between the fundamental dynamical system notions of synchronization vs chaos and explains why in simulations the paradigm is robust regarding differences in network topology and largely independent from the neuron model used. The presented findings reflect the first dozen days of dissociated neuronal in vitro cultures (upon following the developmental period bears similarly universal features but is characterized by the processes of neuronal facilitation and depression that do not require to be considered for the first developmental period).
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Affiliation(s)
- Karlis Kanders
- Institute of Neuroinformatics, University of Zurich and ETH Zurich, 8057 Zurich, Switzerland
| | - Norbert Stoop
- Institute for Building Materials, ETH Zurich, 8092 Zurich, Switzerland
| | - Ruedi Stoop
- Institute of Neuroinformatics, University of Zurich and ETH Zurich, 8057 Zurich, Switzerland
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45
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Abstract
Circadian rhythms are driven by a transcription-translation feedback loop that separates anabolic and catabolic processes across the Earth's 24-h light-dark cycle. Central pacemaker neurons that perceive light entrain a distributed clock network and are closely juxtaposed with hypothalamic neurons involved in regulation of sleep/wake and fast/feeding states. Gaps remain in identifying how pacemaker and extrapacemaker neurons communicate with energy-sensing neurons and the distinct role of circuit interactions versus transcriptionally driven cell-autonomous clocks in the timing of organismal bioenergetics. In this review, we discuss the reciprocal relationship through which the central clock drives appetitive behavior and metabolic homeostasis and the pathways through which nutrient state and sleep/wake behavior affect central clock function.
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Affiliation(s)
- Jonathan Cedernaes
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Nathan Waldeck
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Joseph Bass
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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46
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Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is remarkable. Despite numbering only about 10,000 neurons on each side of the third ventricle, the SCN is our principal circadian clock, directing the daily cycles of behaviour and physiology that set the tempo of our lives. When this nucleus is isolated in organotypic culture, its autonomous timing mechanism can persist indefinitely, with precision and robustness. The discovery of the cell-autonomous transcriptional and post-translational feedback loops that drive circadian activity in the SCN provided a powerful exemplar of the genetic specification of complex mammalian behaviours. However, the analysis of circadian time-keeping is moving beyond single cells. Technical and conceptual advances, including intersectional genetics, multidimensional imaging and network theory, are beginning to uncover the circuit-level mechanisms and emergent properties that make the SCN a uniquely precise and robust clock. However, much remains unknown about the SCN, not least the intrinsic properties of SCN neurons, its circuit topology and the neuronal computations that these circuits support. Moreover, the convention that the SCN is a neuronal clock has been overturned by the discovery that astrocytes are an integral part of the timepiece. As a test bed for examining the relationships between genes, cells and circuits in sculpting complex behaviours, the SCN continues to offer powerful lessons and opportunities for contemporary neuroscience.
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47
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Ono D, Honma KI, Yanagawa Y, Yamanaka A, Honma S. GABA in the suprachiasmatic nucleus refines circadian output rhythms in mice. Commun Biol 2019; 2:232. [PMID: 31263776 PMCID: PMC6588595 DOI: 10.1038/s42003-019-0483-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 05/29/2019] [Indexed: 01/10/2023] Open
Abstract
In mammals, the circadian rhythms are regulated by the central clock located in the hypothalamic suprachiasmatic nucleus (SCN), which is composed of heterogeneous neurons with various neurotransmitters. Among them an inhibitory neurotransmitter, γ-Amino-Butyric-Acid (GABA), is expressed in almost all SCN neurons, however, its role in the circadian physiology is still unclear. Here, we show that the SCN of fetal mice lacking vesicular GABA transporter (VGAT-/-) or GABA synthesizing enzyme, glutamate decarboxylase (GAD65-/-/67-/-), shows burst firings associated with large Ca2+ spikes throughout 24 hours, which spread over the entire SCN slice in synchrony. By contrast, circadian PER2 rhythms in VGAT-/- and GAD65-/-/67-/- SCN remain intact. SCN-specific VGAT deletion in adult mice dampens circadian behavior rhythm. These findings indicate that GABA in the fetal SCN is necessary for refinement of the circadian firing rhythm and, possibly, for stabilizing the output signals, but not for circadian integration of multiple cellular oscillations.
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Affiliation(s)
- Daisuke Ono
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
- Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, 466-8550 Japan
| | - Ken-ichi Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638 Japan
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511 Japan
| | - Akihiro Yamanaka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
- Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya, 466-8550 Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638 Japan
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48
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A Symphony of Signals: Intercellular and Intracellular Signaling Mechanisms Underlying Circadian Timekeeping in Mice and Flies. Int J Mol Sci 2019; 20:ijms20092363. [PMID: 31086044 PMCID: PMC6540063 DOI: 10.3390/ijms20092363] [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: 04/01/2019] [Revised: 05/10/2019] [Accepted: 05/10/2019] [Indexed: 12/11/2022] Open
Abstract
The central pacemakers of circadian timekeeping systems are highly robust yet adaptable, providing the temporal coordination of rhythms in behavior and physiological processes in accordance with the demands imposed by environmental cycles. These features of the central pacemaker are achieved by a multi-oscillator network in which individual cellular oscillators are tightly coupled to the environmental day-night cycle, and to one another via intercellular coupling. In this review, we will summarize the roles of various neurotransmitters and neuropeptides in the regulation of circadian entrainment and synchrony within the mammalian and Drosophila central pacemakers. We will also describe the diverse functions of protein kinases in the relay of input signals to the core oscillator or the direct regulation of the molecular clock machinery.
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49
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Michel S, Meijer JH. From clock to functional pacemaker. Eur J Neurosci 2019; 51:482-493. [PMID: 30793396 PMCID: PMC7027845 DOI: 10.1111/ejn.14388] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/23/2019] [Accepted: 02/11/2019] [Indexed: 12/17/2022]
Abstract
In mammals, the central pacemaker that coordinates 24‐hr rhythms is located in the suprachiasmatic nucleus (SCN). Individual neurons of the SCN have a molecular basis for rhythm generation and hence, they function as cell autonomous oscillators. Communication and synchronization among these neurons are crucial for obtaining a coherent rhythm at the population level, that can serve as a pace making signal for brain and body. Hence, the ability of single SCN neurons to produce circadian rhythms is equally important as the ability of these neurons to synchronize one another, to obtain a bona fide pacemaker at the SCN tissue level. In this chapter we will discuss the mechanisms underlying synchronization, and plasticity herein, which allows adaptation to changes in day length. Furthermore, we will discuss deterioration in synchronization among SCN neurons in aging, and gain in synchronization by voluntary physical activity or exercise.
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Affiliation(s)
- Stephan Michel
- Group Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H Meijer
- Group Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
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El Cheikh Hussein L, Mollard P, Bonnefont X. Molecular and Cellular Networks in The Suprachiasmatic Nuclei. Int J Mol Sci 2019; 20:ijms20082052. [PMID: 31027315 PMCID: PMC6514755 DOI: 10.3390/ijms20082052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/18/2019] [Accepted: 04/23/2019] [Indexed: 12/20/2022] Open
Abstract
Why do we experience the ailments of jetlag when we travel across time zones? Why is working night-shifts so detrimental to our health? In other words, why can’t we readily choose and stick to non-24 h rhythms? Actually, our daily behavior and physiology do not simply result from the passive reaction of our organism to the external cycle of days and nights. Instead, an internal clock drives the variations in our bodily functions with a period close to 24 h, which is supposed to enhance fitness to regular and predictable changes of our natural environment. This so-called circadian clock relies on a molecular mechanism that generates rhythmicity in virtually all of our cells. However, the robustness of the circadian clock and its resilience to phase shifts emerge from the interaction between cell-autonomous oscillators within the suprachiasmatic nuclei (SCN) of the hypothalamus. Thus, managing jetlag and other circadian disorders will undoubtedly require extensive knowledge of the functional organization of SCN cell networks. Here, we review the molecular and cellular principles of circadian timekeeping, and their integration in the multi-cellular complexity of the SCN. We propose that new, in vivo imaging techniques now enable to address these questions directly in freely moving animals.
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Affiliation(s)
- Lama El Cheikh Hussein
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
| | - Patrice Mollard
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
| | - Xavier Bonnefont
- Institut de Génomique Fonctionnelle (IGF), University Montpellier, CNRS, INSERM, 34094 Montpellier, France.
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