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Evans JA, Schwartz WJ. On the origin and evolution of the dual oscillator model underlying the photoperiodic clockwork in the suprachiasmatic nucleus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:503-511. [PMID: 37481773 PMCID: PMC10924288 DOI: 10.1007/s00359-023-01659-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 07/07/2023] [Accepted: 07/13/2023] [Indexed: 07/25/2023]
Abstract
Decades have now passed since Colin Pittendrigh first proposed a model of a circadian clock composed of two coupled oscillators, individually responsive to the rising and setting sun, as a flexible solution to the challenge of behavioral and physiological adaptation to the changing seasons. The elegance and predictive power of this postulation has stimulated laboratories around the world in searches to identify and localize such hypothesized evening and morning oscillators, or sets of oscillators, in insects, rodents, and humans, with experimental designs and approaches keeping pace over the years with technological advances in biology and neuroscience. Here, we recount the conceptual origin and highlight the subsequent evolution of this dual oscillator model for the circadian clock in the mammalian suprachiasmatic nucleus; and how, despite our increasingly sophisticated view of this multicellular pacemaker, Pittendrigh's binary conception has remained influential in our clock models and metaphors.
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Affiliation(s)
- Jennifer A Evans
- Department of Biomedical Sciences, College of Health Sciences, Marquette University, Milwaukee, WI, USA.
| | - William J Schwartz
- Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, USA
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and Engineering, University of Groningen, Groningen, The Netherlands
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2
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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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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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Bonnefont X. Cell Signaling in the Circadian Pacemaker: New Insights from in vivo Imaging. Neuroendocrinology 2024:1-8. [PMID: 38754404 DOI: 10.1159/000539344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 05/12/2024] [Indexed: 05/18/2024]
Abstract
BACKGROUND "One for all, and all for one," the famous rallying cry of the Three Musketeers, in Alexandre Dumas's popular novel, certainly applies to the 20,000 cells composing the suprachiasmatic nuclei (SCN). These cells work together to form the central clock that coordinates body rhythms in tune with the day-night cycle. Like virtually every body cell, individual SCN cells exhibit autonomous circadian oscillations, but this rhythmicity only reaches a high level of precision and robustness when the cells are coupled with their neighbors. Therefore, understanding the functional network organization of SCN cells beyond their core rhythmicity is an important issue in circadian biology. SUMMARY The present review summarizes the main results from our recent study demonstrating the feasibility of recording SCN cells in freely moving mice and the significance of variations in intracellular calcium over several timescales. KEY MESSAGE We discuss how in vivo imaging at the cell level will be pivotal to interrogate the mammalian master clock, in an integrated context that preserves the SCN network organization, with intact inputs and outputs.
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Affiliation(s)
- Xavier Bonnefont
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, Montpellier, France
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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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Oka S, Ogawa A, Osada T, Tanaka M, Nakajima K, Kamagata K, Aoki S, Oshima Y, Tanaka S, Kirino E, Nakamura TJ, Konishi S. Diurnal Variation of Brain Activity in the Human Suprachiasmatic Nucleus. J Neurosci 2024; 44:e1730232024. [PMID: 38238074 PMCID: PMC10883613 DOI: 10.1523/jneurosci.1730-23.2024] [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: 09/13/2023] [Revised: 11/29/2023] [Accepted: 01/09/2024] [Indexed: 02/23/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) is the central clock for circadian rhythms. Animal studies have revealed daily rhythms in the neuronal activity in the SCN. However, the circadian activity of the human SCN has remained elusive. In this study, to reveal the diurnal variation of the SCN activity in humans, we localized the SCN by employing an areal boundary mapping technique to resting-state functional images and investigated the SCN activity using perfusion imaging. In the first experiment (n = 27, including both sexes), we scanned each participant four times a day, every 6 h. Higher activity was observed at noon, while lower activity was recorded in the early morning. In the second experiment (n = 20, including both sexes), the SCN activity was measured every 30 min for 6 h from midnight to dawn. The results showed that the SCN activity gradually decreased and was not associated with the electroencephalography. Furthermore, the SCN activity was compatible with the rodent SCN activity after switching off the lights. These results suggest that the diurnal variation of the human SCN follows the zeitgeber cycles of nocturnal and diurnal mammals and is modulated by physical lights rather than the local time.
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Affiliation(s)
- Satoshi Oka
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Akitoshi Ogawa
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Takahiro Osada
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Masaki Tanaka
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Koji Nakajima
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
- Department of Orthopaedic Surgery, The University of Tokyo School of Medicine, Tokyo 113-0033, Japan
| | - Koji Kamagata
- Department of Radiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Shigeki Aoki
- Department of Radiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Yasushi Oshima
- Department of Orthopaedic Surgery, The University of Tokyo School of Medicine, Tokyo 113-0033, Japan
| | - Sakae Tanaka
- Department of Orthopaedic Surgery, The University of Tokyo School of Medicine, Tokyo 113-0033, Japan
| | - Eiji Kirino
- Department of Psychiatry, Juntendo Shizuoka Hospital, Shizuoka 410-2211, Japan
| | - Takahiro J Nakamura
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kanagawa 214-8571, Japan
| | - Seiki Konishi
- Department of Neurophysiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
- Sportology Center, Juntendo University School of Medicine, Tokyo 113-8421, Japan
- Research Institute for Diseases of Old Age, Juntendo University School of Medicine, Tokyo 113-8421, Japan
- Advanced Research Institute for Health Science, Juntendo University School of Medicine, Tokyo 113-8421, Japan
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Engin A. Misalignment of Circadian Rhythms in Diet-Induced Obesity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1460:27-71. [PMID: 39287848 DOI: 10.1007/978-3-031-63657-8_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/19/2024]
Abstract
The biological clocks of the circadian timing system coordinate cellular and physiological processes and synchronize them with daily cycles. While the central clock in the suprachiasmatic nucleus (SCN) is mainly synchronized by the light/dark cycles, the peripheral clocks react to other stimuli, including the feeding/fasting state, nutrients, sleep-wake cycles, and physical activity. During the disruption of circadian rhythms due to genetic mutations or social and occupational obligations, incorrect arrangement between the internal clock system and environmental rhythms leads to the development of obesity. Desynchronization between the central and peripheral clocks by altered timing of food intake and diet composition leads to uncoupling of the peripheral clocks from the central pacemaker and to the development of metabolic disorders. The strong coupling of the SCN to the light-dark cycle creates a situation of misalignment when food is ingested during the "wrong" time of day. Food-anticipatory activity is mediated by a self-sustained circadian timing, and its principal component is a food-entrainable oscillator. Modifying the time of feeding alone greatly affects body weight, whereas ketogenic diet (KD) influences circadian biology, through the modulation of clock gene expression. Night-eating behavior is one of the causes of circadian disruption, and night eaters have compulsive and uncontrolled eating with severe obesity. By contrast, time-restricted eating (TRE) restores circadian rhythms through maintaining an appropriate daily rhythm of the eating-fasting cycle. The hypothalamus has a crucial role in the regulation of energy balance rather than food intake. While circadian locomotor output cycles kaput (CLOCK) expression levels increase with high-fat diet-induced obesity, peroxisome proliferator-activated receptor-alpha (PPARα) increases the transcriptional level of brain and muscle aryl hydrocarbon receptor nuclear translocator (ARNT)-like 1 (BMAL1) in obese subjects. In this context, effective timing of chronotherapies aiming to correct SCN-driven rhythms depends on an accurate assessment of the SCN phase. In fact, in a multi-oscillator system, local rhythmicity and its disruption reflects the disruption of either local clocks or central clocks, thus imposing rhythmicity on those local tissues, whereas misalignment of peripheral oscillators is due to exosome-based intercellular communication.Consequently, disruption of clock genes results in dyslipidemia, insulin resistance, and obesity, while light exposure during the daytime, food intake during the daytime, and sleeping during the biological night promote circadian alignment between the central and peripheral clocks. Thus, shift work is associated with an increased risk of obesity, diabetes, and cardiovascular diseases because of unusual eating times as well as unusual light exposure and disruption of the circadian rhythm.
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Affiliation(s)
- Atilla Engin
- Faculty of Medicine, Department of General Surgery, Gazi University, Besevler, Ankara, Turkey.
- Mustafa Kemal Mah. 2137. Sok. 8/14, 06520, Cankaya, Ankara, Turkey.
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Hiro S, Kobayashi K, Nemoto T, Enoki R. In-phasic cytosolic-nuclear Ca 2+ rhythms in suprachiasmatic nucleus neurons. Front Neurosci 2023; 17:1323565. [PMID: 38178840 PMCID: PMC10765503 DOI: 10.3389/fnins.2023.1323565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/30/2023] [Indexed: 01/06/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is the master circadian clock in mammals. SCN neurons exhibit circadian Ca2+ rhythms in the cytosol, which is thought to act as a messenger linking the transcriptional/translational feedback loop (TTFL) and physiological activities. Transcriptional regulation occurs in the nucleus in the TTFL model, and Ca2+-dependent kinase regulates the clock gene transcription. However, the Ca2+ regulatory mechanisms between cytosol and nucleus as well as the ionic origin of Ca2+ rhythms remain unclear. In the present study, we monitored circadian-timescale Ca2+ dynamics in the nucleus and cytosol of SCN neurons at the single-cell and network levels. We observed robust nuclear Ca2+ rhythm in the same phase as the cytosolic rhythm in single SCN neurons and entire regions. Neuronal firing inhibition reduced the amplitude of both nuclear and cytosolic Ca2+ rhythms, whereas blocking of Ca2+ release from the endoplasmic reticulum (ER) via ryanodine and inositol 1,4,5-trisphosphate (IP3) receptors had a minor effect on either Ca2+ rhythms. We conclude that the in-phasic circadian Ca2+ rhythms in the cytosol and nucleus are mainly driven by Ca2+ influx from the extracellular space, likely through the nuclear pore. It also raises the possibility that nuclear Ca2+ rhythms directly regulate transcription in situ.
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Affiliation(s)
- Sota Hiro
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Kenta Kobayashi
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
- Section of Viral Vector Development, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Tomomi Nemoto
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Ryosuke Enoki
- Biophotonics Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- Division of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
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Tsuno Y, Peng Y, Horike SI, Wang M, Matsui A, Yamagata K, Sugiyama M, Nakamura TJ, Daikoku T, Maejima T, Mieda M. In vivo recording of suprachiasmatic nucleus dynamics reveals a dominant role of arginine vasopressin neurons in circadian pacesetting. PLoS Biol 2023; 21:e3002281. [PMID: 37643163 PMCID: PMC10465001 DOI: 10.1371/journal.pbio.3002281] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 07/28/2023] [Indexed: 08/31/2023] Open
Abstract
The central circadian clock of the suprachiasmatic nucleus (SCN) is a network consisting of various types of neurons and glial cells. Individual cells have the autonomous molecular machinery of a cellular clock, but their intrinsic periods vary considerably. Here, we show that arginine vasopressin (AVP) neurons set the ensemble period of the SCN network in vivo to control the circadian behavior rhythm. Artificial lengthening of cellular periods by deleting casein kinase 1 delta (CK1δ) in the whole SCN lengthened the free-running period of behavior rhythm to an extent similar to CK1δ deletion specific to AVP neurons. However, in SCN slices, PER2::LUC reporter rhythms of these mice only partially and transiently recapitulated the period lengthening, showing a dissociation between the SCN shell and core with a period instability in the shell. In contrast, in vivo calcium rhythms of both AVP and vasoactive intestinal peptide (VIP) neurons in the SCN of freely moving mice demonstrated stably lengthened periods similar to the behavioral rhythm upon AVP neuron-specific CK1δ deletion, without changing the phase relationships between each other. Furthermore, optogenetic activation of AVP neurons acutely induced calcium increase in VIP neurons in vivo. These results indicate that AVP neurons regulate other SCN neurons, such as VIP neurons, in vivo and thus act as a primary determinant of the SCN ensemble period.
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Affiliation(s)
- Yusuke Tsuno
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Yubo Peng
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Shin-ichi Horike
- Division of Integrated Omics Research, Research Center for Experimental Modeling of Human Disease, Kanazawa University, Kanazawa, Japan
| | - Mohan Wang
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Ayako Matsui
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Kanato Yamagata
- Child Brain Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Mizuki Sugiyama
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kawasaki, Japan
| | - Takahiro J. Nakamura
- Laboratory of Animal Physiology, School of Agriculture, Meiji University, Kawasaki, Japan
| | - Takiko Daikoku
- Division of Animal Disease Model, Research Center for Experimental Modeling of Human Disease, Kanazawa University, Kanazawa, Japan
| | - Takashi Maejima
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Michihiro Mieda
- Department of Integrative Neurophysiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
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10
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Carmona-Alcocer V, Brown LS, Anchan A, Rohr KE, Evans JA. Developmental patterning of peptide transcription in the central circadian clock in both sexes. Front Neurosci 2023; 17:1177458. [PMID: 37274219 PMCID: PMC10235759 DOI: 10.3389/fnins.2023.1177458] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 04/21/2023] [Indexed: 06/06/2023] Open
Abstract
Introduction Neuropeptide signaling modulates the function of central clock neurons in the suprachiasmatic nucleus (SCN) during development and adulthood. Arginine vasopressin (AVP) and vasoactive intestinal peptide (VIP) are expressed early in SCN development, but the precise timing of transcriptional onset has been difficult to establish due to age-related changes in the rhythmic expression of each peptide. Methods To provide insight into spatial patterning of peptide transcription during SCN development, we used a transgenic approach to define the onset of Avp and Vip transcription. Avp-Cre or Vip-Cre males were crossed to Ai9+/+ females, producing offspring in which the fluorescent protein tdTomato (tdT) is expressed at the onset of Avp or Vip transcription. Spatial patterning of Avp-tdT and Vip-tdT expression was examined at critical developmental time points spanning mid-embryonic age to adulthood in both sexes. Results We find that Avp-tdT and Vip-tdT expression is initiated at different developmental time points in spatial subclusters of SCN neurons, with developmental patterning that differs by sex. Conclusions These data suggest that SCN neurons can be distinguished into further subtypes based on the developmental patterning of neuropeptide expression, which may contribute to regional and/or sex differences in cellular function in adulthood.
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Affiliation(s)
- Vania Carmona-Alcocer
- Department of Biomedical Science, Marquette University, Milwaukee, WI, United States
| | - Lindsey S. Brown
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Allston, MA, United States
| | - Aiesha Anchan
- Department of Biomedical Science, Marquette University, Milwaukee, WI, United States
| | - Kayla E. Rohr
- Department of Biomedical Science, Marquette University, Milwaukee, WI, United States
| | - Jennifer A. Evans
- Department of Biomedical Science, Marquette University, Milwaukee, WI, United States
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Waddell H, Stevenson TJ, Mole DJ. The role of the circadian rhythms in critical illness with a focus on acute pancreatitis. Heliyon 2023; 9:e15335. [PMID: 37089281 PMCID: PMC10119767 DOI: 10.1016/j.heliyon.2023.e15335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 01/20/2023] [Accepted: 04/03/2023] [Indexed: 04/25/2023] Open
Abstract
Circadian rhythms are responsible for governing various physiological processes, including hormone secretion, immune responses, metabolism, and the sleep/wake cycle. In critical illnesses such as acute pancreatitis (AP), circadian rhythms can become dysregulated due to disease. Evidence suggests that time of onset of disease, coupled with peripheral inflammation brought about by AP will impact on the circadian rhythms generated in the central pacemaker and peripheral tissues. Cells of the innate and adaptive immune system are governed by circadian rhythms and the diurnal pattern of expression can be disrupted during disease. Peak circadian immune cell release and gene expression can coincide with AP onset, that may increase pancreatic injury, tissue damage and the potential for systemic inflammation and multiple organ failure to develop. Here, we provide an overview of the role of circadian rhythms in AP and the underpinning inflammatory mechanisms to contextualise ongoing research into the chronobiology and chronotherapeutics of AP.
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Affiliation(s)
- Heather Waddell
- Medical Research Council Centre for Inflammation Research, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh, EH16 4TJ, UK
| | - Tyler J. Stevenson
- Institute of Biodiversity and Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, G61 1QH, UK
| | - Damian J. Mole
- Medical Research Council Centre for Inflammation Research, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh, EH16 4TJ, UK
- Clinical Surgery, School of Clinical Sciences and Community Health, The University of Edinburgh, Edinburgh, EH16 4SB, UK
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12
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Stangherlin A. Ion dynamics and the regulation of circadian cellular physiology. Am J Physiol Cell Physiol 2023; 324:C632-C643. [PMID: 36689675 DOI: 10.1152/ajpcell.00378.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Circadian rhythms in physiology and behavior allow organisms to anticipate the daily environmental changes imposed by the rotation of our planet around its axis. Although these rhythms eventually manifest at the organismal level, a cellular basis for circadian rhythms has been demonstrated. Significant contributors to these cell-autonomous rhythms are daily cycles in gene expression and protein translation. However, recent data revealed cellular rhythms in other biological processes, including ionic currents, ion transport, and cytosolic ion abundance. Circadian rhythms in ion currents sustain circadian variation in action potential firing rate, which coordinates neuronal behavior and activity. Circadian regulation of metal ions abundance and dynamics is implicated in distinct cellular processes, from protein translation to membrane activity and osmotic homeostasis. In turn, studies showed that manipulating ion abundance affects the expression of core clock genes and proteins, suggestive of a close interplay. However, the relationship between gene expression cycles, ion dynamics, and cellular function is still poorly characterized. In this review, I will discuss the mechanisms that generate ion rhythms, the cellular functions they govern, and how they feed back to regulate the core clock machinery.
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Affiliation(s)
- Alessandra Stangherlin
- Faculty of Medicine and University Hospital Cologne, Cluster of Excellence Cellular Stress Responses in Aging-associated Diseases (CECAD), Institute for Mitochondrial Diseases and Ageing, University of Cologne, Cologne, Germany
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13
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Arginine-vasopressin-expressing neurons in the murine suprachiasmatic nucleus exhibit a circadian rhythm in network coherence in vivo. Proc Natl Acad Sci U S A 2023; 120:e2209329120. [PMID: 36656857 PMCID: PMC9942887 DOI: 10.1073/pnas.2209329120] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The suprachiasmatic nucleus (SCN) is composed of functionally distinct subpopulations of GABAergic neurons which form a neural network responsible for synchronizing most physiological and behavioral circadian rhythms in mammals. To date, little is known regarding which aspects of SCN rhythmicity are generated by individual SCN neurons, and which aspects result from neuronal interaction within a network. Here, we utilize in vivo miniaturized microscopy to measure fluorescent GCaMP-reported calcium dynamics in arginine vasopressin (AVP)-expressing neurons in the intact SCN of awake, behaving mice. We report that SCN AVP neurons exhibit periodic, slow calcium waves which we demonstrate, using in vivo electrical recordings, likely reflect burst firing. Further, we observe substantial heterogeneity of function in that AVP neurons exhibit unstable rhythms, and relatively weak rhythmicity at the population level. Network analysis reveals that correlated cellular behavior, or coherence, among neuron pairs also exhibited stochastic rhythms with about 33% of pairs rhythmic at any time. Unlike single-cell variables, coherence exhibited a strong rhythm at the population level with time of maximal coherence among AVP neuronal pairs at CT/ZT 6 and 9, coinciding with the timing of maximal neuronal activity for the SCN as a whole. These results demonstrate robust circadian variation in the coordination between stochastically rhythmic neurons and that interactions between AVP neurons in the SCN may be more influential than single-cell activity in the regulation of circadian rhythms. Furthermore, they demonstrate that cells in this circuit, like those in many other circuits, exhibit profound heterogenicity of function over time and space.
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14
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Ono D, Wang H, Hung CJ, Wang HT, Kon N, Yamanaka A, Li Y, Sugiyama T. Network-driven intracellular cAMP coordinates circadian rhythm in the suprachiasmatic nucleus. SCIENCE ADVANCES 2023; 9:eabq7032. [PMID: 36598978 PMCID: PMC11318661 DOI: 10.1126/sciadv.abq7032] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
The mammalian central circadian clock, located in the suprachiasmatic nucleus (SCN), coordinates the timing of physiology and behavior to local time cues. In the SCN, second messengers, such as cAMP and Ca2+, are suggested to be involved in the input and/or output of the molecular circadian clock. However, the functional roles of second messengers and their dynamics in the SCN remain largely unclear. In the present study, we visualized the spatiotemporal patterns of circadian rhythms of second messengers and neurotransmitter release in the SCN. Here, we show that neuronal activity regulates the rhythmic release of vasoactive intestinal peptides from the SCN, which drives the circadian rhythms of intracellular cAMP in the SCN. Furthermore, optical manipulation of intracellular cAMP levels in the SCN shifts molecular and behavioral circadian rhythms. Together, our study demonstrates that intracellular cAMP is a key molecule in the organization of the SCN circadian neuronal network.
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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
| | - Huan Wang
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China
| | - Chi Jung Hung
- 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
| | - Hsin-tzu Wang
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Laboratory of Animal Integrative Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Department of Biological Sciences, School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Naohiro Kon
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Laboratory of Animal Integrative Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Akihiro Yamanaka
- Chinese Institute for Brain Research (CIBR), Beijing, 102206, China
| | - Yulong Li
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China
| | - Takashi Sugiyama
- Advanced Optics and Biological Engineering, Evident Corporation, Tokyo, Japan
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15
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Wang Y, Minami Y, Ode KL, Ueda HR. The role of calcium and CaMKII in sleep. Front Syst Neurosci 2022; 16:1059421. [PMID: 36618010 PMCID: PMC9815122 DOI: 10.3389/fnsys.2022.1059421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Sleep is an evolutionarily conserved phenotype shared by most of the animals on the planet. Prolonged wakefulness will result in increased sleep need or sleep pressure. However, its mechanisms remain elusive. Recent findings indicate that Ca2+ signaling, known to control diverse physiological functions, also regulates sleep. This review intends to summarize research advances in Ca2+ and Ca2+/calmodulin-dependent protein kinase II (CaMKII) in sleep regulation. Significant changes in sleep phenotype have been observed through calcium-related channels, receptors, and pumps. Mathematical modeling for neuronal firing patterns during NREM sleep suggests that these molecules compose a Ca2+-dependent hyperpolarization mechanism. The intracellular Ca2+ may then trigger sleep induction and maintenance through the activation of CaMKII, one of the sleep-promoting kinases. CaMKII and its multisite phosphorylation status may provide a link between transient calcium dynamics typically observed in neurons and sleep-wake dynamics observed on the long-time scale.
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Affiliation(s)
- Yuyang Wang
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yoichi Minami
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Koji L. Ode
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroki R. Ueda
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan,Laboratory for Synthetic Biology, RIKEN Center for Biosystems Dynamics Research, Suita, Japan,*Correspondence: Hiroki R. Ueda,
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16
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ISX-9 potentiates CaMKIIδ-mediated BMAL1 activation to enhance circadian amplitude. Commun Biol 2022; 5:750. [PMID: 35902736 PMCID: PMC9334596 DOI: 10.1038/s42003-022-03725-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 07/15/2022] [Indexed: 11/09/2022] Open
Abstract
Circadian dysregulation associates with numerous diseases including metabolic dysfunction, sleep disorder, depression and aging. Given that declined circadian amplitude is a trait commonly found with compromised health, interventions that design in precluding circadian amplitude from dampening will aid to mitigate complex, circadian-related diseases. Here we identify a neurogenic small molecule ISX-9 that is able to support persistent and higher amplitude of circadian oscillations. ISX-9 improves diurnal metabolic rhythms in middle-aged mice. Moreover, the ISX-9-treated mice show better sleep homeostasis with increased delta power during the day time and higher locomotive activity in the dark period. ISX-9 augments CaMKIIδ expression and increases BMAL1 activity via eliciting CaMKIIδ-mediated phosphorylation on BMAL1 residues S513/S515/S516, accordingly composes a positive feedback effect on enhancing circadian amplitude. CaMKIIδ-targeting, and the use of ISX-9 may serve as decent choices for treating circadian-related disorders.
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17
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Kim H, Min C, Jeong B, Lee KJ. Deciphering clock cell network morphology within the biological master clock, suprachiasmatic nucleus: From the perspective of circadian wave dynamics. PLoS Comput Biol 2022; 18:e1010213. [PMID: 35666776 PMCID: PMC9203024 DOI: 10.1371/journal.pcbi.1010213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 06/16/2022] [Accepted: 05/16/2022] [Indexed: 11/18/2022] Open
Abstract
The biological master clock, suprachiasmatic nucleus (of rat and mouse), is composed of ~10,000 clock cells which are heterogeneous with respect to their circadian periods. Despite this inhomogeneity, an intact SCN maintains a very good degree of circadian phase (time) coherence which is vital for sustaining various circadian rhythmic activities, and it is supposedly achieved by not just one but a few different cell-to-cell coupling mechanisms, among which action potential (AP)-mediated connectivity is known to be essential. But, due to technical difficulties and limitations in experiments, so far very little information is available about the morphology of the connectivity at a cellular scale. Building upon this limited amount of information, here we exhaustively and systematically explore a large pool (~25,000) of various network morphologies to come up with some plausible network features of SCN networks. All candidates under consideration reflect an experimentally obtained 'indegree distribution' as well as a 'physical range distribution of afferent clock cells.' Then, importantly, with a set of multitude criteria based on the properties of SCN circadian phase waves in extrinsically perturbed as well as in their natural states, we select out appropriate model networks: Some important measures are, 1) level of phase dispersal and direction of wave propagation, 2) phase-resetting ability of the model networks subject to external circadian forcing, and 3) decay rate of perturbation induced "phase-singularities." The successful, realistic networks have several common features: 1) "indegree" and "outdegree" should have a positive correlation; 2) the cells in the SCN ventrolateral region (core) have a much larger total degree than that of the dorsal medial region (shell); 3) The number of intra-core edges is about 7.5 times that of intra-shell edges; and 4) the distance probability density function for the afferent connections fits well to a beta function. We believe that these newly identified network features would be a useful guide for future explorations on the very much unknown AP-mediated clock cell connectome within the SCN.
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Affiliation(s)
- Hyun Kim
- Department of Physics, Korea University, Seoul, Korea
| | - Cheolhong Min
- Department of Physics, Korea University, Seoul, Korea
| | - Byeongha Jeong
- University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Kyoung J. Lee
- Department of Physics, Korea University, Seoul, Korea
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18
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Morioka E, Kasuga Y, Kanda Y, Moritama S, Koizumi H, Yoshikawa T, Miura N, Ikeda M, Higashida H, Holmes TC, Ikeda M. Mitochondrial LETM1 drives ionic and molecular clock rhythms in circadian pacemaker neurons. Cell Rep 2022; 39:110787. [PMID: 35545046 DOI: 10.1016/j.celrep.2022.110787] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/14/2022] [Accepted: 04/14/2022] [Indexed: 11/18/2022] Open
Abstract
The mechanisms that generate robust ionic oscillation in circadian pacemaker neurons are under investigation. Here, we demonstrate critical functions of the mitochondrial cation antiporter leucine zipper-EF-hand-containing transmembrane protein 1 (LETM1), which exchanges K+/H+ in Drosophila and Ca2+/H+ in mammals, in circadian pacemaker neurons. Letm1 knockdown in Drosophila pacemaker neurons reduced circadian cytosolic H+ rhythms and prolonged nuclear PERIOD/TIMELESS expression rhythms and locomotor activity rhythms. In rat pacemaker neurons in the hypothalamic suprachiasmatic nucleus (SCN), circadian rhythms in cytosolic Ca2+ and Bmal1 transcription were dampened by Letm1 knockdown. Mitochondrial Ca2+ uptake peaks late during the day were also observed in rat SCN neurons following photolytic elevation of cytosolic Ca2+. Since cation transport by LETM1 is coupled to mitochondrial energy synthesis, we propose that LETM1 integrates metabolic, ionic, and molecular clock rhythms in the central clock system in both invertebrates and vertebrates.
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Affiliation(s)
- Eri Morioka
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Yusuke Kasuga
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Yuzuki Kanda
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Saki Moritama
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Hayato Koizumi
- Graduate School of Innovative Life Science, University of Toyama, Gofuku, Toyama 930-8555, Japan
| | - Tomoko Yoshikawa
- Organization for International Education and Exchange, University of Toyama, Toyama 930-8555, Japan
| | - Nobuhiko Miura
- Department of Health Medicine, Yokohama University of Pharmacy, Yokohama, Kanagawa 245-0061, Japan
| | - Masaaki Ikeda
- Department of Physiology, Faculty of Medicine, Saitama Medical University, Saitama 350-0495, Japan
| | - Haruhiro Higashida
- Research Center for Child Mental Development, Kanazawa University, Ishikawa 920-8640, Japan
| | - Todd C Holmes
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA 92697, USA
| | - Masayuki Ikeda
- Graduate School of Innovative Life Science, University of Toyama, Gofuku, Toyama 930-8555, Japan; Organization for International Education and Exchange, University of Toyama, Toyama 930-8555, Japan.
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19
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Liang X, Holy TE, Taghert PH. Circadian pacemaker neurons display cophasic rhythms in basal calcium level and in fast calcium fluctuations. Proc Natl Acad Sci U S A 2022; 119:e2109969119. [PMID: 35446620 PMCID: PMC9173584 DOI: 10.1073/pnas.2109969119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 03/17/2022] [Indexed: 12/02/2022] Open
Abstract
Circadian pacemaker neurons in the Drosophila brain display daily rhythms in the levels of intracellular calcium. These calcium rhythms are driven by molecular clocks and are required for normal circadian behavior. To study their biological basis, we employed genetic manipulations in conjunction with improved methods of in vivo light-sheet microscopy to measure calcium dynamics in individual pacemaker neurons over complete 24-h durations at sampling frequencies as high as 5 Hz. This technological advance unexpectedly revealed cophasic daily rhythms in basal calcium levels and in high-frequency calcium fluctuations. Further, we found that the rhythms of basal calcium levels and of fast calcium fluctuations reflect the activities of two proteins that mediate distinct forms of calcium fluxes. One is the inositol trisphosphate receptor (ITPR), a channel that mediates calcium fluxes from internal endoplasmic reticulum calcium stores, and the other is a T-type voltage-gated calcium channel, which mediates extracellular calcium influx. These results suggest that Drosophila molecular clocks regulate ITPR and T-type channels to generate two distinct but coupled rhythms in basal calcium and in fast calcium fluctuations. We propose that both internal and external calcium fluxes are essential for circadian pacemaker neurons to provide rhythmic outputs and thereby, regulate the activities of downstream brain centers.
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Affiliation(s)
- Xitong Liang
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
| | - Timothy E. Holy
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
| | - Paul H. Taghert
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110
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20
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Plante AE, Rao VP, Rizzo MA, Meredith AL. Comparative Ca 2+ channel contributions to intracellular Ca 2+ levels in the circadian clock. BIOPHYSICAL REPORTS 2021; 1:100005. [PMID: 35330949 PMCID: PMC8942421 DOI: 10.1016/j.bpr.2021.100005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/08/2021] [Indexed: 11/22/2022]
Abstract
Circadian rhythms in mammals are coordinated by the central clock in the brain, located in the suprachiasmatic nucleus (SCN). Multiple molecular and cellular signals display a circadian variation within SCN neurons, including intracellular Ca2+, but the mechanisms are not definitively established. SCN cytosolic Ca2+ levels exhibit a peak during the day, when both action potential firing and Ca2+ channel activity are increased, and are decreased at night, correlating with a reduction in firing rate. In this study, we employ a single-color fluorescence anisotropy reporter (FLARE), Venus FLARE-Cameleon, and polarization inverted selective-plane illumination microscopy to measure rhythmic changes in cytosolic Ca2+ in SCN neurons. Using this technique, the Ca2+ channel subtypes contributing to intracellular Ca2+ at the peak and trough of the circadian cycle were assessed using a pharmacological approach with Ca2+ channel inhibitors. Peak (218 ± 16 nM) and trough (172 ± 13 nM) Ca2+ levels were quantified, indicating a 1.3-fold circadian variance in Ca2+ concentration. Inhibition of ryanodine-receptor-mediated Ca2+ release produced a larger relative decrease in cytosolic Ca2+ at both time points compared to voltage-gated Ca2+channels. These results support the hypothesis that circadian Ca2+ rhythms in SCN neurons are predominantly driven by intracellular Ca2+ channels, although not exclusively so. The study provides a foundation for future experiments to probe Ca2+ signaling in a dynamic biological context using FLAREs.
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Affiliation(s)
- Amber E. Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Vishnu P. Rao
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Megan A. Rizzo
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L. Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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21
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Abdel-Rahman EA, Hosseiny S, Aaliya A, Adel M, Yasseen B, Al-Okda A, Radwan Y, Saber SH, Elkholy N, Elhanafy E, Walker EE, Zuniga-Hertz JP, Patel HH, Griffiths HR, Ali SS. Sleep/wake calcium dynamics, respiratory function, and ROS production in cardiac mitochondria. J Adv Res 2021; 31:35-47. [PMID: 34194831 PMCID: PMC8240107 DOI: 10.1016/j.jare.2021.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/24/2020] [Accepted: 01/07/2021] [Indexed: 12/22/2022] Open
Abstract
Introduction Incidents of myocardial infarction and sudden cardiac arrest vary with time of the day, but the mechanism for this effect is not clear. We hypothesized that diurnal changes in the ability of cardiac mitochondria to control calcium homeostasis dictate vulnerability to cardiovascular events. Objectives Here we investigate mitochondrial calcium dynamics, respiratory function, and reactive oxygen species (ROS) production in mouse heart during different phases of wake versus sleep periods. Methods We assessed time-of-the-day dependence of calcium retention capacity of isolated heart mitochondria from young male C57BL6 mice. Rhythmicity of mitochondrial-dependent oxygen consumption, ROS production and transmembrane potential in homogenates were explored using the Oroboros O2k Station equipped with a fluorescence detection module. Changes in expression of essential clock and calcium dynamics genes/proteins were also determined at sleep versus wake time points. Results Our results demonstrate that cardiac mitochondria exhibit higher calcium retention capacity and higher rates of calcium uptake during sleep period. This was associated with higher expression of clock gene Bmal1, lower expression of per2, greater expression of MICU1 gene (mitochondrial calcium uptake 1), and lower expression of the mitochondrial transition pore regulator gene cyclophilin D. Protein levels of mitochondrial calcium uniporter (MCU), MICU2, and sodium/calcium exchanger (NCLX) were also higher at sleep onset relative to wake period. While complex I and II-dependent oxygen utilization and transmembrane potential of cardiac mitochondria were lower during sleep, ROS production was increased presumably due to mitochondrial calcium sequestration. Conclusions Taken together, our results indicate that retaining mitochondrial calcium in the heart during sleep dissipates membrane potential, slows respiratory activities, and increases ROS levels, which may contribute to increased vulnerability to cardiac stress during sleep-wake transition. This pronounced daily oscillations in mitochondrial functions pertaining to stress vulnerability may at least in part explain diurnal prevalence of cardiac pathologies.
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Affiliation(s)
- Engy A. Abdel-Rahman
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
- 57357 Children's Cancer Hospital, Basic Research Department, Cairo, Egypt
- Department of Pharmacology, Faculty of Medicine, Assuit University, Assuit, Egypt
| | - Salma Hosseiny
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Abdullah Aaliya
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Mohamed Adel
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Basma Yasseen
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
- 57357 Children's Cancer Hospital, Basic Research Department, Cairo, Egypt
| | - Abdelrahman Al-Okda
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Yasmine Radwan
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Saber H. Saber
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Nada Elkholy
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Eslam Elhanafy
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
| | - Emily E. Walker
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Juan P. Zuniga-Hertz
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Hemal H. Patel
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
- Department of Anesthesiology, University of California, San Diego, La Jolla, CA 92093, USA
| | | | - Sameh S. Ali
- Center for Aging and Associated Diseases, Zewail City of Science and Technology, Giza, Egypt
- 57357 Children's Cancer Hospital, Basic Research Department, Cairo, Egypt
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22
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Cavieres-Lepe J, Ewer J. Reciprocal Relationship Between Calcium Signaling and Circadian Clocks: Implications for Calcium Homeostasis, Clock Function, and Therapeutics. Front Mol Neurosci 2021; 14:666673. [PMID: 34045944 PMCID: PMC8144308 DOI: 10.3389/fnmol.2021.666673] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/09/2021] [Indexed: 12/03/2022] Open
Abstract
In animals, circadian clocks impose a daily rhythmicity to many behaviors and physiological processes. At the molecular level, circadian rhythms are driven by intracellular transcriptional/translational feedback loops (TTFL). Interestingly, emerging evidence indicates that they can also be modulated by multiple signaling pathways. Among these, Ca2+ signaling plays a key role in regulating the molecular rhythms of clock genes and of the resulting circadian behavior. In addition, the application of in vivo imaging approaches has revealed that Ca2+ is fundamental to the synchronization of the neuronal networks that make up circadian pacemakers. Conversely, the activity of circadian clocks may influence Ca2+ signaling. For instance, several genes that encode Ca2+ channels and Ca2+-binding proteins display a rhythmic expression, and a disruption of this cycling affects circadian function, underscoring their reciprocal relationship. Here, we review recent advances in our understanding of how Ca2+ signaling both modulates and is modulated by circadian clocks, focusing on the regulatory mechanisms described in Drosophila and mice. In particular, we examine findings related to the oscillations in intracellular Ca2+ levels in circadian pacemakers and how they are regulated by canonical clock genes, neuropeptides, and light stimuli. In addition, we discuss how Ca2+ rhythms and their associated signaling pathways modulate clock gene expression at the transcriptional and post-translational levels. We also review evidence based on transcriptomic analyzes that suggests that mammalian Ca2+ channels and transporters (e.g., ryanodine receptor, ip3r, serca, L- and T-type Ca2+ channels) as well as Ca2+-binding proteins (e.g., camk, cask, and calcineurin) show rhythmic expression in the central brain clock and in peripheral tissues such as the heart and skeletal muscles. Finally, we discuss how the discovery that Ca2+ signaling is regulated by the circadian clock could influence the efficacy of pharmacotherapy and the outcomes of clinical interventions.
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Affiliation(s)
- Javier Cavieres-Lepe
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - John Ewer
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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Song BJ, Sharp SJ, Rogulja D. Daily rewiring of a neural circuit generates a predictive model of environmental light. SCIENCE ADVANCES 2021; 7:7/13/eabe4284. [PMID: 33762336 PMCID: PMC7990339 DOI: 10.1126/sciadv.abe4284] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 02/03/2021] [Indexed: 05/02/2023]
Abstract
Behavioral responsiveness to external stimulation is shaped by context. We studied how sensory information can be contextualized, by examining light-evoked locomotor responsiveness of Drosophila relative to time of day. We found that light elicits an acute increase in locomotion (startle) that is modulated in a time-of-day-dependent manner: Startle is potentiated during the nighttime, when light is unexpected, but is suppressed during the daytime. The internal daytime-nighttime context is generated by two interconnected and functionally opposing populations of circadian neurons-LNvs generating the daytime state and DN1as generating the nighttime state. Switching between the two states requires daily remodeling of LNv and DN1a axons such that the maximum presynaptic area in one population coincides with the minimum in the other. We propose that a dynamic model of environmental light resides in the shifting connectivities of the LNv-DN1a circuit, which helps animals evaluate ongoing conditions and choose a behavioral response.
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Affiliation(s)
- Bryan J Song
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Slater J Sharp
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Dragana Rogulja
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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Lin HY, Huang RC. Glycolytic metabolism and activation of Na + pumping contribute to extracellular acidification in the central clock of the suprachiasmatic nucleus: Differential glucose sensitivity and utilization between oxidative and non-oxidative glycolytic pathways. Biomed J 2021; 45:143-154. [PMID: 35341719 PMCID: PMC9133309 DOI: 10.1016/j.bj.2021.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/07/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The central clock of the suprachiasmatic nucleus (SCN) controls the metabolism of glucose and is sensitive to glucose shortage. However, it is only beginning to be understood how metabolic signals such as glucose availability regulate the SCN physiology. We previously showed that the ATP-sensitive K+ channel plays a glucose-sensing role in regulating SCN neuronal firing at times of glucose shortage. Nevertheless, it is unknown whether the energy-demanding Na+/K+-ATPase (NKA) is also sensitive to glucose availability. Furthermore, we recently showed that the metabolically active SCN constantly extrudes H+ to acidify extracellular pH (pHe). This study investigated whether the standing acidification is associated with Na+ pumping activity, energy metabolism, and glucose utilization, and whether glycolysis- and mitochondria-fueled NKAs may be differentially sensitive to glucose shortage. METHODS Double-barreled pH-selective microelectrodes were used to determine the pHe in the SCN in hypothalamic slices. RESULTS NKA inhibition with K+-free (0-K+) solution rapidly and reversibly alkalinized the pHe, an effect abolished by ouabain. Mitochondrial inhibition with cyanide acidified the pHe but did not inhibit 0-K+-induced alkalinization. Glycolytic inhibition with iodoacetate alkalinized the pHe, completely blocked cyanide-induced acidification, and nearly completely blocked 0-K+-induced alkalinization. The results indicate that glycolytic metabolism and activation of Na+ pumping contribute to the standing acidification. Glucoprivation also alkalinized the pHe, nearly completely eliminated cyanide-induced acidification, but only partially reduced 0-K+-induced alkalinization. In contrast, hypoglycemia preferentially and partially blocked cyanide-induced acidification. The result indicates sensitivity to glucose shortage for the mitochondria-associated oxidative glycolytic pathway. CONCLUSION Glycolytic metabolism and activation of glycolysis-fueled NKA Na+ pumping activity contribute to the standing acidification in the SCN. Furthermore, the oxidative and non-oxidative glycolytic pathways differ in their glucose sensitivity and utilization, with the oxidative glycolytic pathway susceptible to glucose shortage, and the non-oxidative glycolytic pathway able to maintain Na+ pumping even in glucoprivation.
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Affiliation(s)
- Hsin-Yi Lin
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Rong-Chi Huang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Healthy Aging Research Center, Chang Gung University, Taoyuan, Taiwan; Neuroscience Research Center, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan.
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25
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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: 28] [Impact Index Per Article: 9.3] [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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Computational Analysis of PER2::LUC Imaging Data. Methods Mol Biol 2020. [PMID: 33284453 DOI: 10.1007/978-1-0716-0381-9_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Advances in imaging technology, combined with the development of bioluminescent reporters for core clock genes, has enabled the observation of spatiotemporal patterns of circadian rhythms in the suprachiasmatic nuclei (SCN). In particular, the PERIOD2::luciferase (PER2::LUC) knockin mouse has led to novel approaches for studying the heterogeneous circadian network in the SCN. This chapter describes how to automate the processing of PER2::LUC imaging data from SCN slices for generating spatiotemporal maps of circadian parameters like phase, period, and amplitude. These maps can be aligned and averaged to produce composite maps displaying common features across multiple slices. In addition, we describe a method for automated detection of cell-like regions of interest, to support the study of the neural network in the SCN.
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Zhang Z, Zhai Q, Gu Y, Zhang T, Huang Z, Liu Z, Liu Y, Xu Y. Impaired function of the suprachiasmatic nucleus rescues the loss of body temperature homeostasis caused by time-restricted feeding. Sci Bull (Beijing) 2020; 65:1268-1280. [PMID: 32864176 PMCID: PMC7455017 DOI: 10.1016/j.scib.2020.03.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The suprachiasmatic nucleus (SCN) is the master circadian pacemaker that drives body temperature rhythm. Time-restricted feeding (TRF) has potential as a preventative or therapeutic approach against many diseases. The potential side effects of TRF remain unknown. Here we show that a 4-hour TRF stimulus in mice can severely impair body temperature homeostasis and can result in lethality. Nearly half of the mice died at 21 °C, and all mice died at 18 °C during 4-hour TRF. Moreover, this effect was modulated by the circadian clock and was associated with severe hypothermia due to loss of body temperature homeostasis, which is different from "torpor", an adaptive response under food deprivation. Disrupting the circadian clock by the SCN lesions or a non-invasive method (constant light) which disrupts circadian clock rescued lethality during TRF. Analysis of circadian gene expression in the dorsomedial hypothalamus (DMH) demonstrated that TRF reprograms rhythmic transcriptome in DMH and suppresses expression of genes, such as Ccr5 and Calcrl, which are involved in thermoregulation. We demonstrate a side effect of 4-hour TRF on the homeostasis of body temperature and a rescue function by impairing the SCN function. Altogether, our results suggested that constructing a circadian arrhythmicity may have a beneficial effect on the host response to an acute stress.
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Affiliation(s)
- Zhihui Zhang
- Model Animal Research Center, Nanjing University, 12 Xuefu Road, Pukou District, Nanjing 210061, China
| | - Qiaocheng Zhai
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China
| | - Yue Gu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China
| | - Tao Zhang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China
| | - Zhengyun Huang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China
| | - Zhiwei Liu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China
| | - Yi Liu
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390,Correspondence to: (Y.X.), (Y.L.)
| | - Ying Xu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda Genomic Resource Center, Soochow University, Suzhou, Jiangsu 215123, China,State Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou 215123, China,Correspondence to: (Y.X.), (Y.L.)
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28
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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: 3.0] [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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29
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Harvey JRM, Plante AE, Meredith AL. Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability. Physiol Rev 2020; 100:1415-1454. [PMID: 32163720 DOI: 10.1152/physrev.00027.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na+ and Ca2+ currents, as well as several K+ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K+ currents, including Ca2+-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.
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Affiliation(s)
- Jenna R M Harvey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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30
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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: 22] [Impact Index Per Article: 5.5] [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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31
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Circadian rhythms in Per1, PER2 and Ca 2+ of a solitary SCN neuron cultured on a microisland. Sci Rep 2019; 9:18271. [PMID: 31797953 PMCID: PMC6892917 DOI: 10.1038/s41598-019-54654-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 11/01/2019] [Indexed: 01/08/2023] Open
Abstract
Circadian rhythms in Per1, PER2 expression and intracellular Ca2+ were measured from a solitary SCN neuron or glial cell which was physically isolated from other cells. Dispersed cells were cultured on a platform of microisland (100–200 μm in diameter) in a culture dish. Significant circadian rhythms were detected in 57.1% for Per1 and 70.0% for PER2 expression. When two neurons were located on the same island, the circadian rhythms showed desynchronization, indicating a lack of oscillatory coupling. Circadian rhythms were also detected in intracellular Ca2+ of solitary SCN neurons. The ratio of circadian positive neurons was significantly larger without co-habitant of glial cells (84.4%) than with it (25.0%). A relatively large fraction of SCN neurons generates the intrinsic circadian oscillation without neural or humoral networks. In addition, glial cells seem to interrupt the expression of the circadian rhythmicity of intracellular Ca2+ under these conditions.
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32
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Role of Intracellular Na + in the Regulation of [Ca 2+] i in the Rat Suprachiasmatic Nucleus Neurons. Int J Mol Sci 2019; 20:ijms20194868. [PMID: 31575032 PMCID: PMC6801571 DOI: 10.3390/ijms20194868] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 09/28/2019] [Indexed: 12/17/2022] Open
Abstract
Transmembrane Ca2+ influx is essential to the proper functioning of the central clock in the suprachiasmatic nucleus (SCN). In the rat SCN neurons, the clearance of somatic Ca2+ following depolarization-induced Ca2+ transients involves Ca2+ extrusion via Na+/Ca2+ exchanger (NCX) and mitochondrial Ca2+ buffering. Here we show an important role of intracellular Na+ in the regulation of [Ca2+]i in these neurons. The effect of Na+ loading on [Ca2+]i was determined with the Na+ ionophore monensin and the cardiac glycoside ouabain to block Na+/K+-ATPase (NKA). Ratiometric Na+ and Ca2+ imaging was used to measure the change in [Na+]i and [Ca2+]i, and cell-attached recordings to investigate the effects of monensin and ouabain on spontaneous firing. Our results show that in spite of opposite effects on spontaneous firing and basal [Ca2+], both monensin and ouabain induced Na+ loading, and increased the peak amplitude, slowed the fast decay rate, and enhanced the slow decay phase of 20 mM K+-evoked Ca2+ transients. Furthermore, both ouabain and monensin preferentially enhanced nimodipine-insensitive Ca2+ transients. Together, our results indicate that in the SCN neurons the NKA plays an important role in regulating [Ca2+]i, in particular, associated with nimodipine-insensitive Ca2+ channels.
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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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Zhao J, Warman GR, Cheeseman JF. The functional changes of the circadian system organization in aging. Ageing Res Rev 2019; 52:64-71. [PMID: 31048031 DOI: 10.1016/j.arr.2019.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 04/14/2019] [Accepted: 04/24/2019] [Indexed: 01/12/2023]
Abstract
The circadian clock drives periodic oscillations at different levels of an organism from genes to behavior. This timing system is highly conserved across species from insects to mammals and human beings. The question of how the circadian clock is involved in the aging process continues to attract more attention. We aim to characterize the detrimental impact of aging on the circadian clock organization. We review studies on different components of the circadian clock at the central and periperal levels, and their changes in aged rodents and humans, and the fruit fly Drosophila. Intracellular signaling, cellular activity and intercellular coupling in the central pacemaker have been found to decline with advancing age. Evidence of degradation of the molecular clockwork reflected by clock gene expression in both central and peripheral oscillators due to aging is inadequate. The findings on age-associated molecular and functional changes of peripheral clocks are mixed. We conclude that aging can affect the circadian clock organization at various levels, and the impairment of the central network may be a fundamental mechanism of circadian disruption seen in aged species.
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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: 40] [Impact Index Per Article: 8.0] [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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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: 2.2] [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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37
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Song Q, Feng G, Zhang J, Xia X, Ji M, Lv L, Ping Y. NMDA Receptor-mediated Ca2+ Influx in the Absence of Mg2+ Block Disrupts Rest: Activity Rhythms in Drosophila. Sleep 2018; 40:4330652. [PMID: 29029290 DOI: 10.1093/sleep/zsx166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Study Objectives The correlated activation of pre- and postsynaptic neurons is essential for the NMDA receptor-mediated Ca2+ influx by removing Mg2+ from block site and NMDA receptors have been implicated in phase resetting of circadian clocks. So we assessed rest:activity rhythms in Mg2+ block defective animals. Methods Using Drosophila locomotor monitoring system, we checked circadian rest:activity rhythms of different mutants under constant darkness (DD) and light:dark (LD) conditions. We recorded NMDA receptor-mediated currents or Ca2+ increase in neurons using patch-clamp and Ca2+ imaging techniques. Results We found that Mg2+ block defective mutant flies were completely arrhythmic under DD. To further understand the role of Mg2+ block in daily circadian rest:activity, we observed the mutant files under LD cycles, and we found severely reduced morning anticipation and advanced evening peak compared to control flies. We also used tissue-specific expression of Mg2+ block defective NMDA receptors and demonstrated pigment-dispersing factor receptor (PDFR)-expressing circadian neurons were implicated in mediating the circadian rest:activity deficits. Endogenous functional NMDA receptors are expressed in most Drosophila neurons, including in a subgroup of dorsal neurons (DN1s). Subsequently, we determined that the uncorrelated extra Ca2+ influx may act in part through Ca2+/Calmodulin (CaM)-stimulated PDE1c pathway leading to morning behavior phenotypes. Conclusions These results demonstrate that Mg2+ block of NMDA receptors at resting potential is essential for the daily circadian rest:activity rhythms and we propose that Mg2+ block functions to suppress CaM-stimulated PDE1c activation at resting potential, thus regulating Ca2+ and cyclic AMP oscillations in circadian and sleep circuits.
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Affiliation(s)
- Qian Song
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Ge Feng
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Jiaxing Zhang
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Xuechun Xia
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China
| | - Min Ji
- Affiliated Hospital of Nantong University, Nantong, Jiangsu, China
| | - Lei Lv
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yong Ping
- Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory of Psychotic Disorders (No.13dz2260500), Shanghai Mental Health Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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38
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Carmona-Alcocer V, Rohr KE, Joye DAM, Evans JA. Circuit development in the master clock network of mammals. Eur J Neurosci 2018; 51:82-108. [PMID: 30402923 DOI: 10.1111/ejn.14259] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/08/2018] [Accepted: 10/31/2018] [Indexed: 12/24/2022]
Abstract
Daily rhythms are generated by the circadian timekeeping system, which is orchestrated by the master circadian clock in the suprachiasmatic nucleus (SCN) of mammals. Circadian timekeeping is endogenous and does not require exposure to external cues during development. Nevertheless, the circadian system is not fully formed at birth in many mammalian species and it is important to understand how SCN development can affect the function of the circadian system in adulthood. The purpose of the current review is to discuss the ontogeny of cellular and circuit function in the SCN, with a focus on work performed in model rodent species (i.e., mouse, rat, and hamster). Particular emphasis is placed on the spatial and temporal patterns of SCN development that may contribute to the function of the master clock during adulthood. Additional work aimed at decoding the mechanisms that guide circadian development is expected to provide a solid foundation upon which to better understand the sources and factors contributing to aberrant maturation of clock function.
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Affiliation(s)
| | - Kayla E Rohr
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Deborah A M Joye
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
| | - Jennifer A Evans
- Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin
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39
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Nishide S, Honma S, Honma KI. Two coupled circadian oscillations regulate Bmal1-ELuc and Per2-SLR2 expression in the mouse suprachiasmatic nucleus. Sci Rep 2018; 8:14765. [PMID: 30283092 PMCID: PMC6170461 DOI: 10.1038/s41598-018-32516-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 08/01/2018] [Indexed: 11/08/2022] Open
Abstract
Circadian rhythms in clock genes, Bmal1 and Per2 expression were monitored simultaneously in the cultured slice of mouse suprachiasmatic nucleus (SCN) by dual bioluminescent reporters. In the neonatal SCN, the phase-relation between the Bmal1 and Per2 rhythms were significantly changed during culture. Medium exchange produced phase-dependent phase shifts (PRCm) in the Bmal1 rhythms, but not in the Per2 rhythms. As a result, the two circadian rhythms were temporally dissociated after medium exchange. In the adult SCN, the phase-relation between the two rhythms was kept constant during culture at least up to 20 cycles. The amplitude of PRCm in the adult SCN was significantly attenuated in the Bmal1 rhythm, whereas a PRCm was developed in the Per2 rhythm. The circadian period was not systematically affected by medium exchange in either of rhythms, regardless of whether it was in the neonatal or the adult SCN. Tetrodotoxin, a sodium channel blocker, enhanced the phase-response in both rhythms but abolished the phase-dependency. In addition, tetrodotoxin lengthened the circadian period independent of the phase of administration. Thus, the Bmal1 and Per2 rhythms in the SCN are dissociable and likely regulated by distinct circadian oscillators. Bmal1 is the component of a Bmal1/REV-ERBa/ROR loop and Per2 a Per/Cry/BMAL1/CLOCK loop. Both loops could be molecular mechanisms of the two circadian oscillators that are coupled through the protein product of Bmal1. The coupling strength between the two oscillations depends on developmental stages.
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Affiliation(s)
- Shinya Nishide
- Department of Physiology, Faculty of Medicine, Hokkaido University, Hokkaido, Japan
- Department of Occupational Therapy, School of Rehabilitation Science, Health Science University of Hokkaido, Hokkaido, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University, Hokkaido, Japan
| | - Ken-Ichi Honma
- Study Group for Monitoring of Brain Functions, Hokkaido University Graduate School of Medicine, Hokkaido, Japan.
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40
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Ultradian calcium rhythms in the paraventricular nucleus and subparaventricular zone in the hypothalamus. Proc Natl Acad Sci U S A 2018; 115:E9469-E9478. [PMID: 30228120 PMCID: PMC6176559 DOI: 10.1073/pnas.1804300115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Despite that the various functions in mammals fluctuate in the ultradian fashion, the origin and mechanism of the rhythm are largely unknown. In this study, we found synchronous ultradian calcium rhythms in the hypothalamic paraventricular nucleus (PVN), subparaventricular zone (SPZ), and suprachiasmatic nucleus (SCN). The ultradian rhythms were originated from the SPZ-PVN region and transmitted to the SCN. Neurochemical interventions revealed that the glutamatergic mechanism is critical for generation and a tetrodotoxin-sensitive neural network for synchrony of the ultradian rhythm. The GABAergic system could have a role in refining the circadian output signals. The study provides the first clue to understand the loci and mechanism of ultradian rhythm in the hypothalamus. The suprachiasmatic nucleus (SCN), the master circadian clock in mammals, sends major output signals to the subparaventricular zone (SPZ) and further to the paraventricular nucleus (PVN), the neural mechanism of which is largely unknown. In this study, the intracellular calcium levels were measured continuously in cultured hypothalamic slices containing the PVN, SPZ, and SCN. We detected ultradian calcium rhythms in both the SPZ-PVN and SCN regions with periods of 0.5–4.0 hours, the frequency of which depended on the local circadian rhythm in the SPZ-PVN region. The ultradian rhythms were synchronous in the entire SPZ-PVN region and a part of the SCN. Because the ultradian rhythms were not detected in the SCN-only slice, the origin of ultradian rhythm is the SPZ-PVN region. In association with an ultradian bout, a rapid increase of intracellular calcium in a millisecond order was detected, the frequency of which determined the amplitude of an ultradian bout. The synchronous ultradian rhythms were desynchronized and depressed by a sodium channel blocker tetrodotoxin, suggesting that a tetrodotoxin-sensitive network is involved in synchrony of the ultradian bouts. In contrast, the ultradian rhythm is abolished by glutamate receptor blockers, indicating the critical role of glutamatergic mechanism in ultradian rhythm generation, while a GABAA receptor blocker increased the frequency of ultradian rhythm and modified the circadian rhythm in the SCN. A GABAergic network may refine the circadian output signals. The present study provides a clue to unraveling the loci and network mechanisms of the ultradian rhythm.
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41
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Freyberg Z, Logan RW. The Intertwined Roles of Circadian Rhythms and Neuronal Metabolism Fueling Drug Reward and Addiction. CURRENT OPINION IN PHYSIOLOGY 2018; 5:80-89. [PMID: 30631826 DOI: 10.1016/j.cophys.2018.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Drug addiction is a highly prevalent and devastating disorder with few effective treatments, resulting in enormous burdens on family and society. The cellular and behavioral effects of drugs of abuse are related to their abilities to elevate synaptic dopamine levels. Midbrain dopaminergic neurons projecting from the ventral tegmental area to the nucleus accumbens play crucial roles in substance-induced neural and behavioral plasticity. Significantly, increasing work suggests that interplay between the brain circadian system and the cellular bioenergetic machinery in these dopamine neurons plays a critical role in mediating the actions of drugs of abuse. Here, we describe recent progress in elucidating the interconnections between circadian and metabolic systems at the molecular and cellular levels and their relationships to modulation of drug reward and addiction.
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Affiliation(s)
- Zachary Freyberg
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, pittsburgh, PA, USA 15219.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA USA 15213
| | - Ryan W Logan
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, pittsburgh, PA, USA 15219.,Center for Systems Neurogenetics of Addiction, The Jackson Laboratory, Bar Harbor, ME, 04609
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42
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SCN VIP Neurons Are Essential for Normal Light-Mediated Resetting of the Circadian System. J Neurosci 2018; 38:7986-7995. [PMID: 30082421 DOI: 10.1523/jneurosci.1322-18.2018] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/10/2018] [Accepted: 07/14/2018] [Indexed: 12/21/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) synchronizes circadian rhythms in behavior and physiology to the external light cycle, but the mechanisms by which this occurs are unclear. As the neuropeptide vasoactive intestinal peptide (VIP) is important for circadian light responses, we tested the hypothesis that rhythmic VIP-producing SCN neurons mediate circadian light responses in male and female mice. Using in vivo fiber photometry over multiple days, we found daily rhythms in spontaneous calcium events of SCN VIP neurons that peaked during the subjective day and were disrupted by constant light. The light-evoked calcium responses peaked around subjective dusk and were greater during the subjective night. Using novel VIP sensor cells, we found that the activity patterns in SCN VIP neurons correlated tightly with spontaneous and NMDA-evoked VIP release. Finally, in vivo hyperpolarization of VIP neurons attenuated light-induced shifts of daily rhythms in locomotion. We conclude that SCN VIP neurons exhibit circadian rhythms in spontaneous and light-responsive activity and are essential for the normal resetting of daily rhythms by environmental light.SIGNIFICANCE STATEMENT Daily rhythms in behavior and physiology, including sleep/wake and hormone release, are synchronized to local time by the master circadian pacemaker, the suprachiasmatic nucleus (SCN). The advent of artificial lighting and, consequently, light exposure at night, is associated with an increased risk of disease due to disrupted circadian rhythms. However, the mechanisms by which the SCN encodes normal and pathological light information are unclear. Here, we find that vasoactive intestinal peptide (VIP)-producing SCN neurons exhibit daily rhythms in neuronal activity and VIP release, and that blocking the activity of these neurons attenuates light-induced phase shifts. We conclude that rhythmic VIP neurons are an essential component of the circadian light transduction pathway.
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43
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Cheng PC, Wang YC, Chen YS, Cheng RC, Yang JJ, Huang RC. Differential regulation of nimodipine-sensitive and -insensitive Ca 2+ influx by the Na +/Ca 2+ exchanger and mitochondria in the rat suprachiasmatic nucleus neurons. J Biomed Sci 2018; 25:44. [PMID: 29788971 PMCID: PMC5964920 DOI: 10.1186/s12929-018-0447-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 05/14/2018] [Indexed: 11/25/2022] Open
Abstract
Background Transmembrane Ca2+ influx is critical for molecular rhythmicity, metabolic activity, and neuropeptide release in the central clock of the suprachiasmatic nucleus (SCN). We previously reported that both the Na+/Ca2+ exchanger (NCX) and mitochondria play a role in regulating intracellular Ca2+ homeostasis in the rat SCN neurons. Here we present evidence to show differential regulation by NCX and mitochondria of nimodipine-sensitive and -insensitive Ca2+ influx. Methods Ratiometric Ca2+ imaging was used to measure change in [Ca2+]i and patch clamp recordings to study spontaneous firing, membrane potential, and voltage-dependent Ca2+ channels in neurons from reduced SCN slice preparations. Immunofluorescent staining was used to determine the distribution pattern of CaV1.2 and CaV1.3 and their colocalization with NCX1. Results Ratiometric Ca2+ imaging indicates that nimodipine (2 μM) blocked most of 20 (mM) K+-induced, but less so of 50 K+-induced, Ca2+ rise. The nimodipine-sensitive 50 K+-induced Ca2+ transient rose more rapidly but decayed similarly with the nimodipine-insensitive component, suggesting both components were extruded by NCX. Immunofluorescent stains showed the expression of both CaV1.2 and CaV1.3 and their colocalization with NCX1, whereas functional studies suggest that CaV1.2 mediated most of the nimodipine-sensitive Ca2+ rise but had insignificant effect on spontaneous firing. After normalization relative to the Ca2+-free solution, nimodipine reduced ~ 65% of basal Ca2+ influx, and TTX lowered it by ~ 35%, leaving ~ 25% basal Ca2+ influx in the combined presence of TTX and nimodipine. With the mitochondrial uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) to inhibit mitochondrial Ca2+ uptake, 20 K+-induced Ca2+ transients became larger and slower, both in the absence and presence of nimodipine. FCCP markedly enhanced nimodipine-insensitive, but not nimodipine-sensitive, Ca2+ transients, suggesting that mitochondria preferentially buffer nimodipine-insensitive Ca2+ influx. Results from using CaV2 channel blockers further indicate that FCCP enhanced Ca2+ transients mediated by N-, P/Q-, and the blocker cocktail-insensitive Ca2+ channels. Conclusions The differential regulation of transmembrane Ca2+ influx by NCX and mitochondria suggests that Ca2+ entry via different sources may be regulated differently to play different roles in SCN physiology.
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Affiliation(s)
- Pi-Cheng Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Yi-Chi Wang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Ya-Shuan Chen
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Ruo-Ciao Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Jyh-Jeen Yang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan
| | - Rong-Chi Huang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, 33302, Taiwan. .,Healthy Aging Research Center, Chang Gung University, Tao-Yuan, 33302, Taiwan. .,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, 33305, Taiwan.
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44
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Honma S. The mammalian circadian system: a hierarchical multi-oscillator structure for generating circadian rhythm. J Physiol Sci 2018; 68:207-219. [PMID: 29460036 PMCID: PMC10717972 DOI: 10.1007/s12576-018-0597-5] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 01/25/2018] [Indexed: 10/18/2022]
Abstract
The circadian nature of physiology and behavior is regulated by a circadian clock that generates intrinsic rhythms with a periodicity of approximately 24 h. The mammalian circadian system is composed of a hierarchical multi-oscillator structure, with the central clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus regulating the peripheral clocks found throughout the body. In the past two decades, key clock genes have been discovered in mammals and shown to be interlocked in transcriptional and translational feedback loops. At the cellular level, each cell is governed by its own independent clock; and yet, these cellular circadian clocks in the SCN form regional oscillators that are further coupled to one another to generate a single rhythm for the tissue. The oscillatory coupling within and between the regional oscillators appears to be critical for the extraordinary stability and the wide range of adaptability of the circadian clock, the mechanism of which is now being elucidated with newly advanced molecular tools.
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Affiliation(s)
- Sato Honma
- Research and Education Center for Brain Science, Hokkaido University, North 15, West 7, Kita-ku, Sapporo, 060-8638, Japan.
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45
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Whitt JP, McNally BA, Meredith AL. Differential contribution of Ca 2+ sources to day and night BK current activation in the circadian clock. J Gen Physiol 2017; 150:259-275. [PMID: 29237755 PMCID: PMC5806683 DOI: 10.1085/jgp.201711945] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 11/28/2017] [Indexed: 01/16/2023] Open
Abstract
Large conductance K+ (BK) channels are expressed widely in neurons, where their activation is regulated by membrane depolarization and intracellular Ca2+ (Ca2+i). To enable this regulation, BK channels functionally couple to both voltage-gated Ca2+ channels (VGCCs) and channels mediating Ca2+ release from intracellular stores. However, the relationship between BK channels and their specific Ca2+ source for particular patterns of excitability is not well understood. In neurons within the suprachiasmatic nucleus (SCN)-the brain's circadian clock-BK current, VGCC current, and Ca2+i are diurnally regulated, but paradoxically, BK current is greatest at night when VGCC current and Ca2+i are reduced. Here, to determine whether diurnal regulation of Ca2+ is relevant for BK channel activation, we combine pharmacology with day and night patch-clamp recordings in acute slices of SCN. We find that activation of BK current depends primarily on three types of channels but that the relative contribution changes between day and night. BK current can be abrogated with nimodipine during the day but not at night, establishing that L-type Ca2+ channels (LTCCs) are the primary daytime Ca2+ source for BK activation. In contrast, dantrolene causes a significant decrease in BK current at night, suggesting that nighttime BK activation is driven by ryanodine receptor (RyR)-mediated Ca2+i release. The N- and P/Q-type Ca2+ channel blocker ω-conotoxin MVIIC causes a smaller reduction of BK current that does not differ between day and night. Finally, inhibition of LTCCs, but not RyRs, eliminates BK inactivation, but the BK β2 subunit was not required for activation of BK current by LTCCs. These data reveal a dynamic coupling strategy between BK channels and their Ca2+ sources in the SCN, contributing to diurnal regulation of SCN excitability.
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Affiliation(s)
- Joshua P Whitt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Beth A McNally
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
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46
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Abstract
Modern imaging techniques allow the monitoring of circadian rhythms of single cells. Coupling between these single cellular circadian oscillators can generate coherent periodic signals on the tissue level that subsequently orchestrate physiological outputs. The strength of coupling in such systems of oscillators is often unclear. In particular, effects on coupling strength by varying cell densities, by knockouts, and by inhibitor applications are debated. In this study, we suggest to quantify the relative coupling strength via analyzing period, phase, and amplitude distributions in ensembles of individual circadian oscillators. Simulations of different oscillator networks show that period and phase distributions become narrower with increasing coupling strength. Moreover, amplitudes can increase due to resonance effects. Variances of periods and phases decay monotonically with coupling strength, and can serve therefore as measures of relative coupling strength. Our theoretical predictions are confirmed by studying recently published experimental data from PERIOD2 expression in slices of the suprachiasmatic nucleus during and after the application of tetrodotoxin (TTX). On analyzing the corresponding period, phase, and amplitude distributions, we can show that treatment with TTX can be associated with a reduced coupling strength in the system of coupled oscillators. Analysis of an oscillator network derived directly from the data confirms our conclusions. We suggest that our approach is also applicable to quantify coupling in fibroblast cultures and hepatocyte networks, and for social synchronization of circadian rhythmicity in rodents, flies, and bees.
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Affiliation(s)
- Christoph Schmal
- Institute for Theoretical Biology, Charité-Universitätsmedizin, Berlin, Germany
| | - Erik D Herzog
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - Hanspeter Herzel
- Institute for Theoretical Biology, Humboldt Universität zu Berlin, Berlin, Germany
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47
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Myung J, Pauls SD. Encoding seasonal information in a two-oscillator model of the multi-oscillator circadian clock. Eur J Neurosci 2017; 48:2718-2727. [PMID: 28921823 DOI: 10.1111/ejn.13697] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 09/01/2017] [Accepted: 09/11/2017] [Indexed: 02/01/2023]
Abstract
The suprachiasmatic nucleus (SCN) is a collection of about 10 000 neurons, each of which functions as a circadian clock with slightly different periods and phases, that work in concert with form and maintain the master circadian clock for the organism. The diversity among neurons confers on the SCN the ability to robustly encode both the 24-h light pattern as well as the seasonal time. Cluster synchronization brings the different neurons into line and reduces the large population to essentially two oscillators, coordinated by a macroscopic network motif of asymmetric repulsive-attractive coupling. We recount the steps leading to this simplification and rigorously examine the two-oscillator case by seeking an analytical solution. Through these steps, we identify physiologically relevant parameters that shape the behaviour of the SCN network and delineate its ability to store past details of seasonal variation in photoperiod.
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Affiliation(s)
- Jihwan Myung
- Computational Neuroscience Unit, Okinawa Institute of Science and Technology, Lab 2 Level B, 1919-1 Tancha Onna-son, Kunigami, Okinawa 904-0495, Japan.,Graduate Institute of Humanities in Medicine, Taipei Medical University, Taipei, Taiwan.,TMU-Research Center of Brain and Consciousness, Shuang Ho Hospital, New Taipei City, Taiwan
| | - Scott D Pauls
- Department of Mathematics, Dartmouth College, 6188 Kemeny Hall, Hanover, NH 03755, USA
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48
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Calcium Circadian Rhythmicity in the Suprachiasmatic Nucleus: Cell Autonomy and Network Modulation. eNeuro 2017; 4:eN-NWR-0160-17. [PMID: 28828400 PMCID: PMC5562299 DOI: 10.1523/eneuro.0160-17.2017] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 07/26/2017] [Indexed: 11/25/2022] Open
Abstract
Circadian rhythms of mammalian physiology and behavior are coordinated by the suprachiasmatic nucleus (SCN) in the hypothalamus. Within SCN neurons, various aspects of cell physiology exhibit circadian oscillations, including circadian clock gene expression, levels of intracellular Ca2+ ([Ca2+]i), and neuronal firing rate. [Ca2+]i oscillates in SCN neurons even in the absence of neuronal firing. To determine the causal relationship between circadian clock gene expression and [Ca2+]i rhythms in the SCN, as well as the SCN neuronal network dependence of [Ca2+]i rhythms, we introduced GCaMP3, a genetically encoded fluorescent Ca2+ indicator, into SCN neurons from PER2::LUC knock-in reporter mice. Then, PER2 and [Ca2+]i were imaged in SCN dispersed and organotypic slice cultures. In dispersed cells, PER2 and [Ca2+]i both exhibited cell autonomous circadian rhythms, but [Ca2+]i rhythms were typically weaker than PER2 rhythms. This result matches the predictions of a detailed mathematical model in which clock gene rhythms drive [Ca2+]i rhythms. As predicted by the model, PER2 and [Ca2+]i rhythms were both stronger in SCN slices than in dispersed cells and were weakened by blocking neuronal firing in slices but not in dispersed cells. The phase relationship between [Ca2+]i and PER2 rhythms was more variable in cells within slices than in dispersed cells. Both PER2 and [Ca2+]i rhythms were abolished in SCN cells deficient in the essential clock gene Bmal1. These results suggest that the circadian rhythm of [Ca2+]i in SCN neurons is cell autonomous and dependent on clock gene rhythms, but reinforced and modulated by a synchronized SCN neuronal network.
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49
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Delayed Cryptochrome Degradation Asymmetrically Alters the Daily Rhythm in Suprachiasmatic Clock Neuron Excitability. J Neurosci 2017; 37:7824-7836. [PMID: 28698388 PMCID: PMC5559760 DOI: 10.1523/jneurosci.0691-17.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/01/2017] [Accepted: 06/08/2017] [Indexed: 11/30/2022] Open
Abstract
Suprachiasmatic nuclei (SCN) neurons contain an intracellular molecular circadian clock and the Cryptochromes (CRY1/2), key transcriptional repressors of this molecular apparatus, are subject to post-translational modification through ubiquitination and targeting for proteosomal degradation by the ubiquitin E3 ligase complex. Loss-of-function point mutations in a component of this ligase complex, Fbxl3, delay CRY1/2 degradation, reduce circadian rhythm strength, and lengthen the circadian period by ∼2.5 h. The molecular clock drives circadian changes in the membrane properties of SCN neurons, but it is unclear how alterations in CRY1/2 stability affect SCN neurophysiology. Here we use male and female Afterhours mice which carry the circadian period lengthening loss-of-function Fbxl3Afh mutation and perform patch-clamp recordings from SCN brain slices across the projected day/night cycle. We find that the daily rhythm in membrane excitability in the ventral SCN (vSCN) was enhanced in amplitude and delayed in timing in Fbxl3Afh/Afh mice. At night, vSCN cells from Fbxl3Afh/Afh mice were more hyperpolarized, receiving more GABAergic input than their Fbxl3+/+ counterparts. Unexpectedly, the progression to daytime hyperexcited states was slowed by Afh mutation, whereas the decline to hypoexcited states was accelerated. In long-term bioluminescence recordings, GABAA receptor blockade desynchronized the Fbxl3+/+ but not the Fbxl3Afh/Afh vSCN neuronal network. Further, a neurochemical mimic of the light input pathway evoked larger shifts in molecular clock rhythms in Fbxl3Afh/Afh compared with Fbxl3+/+ SCN slices. These results reveal unanticipated consequences of delaying CRY degradation, indicating that the Afh mutation prolongs nighttime hyperpolarized states of vSCN cells through increased GABAergic synaptic transmission. SIGNIFICANCE STATEMENT The intracellular molecular clock drives changes in SCN neuronal excitability, but it is unclear how mutations affecting post-translational modification of molecular clock proteins influence the temporal expression of SCN neuronal state or intercellular communication within the SCN network. Here we show for the first time, that a mutation that prolongs the stability of key components of the intracellular clock, the cryptochrome proteins, unexpectedly increases in the expression of hypoexcited neuronal state in the ventral SCN at night and enhances hyperpolarization of ventral SCN neurons at this time. This is accompanied by increased GABAergic signaling and by enhanced responsiveness to a neurochemical mimic of the light input pathway to the SCN. Therefore, post-translational modification shapes SCN neuronal state and network properties.
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50
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Liang X, Holy TE, Taghert PH. A Series of Suppressive Signals within the Drosophila Circadian Neural Circuit Generates Sequential Daily Outputs. Neuron 2017; 94:1173-1189.e4. [PMID: 28552314 DOI: 10.1016/j.neuron.2017.05.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/11/2017] [Accepted: 05/03/2017] [Indexed: 11/19/2022]
Abstract
We studied the Drosophila circadian neural circuit using whole-brain imaging in vivo. Five major groups of pacemaker neurons display synchronized molecular clocks, yet each exhibits a distinct phase of daily Ca2+ activation. Light and neuropeptide pigment dispersing factor (PDF) from morning cells (s-LNv) together delay the phase of the evening (LNd) group by ∼12 hr; PDF alone delays the phase of the DN3 group by ∼17 hr. Neuropeptide sNPF, released from s-LNv and LNd pacemakers, produces Ca2+ activation in the DN1 group late in the night. The circuit also features negative feedback by PDF to truncate the s-LNv Ca2+ wave and terminate PDF release. Both PDF and sNPF suppress basal Ca2+ levels in target pacemakers with long durations by cell-autonomous actions. Thus, light and neuropeptides act dynamically at distinct hubs of the circuit to produce multiple suppressive events that create the proper tempo and sequence of circadian pacemaker neuronal activities.
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Affiliation(s)
- Xitong Liang
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Timothy E Holy
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Paul H Taghert
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
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