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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: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [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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Pierre-Ferrer S, Collins B, Lukacsovich D, Wen S, Cai Y, Winterer J, Yan J, Pedersen L, Földy C, Brown SA. A phosphate transporter in VIPergic neurons of the suprachiasmatic nucleus gates locomotor activity during the light/dark transition in mice. Cell Rep 2024; 43:114220. [PMID: 38735047 DOI: 10.1016/j.celrep.2024.114220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 02/23/2024] [Accepted: 04/25/2024] [Indexed: 05/14/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) encodes time of day through changes in daily firing; however, the molecular mechanisms by which the SCN times behavior are not fully understood. To identify factors that could encode day/night differences in activity, we combine patch-clamp recordings and single-cell sequencing of individual SCN neurons in mice. We identify PiT2, a phosphate transporter, as being upregulated in a population of Vip+Nms+ SCN neurons at night. Although nocturnal and typically showing a peak of activity at lights off, mice lacking PiT2 (PiT2-/-) do not reach the activity level seen in wild-type mice during the light/dark transition. PiT2 loss leads to increased SCN neuronal firing and broad changes in SCN protein phosphorylation. PiT2-/- mice display a deficit in seasonal entrainment when moving from a simulated short summer to longer winter nights. This suggests that PiT2 is responsible for timing activity and is a driver of SCN plasticity allowing seasonal entrainment.
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Affiliation(s)
- Sara Pierre-Ferrer
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Ben Collins
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland; Department of Biology, Sacred Heart University, 5151 Park Ave., Fairfield, CT 06825, USA
| | - David Lukacsovich
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Shao'Ang Wen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yuchen Cai
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jochen Winterer
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Jun Yan
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Lene Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus, Denmark
| | - Csaba Földy
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Steven A Brown
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
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Cox OH, Gianonni-Guzmán MA, Cartailler JP, Cottam MA, McMahon DG. Gene expression plasticity of the mammalian brain circadian clock in response to photoperiod. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.16.580759. [PMID: 38586021 PMCID: PMC10996532 DOI: 10.1101/2024.02.16.580759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Seasonal daylength, or circadian photoperiod, is a pervasive environmental signal that profoundly influences physiology and behavior. In mammals, the central circadian clock resides in the suprachiasmatic nuclei (SCN) of the hypothalamus where it receives retinal input and synchronizes, or entrains, organismal physiology and behavior to the prevailing light cycle. The process of entrainment induces sustained plasticity in the SCN, but the molecular mechanisms underlying SCN plasticity are incompletely understood. Entrainment to different photoperiods persistently alters the timing, waveform, period, and light resetting properties of the SCN clock and its driven rhythms. To elucidate novel molecular mechanisms of photoperiod plasticity, we performed RNAseq on whole SCN dissected from mice raised in Long (LD 16:8) and Short (LD 8:16) photoperiods. Fewer rhythmic genes were detected in Long photoperiod and in general the timing of gene expression rhythms was advanced 4-6 hours. However, a few genes showed significant delays, including Gem . There were significant changes in the expression clock-associated gene Timeless and in SCN genes related to light responses, neuropeptides, GABA, ion channels, and serotonin. Particularly striking were differences in the expression of the neuropeptide signaling genes Prokr2 and Cck , as well as convergent regulation of the expression of three SCN light response genes, Dusp4 , Rasd1 , and Gem . Transcriptional modulation of Dusp4 and Rasd1, and phase regulation of Gem, are compelling candidate molecular mechanisms for plasticity in the SCN light response through their modulation of the critical NMDAR-MAPK/ERK-CREB/CRE light signaling pathway in SCN neurons. Modulation of Prokr2 and Cck may critically support SCN neural network reconfiguration during photoperiodic entrainment. Our findings identify the SCN light response and neuropeptide signaling gene sets as rich substrates for elucidating novel mechanisms of photoperiod plasticity.
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van Beurden AW, Tersteeg MMH, Michel S, van Veldhoven JPD, IJzerman AP, Rohling JHT, Meijer JH. Small-molecule CEM3 strengthens single-cell oscillators in the suprachiasmatic nucleus. FASEB J 2024; 38:e23348. [PMID: 38084798 DOI: 10.1096/fj.202300597rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 10/25/2023] [Accepted: 11/20/2023] [Indexed: 12/18/2023]
Abstract
A robust endogenous clock is required for proper function of many physiological processes. The suprachiasmatic nucleus (SCN) constitutes our central circadian clock and allows us to adapt to daily changes in the environment. Aging can cause a decline in the amplitude of circadian rhythms in SCN and peripheral clocks, which contributes to increased risk of several chronic diseases. Strengthening clock function would therefore be an effective strategy to improve health. A high-throughput chemical screening has identified clock-enhancing molecule 3 (CEM3) as small molecule that increases circadian rhythm amplitude in cell lines and SCN explants. It is, however, currently not known whether CEM3 acts by enhancing the amplitude of individual single-cell oscillators or by enhancing synchrony among neurons. In view of CEM3's potential, it is of evident importance to clarify the mode of action of CEM3. Here, we investigated the effects of CEM3 on single-cell PERIOD2::LUCIFERASE rhythms in mouse SCN explants. CEM3 increased the amplitude in approximately 80%-90% of the individual cells in the SCN without disrupting the phase and/or period of their rhythms. Noticeably, CEM3's effect on amplitude is independent of the cell's initial amplitude. These findings make CEM3 a potential therapeutic candidate to restore compromised amplitude in circadian rhythms and will boost the development of other molecular approaches to improve health.
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Affiliation(s)
- Anouk W van Beurden
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Mayke M H Tersteeg
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Stephan Michel
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jaco P D van Veldhoven
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Adriaan P IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Jos H T Rohling
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H Meijer
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
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Li Y, Lu L, Androulakis IP. The Physiological and Pharmacological Significance of the Circadian Timing of the HPA Axis: A Mathematical Modeling Approach. J Pharm Sci 2024; 113:33-46. [PMID: 37597751 PMCID: PMC10840710 DOI: 10.1016/j.xphs.2023.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 08/02/2023] [Accepted: 08/02/2023] [Indexed: 08/21/2023]
Abstract
As a potent endogenous regulator of homeostasis, the circadian time-keeping system synchronizes internal physiology to periodic changes in the external environment to enhance survival. Adapting endogenous rhythms to the external time is accomplished hierarchically with the central pacemaker located in the suprachiasmatic nucleus (SCN) signaling the hypothalamus-pituitary-adrenal (HPA) axis to release hormones, notably cortisol, which help maintain the body's circadian rhythm. Given the essential role of HPA-releasing hormones in regulating physiological functions, including immune response, cell cycle, and energy metabolism, their daily variation is critical for the proper function of the circadian timing system. In this review, we focus on cortisol and key fundamental properties of the HPA axis and highlight their importance in controlling circadian dynamics. We demonstrate how systems-driven, mathematical modeling of the HPA axis complements experimental findings, enhances our understanding of complex physiological systems, helps predict potential mechanisms of action, and elucidates the consequences of circadian disruption. Finally, we outline the implications of circadian regulation in the context of personalized chronotherapy. Focusing on the chrono-pharmacology of synthetic glucocorticoids, we review the challenges and opportunities associated with moving toward personalized therapies that capitalize on circadian rhythms.
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Affiliation(s)
- Yannuo Li
- Chemical & Biochemical Engineering Department, Piscataway, NJ 08854, USA
| | - Lingjun Lu
- Chemical & Biochemical Engineering Department, Piscataway, NJ 08854, USA
| | - Ioannis P Androulakis
- Chemical & Biochemical Engineering Department, Piscataway, NJ 08854, USA; Biomedical Engineering Department, Rutgers University, Piscataway, NJ 08540, USA.
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van Beurden AW, Meylahn JM, Achterhof S, Buijink R, Olde Engberink A, Michel S, Meijer JH, Rohling JHT. Reduced Plasticity in Coupling Strength in the Aging SCN Clock as Revealed by Kuramoto Modeling. J Biol Rhythms 2023; 38:461-475. [PMID: 37329153 PMCID: PMC10475211 DOI: 10.1177/07487304231175191] [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: 06/18/2023]
Abstract
The mammalian circadian clock is located in the suprachiasmatic nucleus (SCN) and consists of a network of coupled neurons, which are entrained to the environmental light-dark cycle. The phase coherence of the neurons is plastic and driven by the duration of daylight. With aging, the capacity to behaviorally adapt to seasonal changes in photoperiod reduces. The mechanisms underlying photoperiodic adaptation are largely unknown, but are important to unravel for the development of novel interventions to improve the quality of life of the elderly. We analyzed the phase coherence of single-cell PERIOD2::LUCIFERASE (PER2::LUC) expression rhythms in the SCN of young and old mice entrained to either long or short photoperiod. The phase coherence was used as input to a 2-community noisy Kuramoto model to estimate the coupling strength between and within neuronal subpopulations. The model revealed a correlation between coupling strength and photoperiod-induced changes in the phase relationship among neurons, suggesting a functional link. We found that the SCN of young mice adapts in coupling strength over a large range, with weak coupling in long photoperiod (LP) and strong coupling in short photoperiod (SP). In aged mice, we also found weak coupling in LP, but a reduced capacity to reach strong coupling in SP. The inability to respond with an increase in coupling strength suggests that manipulation of photoperiod is not a suitable strategy to enhance clock function with aging. We conclude that the inability of aged mice to reach strong coupling contributes to deficits in behavioral adaptation to seasonal changes in photoperiod.
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Affiliation(s)
- Anouk W. van Beurden
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Janusz M. Meylahn
- Dutch Institute for Emergent Phenomena, University of Amsterdam, Amsterdam, The Netherlands
- Department of Applied Mathematics, University of Twente, Enschede, The Netherlands
| | - Stefan Achterhof
- Mathematical Institute, Leiden University, Leiden, The Netherlands
| | - Renate Buijink
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Anneke Olde Engberink
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Stephan Michel
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H. Meijer
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jos H. T. Rohling
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
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Olde Engberink AHO, de Torres Gutiérrez P, Chiosso A, Das A, Meijer JH, Michel S. Aging affects GABAergic function and calcium homeostasis in the mammalian central clock. Front Neurosci 2023; 17:1178457. [PMID: 37260848 PMCID: PMC10229097 DOI: 10.3389/fnins.2023.1178457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 04/24/2023] [Indexed: 06/02/2023] Open
Abstract
Introduction Aging impairs the function of the central circadian clock in mammals, the suprachiasmatic nucleus (SCN), leading to a reduction in the output signal. The weaker timing signal from the SCN results in a decline in rhythm strength in many physiological functions, including sleep-wake patterns. Accumulating evidence suggests that the reduced amplitude of the SCN signal is caused by a decreased synchrony among the SCN neurons. The present study was aimed to investigate the hypothesis that the excitation/inhibition (E/I) balance plays a role in synchronization within the network. Methods Using calcium (Ca2+) imaging, the polarity of Ca2+ transients in response to GABA stimulation in SCN slices of old mice (20-24 months) and young controls was studied. Results We found that the amount of GABAergic excitation was increased, and that concordantly the E/I balance was higher in SCN slices of old mice when compared to young controls. Moreover, we showed an effect of aging on the baseline intracellular Ca2+ concentration, with higher Ca2+ levels in SCN neurons of old mice, indicating an alteration in Ca2+ homeostasis in the aged SCN. We conclude that the change in GABAergic function, and possibly the Ca2+ homeostasis, in SCN neurons may contribute to the altered synchrony within the aged SCN network.
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Xie L, Xiong Y, Ma D, Shi K, Chen J, Yang Q, Yan J. Cholecystokinin neurons in mouse suprachiasmatic nucleus regulate the robustness of circadian clock. Neuron 2023:S0896-6273(23)00301-X. [PMID: 37172583 DOI: 10.1016/j.neuron.2023.04.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/09/2023] [Accepted: 04/14/2023] [Indexed: 05/15/2023]
Abstract
The suprachiasmatic nucleus (SCN) can generate robust circadian behaviors in mammals under different environments, but the underlying neural mechanisms remained unclear. Here, we showed that the activities of cholecystokinin (CCK) neurons in the mouse SCN preceded the onset of behavioral activities under different photoperiods. CCK-neuron-deficient mice displayed shortened free-running periods, failed to compress their activities under a long photoperiod, and developed rapid splitting or became arrhythmic under constant light. Furthermore, unlike vasoactive intestinal polypeptide (VIP) neurons, CCK neurons are not directly light sensitive, but their activation can elicit phase advance and counter light-induced phase delay mediated by VIP neurons. Under long photoperiods, the impact of CCK neurons on SCN dominates over that of VIP neurons. Finally, we found that the slow-responding CCK neurons control the rate of recovery during jet lag. Together, our results demonstrated that SCN CCK neurons are crucial for the robustness and plasticity of the mammalian circadian clock.
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Affiliation(s)
- Lucheng Xie
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Yangyang Xiong
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Danyi Ma
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Kaiwen Shi
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jiu Chen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Qiaoqiao Yang
- Department of Neurosurgery, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Jun Yan
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China; School of Future Technology, University of Chinese Academy of Sciences, Beijing 101408, China.
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van Beurden AW, Schoonderwoerd RA, Tersteeg MMH, de Torres Gutiérrez P, Michel S, Blommers R, Rohling JHT, Meijer JH. Single cell model for re-entrainment to a shifted light cycle. FASEB J 2022; 36:e22518. [PMID: 36057093 PMCID: PMC9543151 DOI: 10.1096/fj.202200478r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 07/25/2022] [Accepted: 08/15/2022] [Indexed: 11/11/2022]
Abstract
Our daily 24-h rhythm is synchronized to the external light-dark cycle resulting from the Earth's daily rotation. In the mammalian brain, the suprachiasmatic nucleus (SCN) serves as the master clock and receives light-mediated input via the retinohypothalamic tract. Abrupt changes in the timing of the light-dark cycle (e.g., due to jet lag) cause a phase shift in the circadian rhythms in the SCN. Here, we investigated the effects of a 6-h delay in the light-dark cycle on PERIOD2::LUCIFERASE expression at the single-cell level in mouse SCN organotypic explants. The ensemble pattern in phase shift response obtained from individual neurons in the anterior and central SCN revealed a bimodal distribution; specifically, neurons in the ventrolateral SCN responded with a rapid phase shift, while neurons in the dorsal SCN generally did not respond to the shift in the light-dark cycle. We also stimulated the hypothalamic tract in acute SCN slices to simulate light-mediated input to the SCN; interestingly, we found similarities between the distribution and fraction of rapid shifting neurons (in response to the delay) and neurons that were excited in response to electrical stimulation. These results suggest that a subpopulation of neurons in the ventral SCN that have an excitatory response to light input, shift their clock more readily than dorsal located neurons, and initiate the SCN's entrainment to the new light-dark cycle. Thus, we propose that light-excited neurons in the anterior and central SCN play an important role in the organism's ability to adjust to changes in the external light-dark cycle.
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Affiliation(s)
- Anouk W van Beurden
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin A Schoonderwoerd
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Mayke M H Tersteeg
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Stephan Michel
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ruben Blommers
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jos H T Rohling
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H Meijer
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
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Li Y, Androulakis IP. Light-induced synchronization of the SCN coupled oscillators and implications for entraining the HPA axis. Front Endocrinol (Lausanne) 2022; 13:960351. [PMID: 36387856 PMCID: PMC9648564 DOI: 10.3389/fendo.2022.960351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 10/10/2022] [Indexed: 11/13/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) synchronizes the physiological rhythms to the external light-dark cycle and tunes the dynamics of circadian rhythms to photoperiod fluctuations. Changes in the neuronal network topologies are suggested to cause adaptation of the SCN in different photoperiods, resulting in the broader phase distribution of neuron activities in long photoperiods (LP) compared to short photoperiods (SP). Regulated by the SCN output, the level of glucocorticoids is elevated in short photoperiod, which is associated with peak disease incidence. The underlying coupling mechanisms of the SCN and the interplay between the SCN and the HPA axis have yet to be fully elucidated. In this work, we propose a mathematical model including a multiple-cellular SCN compartment and the HPA axis to investigate the properties of the circadian timing system under photoperiod changes. Our model predicts that the probability-dependent network is more energy-efficient than the distance-dependent network. Coupling the SCN network by intra-subpopulation and inter-subpopulation forces, we identified the negative correlation between robustness and plasticity of the oscillatory network. The HPA rhythms were predicted to be strongly entrained to the SCN rhythms with a pro-inflammatory high-amplitude glucocorticoid profile under SP. The fast temporal topology switch of the SCN network was predicted to enhance synchronization when the synchronization is not complete. These synchronization and circadian dynamics alterations might govern the seasonal variation of disease incidence and its symptom severity.
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Affiliation(s)
- Yannuo Li
- Chemical & Biochemical Engineering Department, Rutgers University, Piscataway, NJ, United States
| | - Ioannis P. Androulakis
- Chemical & Biochemical Engineering Department, Rutgers University, Piscataway, NJ, United States
- Biomedical Engineering Department, Rutgers University, Piscataway, NJ, United States
- *Correspondence: Ioannis P. Androulakis,
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Tackenberg MC, Hughey JJ, McMahon DG. Optogenetic stimulation of VIPergic SCN neurons induces photoperiodic-like changes in the mammalian circadian clock. Eur J Neurosci 2021; 54:7063-7071. [PMID: 34486778 PMCID: PMC8796658 DOI: 10.1111/ejn.15442] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 07/30/2021] [Accepted: 08/23/2021] [Indexed: 02/01/2023]
Abstract
Circadian clocks play key roles in how organisms respond to and even anticipate seasonal change in day length, or photoperiod. In mammals, photoperiod is encoded by the central circadian pacemaker in the brain, the suprachiasmatic nucleus (SCN). The subpopulation of SCN neurons that secrete the neuropeptide VIP mediates the transmission of light information within the SCN neural network, suggesting a role for these neurons in circadian plasticity in response to light information that has yet to be directly tested. Here, we used in vivo optogenetic stimulation of VIPergic SCN neurons followed by ex vivo PERIOD 2::LUCIFERASE (PER2::LUC) bioluminescent imaging to test whether activation of this SCN neuron subpopulation can induce SCN network changes that are hallmarks of photoperiodic encoding. We found that optogenetic stimulation designed to mimic a long photoperiod indeed altered subsequent SCN entrained phase, increased the phase dispersal of PER2 rhythms within the SCN network, and shortened SCN free-running period-similar to the effects of a true extension of photoperiod. Optogenetic stimulation also induced analogous changes on related aspects of locomotor behaviour in vivo. Thus, selective activation of VIPergic SCN neurons induces photoperiodic network plasticity in the SCN that underpins photoperiodic entrainment of behaviour.
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Affiliation(s)
- Michael C. Tackenberg
- Department of Biological Sciences, Vanderbilt University, Nashville TN
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville TN
| | - Jacob J. Hughey
- Department of Biological Sciences, Vanderbilt University, Nashville TN
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville TN
| | - Douglas G. McMahon
- Department of Biological Sciences, Vanderbilt University, Nashville TN
- Vanderbilt Brain Institute, Vanderbilt University, Nashville TN
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Gu C, Li J, Zhou J, Yang H, Rohling J. Network Structure of the Master Clock Is Important for Its Primary Function. Front Physiol 2021; 12:678391. [PMID: 34483953 PMCID: PMC8415478 DOI: 10.3389/fphys.2021.678391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 07/22/2021] [Indexed: 11/13/2022] Open
Abstract
A master clock located in the suprachiasmatic nucleus (SCN) regulates the circadian rhythm of physiological and behavioral activities in mammals. The SCN has two main functions in the regulation: an endogenous clock produces the endogenous rhythmic signal in body rhythms, and a calibrator synchronizes the body rhythms to the external light-dark cycle. These two functions have been determined to depend on either the dynamic behaviors of individual neurons or the whole SCN neuronal network. In this review, we first introduce possible network structures for the SCN, as revealed by time series analysis from real experimental data. It was found that the SCN network is heterogeneous and sparse, that is, the average shortest path length is very short, some nodes are hubs with large node degrees but most nodes have small node degrees, and the average node degree of the network is small. Secondly, the effects of the SCN network structure on the SCN function are reviewed based on mathematical models of the SCN network. It was found that robust rhythms with large amplitudes, a high synchronization between SCN neurons and a large entrainment ability exists mainly in small-world and scale-free type networks, but not other types. We conclude that the SCN most probably is an efficient small-world type or scale-free type network, which drives SCN function.
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Affiliation(s)
- Changgui Gu
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jiahui Li
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jian Zhou
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Huijie Yang
- Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Jos Rohling
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
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Bano-Otalora B, Martial F, Harding C, Bechtold DA, Allen AE, Brown TM, Belle MDC, Lucas RJ. Bright daytime light enhances circadian amplitude in a diurnal mammal. Proc Natl Acad Sci U S A 2021; 118:e2100094118. [PMID: 34031246 PMCID: PMC8179182 DOI: 10.1073/pnas.2100094118] [Citation(s) in RCA: 24] [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] [Indexed: 11/18/2022] Open
Abstract
Mammalian circadian rhythms are orchestrated by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN), which receives information about the 24 h light-dark cycle from the retina. The accepted function of this light signal is to reset circadian phase in order to ensure appropriate synchronization with the celestial day. Here, we ask whether light also impacts another key property of the circadian oscillation, its amplitude. To this end, we measured circadian rhythms in behavioral activity, body temperature, and SCN electrophysiological activity in the diurnal murid rodent Rhabdomys pumilio following stable entrainment to 12:12 light-dark cycles at four different daytime intensities (ranging from 18 to 1,900 lx melanopic equivalent daylight illuminance). R. pumilio showed strongly diurnal activity and body temperature rhythms in all conditions, but measures of rhythm robustness were positively correlated with daytime irradiance under both entrainment and subsequent free run. Whole-cell and extracellular recordings of electrophysiological activity in ex vivo SCN revealed substantial differences in electrophysiological activity between dim and bright light conditions. At lower daytime irradiance, daytime peaks in SCN spontaneous firing rate and membrane depolarization were substantially depressed, leading to an overall marked reduction in the amplitude of circadian rhythms in spontaneous activity. Our data reveal a previously unappreciated impact of daytime light intensity on SCN physiology and the amplitude of circadian rhythms and highlight the potential importance of daytime light exposure for circadian health.
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Affiliation(s)
- Beatriz Bano-Otalora
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Franck Martial
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Court Harding
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - David A Bechtold
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Annette E Allen
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Timothy M Brown
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Mino D C Belle
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter EX4 4PS, United Kingdom
| | - Robert J Lucas
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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14
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Achterhof S, Meylahn JM. Two-community noisy Kuramoto model with general interaction strengths. I. CHAOS (WOODBURY, N.Y.) 2021; 31:033115. [PMID: 33810750 DOI: 10.1063/5.0022624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 01/19/2021] [Indexed: 06/12/2023]
Abstract
We generalize the study of the noisy Kuramoto model, considered on a network of two interacting communities, to the case where the interaction strengths within and across communities are taken to be different in general. By developing a geometric interpretation of the self-consistency equations, we are able to separate the parameter space into ten regions in which we identify the maximum number of solutions in the steady state. Furthermore, we prove that in the steady state, only the angles 0 and π are possible between the average phases of the two communities and derive the solution boundary for the unsynchronized solution. Last, we identify the equivalence class relation in the parameter space corresponding to the symmetrically synchronized solution.
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Affiliation(s)
- S Achterhof
- Mathematical Institute, Leiden University, P.O. Box 9512, 2300 RA Leiden, The Netherlands
| | - J M Meylahn
- Amsterdam Business School, University of Amsterdam, P.O. Box 15953, 1001 NL Amsterdam, The Netherlands
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15
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Tackenberg MC, Hughey JJ. The risks of using the chi-square periodogram to estimate the period of biological rhythms. PLoS Comput Biol 2021; 17:e1008567. [PMID: 33406069 PMCID: PMC7815206 DOI: 10.1371/journal.pcbi.1008567] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 01/19/2021] [Accepted: 11/27/2020] [Indexed: 11/29/2022] Open
Abstract
The chi-square periodogram (CSP), developed over 40 years ago, continues to be one of the most popular methods to estimate the period of circadian (circa 24-h) rhythms. Previous work has indicated the CSP is sometimes less accurate than other methods, but understanding of why and under what conditions remains incomplete. Using simulated rhythmic time-courses, we found that the CSP is prone to underestimating the period in a manner that depends on the true period and the length of the time-course. This underestimation bias is most severe in short time-courses (e.g., 3 days), but is also visible in longer simulated time-courses (e.g., 12 days) and in experimental time-courses of mouse wheel-running and ex vivo bioluminescence. We traced the source of the bias to discontinuities in the periodogram that are related to the number of time-points the CSP uses to calculate the observed variance for a given test period. By revising the calculation to avoid discontinuities, we developed a new version, the greedy CSP, that shows reduced bias and improved accuracy. Nonetheless, even the greedy CSP tended to be less accurate on our simulated time-courses than an alternative method, namely the Lomb-Scargle periodogram. Thus, although our study describes a major improvement to a classic method, it also suggests that users should generally avoid the CSP when estimating the period of biological rhythms. The chi-square periodogram is a popular method for estimating period length, one of the most important properties of the daily biological rhythms found throughout nature. In this study, we identify a major source of inaccuracy in the chi-square periodogram, and quantify the inaccuracy using a broad array of simulated and experimentally observed biological rhythms. Although we revise the chi-square periodogram calculation to improve its accuracy, we also show that the revised version is still less accurate than an alternative method, the Lomb-Scargle periodogram. Our work thus provides evidence on how to obtain better estimates of the period of biological rhythms.
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Affiliation(s)
- Michael C. Tackenberg
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Jacob J. Hughey
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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16
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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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17
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Seasonality and light phase-resetting in the mammalian circadian rhythm. Sci Rep 2020; 10:19506. [PMID: 33177530 PMCID: PMC7658258 DOI: 10.1038/s41598-020-74002-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/18/2020] [Indexed: 11/13/2022] Open
Abstract
We study the impact of light on the mammalian circadian system using the theory of phase response curves. Using a recently developed ansatz we derive a low-dimensional macroscopic model for the core circadian clock in mammals. Significantly, the variables and parameters in our model have physiological interpretations and may be compared with experimental results. We focus on the effect of four key factors which help shape the mammalian phase response to light: heterogeneity in the population of oscillators, the structure of the typical light phase response curve, the fraction of oscillators which receive direct light input and changes in the coupling strengths associated with seasonal day-lengths. We find these factors can explain several experimental results and provide insight into the processing of light information in the mammalian circadian system. In particular, we find that the sensitivity of the circadian system to light may be modulated by changes in the relative coupling forces between the light sensing and non-sensing populations. Finally, we show how seasonal day-length, after-effects to light entrainment and seasonal variations in light sensitivity in the mammalian circadian clock are interrelated.
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18
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Shan Y, Abel JH, Li Y, Izumo M, Cox KH, Jeong B, Yoo SH, Olson DP, Doyle FJ, Takahashi JS. Dual-Color Single-Cell Imaging of the Suprachiasmatic Nucleus Reveals a Circadian Role in Network Synchrony. Neuron 2020; 108:164-179.e7. [PMID: 32768389 PMCID: PMC8265161 DOI: 10.1016/j.neuron.2020.07.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 06/17/2020] [Accepted: 07/10/2020] [Indexed: 01/08/2023]
Abstract
The suprachiasmatic nucleus (SCN) acts as a master pacemaker driving circadian behavior and physiology. Although the SCN is small, it is composed of many cell types, making it difficult to study the roles of particular cells. Here we develop bioluminescent circadian reporter mice that are Cre dependent, allowing the circadian properties of genetically defined populations of cells to be studied in real time. Using a Color-Switch PER2::LUCIFERASE reporter that switches from red PER2::LUCIFERASE to green PER2::LUCIFERASE upon Cre recombination, we assess circadian rhythms in two of the major classes of peptidergic neurons in the SCN: AVP (arginine vasopressin) and VIP (vasoactive intestinal polypeptide). Surprisingly, we find that circadian function in AVP neurons, not VIP neurons, is essential for autonomous network synchrony of the SCN and stability of circadian rhythmicity.
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Affiliation(s)
- Yongli Shan
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - John H Abel
- Department of Anesthesiology, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA; Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yan Li
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Mariko Izumo
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Kimberly H Cox
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Byeongha Jeong
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Seung-Hee Yoo
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - David P Olson
- Department of Pediatrics, Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Francis J Doyle
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115, 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.
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19
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Circadian disruption impairs fear extinction and memory of conditioned safety in mice. Behav Brain Res 2020; 393:112788. [DOI: 10.1016/j.bbr.2020.112788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 06/21/2020] [Accepted: 06/22/2020] [Indexed: 02/06/2023]
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20
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Olde Engberink AHO, Huisman J, Michel S, Meijer JH. Brief light exposure at dawn and dusk can encode day-length in the neuronal network of the mammalian circadian pacemaker. FASEB J 2020; 34:13685-13695. [PMID: 32869393 DOI: 10.1096/fj.202001133rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 07/23/2020] [Accepted: 07/29/2020] [Indexed: 11/11/2022]
Abstract
The central circadian pacemaker in mammals, the suprachiasmatic nucleus (SCN), is important for daily as well as seasonal rhythms. The SCN encodes seasonal changes in day length by adjusting phase distribution among oscillating neurons thereby shaping the output signal used for adaptation of physiology and behavior. It is well-established that brief light exposure at the beginning and end of the day, also referred to as "skeleton" light pulses, are sufficient to evoke the seasonal behavioral phenotype. However, the effect of skeleton light exposure on SCN network reorganization remains unknown. Therefore, we exposed mice to brief morning and evening light pulses that mark the time of dawn and dusk in a short winter- or a long summer day. Single-cell PER2::LUC recordings, electrophysiological recordings of SCN activity, and measurements of GABA response polarity revealed that skeleton light-regimes affected the SCN network to the same degree as full photoperiod. These results indicate the powerful, yet potentially harmful effects of even relatively short light exposures during the evening or night for nocturnal animals.
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Affiliation(s)
- Anneke H O Olde Engberink
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Job Huisman
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Stephan Michel
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Johanna H Meijer
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
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21
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Food anticipatory circadian rhythms in mice entrained to long or short day photoperiods. Physiol Behav 2020; 222:112939. [PMID: 32407832 DOI: 10.1016/j.physbeh.2020.112939] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 04/03/2020] [Accepted: 04/23/2020] [Indexed: 11/21/2022]
Abstract
Food anticipatory activity (FAA) rhythms that emerge in nocturnal rodents fed once daily are mediated by food-entrainable circadian oscillators (FEOs) located outside of the suprachiasmatic nucleus (SCN), the site of a circadian pacemaker required for entrainment to daily light-dark (LD) cycles. Specification of the neural and molecular substrates of FEOs driving FAA is complicated by homeostatic, hedonic and environmental factors that can modulate expression of activity independent of circadian timing. Here, we examined the effect of photoperiod (duration of the daily light period) on FAA in mice fed during the last 4 h or middle 4 h of the light period for at least 5 weeks. Long photoperiods decrease SCN pacemaker amplitude, which may favor expression of FAA during the day, when the SCN normally opposes activity in nocturnal rodents. To test this prediction, in Experiment 1, mice housed with or without running discs were entrained to 24 h LD cycles with 8 h (L8) or 16 h (L16) photoperiods. When food was restricted to the last 4 h of the light period (late-day), mice housed with running discs showed more FAA in L16, whereas mice without running discs showed more FAA in L8. In Experiment 2, mice were entrained to L8 or L16 photoperiods, and the 4 h daily meal was centered in the light period (mid-day). FAA was decreased relative to late-day fed mice, but did not vary by photoperiod. In Experiment 3, mice with or without running discs were entrained to L12 or L18 photoperiods, with mealtime centered in the light period. FAA again did not differ between photoperiods. In constant dark (DD) prior to food restriction, the period (τ) of free-running rhythms was shorter in mice entrained to long days. This known after-effect of photoperiod on τ was absent in DD immediately following restricted feeding. The phase of LD entrainment, unmasked on the first day of DD with food ad-libitum, was significantly advanced in mice from the late-day feeding schedule, compared to mice from the mid-day schedules. These results indicate that FAA in mice does not vary systematically with photoperiod, possibly because daytime feeding schedules attenuate the effect of photoperiod on the mouse SCN pacemaker. FAA in the present study was more strongly influenced by running disc availability and by meal time within the light period, possibly due to effects on LD entrainment, which was phase advanced by late-day but not midday feeding.
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22
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Tackenberg MC, Hughey JJ, McMahon DG. Distinct Components of Photoperiodic Light Are Differentially Encoded by the Mammalian Circadian Clock. J Biol Rhythms 2020; 35:353-367. [PMID: 32527181 DOI: 10.1177/0748730420929217] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Seasonal light cycles influence multiple physiological functions and are mediated through photoperiodic encoding by the circadian system. Despite our knowledge of the strong connection between seasonal light input and downstream circadian changes, less is known about the specific components of seasonal light cycles that are encoded and induce persistent changes in the circadian system. Using combinations of 3 T cycles (23, 24, 26 h) and 2 photoperiods per T cycle (long and short, with duty cycles scaled to each T cycle), we investigate the after-effects of entrainment to these 6 light cycles. We measure locomotor behavior duration (α), period (τ), and entrained phase angle (ψ) in vivo and SCN phase distribution (σφ), τ, and ψ ex vivo to refine our understanding of critical light components for influencing particular circadian properties. We find that both photoperiod and T-cycle length drive determination of in vivo ψ but differentially influence after-effects in α and τ, with photoperiod driving changes in α and photoperiod length and T-cycle length combining to influence τ. Using skeleton photoperiods, we demonstrate that in vivo ψ is determined by both parametric and nonparametric components, while changes in α are driven nonparametrically. Within the ex vivo SCN, we find that ψ and σφ of the PER2∷LUCIFERASE rhythm follow closely with their likely behavioral counterparts (ψ and α of the locomotor activity rhythm) while also confirming previous reports of τ after-effects of gene expression rhythms showing negative correlations with behavioral τ after-effects in response to T cycles. We demonstrate that within-SCN σφ changes, thought to underlie α changes in vivo, are induced primarily nonparametrically. Taken together, our results demonstrate that distinct components of seasonal light input differentially influence ψ, α, and τ and suggest the possibility of separate mechanisms driving the persistent changes in circadian behaviors mediated by seasonal light.
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Affiliation(s)
| | - Jacob J Hughey
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee.,Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Douglas G McMahon
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee.,Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee
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23
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Schomann T, Mezzanotte L, de Groot JCMJ, Löwik CWGM, Frijns JHM, Huisman MA. Imaging Bioluminescent Exogenous Stem Cells in the Intact Guinea Pig Cochlea. Anat Rec (Hoboken) 2020; 303:427-440. [PMID: 30635981 PMCID: PMC7065152 DOI: 10.1002/ar.24068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 06/25/2018] [Accepted: 08/27/2018] [Indexed: 11/07/2022]
Abstract
Stem-cell-based therapy may be used to replace damaged or lost neurons in the cochlear nerve of patients suffering from severe-to-profound sensorineural hearing loss. In order to achieve functional recovery in future clinical trials, knowledge about survival of grafted cells and their differentiation into functional neurons is a prerequisite. This calls for non-invasive in vivo visualization of cells and long-term monitoring of their survival and fate after cochlear transplantation. We have investigated if molecular optical imaging enables visualization of exogenous cells in the intact cochlea of guinea pig cadaver heads. Transduced (stem) cells, stably co-expressing fluorescent (copGFP) and bioluminescent (Luc2) reporter molecules, were injected into the internal auditory meatus or directly into the cochlea through the round window. After injection of the cells into the internal auditory meatus, a bright bioluminescent signal was observed in the cavum conchae of the auricle, indicating that light generated by Luc2 is passing through the tympanic membrane and the external auditory meatus. Similar results were obtained after injection of the cells through the round window membrane, either directly into the scala tympani or in Rosenthal's canal within the modiolus of the basal cochlear turn. Imaging of the auditory bulla demonstrated that the bioluminescent signal passes through the tympanic membrane and crevices in the bony wall of the bulla. After opening the auditory bulla, the bioluminescent signal was emanating from the round window. This is the first study demonstrating that bioluminescence imaging enables visualization of luciferase-expressing cells injected into the intact guinea pig cochlea. Anat Rec, 303:427-440, 2020. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- Timo Schomann
- Auditory Neurobiology Laboratory, Department of Otorhinolaryngology and Head and Neck SurgeryLeiden University Medical CenterLeidenThe Netherlands
| | - Laura Mezzanotte
- Optical Molecular Imaging, Department of RadiologyErasmus Medical Center RotterdamRotterdamThe Netherlands
| | - John C. M. J. de Groot
- Auditory Neurobiology Laboratory, Department of Otorhinolaryngology and Head and Neck SurgeryLeiden University Medical CenterLeidenThe Netherlands
| | - Clemens W. G. M. Löwik
- Optical Molecular Imaging, Department of RadiologyErasmus Medical Center RotterdamRotterdamThe Netherlands
| | - Johan H. M. Frijns
- Auditory Neurobiology Laboratory, Department of Otorhinolaryngology and Head and Neck SurgeryLeiden University Medical CenterLeidenThe Netherlands
| | - Margriet A. Huisman
- Auditory Neurobiology Laboratory, Department of Otorhinolaryngology and Head and Neck SurgeryLeiden University Medical CenterLeidenThe Netherlands
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24
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Flôres DEFL, Oda GA. Quantitative Study of Dual Circadian Oscillator Models under Different Skeleton Photoperiods. J Biol Rhythms 2020; 35:302-316. [DOI: 10.1177/0748730420901939] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The daily proportion of light and dark hours (photoperiod) changes annually and plays an important role in the synchronization of seasonal biological phenomena, such as reproduction, hibernation, and migration. In mammals, the first step of photoperiod transduction occurs in the suprachiasmatic nuclei (SCN), the circadian pacemaker that also coordinates 24-h activity rhythms. Thus, in parallel with its role in annual synchronization, photoperiod variation acutely shapes day/night activity patterns, which vary throughout the year. Systematic studies of this behavioral modulation help understand the mechanisms behind its transduction at the SCN level. To explain how entrainment mechanisms could account for daily activity patterns under different photoperiods, Colin Pittendrigh and Serge Daan proposed a conceptual model in which the pacemaker would be composed of 2 coupled, evening (E) and morning (M), oscillators. Although the E-M model has existed for more than 40 years now, its physiological bases are still not fully resolved, and it has not been tested quantitatively under different photoperiods. To better explore the implications of the E-M model, we performed computer simulations of 2 coupled limit-cycle oscillators. Four model configurations were exposed to systematic variation of skeleton photoperiods, and the resulting daily activity patterns were assessed. The criterion for evaluating different model configurations was the successful reproduction of 2 key behavioral phenomena observed experimentally: activity psi-jumps and photoperiod-induced changes in activity phase duration. We compared configurations with either separate light inputs to E and M or the same light inputs to both oscillators. The former replicated experimental results closely, indicating that the configuration with separate E and M light inputs is the mechanism that best reproduces the effects of different skeleton photoperiods on day/night activity patterns. We hope this model can contribute to the search for E and M and their light input organization in the SCN.
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Affiliation(s)
| | - Gisele A. Oda
- Instituto de Biociências, Universidade de São Paulo, Sao Paulo, Brazil
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25
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Buijink MR, Olde Engberink AHO, Wit CB, Almog A, Meijer JH, Rohling JHT, Michel S. Aging Affects the Capacity of Photoperiodic Adaptation Downstream from the Central Molecular Clock. J Biol Rhythms 2020; 35:167-179. [PMID: 31983261 PMCID: PMC7134598 DOI: 10.1177/0748730419900867] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aging impairs circadian clock function, leading to disrupted sleep-wake patterns and a reduced capability to adapt to changes in environmental light conditions. This makes shift work or the changing of time zones challenging for the elderly and, importantly, is associated with the development of age-related diseases. However, it is unclear what levels of the clock machinery are affected by aging, which is relevant for the development of targeted interventions. We found that naturally aged mice of >24 months had a reduced rhythm amplitude in behavior compared with young controls (3-6 months). Moreover, the old animals had a strongly reduced ability to adapt to short photoperiods. Recording PER2::LUC protein expression in the suprachiasmatic nucleus revealed no impairment of the rhythms in PER2 protein under the 3 different photoperiods tested (LD: 8:16, 12:12, and 16:8). Thus, we observed a discrepancy between the behavioral phenotype and the molecular clock, and we conclude that the aging-related deficits emerge downstream of the core molecular clock. Since it is known that aging affects several intracellular and membrane components of the central clock cells, it is likely that an impairment of the interaction between the molecular clock and these components is contributing to the deficits in photoperiod adaptation.
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Affiliation(s)
- M Renate Buijink
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Anneke H O Olde Engberink
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Charlotte B Wit
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Assaf Almog
- Lorentz Institute for Theoretical Physics, Leiden University, Leiden, the Netherlands
| | - Johanna H Meijer
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Jos H T Rohling
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Stephan Michel
- Department of Cellular and Chemical Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands
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26
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Abstract
Mathematical models have a long and influential history in the study of human circadian rhythms. Accurate predictive models for the human circadian light response have been used to study the impact of a host of light exposures on the circadian system. However, generally, these models do not account for the physiological basis of these rhythms. We illustrate a new paradigm for deriving models of the human circadian light response. Beginning from a high-dimensional model of the circadian neural network, we systematically derive low-dimensional models using an approach motivated by experimental measurements of circadian neurons. This systematic reduction allows for the variables and parameters of the derived model to be interpreted in a physiological context. We fit and validate the resulting models to a library of experimental measurements. Finally, we compare model predictions for experimental measurements of light levels and discuss the differences between our model’s predictions and previous models. Our modeling paradigm allows for the integration of experimental measurements across the single-cell, tissue, and behavioral scales, thereby enabling the development of accurate low-dimensional models for human circadian rhythms.
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Affiliation(s)
- Kevin M. Hannay
- Department of Mathematics, Schreiner University, Kerrville, Texas
| | - Victoria Booth
- Department of Mathematics, University of Michigan, Ann Arbor, Michigan
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan
| | - Daniel B. Forger
- Department of Mathematics, University of Michigan, Ann Arbor, Michigan
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan
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Michel S, Meijer JH. From clock to functional pacemaker. Eur J Neurosci 2019; 51:482-493. [PMID: 30793396 PMCID: PMC7027845 DOI: 10.1111/ejn.14388] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/23/2019] [Accepted: 02/11/2019] [Indexed: 12/17/2022]
Abstract
In mammals, the central pacemaker that coordinates 24‐hr rhythms is located in the suprachiasmatic nucleus (SCN). Individual neurons of the SCN have a molecular basis for rhythm generation and hence, they function as cell autonomous oscillators. Communication and synchronization among these neurons are crucial for obtaining a coherent rhythm at the population level, that can serve as a pace making signal for brain and body. Hence, the ability of single SCN neurons to produce circadian rhythms is equally important as the ability of these neurons to synchronize one another, to obtain a bona fide pacemaker at the SCN tissue level. In this chapter we will discuss the mechanisms underlying synchronization, and plasticity herein, which allows adaptation to changes in day length. Furthermore, we will discuss deterioration in synchronization among SCN neurons in aging, and gain in synchronization by voluntary physical activity or exercise.
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Affiliation(s)
- Stephan Michel
- Group Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H Meijer
- Group Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
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28
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Almog A, Buijink MR, Roethler O, Michel S, Meijer JH, Rohling JHT, Garlaschelli D. Uncovering functional signature in neural systems via random matrix theory. PLoS Comput Biol 2019; 15:e1006934. [PMID: 31042698 PMCID: PMC6513117 DOI: 10.1371/journal.pcbi.1006934] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 05/13/2019] [Accepted: 03/10/2019] [Indexed: 11/19/2022] Open
Abstract
Neural systems are organized in a modular way, serving multiple functionalities. This multiplicity requires that both positive (e.g. excitatory, phase-coherent) and negative (e.g. inhibitory, phase-opposing) interactions take place across brain modules. Unfortunately, most methods to detect modules from time series either neglect or convert to positive, any measured negative correlation. This may leave a significant part of the sign-dependent functional structure undetected. Here we present a novel method, based on random matrix theory, for the identification of sign-dependent modules in the brain. Our method filters out both local (unit-specific) noise and global (system-wide) dependencies that typically obfuscate the presence of such structure. The method is guaranteed to identify an optimally contrasted functional 'signature', i.e. a partition into modules that are positively correlated internally and negatively correlated across. The method is purely data-driven, does not use any arbitrary threshold or network projection, and outputs only statistically significant structure. In measurements of neuronal gene expression in the biological clock of mice, the method systematically uncovers two otherwise undetectable, negatively correlated modules whose relative size and mutual interaction strength are found to depend on photoperiod.
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Affiliation(s)
- Assaf Almog
- The Big Data Lab, Department of Industrial Engineering, Tel-Aviv University, Ramat Aviv, Israel
- Instituut-Lorentz for Theoretical Physics, Leiden Institute of Physics, University of Leiden, Leiden, The Netherlands
| | - M. Renate Buijink
- Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ori Roethler
- Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Stephan Michel
- Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johanna H. Meijer
- Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jos H. T. Rohling
- Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
- * E-mail:
| | - Diego Garlaschelli
- Instituut-Lorentz for Theoretical Physics, Leiden Institute of Physics, University of Leiden, Leiden, The Netherlands
- IMT School for Advanced Studies, Lucca, Italy
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29
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Engert LC, Weiler U, Pfaffinger B, Stefanski V, Schmucker SS. Photoperiodic Effects on Diurnal Rhythms in Cell Numbers of Peripheral Leukocytes in Domestic Pigs. Front Immunol 2019; 10:393. [PMID: 30915069 PMCID: PMC6422931 DOI: 10.3389/fimmu.2019.00393] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 02/14/2019] [Indexed: 11/13/2022] Open
Abstract
The photoperiod is known to modulate immune cell number and function and is regarded essential for seasonal disease susceptibility. In addition, diurnal variations in the immune system are regarded important for immune competence. Whereas few studies investigated the influence of season, none investigated the specific effect of the photoperiod on these diurnal immune rhythms until now. Therefore, the present study compared diurnal rhythms in cell numbers of peripheral leukocyte types in domestic pigs held either under long day conditions (LD) or short day conditions (SD). Cosinor analyses of cell numbers of various peripheral leukocyte subtypes investigated over periods of 50 h revealed distinct photoperiodic differences in diurnal immune rhythms. Relative amplitudes of cell numbers of total leukocytes, NK cells, T cells, and monocytes in blood were higher under SD than LD. In addition, cell counts of total leukocytes, NK cells, T cells including various T cell subtypes, and eosinophils peaked earlier relative to the time of lights-on under SD than LD. In contrast, diurnal rhythms of neutrophil counts did not show photoperiodic differences. Mesor values did not differ in any leukocyte type. Generalized linear mixed model analyses revealed associations of leukocyte counts with plasma cortisol concentration and activity behavior in most investigated cell types. Moreover, the present study demonstrated photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior, which is in agreement with human and primate studies. The results of the present study imply stronger rhythmicity in leukocyte counts in general under SD. Common intrinsic mechanisms seem to regulate photoperiodic effects on diurnal rhythms in leukocyte counts, except for neutrophils, in domestic pigs. Our results reveal considerable insights into the regulation of immune rhythms in diurnally active species.
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Affiliation(s)
- Larissa C Engert
- Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Ulrike Weiler
- Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Birgit Pfaffinger
- Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Volker Stefanski
- Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Sonja S Schmucker
- Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
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30
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Connectome of the Suprachiasmatic Nucleus: New Evidence of the Core-Shell Relationship. eNeuro 2018; 5:eN-NWR-0205-18. [PMID: 30283813 PMCID: PMC6168316 DOI: 10.1523/eneuro.0205-18.2018] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 09/05/2018] [Accepted: 09/07/2018] [Indexed: 11/21/2022] Open
Abstract
A brain clock, constituted of ∼20,000 peptidergically heterogeneous neurons, is located in the hypothalamic suprachiasmatic nucleus (SCN). While many peptidergic cell types have been identified, little is known about the connections among these neurons in mice. We first sought to identify contacts among major peptidergic cell types in the SCN using triple-label fluorescent immunocytochemistry (ICC). To this end, contacts among vasoactive intestinal polypeptide (VIP), gastrin-releasing peptide (GRP), and calretinin (CALR) cells of the core, and arginine vasopressin (AVP) and met-enkephalin (ENK) cells of the shell were analyzed. Some core-to-shell and shell-to-core communications are specialized. We found that in wild-type (WT) mice, AVP fibers make extremely sparse contacts onto VIP neurons but contacts in the reverse direction are numerous. In contrast, AVP fibers make more contacts onto GRP neurons than conversely. For the other cell types tested, largely reciprocal connections are made. These results point to peptidergic cell type-specific communications between core and shell SCN neurons. To further understand the impact of VIP-to-AVP communication, we next explored the SCN in VIP-deficient mice (VIP-KO). In these animals, AVP expression is markedly reduced in the SCN, but it is not altered in the paraventricular nucleus (PVN) and supraoptic nucleus (SON). Surprisingly, in VIP-KO mice, the number of AVP appositions onto other peptidergic cell types is not different from controls. Colchicine administration, which blocks AVP transport, restored the numbers of AVP neurons in VIP-KO to that of WT littermates. The results indicate that VIP has an important role in modulating AVP expression levels in the SCN in this mouse.
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31
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Sáenz de Miera C, Sage-Ciocca D, Simonneaux V, Pévet P, Monecke S. Melatonin-independent Photoperiodic Entrainment of the Circannual TSH Rhythm in the Pars Tuberalis of the European Hamster. J Biol Rhythms 2018; 33:302-317. [DOI: 10.1177/0748730418766601] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Cristina Sáenz de Miera
- Department of Neurobiology of Rhythms, Institute for Cellular and Integrative Neuroscience, University of Strasbourg, Strasbourg, France
| | | | - Valérie Simonneaux
- Department of Neurobiology of Rhythms, Institute for Cellular and Integrative Neuroscience, University of Strasbourg, Strasbourg, France
| | - Paul Pévet
- Department of Neurobiology of Rhythms, Institute for Cellular and Integrative Neuroscience, University of Strasbourg, Strasbourg, France
| | - Stefanie Monecke
- Department of Neurobiology of Rhythms, Institute for Cellular and Integrative Neuroscience, University of Strasbourg, Strasbourg, France
- Institute of Chronoecology, Stuttgart, Germany, and Ludwig Maximilians University, Institute of Medical Psychology, Munich, Germany
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32
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Photoperiod-Induced Neuroplasticity in the Circadian System. Neural Plast 2018; 2018:5147585. [PMID: 29681926 PMCID: PMC5851158 DOI: 10.1155/2018/5147585] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/11/2018] [Indexed: 01/01/2023] Open
Abstract
Seasonal changes in light exposure have profound effects on behavioral and physiological functions in many species, including effects on mood and cognitive function in humans. The mammalian brain's master circadian clock, the suprachiasmatic nucleus (SCN), transmits information about external light conditions to other brain regions, including some implicated in mood and cognition. Although the detailed mechanisms are not yet known, the SCN undergoes highly plastic changes at the cellular and network levels under different light conditions. We therefore propose that the SCN may be an essential mediator of the effects of seasonal changes of day length on mental health. In this review, we explore various forms of neuroplasticity that occur in the SCN and other brain regions to facilitate seasonal adaptation, particularly altered phase distribution of cellular circadian oscillators in the SCN and changes in hypothalamic neurotransmitter expression.
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33
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Tackenberg MC, McMahon DG. Photoperiodic Programming of the SCN and Its Role in Photoperiodic Output. Neural Plast 2018; 2018:8217345. [PMID: 29552032 PMCID: PMC5818903 DOI: 10.1155/2018/8217345] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/22/2017] [Indexed: 11/18/2022] Open
Abstract
Though the seasonal response of organisms to changing day lengths is a phenomenon that has been scientifically reported for nearly a century, significant questions remain about how photoperiod is encoded and effected neurobiologically. In mammals, early work identified the master circadian clock, the suprachiasmatic nuclei (SCN), as a tentative encoder of photoperiodic information. Here, we provide an overview of research on the SCN as a coordinator of photoperiodic responses, the intercellular coupling changes that accompany that coordination, as well as the SCN's role in a putative brain network controlling photoperiodic input and output. Lastly, we discuss the importance of photoperiodic research in the context of tangible benefits to human health that have been realized through this research as well as challenges that remain.
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Affiliation(s)
| | - Douglas G. McMahon
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
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34
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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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35
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Ontogeny of Circadian Rhythms and Synchrony in the Suprachiasmatic Nucleus. J Neurosci 2017; 38:1326-1334. [PMID: 29054877 DOI: 10.1523/jneurosci.2006-17.2017] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 10/07/2017] [Accepted: 10/17/2017] [Indexed: 01/16/2023] Open
Abstract
In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates daily rhythms including sleep-wake, hormone release, and gene expression. The cells of the SCN must synchronize to each other to drive these circadian rhythms in the rest of the body. The ontogeny of circadian cycling and intercellular coupling in the SCN remains poorly understood. Recent in vitro studies have recorded circadian rhythms from the whole embryonic SCN. Here, we tracked the onset and precision of rhythms in PERIOD2 (PER2), a clock protein, within the SCN isolated from embryonic and postnatal mice of undetermined sex. We found that a few SCN cells developed circadian periodicity in PER2 by 14.5 d after mating (E14.5) with no evidence for daily cycling on E13.5. On E15.5, the fraction of competent oscillators increased dramatically corresponding with stabilization of their circadian periods. The cells of the SCN harvested at E15.5 expressed sustained, synchronous daily rhythms. By postnatal day 2 (P2), SCN oscillators displayed the daily, dorsal-ventral phase wave in clock gene expression typical of the adult SCN. Strikingly, vasoactive intestinal polypeptide (VIP), a neuropeptide critical for synchrony in the adult SCN, and its receptor, VPAC2R, reached detectable levels after birth and after the onset of circadian synchrony. Antagonists of GABA or VIP signaling or action potentials did not disrupt circadian synchrony in the E15.5 SCN. We conclude that endogenous daily rhythms in the fetal SCN begin with few noisy oscillators on E14.5, followed by widespread oscillations that rapidly synchronize on E15.5 by an unknown mechanism.SIGNIFICANCE STATEMENT We recorded the onset of PER2 circadian oscillations during embryonic development in the mouse SCN. When isolated at E13.5, the anlagen of the SCN expresses high, arrhythmic PER2. In contrast, a few cells show noisy circadian rhythms in the isolated E14.5 SCN and most show reliable, self-sustained, synchronized rhythms in the E15.5 SCN. Strikingly, this synchrony at E15.5 appears before expression of VIP or its receptor and persists in the presence of blockers of VIP, GABA or neuronal firing. Finally, the dorsal-ventral phase wave of PER2 typical of the adult SCN appears ∼P2, indicating that multiple signals may mediate circadian synchrony during the ontogeny of the SCN.
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36
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Yoshikawa T, Inagaki NF, Takagi S, Kuroda S, Yamasaki M, Watanabe M, Honma S, Honma KI. Localization of photoperiod responsive circadian oscillators in the mouse suprachiasmatic nucleus. Sci Rep 2017; 7:8210. [PMID: 28811515 PMCID: PMC5557852 DOI: 10.1038/s41598-017-08186-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 07/07/2017] [Indexed: 11/09/2022] Open
Abstract
The circadian pacemaker in the suprachiasmatic nucleus (SCN) yields photoperiodic response to transfer seasonal information to physiology and behavior. To identify the precise location involved in photoperiodic response in the SCN, we analyzed circadian Period1 and PERIOD2 rhythms in horizontally sectioned SCN of mice exposed to a long or short day. Statistical analyses of bioluminescence images with respective luciferase reporters on pixel level enabled us to identify the distinct localization of three oscillating regions; a large open-ring-shape region, the region at the posterior end and a sharply demarcated oval region at the center of the SCN. The first two regions are the respective sites for the so-called evening and morning oscillators, and the third region is possibly a site for mediating photic signals to the former oscillators. In these regions, there are two classes of oscillating cells in which Per1 and Per2 could play differential roles in photoperiodic responses.
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Affiliation(s)
- Tomoko Yoshikawa
- Photonic Bioimaging Section, Hokkaido University Graduate School of Medicine, Sapporo, Japan. .,Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan. .,Department of Anatomy and Neurobiology, Kindai University Faculty of Medicine, Osaka-sayama, Japan.
| | - Natsuko F Inagaki
- Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Seiji Takagi
- Department of Complex and Intelligent Systems, Future University Hakodate, Hakodate, Japan
| | - Shigeru Kuroda
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Miwako Yamasaki
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Sato Honma
- Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan. .,Research and Education Center for Brain Science, Hokkaido University, Sapporo, Japan.
| | - Ken-Ichi Honma
- Department of Chronomedicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
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