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Calligaro H, Shoghi A, Chen X, Kim KY, Yu HL, Khov B, Finander B, Le H, Ellisman MH, Panda S. Ultrastructure of Synaptic Connectivity within Subregions of the Suprachiasmatic Nucleus Revealed by a Genetically Encoded Tag and Serial Blockface Electron Microscopy. eNeuro 2023; 10:ENEURO.0227-23.2023. [PMID: 37500494 PMCID: PMC10449486 DOI: 10.1523/eneuro.0227-23.2023] [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: 06/29/2023] [Accepted: 07/01/2023] [Indexed: 07/29/2023] Open
Abstract
The hypothalamic suprachiasmatic nucleus (SCN) is the central circadian pacemaker in vertebrates. The SCN receives photic information exclusively through melanopsin-expressing retinal ganglion cells (mRGCs) to synchronize circadian rhythms with the environmental light cycles. The SCN is composed of two major peptidergic neuron types in the core and shell regions of the SCN. Determining how mRGCs interact with the network of synaptic connections onto and between SCN neurons is key to understand how light regulates the circadian clock and to elucidate the relevant local circuits within the SCN. To map these connections, we used a newly developed Cre-dependent electron microscopy (EM) reporter, APEX2, to label the mitochondria of mRGC axons. Serial blockface scanning electron microscopy was then used to resolve the fine 3D structure of mRGC axons and synaptic boutons in the SCN of a male mouse. The resulting maps reveal patterns of connectomic organization in the core and shell of the SCN. We show that these regions are composed of different neuronal subtypes and differ with regard to the pattern of mRGC input, as the shell receives denser mRGC synaptic input compared with the core. This finding challenges the present view that photic information coming directly from the retina is received primarily by the core region of the SCN.
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Affiliation(s)
- Hugo Calligaro
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Azarin Shoghi
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Xinyue Chen
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Keun-Young Kim
- Department of Neurosciences, University of California at San Diego School of Medicine, La Jolla, CA 92161
- National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, CA 92161
| | - Hsin Liu Yu
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Brian Khov
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | | | - Hiep Le
- Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Mark H. Ellisman
- Department of Neurosciences, University of California at San Diego School of Medicine, La Jolla, CA 92161
- National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, CA 92161
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2
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Reyes-Méndez ME, Herrera-Zamora JM, Osuna-Lopez F, Aguilar-Martínez IS, Góngora-Alfaro JL, Navarro-Polanco RA, Sánchez-Pastor E, Moreno-Galindo EG, Alamilla J. Developmental light deprivation transiently reduces the expression of vGluT2 and GluN2B in the rat ventral suprachiasmatic nucleus. Synapse 2023; 77:e22250. [PMID: 36085433 DOI: 10.1002/syn.22250] [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: 04/20/2022] [Revised: 08/05/2022] [Accepted: 08/07/2022] [Indexed: 01/29/2023]
Abstract
The suprachiasmatic nucleus (SCN) is the most important circadian clock in mammals. The SCN synchronizes to environmental light via the retinohypothalamic tract (RHT), which is an axon cluster derived from melanopsin-expressing intrinsic photosensitive retinal ganglion cells. Investigations on the development of the nonimage-forming pathway and the RHT are scarce. Previous studies imply that light stimulation during postnatal development is not needed to make the RHT functional at adult stages. Here, we examined the effects of light deprivation (i.e., constant darkness (DD) rearing) during postnatal development on the expression in the ventral SCN of two crucial proteins for the synchronization of circadian rhythms to light: the presynaptic vesicular glutamate transporter type 2 (vGluT2) and the GluN2B subunit of the postsynaptic NMDA receptor. We found that animals submitted to DD conditions exhibited a transitory reduction in the expression of vGluT2 (at P12-19) and of GluN2B (at P7-9) that was compensated at older stages. These findings support the hypothesis that visual stimulation during early ages is not decisive for normal development of the RHT-SCN pathway.
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Affiliation(s)
- Miriam E Reyes-Méndez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | | | - Fernando Osuna-Lopez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | | | - José L Góngora-Alfaro
- Departamento de Neurociencias, Centro de Investigaciones Regionales "Dr. Hideyo, Noguchi", Universidad Autónoma de Yucatán, Mérida, México
| | | | - Enrique Sánchez-Pastor
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | - Eloy G Moreno-Galindo
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | - Javier Alamilla
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México.,Consejo Nacional de Ciencia y Tecnología (CONACYT), Universidad de Colima, Colima, México
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3
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Beeson KA, Westbrook GL, Schnell E. α2δ-2 is required for depolarization-induced suppression of excitation in Purkinje cells. J Physiol 2022; 600:111-122. [PMID: 34783012 PMCID: PMC8724408 DOI: 10.1113/jp282438] [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: 09/30/2021] [Accepted: 11/11/2021] [Indexed: 01/03/2023] Open
Abstract
α2δ proteins (CACNA2D1-4) are required for normal neurological function and contribute to membrane trafficking of voltage-gated calcium channels, through which calcium entry initiates numerous physiological processes. However, it remains unclear how α2δ proteins influence calcium-mediated signalling to control neuronal output. Using whole-cell recordings of mouse Purkinje cells, we show that α2δ-2 is required for functional coupling of postsynaptic voltage-dependent calcium entry with calcium-dependent effector mechanisms controlling two different outputs, depolarization-induced suppression of excitation and spike afterhyperpolarization. Our findings indicate an important role for α2δ-2 proteins in regulating functional postsynaptic calcium channel coupling in neurons, providing new context for understanding the effects of α2δ mutations on neuronal circuit function and presenting additional potential avenues to manipulate α2δ-mediated signalling for therapeutic gain. KEY POINTS: Calcium influx, via voltage-dependent calcium channels, drives numerous neuronal signalling processes with precision achieved in part by tight coupling between calcium entry and calcium-dependent effectors. α2δ proteins are important for neurological function and contribute to calcium channel membrane trafficking, although how α2δ proteins influence postsynaptic calcium-dependent signalling is largely unexplored. Here it is shown that loss of α2δ-2 proteins disrupts functional calcium coupling to two different postsynaptic calcium-dependent signals in mouse Purkinje cell neurons, retrograde endocannabinoid signalling and the action potential afterhyperpolarization. The findings provide new insights into the control of calcium coupling as well as new roles for α2δ-2 proteins in neurons.
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Affiliation(s)
- Kathleen A. Beeson
- Neuroscience Graduate Program, OHSU, Portland, OR, 97239,Department of Anesthesiology and Perioperative Medicine, OHSU, Portland, OR, 97239
| | | | - Eric Schnell
- Department of Anesthesiology and Perioperative Medicine, OHSU, Portland, OR, 97239,Operative Care Division, Portland VA Health Care System, Portland, OR, 97239,Eric Schnell, MD, PhD,
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4
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Hannibal J. Comparative Neurology of Circadian Photoreception: The Retinohypothalamic Tract (RHT) in Sighted and Naturally Blind Mammals. Front Neurosci 2021; 15:640113. [PMID: 34054403 PMCID: PMC8160255 DOI: 10.3389/fnins.2021.640113] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 03/29/2021] [Indexed: 11/13/2022] Open
Abstract
The mammalian eye contains two systems for light perception: an image detecting system constituted primarily of the classical photoreceptors, rods and cones, and a non-image forming system (NIF) constituted of a small group of intrinsically photosensitive retinal ganglion cells driven by melanopsin (mRGCs). The mRGCs receive input from the outer retina and NIF mediates light entrainment of circadian rhythms, masking behavior, light induced inhibition of nocturnal melatonin secretion, pupillary reflex (PLR), and affect the sleep/wake cycle. This review focuses on the mammalian NIF and its anatomy in the eye as well as its neuronal projection to the brain. This pathway is known as the retinohypothalamic tract (RHT). The development and functions of the NIF as well as the knowledge gained from studying gene modified mice is highlighted. Furthermore, the similarities of the NIF between sighted (nocturnal and diurnal rodent species, monkeys, humans) and naturally blind mammals (blind mole rats Spalax ehrenbergi and the Iberian mole, Talpa occidentalis) are discussed in relation to a changing world where increasing exposure to artificial light at night (ALAN) is becoming a challenge for humans and animals in the modern society.
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Affiliation(s)
- Jens Hannibal
- Department of Clinical Biochemistry, Bispebjerg Frederiksberg Hospital, University of Copenhagen, Copenhagen, Denmark
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5
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Tabuchi M, Coates KE, Bautista OB, Zukowski LH. Light/Clock Influences Membrane Potential Dynamics to Regulate Sleep States. Front Neurol 2021; 12:625369. [PMID: 33854471 PMCID: PMC8039321 DOI: 10.3389/fneur.2021.625369] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 02/15/2021] [Indexed: 11/13/2022] Open
Abstract
The circadian rhythm is a fundamental process that regulates the sleep-wake cycle. This rhythm is regulated by core clock genes that oscillate to create a physiological rhythm of circadian neuronal activity. However, we do not know much about the mechanism by which circadian inputs influence neurons involved in sleep-wake architecture. One possible mechanism involves the photoreceptor cryptochrome (CRY). In Drosophila, CRY is receptive to blue light and resets the circadian rhythm. CRY also influences membrane potential dynamics that regulate neural activity of circadian clock neurons in Drosophila, including the temporal structure in sequences of spikes, by interacting with subunits of the voltage-dependent potassium channel. Moreover, several core clock molecules interact with voltage-dependent/independent channels, channel-binding protein, and subunits of the electrogenic ion pump. These components cooperatively regulate mechanisms that translate circadian photoreception and the timing of clock genes into changes in membrane excitability, such as neural firing activity and polarization sensitivity. In clock neurons expressing CRY, these mechanisms also influence synaptic plasticity. In this review, we propose that membrane potential dynamics created by circadian photoreception and core clock molecules are critical for generating the set point of synaptic plasticity that depend on neural coding. In this way, membrane potential dynamics drive formation of baseline sleep architecture, light-driven arousal, and memory processing. We also discuss the machinery that coordinates membrane excitability in circadian networks found in Drosophila, and we compare this machinery to that found in mammalian systems. Based on this body of work, we propose future studies that can better delineate how neural codes impact molecular/cellular signaling and contribute to sleep, memory processing, and neurological disorders.
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Affiliation(s)
- Masashi Tabuchi
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Kaylynn E Coates
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Oscar B Bautista
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Lauren H Zukowski
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, United States
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6
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Plano SA, Alessandro MS, Trebucq LL, Endo S, Golombek DA, Chiesa JJ. Role of G-Substrate in the NO/cGMP/PKG Signal Transduction Pathway for Photic Entrainment of the Hamster Circadian Clock. ASN Neuro 2021; 13:1759091420984920. [PMID: 33430619 PMCID: PMC7809303 DOI: 10.1177/1759091420984920] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The mammalian circadian clock at the hypothalamic suprachiasmatic nuclei (SCN) entrains biological rhythms to the 24-h cyclic environment, by encoding light-dark transitions in SCN neurons. Light pulses induce phase shifts in the clock and in circadian rhythms; photic signaling for circadian phase advances involves a nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/cGMP-dependent protein kinase (PKG) pathway, increasing the expression of Period (Per) genes. Effectors downstream of PKG remain unknown. Here we investigate the role of G-substrate (GS), a PKG substrate, in the hamster SCN. GS and phosphorylated G-substrate (p-GS) were present in a subset of SCN cells. Moreover, GS phosphorylation (p-GS/GS ratio) increased in SCN homogenates after light pulses delivered at circadian time (CT) 18 and intraperitoneal treatment with sildenafil, an inhibitor of phosphodiesterase 5 (a cGMP-specific phosphodiesterase). On the other hand, intracerebroventricular treatment with the PKG inhibitor KT5823, reduced photic phosphorylation of GS to basal levels. Since p-GS could act as a protein phosphatase 2 A (PP2A) inhibitor, we demonstrated physical interaction between p-GS and PP2A in SCN homogenates, and also a light-pulse dependent decrease of PP2A activity. Intracerebroventricular treatment with okadaic acid, a PP2A inhibitor, increased the magnitude of light-induced phase advances of locomotor rhythms. We provide evidence on the physiological phosphorylation of GS as a new downstream effector in the NO/cGMP/PKG photic pathway in the hamster SCN, including its role as a PP2A inhibitor.
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Affiliation(s)
- Santiago Andrés Plano
- Institute for Biomedical Research (BIOMED), Catholic University of Argentina (UCA) and National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina.,Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - María Soledad Alessandro
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Laura Lucía Trebucq
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Shogo Endo
- Aging Neuroscience Research Team, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Diego Andrés Golombek
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Juan José Chiesa
- Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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7
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Riedel CS, Georg B, Fahrenkrug J, Hannibal J. Altered light induced EGR1 expression in the SCN of PACAP deficient mice. PLoS One 2020; 15:e0232748. [PMID: 32379800 PMCID: PMC7205239 DOI: 10.1371/journal.pone.0232748] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 04/21/2020] [Indexed: 12/16/2022] Open
Abstract
The brain’s biological clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus and generates circadian rhythms in physiology and behavior. The circadian clock needs daily adjustment by light to stay synchronized (entrained) with the astronomical 24 h light/dark cycle. Light entrainment occurs via melanopsin expressing retinal ganglion cells (mRGCs) and two neurotransmitters of the retinohypothalamic tract (RHT), PACAP and glutamate, which transmit light information to the SCN neurons. In SCN neurons, light signaling involves the immediate-early genes Fos, Egr1 and the clock genes Per1 and Per2. In this study, we used PACAP deficient mice to evaluate PACAP’s role in light induced gene expression of EGR1 in SCN neurons during early (ZT17) and late (ZT23) subjective night at high (300 lux) and low (10 lux) white light exposure. We found significantly lower levels of both EGR1 mRNA and protein in the SCN in PACAP deficient mice compared to wild type mice at early subjective night (ZT17) exposed to low but not high light intensity. No difference was found between the two genotypes at late night (ZT23) at neither light intensities. In conclusion, light mediated EGR1 induction in SCN neurons at early night at low light intensities is dependent of PACAP signaling. A role of PACAP in shaping synaptic plasticity during light stimulation at night is discussed.
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Affiliation(s)
- Casper Schwartz Riedel
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Birgitte Georg
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Jan Fahrenkrug
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
| | - Jens Hannibal
- Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, University of Copenhagen, Copenhagen NV, Denmark
- * E-mail:
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8
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del Río-Martín A, Pérez-Taboada I, Fernández-Pérez A, Moratalla R, de la Villa P, Vallejo M. Hypomorphic Expression of Pitx3 Disrupts Circadian Clocks and Prevents Metabolic Entrainment of Energy Expenditure. Cell Rep 2019; 29:3678-3692.e4. [DOI: 10.1016/j.celrep.2019.11.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 05/13/2019] [Accepted: 11/06/2019] [Indexed: 12/11/2022] Open
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9
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Engeland WC, Massman L, Miller L, Leng S, Pignatti E, Pantano L, Carlone DL, Kofuji P, Breault DT. Sex Differences in Adrenal Bmal1 Deletion-Induced Augmentation of Glucocorticoid Responses to Stress and ACTH in Mice. Endocrinology 2019; 160:2215-2229. [PMID: 31398249 PMCID: PMC6735739 DOI: 10.1210/en.2019-00357] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 07/22/2019] [Indexed: 12/23/2022]
Abstract
The circadian glucocorticoid (GC) rhythm is dependent on a molecular clock in the suprachiasmatic nucleus (SCN) and an adrenal clock that is synchronized by the SCN. To determine whether the adrenal clock modulates GC responses to stress, experiments used female and male Cyp11A1Cre/+::Bmal1Fl/Fl knockout [side-chain cleavage (SCC)-KO] mice, in which the core clock gene, Bmal1, is deleted in all steroidogenic tissues, including the adrenal cortex. Following restraint stress, female and male SCC-KO mice demonstrate augmented plasma corticosterone but not plasma ACTH. In contrast, following submaximal scruff stress, plasma corticosterone was elevated only in female SCC-KO mice. Adrenal sensitivity to ACTH was measured in vitro using acutely dispersed adrenocortical cells. Maximal corticosterone responses to ACTH were elevated in cells from female KO mice without affecting the EC50 response. Neither the maximum nor the EC50 response to ACTH was affected in male cells, indicating that female SCC-KO mice show a stronger adrenal phenotype. Parallel experiments were conducted using female Cyp11B2 (Aldosterone Synthase)Cre/+::Bmal1Fl/Fl mice and adrenal cortex-specific Bmal1-null (Ad-KO) mice. Plasma corticosterone was increased in Ad-KO mice following restraint or scruff stress, and in vitro responses to ACTH were elevated in adrenal cells from Ad-KO mice, replicating data from female SCC-KO mice. Gene analysis showed increased expression of adrenal genes in female SCC-KO mice involved in cell cycle control, cell adhesion-extracellular matrix interaction, and ligand receptor activity that could promote steroid production. These observations underscore a role for adrenal Bmal1 as an attenuator of steroid secretion that is most prominent in female mice.
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Affiliation(s)
- William C Engeland
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Logan Massman
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Lauren Miller
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Sining Leng
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Emanuele Pignatti
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Lorena Pantano
- Harvard Chan Bioinformatics Core, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
| | - Diana L Carlone
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Cambridge, Massachusetts
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Cambridge, Massachusetts
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10
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Engeland WC, Massman L, Mishra S, Yoder JM, Leng S, Pignatti E, Piper ME, Carlone DL, Breault DT, Kofuji P. The Adrenal Clock Prevents Aberrant Light-Induced Alterations in Circadian Glucocorticoid Rhythms. Endocrinology 2018; 159:3950-3964. [PMID: 30321360 PMCID: PMC6240903 DOI: 10.1210/en.2018-00769] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 10/08/2018] [Indexed: 12/18/2022]
Abstract
The glucocorticoid (GC) rhythm is entrained to light-dark (LD) cycles via a molecular clock in the suprachiasmatic nucleus (SCN) and is maintained by an adrenal clock synchronized by SCN-dependent signals. Targeted deletion of the core clock gene Bmal1 can disrupt adrenal clock function. The requirement of the adrenal clock to stabilize the circadian GC rhythm during exposure to aberrant LD cycles was determined using novel aldosterone synthase (AS)Cre/+::Bmal1Fl/Fl mice in which Bmal1 deletion occurred during postnatal adrenal transdifferentiation. To examine whether adrenal Bmal1 deletion results in loss of the adrenal clock, mice were crossed with mPER2::Luciferase (mPER2Luc/+) mice. Adrenals from ASCre/+::Bmal1+/+::PER2Luc/+ [control (CTRL)] mice show mPER2Luc rhythms ex vivo, whereas slices from ASCre/+::Bmal1Fl/Fl::PER2Luc/+ [knockout (KO)] mice show dampened rhythms. To monitor corticosterone rhythmicity, mice were implanted with subcutaneous microdialysis probes and sampled at 60-minute intervals for up to 3 days under 12:12-hour [τ (T) 24] LD or 3.5:3.5-hour (T7) LD cycles. Corticosterone rhythms were entrained to T24 LD in CTRL and KO mice. Under T7 LD, circadian corticosterone rhythms persisted in most CTRL mice but not KO mice. Hyperadrenocorticism also was observed in KO mice under T7 LD, reflected by increased corticosterone peak amplitude, total daily corticosterone, and responses to ACTH. Analysis of dysregulated adrenal genes in KO mice exposed to aberrant light identified candidates involved in cholesterol metabolism and trafficking, including steroidogenic acute regulatory protein, which could increase steroidogenesis. Our results show that the adrenal clock functions to buffer steroidogenic responses to aberrant light and stabilize circadian GC rhythmicity.
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Affiliation(s)
- William C Engeland
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Logan Massman
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Shubhendu Mishra
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - J Marina Yoder
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Sining Leng
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Emanuele Pignatti
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Mary E Piper
- Harvard Chan Bioinformatics Core, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - Diana L Carlone
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Cambridge, Massachusetts
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Cambridge, Massachusetts
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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11
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Pfeffer M, Zimmermann Z, Gispert S, Auburger G, Korf HW, von Gall C. Impaired Photic Entrainment of Spontaneous Locomotor Activity in Mice Overexpressing Human Mutant α-Synuclein. Int J Mol Sci 2018; 19:E1651. [PMID: 29865270 PMCID: PMC6032049 DOI: 10.3390/ijms19061651] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 05/31/2018] [Accepted: 06/01/2018] [Indexed: 01/17/2023] Open
Abstract
Parkinson's disease (PD) is characterized by distinct motor and non-motor symptoms. Sleep disorders are the most frequent and challenging non-motor symptoms in PD patients, and there is growing evidence that they are a consequence of disruptions within the circadian system. PD is characterized by a progressive degeneration of the dorsal vagal nucleus and midbrain dopaminergic neurons together with an imbalance of many other neurotransmitters. Mutations in α-synuclein (SNCA), a protein modulating SNARE complex-dependent neurotransmission, trigger dominantly inherited PD variants and sporadic cases of PD. The A53T SNCA missense mutation is associated with an autosomal dominant early-onset familial PD. To test whether this missense mutation affects the circadian system, we analyzed the spontaneous locomotor behavior of non-transgenic wildtype mice and transgenic mice overexpressing mutant human A53T α-synuclein (A53T). The mice were subjected to entrained- and free-running conditions as well as to experimental jet lag. Furthermore, the vesicular glutamate transporter 2 (VGLUT2) in the suprachiasmatic nucleus (SCN) was analyzed by immunohistochemistry. Free-running circadian rhythm and, thus, circadian rhythm generation, were not affected in A53T mice. A53T mice entrained to the light⁻dark cycle, however, with an advanced phase angle of 2.65 ± 0.5 h before lights off. Moreover, re-entrainment after experimental jet lag was impaired in A53T mice. Finally, VGLUT2 immunoreaction was reduced in the SCN of A53T mice. These data suggest an impaired light entrainment of the circadian system in A53T mice.
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Affiliation(s)
- Martina Pfeffer
- Institut für Anatomie II, Fachbereich Medizin, Heinrich Heine Universität, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
| | - Zuzana Zimmermann
- Dr. Senckenbergische Anatomie II, Fachbereich Medizin, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
| | - Suzana Gispert
- Experimental Neurology, Department of Neurology, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
| | - Georg Auburger
- Experimental Neurology, Department of Neurology, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
| | - Horst-Werner Korf
- Institut für Anatomie I, Fachbereich Medizin, Heinrich Heine Universität, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
| | - Charlotte von Gall
- Institut für Anatomie II, Fachbereich Medizin, Heinrich Heine Universität, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
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12
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Circadian Behavioral Responses to Light and Optic Chiasm-Evoked Glutamatergic EPSCs in the Suprachiasmatic Nucleus of ipRGC Conditional vGlut2 Knock-Out Mice. eNeuro 2018; 5:eN-NWR-0411-17. [PMID: 29756029 PMCID: PMC5944003 DOI: 10.1523/eneuro.0411-17.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 04/06/2018] [Accepted: 04/27/2018] [Indexed: 12/26/2022] Open
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) innervate the hypothalamic suprachiasmatic nucleus (SCN), a circadian oscillator that functions as a biological clock. ipRGCs use vesicular glutamate transporter 2 (vGlut2) to package glutamate into synaptic vesicles and light-evoked resetting of the SCN circadian clock is widely attributed to ipRGC glutamatergic neurotransmission. Pituitary adenylate cyclase-activating polypeptide (PACAP) is also packaged into vesicles in ipRGCs and PACAP may be coreleased with glutamate in the SCN. vGlut2 has been conditionally deleted in ipRGCs in mice [conditional knock-outs (cKOs)] and their aberrant photoentrainment and residual attenuated light responses have been ascribed to ipRGC PACAP release. However, there is no direct evidence that all ipRGC glutamatergic neurotransmission is eliminated in vGlut2 cKOs. Here, we examined two lines of ipRGC vGlut2 cKO mice for SCN-mediated behavioral responses under several lighting conditions and for ipRGC glutamatergic neurotransmission in the SCN. Circadian behavioral responses varied from a very limited response to light to near normal photoentrainment. After collecting behavioral data, hypothalamic slices were prepared and evoked EPSCs (eEPSCs) were recorded from SCN neurons by stimulating the optic chiasm. In cKOs, glutamatergic eEPSCs were recorded and all eEPSC parameters examined (stimulus threshold, amplitude, rise time or time-to-peak and stimulus strength to evoke a maximal response) were similar to controls. We conclude that a variable number but functionally significant percentage of ipRGCs in two vGlut2 cKO mouse lines continue to release glutamate. Thus, the residual SCN-mediated light responses in these cKO mouse lines cannot be attributed solely to ipRGC PACAP release.
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13
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Oda S, Tsuneoka Y, Yoshida S, Adachi-Akahane S, Ito M, Kuroda M, Funato H. Immunolocalization of muscarinic M1 receptor in the rat medial prefrontal cortex. J Comp Neurol 2018; 526:1329-1350. [PMID: 29424434 PMCID: PMC5900831 DOI: 10.1002/cne.24409] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 01/23/2018] [Accepted: 01/27/2018] [Indexed: 12/20/2022]
Abstract
The medial prefrontal cortex (mPFC) has been considered to participate in many higher cognitive functions, such as memory formation and spatial navigation. These cognitive functions are modulated by cholinergic afferents via muscarinic acetylcholine receptors. Previous pharmacological studies have strongly suggested that the M1 receptor (M1R) is the most important subtype among muscarinic receptors to perform these cognitive functions. Actually, M1R is abundant in mPFC. However, the proportion of somata containing M1R among cortical cellular types, and the precise intracellular localization of M1R remain unclear. In this study, to clarify the precise immunolocalization of M1R in rat mPFC, we examined three major cellular types, pyramidal neurons, inhibitory neurons, and astrocytes. M1R immunopositivity signals were found in the majority of the somata of both pyramidal neurons and inhibitory neurons. In pyramidal neurons, strong M1R immunopositivity signals were usually found throughout their somata and dendrites including spines. On the other hand, the signal strength of M1R immunopositivity in the somata of inhibitory neurons significantly varied. Some neurons showed strong signals. Whereas about 40% of GAD67‐immunopositive neurons and 30% of parvalbumin‐immunopositive neurons (PV neurons) showed only weak signals. In PV neurons, M1R immunopositivity signals were preferentially distributed in somata. Furthermore, we found that many astrocytes showed substantial M1R immunopositivity signals. These signals were also mainly distributed in their somata. Thus, the distribution pattern of M1R markedly differs between cellular types. This difference might underlie the cholinergic modulation of higher cognitive functions subserved by mPFC.
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Affiliation(s)
- Satoko Oda
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Yousuke Tsuneoka
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Sachine Yoshida
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan.,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Saitama, 332-0012, Japan
| | - Satomi Adachi-Akahane
- Department of Physiology, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Masanori Ito
- Department of Physiology, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Masaru Kuroda
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Hiromasa Funato
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, 143-8540, Japan.,International institute for integrative sleep medicine (IIIS), Tsukuba University, Ibaraki, 305-8575, Japan
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14
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Møller M, Rath MF, Ludvigsen M, Honoré B, Vorum H. Diurnal expression of proteins in the retina of the blind cone-rod homeobox (Crx -/- ) mouse and the 129/Sv mouse: a proteomic study. Acta Ophthalmol 2017; 95:717-726. [PMID: 28371363 DOI: 10.1111/aos.13429] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 02/06/2017] [Indexed: 01/06/2023]
Abstract
PURPOSE The vertebrate retina contains a circadian clock participating in adaptations to day and night vision. This peripheral clock is independent of the master clock in the suprachiasmatic nucleus (SCN). The retinal clock is located in several cell types, including the photoreceptors. To investigate the role of the circadian clock of the photoreceptor cells in regulation of retinal protein rhythms, we analysed diurnal protein expression in the photoreceptor-deficient cone-rod homeobox knockout mouse (Crx-/- ) and the 129/Sv mouse. METHODS 2D gels were made from retinal homogenates of 129/Sv and Crx-/- mice killed at midday and midnight. Stained gels were analysed by use of PDQuest 2D gel analysis software. After trypsin digestion of differential expressed spots, the proteins were identified by LC-MS/MS using a nano-liquid chromatograph connected to a Q-TOF Premier mass spectrometer. These data were used to search the SWISS-PROT database. RESULTS Both the retinae of the control and the Crx-/- mice exhibited diurnal proteins rhythms. As expected, proteins involved in phototransduction were not detected in the Crx-/- mouse; in this phenotype, however, proteins from spots showing diurnal rhythms were specifically identified as enzymes involved in glucose metabolism, Krebs cycle, and mitochondrial enzymes. Data are available via ProteomeXchange with identifier PXD005556. CONCLUSION We show diurnal protein rhythms in the retina of a mouse lacking the rods and cones. The diurnal protein rhythms in this genotype, lacking the circadian clock of the photoreceptors, might be caused by a circadian clock in other retinal cell types or a direct light input to the retina.
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Affiliation(s)
- Morten Møller
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Martin Fredensborg Rath
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Maja Ludvigsen
- Department of Clinical Medicine; Aarhus University; Aarhus Denmark
- Department of Hematology; Aarhus University Hospital; Aarhus Denmark
| | - Bent Honoré
- Department of Biomedicine; Aarhus University; Aarhus Denmark
| | - Henrik Vorum
- Department of Ophthalmology; Aalborg University Hospital; Aalborg Denmark
- Department of Clinical Medicine; Aalborg University; Aalborg Denmark
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15
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Laprell L, Tochitsky I, Kaur K, Manookin MB, Stein M, Barber DM, Schön C, Michalakis S, Biel M, Kramer RH, Sumser MP, Trauner D, Van Gelder RN. Photopharmacological control of bipolar cells restores visual function in blind mice. J Clin Invest 2017; 127:2598-2611. [PMID: 28581442 DOI: 10.1172/jci92156] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 04/18/2017] [Indexed: 11/17/2022] Open
Abstract
Photopharmacological control of neuronal activity using synthetic photochromic ligands, or photoswitches, is a promising approach for restoring visual function in patients suffering from degenerative retinal diseases. Azobenzene photoswitches, such as AAQ and DENAQ, have been shown to restore the responses of retinal ganglion cells to light in mouse models of retinal degeneration but do not recapitulate native retinal signal processing. Here, we describe diethylamino-azo-diethylamino (DAD), a third-generation photoswitch that is capable of restoring retinal ganglion cell light responses to blue or white light. In acute brain slices of murine layer 2/3 cortical neurons, we determined that the photoswitch quickly relaxes to its inactive form in the dark. DAD is not permanently charged, and the uncharged form enables the photoswitch to rapidly and effectively cross biological barriers and thereby access and photosensitize retinal neurons. Intravitreal injection of DAD restored retinal light responses and light-driven behavior to blind mice. Unlike DENAQ, DAD acts upstream of retinal ganglion cells, primarily conferring light sensitivity to bipolar cells. Moreover, DAD was capable of generating ON and OFF visual responses in the blind retina by utilizing intrinsic retinal circuitry, which may be advantageous for restoring visual function.
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Affiliation(s)
- Laura Laprell
- Center for Integrated Protein Science Munich and Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany.,Department of Ophthalmology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Ivan Tochitsky
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Kuldeep Kaur
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Michael B Manookin
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Marco Stein
- Center for Integrated Protein Science Munich and Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - David M Barber
- Center for Integrated Protein Science Munich and Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Christian Schön
- Center for Integrated Protein Science Munich and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Martin Biel
- Center for Integrated Protein Science Munich and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Richard H Kramer
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Martin P Sumser
- Center for Integrated Protein Science Munich and Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Dirk Trauner
- Center for Integrated Protein Science Munich and Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Russell N Van Gelder
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, Washington, USA.,Department of Biological Structure and Department of Pathology, University of Washington School of Medicine, Seattle, Washington, USA
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16
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Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs) Are Necessary for Light Entrainment of Peripheral Clocks. PLoS One 2016; 11:e0168651. [PMID: 27992553 PMCID: PMC5161485 DOI: 10.1371/journal.pone.0168651] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 12/04/2016] [Indexed: 11/23/2022] Open
Abstract
Light is a powerful entrainer of circadian clocks in almost all eukaryotic organisms promoting synchronization of internal circadian rhythms with external environmental light-dark (LD) cycles. In mammals, the circadian system is organized in a hierarchical manner, in which a central pacemaker in the suprachiasmatic nucleus (SCN) synchronizes oscillators in peripheral tissues. Recent evidence demonstrates that photoentrainment of the SCN proceeds via signaling from a subpopulation of retinal ganglion cells (RGCs) which are melanopsin-expressing and intrinsically photosensitive (ipRGCs). However, it is still unclear whether photoentrainment of peripheral clocks is mediated exclusively by the ipRGC system or if signaling from RGCs that do not express melanopsin also plays a role. Here we have used genetic “silencing” of ipRGC neurotransmission in mice to investigate whether this photoreceptive system is obligatory for the photoentrainment of peripheral circadian clocks. Genetic silencing of ipRGC neurotransmission in mice was achieved by expression of tetanus toxin light chain in melanopsin-expressing cells (Opn4::TeNT mouse line). Rhythms of the clock gene Period 2 in various peripheral tissues were measured by crossbreeding Opn4::TeNT mice with PER2 luciferase knock-in mice (mPER2Luc). We found that in Opn4::TeNT mice the pupillary light reflex, light modulation of activity, and circadian photoentrainment of locomotor activity were severely impaired. Furthermore, ex vivo cultures from Opn4::TeNT, mPER2Luc mice of the adrenal gland, cornea, lung, liver, pituitary and spleen exhibited robust circadian rhythms of PER2::LUC bioluminescence. However, their peak bioluminescence rhythms were not aligned to the projected LD cycles indicating their lack of photic entrainment in vivo. Finally, we found that the circadian rhythm in adrenal corticosterone in Opn4::TeNT mice, as monitored by in vivo subcutaneous microdialysis, was desynchronized from environmental LD cycles. Our findings reveal a non-redundant role of ipRGCs for photic entrainment of peripheral tissues, highlighting the importance of this photoreceptive system for the organismal adaptation to daily environmental LD cycles.
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17
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Keenan WT, Rupp AC, Ross RA, Somasundaram P, Hiriyanna S, Wu Z, Badea TC, Robinson PR, Lowell BB, Hattar SS. A visual circuit uses complementary mechanisms to support transient and sustained pupil constriction. eLife 2016; 5:e15392. [PMID: 27669145 PMCID: PMC5079752 DOI: 10.7554/elife.15392] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 09/22/2016] [Indexed: 12/22/2022] Open
Abstract
Rapid and stable control of pupil size in response to light is critical for vision, but the neural coding mechanisms remain unclear. Here, we investigated the neural basis of pupil control by monitoring pupil size across time while manipulating each photoreceptor input or neurotransmitter output of intrinsically photosensitive retinal ganglion cells (ipRGCs), a critical relay in the control of pupil size. We show that transient and sustained pupil responses are mediated by distinct photoreceptors and neurotransmitters. Transient responses utilize input from rod photoreceptors and output by the classical neurotransmitter glutamate, but adapt within minutes. In contrast, sustained responses are dominated by non-conventional signaling mechanisms: melanopsin phototransduction in ipRGCs and output by the neuropeptide PACAP, which provide stable pupil maintenance across the day. These results highlight a temporal switch in the coding mechanisms of a neural circuit to support proper behavioral dynamics.
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Affiliation(s)
| | - Alan C Rupp
- Department of Biology, Johns Hopkins University, Baltimore, United States
| | - Rachel A Ross
- Department of Psychiatry, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, United States
- Department of Psychiatry, Massachusetts General Hospital, Boston, United States
| | - Preethi Somasundaram
- Department of Biological Sciences, University of Marlyand, Baltimore, United States
| | - Suja Hiriyanna
- National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Zhijian Wu
- National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Tudor C Badea
- National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Phyllis R Robinson
- Department of Biological Sciences, University of Marlyand, Baltimore, United States
| | - Bradford B Lowell
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, United States
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, United States
- Program in Neuroscience, Harvard Medical School, Boston, United States
| | - Samer S Hattar
- Department of Biology, Johns Hopkins University, Baltimore, United States
- Department of Neuroscience, Johns Hopkins University, Baltimore, United States
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18
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Abstract
There is a growing recognition that the coordinated timing of behavioral, physiologic, and metabolic circadian rhythms is a requirement for a healthy body and mind. In mammals, the primary circadian oscillator is the hypothalamic suprachiasmatic nucleus (SCN), which is responsible for circadian coordination throughout the organism. Temporal homeostasis is recognized as a complex interplay between rhythmic clock gene expression in brain regions outside the SCN and in peripheral organs. Abnormalities in this intricate circadian orchestration may alter sleep patterns and contribute to the pathophysiology of affective disorders.
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19
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Gompf HS, Fuller PM, Hattar S, Saper CB, Lu J. Impaired circadian photosensitivity in mice lacking glutamate transmission from retinal melanopsin cells. J Biol Rhythms 2015; 30:35-41. [PMID: 25512304 PMCID: PMC4316665 DOI: 10.1177/0748730414561545] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Intrinsically photoreceptive retinal ganglion cells (ipRGCs) contain the photopigment melanopsin and convey retinal light inputs to the circadian system via the retinohypothalamic tract (RHT) projection to the suprachiasmatic nucleus (SCN). The principal neurotransmitter of this projection is glutamate, and ipRGCs use the vesicular glutamate transporter 2 (VGLUT2) to package glutamate into synaptic vesicles. However, these neurons contain other potential neurotransmitters, such as pituitary adenylate cyclase activating polypeptide (PACAP). To test the role of glutamate in mediating ipRGC light inputs into the SCN, we crossed mice in which Cre-recombinase expression is driven by the melanopsin promotor (Opn4(Cre/+)) with mice in which the second exon of VGLUT2 is flanked by loxP sites (VGLUT2(fl/fl)), producing ipRGCs that are unable to package glutamate into synaptic vesicles. Such mice had free-running circadian rhythms that did not entrain to a 12:12 light-dark (12:12 LD) cycle, nor did they show a phase delay after a 45-min light pulse administered at circadian time (CT) 14. A small subset of the mice did appear to entrain to the 12:12 LD cycle with a positive phase angle to lights-off; a similar entrainment pattern could be achieved in free-running mice if they were exposed to a 12:12 LD cycle with light of a greater intensity. Glutamate transmission from the ipRGCs is necessary for normal light entrainment of the SCN at moderate (0.35 W/m(2)) light levels, but residual transmission (possibly by PACAP in ipRGCs or by other RGCs) can weakly entrain animals, particularly at very high (6.53 W/m(2)) light levels, although it may be less effective at suppressing locomotor activity (light masking).
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Affiliation(s)
- Heinrich S Gompf
- Department of Neurology, Division of Sleep Medicine, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | - Patrick M Fuller
- Department of Neurology, Division of Sleep Medicine, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | - Samer Hattar
- Department of Biology, Johns Hopkins University, Baltimore, MD Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, MD
| | - Clifford B Saper
- Department of Neurology, Division of Sleep Medicine, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | - Jun Lu
- Department of Neurology, Division of Sleep Medicine, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
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