Network-mediated encoding of circadian time: the suprachiasmatic nucleus (SCN) from genes to neurons to circuits, and back.
The transcriptional architecture of intracellular circadian clocks is similar across phyla, but in mammals interneuronal mechanisms confer a higher level of circadian integration. The suprachiasmatic nucleus (SCN) is a unique model to study these mechanisms, as it operates as a ∼24 h clock not only in the living animal, but also when isolated in culture. This "clock in a dish" can be used to address fundamental questions, such as how intraneuronal mechanisms are translated by SCN neurons into circuit-level emergent properties and how the circuit decodes, and responds to, light input. This review addresses recent developments in understanding the relationship between electrical activity, [Ca(2+)]i, and intracellular clocks. Furthermore, optogenetic and chemogenetic approaches to investigate the distinct roles of neurons and glial cells in circuit encoding of circadian time will be discussed, as well as the epigenetic and circuit-level mechanisms that enable the SCN to translate light input into coherent daily rhythms.
Division of Neurobiology, Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom, marcob@mrc-lmb.cam.ac.uk.
Marco
M
Brancaccio
Graduate School of Medicine, Hokkaido University, Sapporo 060-0808, Japan.
Ryosuke
R
Enoki
Department of Biology, Washington University, St. Louis, Missouri 63130.
Cristina N
CN
Mazuski
Vanderbilt University Medical Center, Vanderbilt University, Nashville, Tennessee 37235.
Jeff
http://orcid.org/0000-0002-8386-7798
J
Jones
Department of Biomedical Sciences, Marquette University, Milwaukee, Wisconsin 53233, and.
Jennifer A
JA
Evans
Institute of Pharmacology and Toxicology, University of Zurich, 8006 Zurich, Switzerland.
Abdelhalim
A
Azzi
D000818:Animals; D057906:Circadian Clocks / Q000235:genetics* / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000235:genetics; D015870:Gene Expression / Q000502:physiology; D008322:Mammals / Q000502:physiology; D009457:Neuroglia / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D017440:Photoperiod; D013493:Suprachiasmatic Nucleus / Q000166:cytology* / Q000502:physiology*; D013995:Time
D056925:Circadian Rhythm Signaling Peptides and Proteins