Circadian Rhythm in Membrane Conductance Expressed in Isolated Neurons

Michel, Stephan; Geusz, Michael E.; Zaritsky, Joshua J.; Block, Gene D.

doi:10.1126/science.8421785

Cited by 191 publications

(109 citation statements)

References 17 publications

(9 reference statements)

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“…Discussion SCN Neurons Are Weak, Inducible, and Probabilistic Oscillators. The best examples to date of cell-autonomous circadian rhythm generation are unicellular cyanobacteria (21), dinoflagellates (22), and molluscan retinal neurons (23). Here we have demonstrated that when a single SCN neuron expresses PER2 for multiple days, it is likely to be circadian and can contain AVP, VIP, or another unidentified marker.…”

Section: Per2 Accumulation Predicts Oscillatory Abilitymentioning

confidence: 88%

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons

Webb

Angelo

Huettner

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

210

220

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Circadian rhythms are modeled as reliable and self-sustained oscillations generated by single cells. The mammalian suprachiasmatic nucleus (SCN) keeps near 24-h time in vivo and in vitro, but the identity of the individual cellular pacemakers is unknown. We tested the hypothesis that circadian cycling is intrinsic to a unique class of SCN neurons by measuring firing rate or Period2 gene expression in single neurons. We found that fully isolated SCN neurons can sustain circadian cycling for at least 1 week. Plating SCN neurons at <100 cells/mm 2 eliminated synaptic inputs and revealed circadian neurons that contained arginine vasopressin (AVP) or vasoactive intestinal polypeptide (VIP) or neither. Surprisingly, arrhythmic neurons (nearly 80% of recorded neurons) also expressed these neuropeptides. Furthermore, neurons were observed to lose or gain circadian rhythmicity in these dispersed cell cultures, both spontaneously and in response to forskolin stimulation. In SCN explants treated with tetrodotoxin to block spike-dependent signaling, neurons gained or lost circadian cycling over many days. The rate of PERIOD2 protein accumulation on the previous cycle reliably predicted the spontaneous onset of arrhythmicity. We conclude that individual SCN neurons can generate circadian oscillations; however, there is no evidence for a specialized or anatomically localized class of cell-autonomous pacemakers. Instead, these results indicate that AVP, VIP, and other SCN neurons are intrinsic but unstable circadian oscillators that rely on network interactions to stabilize their otherwise noisy cycling.luciferase ͉ pacemaker ͉ Period gene ͉ suprachiasmatic nucleus ͉ vasoactive intestinal polypeptide C ircadian pacemakers are schematized as intracellular transcription-translation negative feedback loops (1). In mammals, transcription factors including CLOCK and BMAL1 promote the expression of clock genes, including Period 1 (Per1) and 2 (Per2). The protein products of these genes return to the nucleus after a delay of many hours to repress their own transcription. Genetic deletion of these repressors abolishes circadian rhythms in behavior and physiology (2). The strongest evidence for cell-autonomous, circadian rhythm generation in mammals comes from transcriptional rhythms measured from primary and immortalized fibroblasts (3, 4).The mammalian suprachiasmatic nucleus (SCN) of the anterior hypothalamus coordinates daily rhythms including sleep-wake and hormone release (5). Multielectrode array (MEA) recordings of neuronal firing and luciferase-based reporters of Per1 and Per2 expression showed dissociated SCN neurons in the same culture with different circadian periods (6, 7). Furthermore, Na ϩ -dependent action potentials, vasoactive intestinal polypeptide (VIP), and its receptor, VPAC2, are required for cellular synchrony and maintaining daily oscillations across the SCN (8, 9). Taken together, these results suggest that single SCN neurons are competent circadian oscillators. However, which, if any, SCN neurons are capable ...

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Section: Per2 Accumulation Predicts Oscillatory Abilitymentioning

confidence: 88%

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons

Webb

Angelo

Huettner

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

210

220

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“…A crucial question early on in the field was whether or not cell-autonomous circadian oscillators also exist in multicellular organisms. The first demonstration of cell-autonomous circadian-rhythm generation in such organisms came from studies in the snail Bulla gouldiana, in which individual neurons in the base of the retina were shown to express circadian rhythms in membrane conductance for at least two days in culture 11 . In other landmark experiments in mammals, Welsh et al 12 established that the oscillatory machinery in rats functions within individual cultured SUPRACHIASMATIC NUCLEUS (SCN) neurons (discussed in detail later).…”

Section: Cell-autonomous Oscillatory Mechanismsmentioning

confidence: 99%

Circadian rhythms from multiple oscillators: lessons from diverse organisms

et al. 2005

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The organization of biological activities into daily cycles is universal in organisms as diverse as cyanobacteria, fungi, algae, plants, flies, birds and man. Comparisons of circadian clocks in unicellular and multicellular organisms using molecular genetics and genomics have provided new insights into the mechanisms and complexity of clock systems. Whereas unicellular organisms require stand-alone clocks that can generate 24-hour rhythms for diverse processes, organisms with differentiated tissues can partition clock function to generate and coordinate different rhythms. In both cases, the temporal coordination of a multi-oscillator system is essential for producing robust circadian rhythms of gene expression and biological activity.The temporal coordination of internal biological processes, both among these processes and with external environmental cycles, is crucial to the health and survival of diverse organisms, from bacteria to humans. Central to this coordination is an internal CLOCK that controls CIRCADIAN RHYTHMS of gene expression and the resulting biological activity (BOX 1). Despite disparate phylogenetic origins and vast differences in complexity among the species that show circadian rhythmicity, at the core of all circadian clocks is at least one internal autonomous circadian OSCILLATOR. These oscillators contain positive and negative elements that form autoregulatory feedback loops, and in many cases these loops are used to generate 24-hour timing circuits 1, 2 . Components of these loops can directly or indirectly receive environmental input to allow ENTRAINMENT of the clock to environmental time and transfer temporal information through output Competing interests statementThe authors declare no competing financial interests. NIH Public Access Author ManuscriptNat Rev Genet. Author manuscript; available in PMC 2009 September 1. Published in final edited form as:Nat Rev Genet. 2005 July ; 6(7): 544-556. doi:10.1038/nrg1633. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript pathways to regulate rhythmic clock-controlled gene (CCG) expression and rhythmic biological activity.Whereas a self-contained clock in single-celled organisms programmes 24-hour rhythms in diverse processes, multicellular organisms with differentiated tissues can partition clock function among different cell types to coordinate tissue-specific rhythms and maintain precision. Now that individual molecular circadian oscillators have been sufficiently described, it has become possible to go beyond single oscillators to try and understand how multiple oscillators are integrated into circadian systems. Evidence accumulated in recent years indicates that the intracellular oscillator systems of single-celled organisms might be more complex than those of higher eukaryotes, whereas the complexity of circadian outputs in multicellular organisms is an emergent property of intercellular interactions. In this review, we discuss the complexity of the circadian clocks on the basis of molecular genetic and geno...

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“…Another conserved feature of circadian mechanisms is that they are cell-autonomous; single cells dissociated in vitro can keep track of time even in complex multicellular animals (Michel et al 1993;Welsh et al 1995), although in vivo such cells are usually grouped into so-called timing centres.…”

Section: The Molecular Components Of Circadian Clocksmentioning

confidence: 99%

Peripheral clocks and their role in circadian timing: insights from insects

Giebułtowicz

2001

Phil. Trans. R. Soc. Lond. B

104

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Impressive advances have been made recently in our understanding of the molecular basis of the cellautonomous circadian feedback loop; however, much less is known about the overall organization of the circadian systems. How many clocks tick in a multicellular animal, such as an insect, and what are their roles and the relationships between them? Most attempts to locate clock-containing tissues were based on the analysis of behavioural rhythms and identi¢ed brain-located timing centres in a variety of animals. Characterization of several essential clock genes and analysis of their expression patterns revealed that molecular components of the clock are active not only in the brain, but also in many peripheral organs of Drosophila and other insects as well as in vertebrates. Subsequent experiments have shown that isolated peripheral organs can maintain self-sustained and light sensitive cycling of clock genes in vitro. This, together with earlier demonstrations that physiological output rhythms persist in isolated organs and tissues, provide strong evidence for the existence of functionally autonomous local circadian clocks in insects and other animals. Circadian systems in complex animals may include many peripheral clocks with tissue-speci¢c functions and a varying degree of autonomy, which seems to be correlated with their sensitivity to external entraining signals.

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Circadian Rhythm in Membrane Conductance Expressed in Isolated Neurons

Cited by 191 publications

References 17 publications

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons

Circadian rhythms from multiple oscillators: lessons from diverse organisms

Peripheral clocks and their role in circadian timing: insights from insects

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