Control of Circadian Rhythms by a Two-Component Clock

Sehgal, Amita; Ousley, Andrea; Hunter-Ensor, Melissa

doi:10.1006/mcne.1996.0013

Cited by 39 publications

(32 citation statements)

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“…In particular, high level of TIM in the DN2 L s during the day was intriguing, considering one of the most salient findings from studying the tim gene product: TIM in the adult head decreases sharply in the face of chronic or pulsatile exposure of the flies to light (for review, see Sehgal et al, 1996). It was suggested that this involves light-induced degradation of TIM, without knowing whether the effect of that stimulus is direct or indirect.…”

Section: Cycling Phases Of Per and Tim In Dorsal Neurons Of Larvaementioning

confidence: 99%

Spatial and Temporal Expression of theperiodandtimelessGenes in the Developing Nervous System ofDrosophila: Newly Identified Pacemaker Candidates and Novel Features of Clock Gene Product Cycling

1997

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The circadian timekeeping system of Drosophila functions from the first larval instar (L1) onward but is not known to require the expression of clock genes in larvae. We show that period ( per) and timeless (tim) are rhythmically expressed in several groups of neurons in the larval CNS both in light/dark cycles and in constant dark conditions. Among the clock gene-expressing cells there is a subset of the putative pacemaker neurons, the "lateral neurons" (LNs), that have been analyzed mainly in adult flies. Like the adult LNs, the larval ones are also immunoreactive to a peptide called pigment-dispersing hormone. Their putative dendritic trees were found to be in close proximity to the terminals of the larval optic nerve Bolwig's nerve, possibly receiving photic input from the larval eyes. The LNs are the only larval cells that maintain a strong cycling in PER from L1 onward, throughout metamorphosis and into adulthood. Therefore, they are the best candidates for being pacemaker neurons responsible for the larval "time memory" (inferred from previous experiments). In addition to the LNs, a subset of the larval dorsal neurons (DN L s) expresses per and tim. Intriguingly, two neurons of this DN L group cycle in PER and TIM immunoreactivity almost in antiphase to the other DN L s and to the LNs. Thus, the temporal expression of per and tim are regulated differentially in different cells. Furthermore, the light sensitivity associated with levels of the TIM protein is different from that in the heads of adult Drosophila. Key words: larval CNS; period; timeless; pigment-dispersing hormone; pacemaker; circadian; Bolwig's nerveThe period ( per) and timeless (tim) genes specif y important components of the circadian clock in Drosophila. This is supported by the isolation of arrhythmic as well as period-altered mutants at both the per and tim loci (Konopka and Benzer, 1971;Sehgal et al., 1994;Rutila et al., 1996), cycling of the abundance of their RNA and protein products, and the fact that these molecular oscillations are dependent on the normal f unctions of both genes (Hardin et al

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Section: Cycling Phases Of Per and Tim In Dorsal Neurons Of Larvaementioning

confidence: 99%

Spatial and Temporal Expression of theperiodandtimelessGenes in the Developing Nervous System ofDrosophila: Newly Identified Pacemaker Candidates and Novel Features of Clock Gene Product Cycling

1997

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“…Several studies have found that the suprachiasmatic nuclei (SCN), located in the anterior hypothalamus, are responsible for many aspects of circadian rhythmicity [6,23,26] in mammals. It is generally agreed that aging in rodents is associated with alterations in the structure and metabolic activity of these nuclei [16,24,28,30,35,36,38,39].…”

Section: Introductionmentioning

confidence: 99%

Effect of a short photoperiod on circadian rhythms of body temperature and motor activity in old rats

Benstaali¹,

Bogdan²,

Touitou³

2002

Pflügers Arch - Eur J Physiol

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Circadian rhythms of body temperature and motor activity were documented in young and old rats (four 8-week-old and five 22-month-old male Wistars, implanted with telemetric probes and housed in a chronobiological facility) under two different photoperiod conditions. The animals were maintained in a light:dark (LD) cycle of 12 h each (LD 12:12) for 4 weeks and then exposed to a LD 6:18 cycle for 7 weeks to assess the effect of age on the desynchronization of the temporal structure of the rhythms. In old rats under LD 12:12, the power of the 24-h component and the circadian amplitude of body temperature and motor activity were markedly lower than in the young and both rhythms were phase-advanced. After the shift to LD 6:18, the circadian rhythmicity was maintained for both variables and the same phase delay (+5+/-1 h) was observed in both age groups, as was a gradual expansion of the patterns of both functions with the longer night. The photoperiod reduction (6 weeks under LD 6:18) did not modify the power of the 24-h component of body temperature and motor activity in old rats. In young rats, however, the power and amplitude of the 24-h component of motor activity rhythm fell to the levels of those in old rats, while the power of the 24-h component of body temperature rhythm and the amplitude did not change. Our data show that the circadian rhythm of motor activity, but not of body temperature, responds age dependently to a photoperiod reduction.

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“…The phase of the rhythm can be reset (entrained) by pulses of daylight, and the period of the rhythm shows little tendency to vary with changes in temperature. Molecular mechanisms underlying these biological oscillators are being studied in humans (9, 9a), hamsters (10), mice (9, 9a, 11), Drosophila (12)(13)(14), Neurospora (15), Arabidopsis (16), and Cyanobacteria (17). For each of these systems, genetic screening for clock mutations has been directly or indirectly responsible for most progress.…”

Section: Introductionmentioning

confidence: 99%

THE MOLECULAR CONTROL OF CIRCADIAN BEHAVIORAL RHYTHMS AND THEIR ENTRAINMENT IN DROSOPHILA

Young

1998

Annu. Rev. Biochem.

189

125

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Molecular and genetic characterizations of circadian rhythms in Drosophila indicate that function of an intracellular pacemaker requires the activities of proteins encoded by three genes: period ( per), timeless (tim), and doubletime (dbt). RNA from two of these genes, per and tim, is expressed with a circadian rhythm. Heterodimerization of PER and TIM proteins allows nuclear localization and suppression of further RNA synthesis by a PER/TIM complex. These protein interactions promote cyclical gene expression because heterodimers are observed only at high concentrations of per and tim RNA, separating intervals of RNA accumulation from times of PER/TIM complex activity. Light resets these molecular cycles by eliminating TIM. The product of dbt also regulates accumulation of per and tim RNA, and it may influence action of the PER/TIM complex. The recent discovery of PER homologues in mice and humans suggests that a related mechanism controls mammalian circadian behavioral rhythms. CONTENTS

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Control of Circadian Rhythms by a Two-Component Clock

Cited by 39 publications

References 0 publications

Spatial and Temporal Expression of theperiodandtimelessGenes in the Developing Nervous System ofDrosophila: Newly Identified Pacemaker Candidates and Novel Features of Clock Gene Product Cycling

Spatial and Temporal Expression of theperiodandtimelessGenes in the Developing Nervous System ofDrosophila: Newly Identified Pacemaker Candidates and Novel Features of Clock Gene Product Cycling

Effect of a short photoperiod on circadian rhythms of body temperature and motor activity in old rats

THE MOLECULAR CONTROL OF CIRCADIAN BEHAVIORAL RHYTHMS AND THEIR ENTRAINMENT IN DROSOPHILA

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