On the molecular mechanism of the circadian clock: The 64000-Mr protein of Chlamydomonas reinhardtii might be related to the biological clock

Planta ◽  
1992 ◽  
Vol 186 (4) ◽  
pp. 593-599 ◽  
Author(s):  
Ina Wiedemann ◽  
Egon J. de Groot ◽  
Manfred Schweiger
Keyword(s):  
Circadian Clock ◽  
Chlamydomonas Reinhardtii ◽  
Molecular Mechanism ◽  
Biological Clock

Entrainment of circadian phase in developing gray short-tailed opossums: mother vs. environment.

1990 ◽  
Vol 259 (3) ◽  
pp. E384
Author(s):  
S A Rivkees ◽  
S M Reppert
Keyword(s):  
Circadian Clock ◽  
Metabolic Activity ◽  
Biological Clock ◽  
Monodelphis Domestica ◽  
Dark Cycle ◽  
Circadian Phase ◽  
Environmental Light ◽  
Circadian Time ◽  
Retinohypothalamic Tract ◽  
Marsupial Species

In a marsupial species, the gray short-tailed opossum (Monodelphis domestica), the suprachiasmatic nuclei (SCN), the site of a circadian clock, are formed postnatally and begin oscillating as a circadian clock on day 20. In this study, we examined how the timing (phase) of the SCN clock in the developing opossum is coordinated to the environmental light-dark cycle. When pups were reared from birth in darkness by intact dams, the circadian phases in SCN metabolic activity (monitored by 2-deoxy-D-[14C]glucose autoradiography) in 27-day-old pups were desynchronized. When pups were reared in a light-dark cycle that was 12 h out of phase with the circadian time of blinded dams, the pattern of SCN metabolic activity on day 20 was rhythmic and in phase with the light-dark cycle but out of phase with the circadian time of the dam. On day 20, retina-mediated light activation of SCN metabolic activity was also demonstrated, and anterograde tract-tracing studies revealed the presence of the retinohypothalamic tract within the SCN. These results show there is no influence of the opossum dam on the timing of the pup's biological clock. Instead, from the inception of the daily rhythm in SCN metabolic activity, its timing is regulated by retina-mediated light-dark entrainment.

The Circadian Clock of the Unicellular Eukaryotic Model Organism Chlamydomonas reinhardtii

2003 ◽  
Vol 384 (5) ◽  
pp. 689-695 ◽  
Author(s):  
M. Mittag ◽  
V. Wagner
Keyword(s):  
Circadian Clock ◽  
Chlamydomonas Reinhardtii ◽  
Rna Binding ◽  
Outer Space ◽  
Expression Patterns ◽  
Model Organism ◽  
Nuclear Genome ◽  
Circadian System ◽  
Transcriptional Level ◽  
Circadian Expression

Abstract The green unicellular alga Chlamydomonas reinhardtii, also called 'green yeast', emerged in the past years as a model organism for specific scientific questions such as chloroplast biogenesis and function, the composition of the flagella including its basal apparatus, or the mechanism of the circadian clock. Sequencing of its chloroplast and mitochondrial genomes have already been completed and a first draft of its nuclear genome has also been released recently. In C. reinhardtii several circadian rhythms are physiologically well characterized, and one of them has even been shown to operate in outer space. Circadian expression patterns of nuclear and plastid genes have been studied. The mode of regulation of these genes occurs at the transcriptional level, although there is also evidence for posttranscriptional control. A clock-controlled, phylogenetically conserved RNA-binding protein was characterized in this alga, which interacts with several mRNAs that all contain a common cis-acting motif. Its function within the circadian system is currently under investigation. This review summarizes the current state of the knowledge about the circadian system in C. reinhardtii and points out its potential for future studies.

scholarly journals Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness

2014 ◽  
Vol 112 (4) ◽  
pp. 1232-1237 ◽  
Author(s):  
Anne-Marie Chang ◽  
Daniel Aeschbach ◽  
Jeanne F. Duffy ◽  
Charles A. Czeisler
Keyword(s):  
Circadian Clock ◽  
Technology Use ◽  
Negative Impact ◽  
Light Exposure ◽  
Biological Effects ◽  
Biological Clock ◽  
Health And Safety ◽  
Light Emitting ◽  
Circadian Phase ◽  
The Impact

In the past 50 y, there has been a decline in average sleep duration and quality, with adverse consequences on general health. A representative survey of 1,508 American adults recently revealed that 90% of Americans used some type of electronics at least a few nights per week within 1 h before bedtime. Mounting evidence from countries around the world shows the negative impact of such technology use on sleep. This negative impact on sleep may be due to the short-wavelength–enriched light emitted by these electronic devices, given that artificial-light exposure has been shown experimentally to produce alerting effects, suppress melatonin, and phase-shift the biological clock. A few reports have shown that these devices suppress melatonin levels, but little is known about the effects on circadian phase or the following sleep episode, exposing a substantial gap in our knowledge of how this increasingly popular technology affects sleep. Here we compare the biological effects of reading an electronic book on a light-emitting device (LE-eBook) with reading a printed book in the hours before bedtime. Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book. These results demonstrate that evening exposure to an LE-eBook phase-delays the circadian clock, acutely suppresses melatonin, and has important implications for understanding the impact of such technologies on sleep, performance, health, and safety.

scholarly journals Chrono-pharmaceutical approaches to optimize dosing regimens based on the circadian clock machinery

2022 ◽  
Vol 8 (4) ◽  
pp. 238-242
Author(s):  
Shoheb S Shaikh ◽  
Sachin M Kokate
Keyword(s):  
Circadian Clock ◽  
Biological Clock ◽  
Drug Efficacy ◽  
Therapeutic Index ◽  
Expression Of Genes ◽  
Symptom Intensity ◽  
Dosing Regimens ◽  
The Difference ◽  
Toxicity Of Drugs ◽  
And Behavior

Daily rhythmic variations in biological functions affect the efficacy and/or toxicity of drugs: a large number of drugs cannot be expected to exhibit the same potency at different administration times. The “circadian clock” is an endogenous timing system that broadly regulates metabolism, physiology and behavior. In mammals, this clock governs the oscillatory expression of the majority of genes with a period length of approximately 24 h. Genetic studies have revealed that molecular components of the circadian clock regulate the expression of genes responsible for the sensitivity to drugs and their disposition. The circadian control of pharmacodynamics and pharmacokinetics enables ‘chrono-pharmaceutical’ applications, namely drug administration at appropriate times of day to optimize the therapeutic index (efficacy vs. toxicity). On the other hand, a variety of pathological conditions also exhibit marked day-night changes in symptom intensity. Currently, novel therapeutic approaches are facilitated by the development of chemical compound targeted to key proteins that cause circadian exacerbation of disease events. This review presents an overview of the current understanding of the role of the circadian biological clock in regulating drug efficacy and disease conditions, and also describes the importance of identifying the difference in the circadian machinery between diurnal and nocturnal animals to select the most appropriate times of day to administer drugs in humans.

scholarly journals A possible molecular mechanism of Chlamydomonas reinhardtii adaptation to different trophic conditions

Protistology ◽  
2021 ◽  
Author(s):  
Roman Puzanskiy ◽  
◽  
Daria Romanyuk ◽  
Alexey Shavarda ◽  
Vladislav Yemelyanov ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Molecular Mechanism ◽  
Trophic Conditions

scholarly journals Identification and temporal expression of putative circadian clock transcripts in the amphipod crustaceanTalitrus saltator

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2555 ◽  
Author(s):  
Joseph F. O’Grady ◽  
Laura S. Hoelters ◽  
Martin T. Swain ◽  
David C. Wilcockson
Keyword(s):  
Circadian Clock ◽  
Time Course ◽  
Clock Genes ◽  
Biological Clock ◽  
Experimental Manipulation ◽  
Sandy Beaches ◽  
Sequencing Data ◽  
Temporal Expression ◽  
Activity Rhythms ◽  
The Core

BackgroundTalitrus saltatoris an amphipod crustacean that inhabits the supralittoral zone on sandy beaches in the Northeast Atlantic and Mediterranean.T. saltatorexhibits endogenous locomotor activity rhythms and time-compensated sun and moon orientation, both of which necessitate at least one chronometric mechanism. Whilst their behaviour is well studied, currently there are no descriptions of the underlying molecular components of a biological clock in this animal, and very few in other crustacean species.MethodsWe harvested brain tissue from animals expressing robust circadian activity rhythms and used homology cloning and Illumina RNAseq approaches to sequence and identify the core circadian clock and clock-related genes in these samples. We assessed the temporal expression of these genes in time-course samples from rhythmic animals using RNAseq.ResultsWe identified a comprehensive suite of circadian clock gene homologues inT. saltatorincluding the ‘core’ clock genesperiod(Talper),cryptochrome 2(Talcry2),timeless(Taltim),clock(Talclk), andbmal1(Talbmal1). In addition we describe the sequence and putative structures of 23 clock-associated genes including two unusual, extended isoforms of pigment dispersing hormone (Talpdh). We examined time-course RNAseq expression data, derived from tissues harvested from behaviourally rhythmic animals, to reveal rhythmic expression of these genes with approximately circadian period inTalperandTalbmal1. Of the clock-related genes,casein kinase IIβ(TalckIIβ),ebony(Talebony),jetlag(Taljetlag),pigment dispensing hormone(Talpdh),protein phosphatase 1(Talpp1),shaggy(Talshaggy),sirt1(Talsirt1), sirt7 (Talsirt7) and supernumerary limbs (Talslimb) show temporal changes in expression.DiscussionWe report the sequences of principle genes that comprise the circadian clock ofT. saltatorand highlight the conserved structural and functional domains of their deduced cognate proteins. Our sequencing data contribute to the growing inventory of described comparative clocks. Expression profiling of the identified clock genes illuminates tantalising targets for experimental manipulation to elucidate the molecular and cellular control of clock-driven phenotypes in this crustacean.

Modeling the circadian clock: From molecular mechanism to physiological disorders

BioEssays ◽  
2008 ◽  
Vol 30 (6) ◽  
pp. 590-600 ◽  
Author(s):  
Jean-Christophe Leloup ◽  
Albert Goldbeter
Keyword(s):  
Circadian Clock ◽  
Molecular Mechanism ◽  
Physiological Disorders
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