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The Optic Lobes Regulate Circadian Rhythms of Olfactory Learning and Memory in the Cockroach.
Lubinski AJ, Page TL
(2016) J Biol Rhythms 31: 161-9
MeSH Terms: Animals, Circadian Clocks, Circadian Rhythm, Cockroaches, Conditioning, Classical, Conditioning, Operant, Learning, Light, Mental Recall, Olfactory Receptor Neurons, Optic Lobe, Nonmammalian, Pyrazoles, Smell
Show Abstract · Added February 8, 2016
The cockroach, Leucophaea maderae, can be trained in an associative olfactory memory task by either classical or operant conditioning. When trained by classical conditioning, memory formation is regulated by a circadian clock, but once the memory is formed, it can be recalled at any circadian time. In contrast, when trained via operant conditioning, animals can learn the task at any circadian phase, but the ability to recall the long-term memory is tied to the phase of training. The optic lobes of the cockroach contain a circadian clock that drives circadian rhythms of locomotor activity, mating behavior, sensitivity of the compound eye to light, and the sensitivity of olfactory receptors in the antennae. To evaluate the role of the optic lobes in regulating learning and memory processes, the authors examined the effects of surgical ablation of the optic lobes on memory formation in classical conditioning and memory recall following operant conditioning. The effect of optic lobe ablation was to "rescue" the deficit in memory acquisition at a time the animals normally cannot learn and "rescue" the animal's ability to recall a memory formed by operant conditioning at a phase where memory was not normally expressed. The results suggested that the optic lobe pacemaker regulates these processes through inhibition at "inappropriate" times of day. As a pharmacological test of this hypothesis, the authors showed that injections of fipronil, an antagonist of GABA and glutamate-activated chloride channels, had the same effects as optic lobe ablation on memory formation and recall. The data suggest that the optic lobes contain the circadian clock(s) that regulate learning and memory processes via inhibition of neural processes in the brain.
© 2015 The Author(s).
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13 MeSH Terms
Genetics of Plasminogen Activator Inhibitor-1 (PAI-1) in a Ghanaian Population.
White MJ, Kodaman NM, Harder RH, Asselbergs FW, Vaughan DE, Brown NJ, Moore JH, Williams SM
(2015) PLoS One 10: e0136379
MeSH Terms: Adult, Cardiovascular Diseases, Circadian Rhythm, European Continental Ancestry Group, Female, Ghana, Humans, Male, N-Acetylgalactosamine-4-Sulfatase, Period Circadian Proteins, Plasminogen Activator Inhibitor 1, Polymorphism, Single Nucleotide
Show Abstract · Added April 6, 2017
Plasminogen activator inhibitor 1 (PAI-1), a major modulator of the fibrinolytic system, is an important factor in cardiovascular disease (CVD) susceptibility and severity. PAI-1 is highly heritable, but the few genes associated with it explain only a small portion of its variation. Studies of PAI-1 typically employ linear regression to estimate the effects of genetic variants on PAI-1 levels, but PAI-1 is not normally distributed, even after transformation. Therefore, alternative statistical methods may provide greater power to identify important genetic variants. Additionally, most genetic studies of PAI-1 have been performed on populations of European descent, limiting the generalizability of their results. We analyzed >30,000 variants for association with PAI-1 in a Ghanaian population, using median regression, a non-parametric alternative to linear regression. Three variants associated with median PAI-1, the most significant of which was in the gene arylsulfatase B (ARSB) (p = 1.09 x 10(-7)). We also analyzed the upper quartile of PAI-1, the most clinically relevant part of the distribution, and found 19 SNPs significantly associated in this quartile. Of note an association was found in period circadian clock 3 (PER3). Our results reveal novel associations with median and elevated PAI-1 in an understudied population. The lack of overlap between the two analyses indicates that the genetic effects on PAI-1 are not uniform across its distribution. They also provide evidence of the generalizability of the circadian pathway's effect on PAI-1, as a recent meta-analysis performed in Caucasian populations identified another circadian clock gene (ARNTL).
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Circadian modulation of dopamine levels and dopaminergic neuron development contributes to attention deficiency and hyperactive behavior.
Huang J, Zhong Z, Wang M, Chen X, Tan Y, Zhang S, He W, He X, Huang G, Lu H, Wu P, Che Y, Yan YL, Postlethwait JH, Chen W, Wang H
(2015) J Neurosci 35: 2572-87
MeSH Terms: Animals, Animals, Genetically Modified, Attention Deficit Disorder with Hyperactivity, Avoidance Learning, Behavior, Animal, Circadian Rhythm, Dopamine, Dopaminergic Neurons, Impulsive Behavior, Larva, Mice, Motor Activity, NIH 3T3 Cells, Period Circadian Proteins, Tyrosine 3-Monooxygenase, Zebrafish, Zebrafish Proteins
Show Abstract · Added February 20, 2015
Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders in children and adults. While ADHD patients often display circadian abnormalities, the underlying mechanisms are unclear. Here we found that the zebrafish mutant for the circadian gene period1b (per1b) displays hyperactive, impulsive-like, and attention deficit-like behaviors and low levels of dopamine, reminiscent of human ADHD patients. We found that the circadian clock directly regulates dopamine-related genes monoamine oxidase and dopamine β hydroxylase, and acts via genes important for the development or maintenance of dopaminergic neurons to regulate their number and organization in the ventral diencephalic posterior tuberculum. We then found that Per1 knock-out mice also display ADHD-like symptoms and reduced levels of dopamine, thereby showing highly conserved roles of the circadian clock in ADHD. Our studies demonstrate that disruption of a circadian clock gene elicits ADHD-like syndrome. The circadian model for attention deficiency and hyperactive behavior sheds light on ADHD pathogenesis and opens avenues for exploring novel targets for diagnosis and therapy for this common psychiatric disorder.
Copyright © 2015 the authors 0270-6474/15/352572-16$15.00/0.
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Ube3a imprinting impairs circadian robustness in Angelman syndrome models.
Shi SQ, Bichell TJ, Ihrie RA, Johnson CH
(2015) Curr Biol 25: 537-45
MeSH Terms: ARNTL Transcription Factors, Analysis of Variance, Angelman Syndrome, Animals, Body Weight, Chronotherapy, Circadian Rhythm, Gene Deletion, Genomic Imprinting, Humans, Liver, Mice, Neurons, Sleep Wake Disorders, Ubiquitin-Protein Ligases
Show Abstract · Added February 12, 2015
BACKGROUND - The paternal allele of Ube3a is silenced by imprinting in neurons, and Angelman syndrome (AS) is a disorder arising from a deletion or mutation of the maternal Ube3a allele, which thereby eliminates Ube3a neuronal expression. Sleep disorders such as short sleep duration and increased sleep onset latency are very common in AS.
RESULTS - We found a unique link between neuronal imprinting of Ube3a and circadian rhythms in two mouse models of AS, including enfeebled circadian activity behavior and slowed molecular rhythms in ex vivo brain tissues. As a consequence of compromised circadian behavior, metabolic homeostasis is also disrupted in AS mice. Unsilencing the paternal Ube3a allele restores functional circadian periodicity in neurons deficient in maternal Ube3a but does not affect periodicity in peripheral tissues that are not imprinted for uniparental Ube3a expression. The ubiquitin ligase encoded by Ube3a interacts with the central clock components BMAL1 and BMAL2. Moreover, inactivation of Ube3a expression elevates BMAL1 levels in brain regions that control circadian behavior of AS-model mice, indicating an important role for Ube3a in modulating BMAL1 turnover.
CONCLUSIONS - Ube3a expression constitutes a direct mechanistic connection between symptoms of a human neurological disorder and the central circadian clock mechanism. The lengthened circadian period leads to delayed phase, which could explain the short sleep duration and increased sleep onset latency of AS subjects. Moreover, we report the pharmacological rescue of an AS phenotype, in this case, altered circadian period. These findings reveal potential treatments for sleep disorders in AS patients.
Copyright © 2015 Elsevier Ltd. All rights reserved.
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15 MeSH Terms
Cocaine modulates mammalian circadian clock timing by decreasing serotonin transport in the SCN.
Prosser RA, Stowie A, Amicarelli M, Nackenoff AG, Blakely RD, Glass JD
(2014) Neuroscience 275: 184-93
MeSH Terms: 8-Hydroxy-2-(di-n-propylamino)tetralin, Animals, Circadian Clocks, Circadian Rhythm, Cocaine, Dopamine Uptake Inhibitors, Mice, Mice, Transgenic, Serotonin, Serotonin Plasma Membrane Transport Proteins, Serotonin Receptor Agonists, Suprachiasmatic Nucleus
Show Abstract · Added February 12, 2015
Cocaine abuse disrupts reward and homeostatic processes through diverse processes, including those involved in circadian clock regulation. Recently we showed that cocaine administration to mice disrupts nocturnal photic phase resetting of the suprachiasmatic (SCN) circadian clock, whereas administration during the day induces non-photic phase shifts. Importantly, the same effects are seen when cocaine is applied to the SCN in vitro, where it blocks photic-like (glutamate-induced) phase shifts at night and induces phase advances during the day. Furthermore, our previous data suggest that cocaine acts in the SCN by enhancing 5-HT signaling. For example, the in vitro actions of cocaine mimic those of 5-HT and are blocked by the 5-HT antagonist, metergoline, but not the dopamine receptor antagonist, fluphenazine. Although our data are consistent with cocaine acting through enhanced 5-HT signaling, the nonselective actions of cocaine as an antagonist of monoamine transporters raises the question of whether inhibition of the 5-HT transporter (SERT) is key to its circadian effects. Here we investigate this issue using transgenic mice expressing a SERT that exhibits normal 5-HT recognition and transport but significantly reduced cocaine potency (SERT Met172). Circadian patterns of SCN behavioral and neuronal activity did not differ between wild-type (WT) and SERT Met172 mice, nor did they differ in the ability of the 5-HT1A,2,7 receptor agonist, 8-OH-DPAT to reset SCN clock phase, consistent with the normal SERT expression and activity in the transgenic mice. However, (1) cocaine administration does not induce phase advances when administered in vivo or in vitro in SERT Met172 mice; (2) cocaine does not block photic or glutamate-induced phase shifts in SERT Met172 mice; and (3) cocaine does not induce long-term changes in free-running period in SERT Met172 mice. We conclude that SERT antagonism is required for the phase shifting of the SCN circadian clock induced by cocaine.
Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.
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Metabolic compensation and circadian resilience in prokaryotic cyanobacteria.
Johnson CH, Egli M
(2014) Annu Rev Biochem 83: 221-47
MeSH Terms: Bacterial Proteins, Circadian Clocks, Circadian Rhythm, Circadian Rhythm Signaling Peptides and Proteins, Cyanobacteria, Feedback, Physiological, Gene Expression Regulation, Bacterial, Homeostasis, Protein Biosynthesis, Protein Processing, Post-Translational, Temperature, Transcription, Genetic
Show Abstract · Added June 26, 2014
For a biological oscillator to function as a circadian pacemaker that confers a fitness advantage, its timing functions must be stable in response to environmental and metabolic fluctuations. One such stability enhancer, temperature compensation, has long been a defining characteristic of these timekeepers. However, an accurate biological timekeeper must also resist changes in metabolism, and this review suggests that temperature compensation is actually a subset of a larger phenomenon, namely metabolic compensation, which maintains the frequency of circadian oscillators in response to a host of factors that impinge on metabolism and would otherwise destabilize these clocks. The circadian system of prokaryotic cyanobacteria is an illustrative model because it is composed of transcriptional and nontranscriptional oscillators that are coupled to promote resilience. Moreover, the cyanobacterial circadian program regulates gene activity and metabolic pathways, and it can be manipulated to improve the expression of bioproducts that have practical value.
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An arginine tetrad as mediator of input-dependent and input-independent ATPases in the clock protein KaiC.
Pattanayek R, Xu Y, Lamichhane A, Johnson CH, Egli M
(2014) Acta Crystallogr D Biol Crystallogr 70: 1375-90
MeSH Terms: Adenosine Triphosphatases, Arginine, Bacterial Proteins, Binding Sites, Circadian Rhythm Signaling Peptides and Proteins, Crystallography, X-Ray, Models, Molecular, Mutagenesis, Site-Directed, Phosphorylation, Protein Structure, Tertiary, Synechococcus
Show Abstract · Added May 27, 2014
A post-translational oscillator (PTO) composed of the proteins KaiA, KaiB and KaiC is at the heart of the cyanobacterial circadian clock. KaiC interacts with KaiA and KaiB over the daily cycle, and CII domains undergo rhythmic phosphorylation/dephosphorylation with a 24 h period. Both the N-terminal (CI) and C-terminal (CII) rings of KaiC exhibit ATPase activity. The CI ATPase proceeds in an input-independent fashion, but the CII ATPase is subject to metabolic input signals. The crystal structure of KaiC from Thermosynechococcus elongatus allows insight into the different anatomies of the CI and CII ATPases. Four consecutive arginines in CI (Arg linker) that connect the P-loop, CI subunits and CI and CII at the ring interface are primary candidates for the coordination of the CI and CII activities. The mutation of linker residues alters the period or triggers arhythmic behavior. Comparison between the CI and CII structures also reveals differences in loop regions that are key to KaiA and KaiB binding and activation of CII ATPase and kinase. Common packing features in KaiC crystals shed light on the KaiB-KaiC interaction.
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11 MeSH Terms
Understanding the placebo effect in clinical trials for postural tachycardia syndrome.
Nwazue VC, Arnold AC, Raj V, Black BK, Biaggioni I, Paranjape SY, Orozco C, Dupont WD, Robertson D, Raj SR
(2014) Clin Exp Pharmacol Physiol 41: 325-30
MeSH Terms: Adult, Analysis of Variance, Blood Pressure, Cardiovascular Physiological Phenomena, Circadian Rhythm, Cross-Over Studies, Female, Heart Rate, Humans, Male, Placebo Effect, Placebos, Postural Orthostatic Tachycardia Syndrome, Posture, Prospective Studies, Time Factors
Show Abstract · Added March 21, 2014
Postural tachycardia syndrome (POTS) is characterized by excessive increases in heart rate (HR) upon standing. Previous studies have shown that standing HR decreases over time in POTS patients given placebo. We hypothesized that this reduction is due to cardiovascular physiological alteration, as opposed to psychological benefit from perceived therapy. To prospectively test this hypothesis, we examined the effects of an open-label 'no treatment' intervention (NoRx) compared with a patient-blinded placebo on standing HR in POTS patients. Twenty-one POTS patients participated in a randomized cross-over trial with oral placebo versus NoRx administered at 0900 h. Seated blood pressure (BP) and HR were measured at baseline and every hour for 4 h. Similarly, BP and HR were measured while patients stood for 10 min at these time points. Standing HR decreased significantly over time with both NoRx (112±13 and 103±16 b.p.m. at baseline and 4 h, respectively) and placebo (112±14 and 102±16 b.p.m. at baseline and 4 h, respectively; Ptime<0.001), but this effect was not different between interventions (Pdrug=0.771). Postural tachycardia syndrome patients have exaggerated orthostatic tachycardia in the morning that decreases over time with either placebo or NoRx interventions, suggesting this phenomenon is due to cardiovascular physiological variation. These data highlight the need for a placebo arm in haemodynamic clinical trials in POTS and may have important implications for the diagnosis of these patients.
© 2014 Wiley Publishing Asia Pty Ltd.
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Circadian variability of fibrinolytic markers and endothelial function in patients with obstructive sleep apnea.
Bagai K, Muldowney JA, Song Y, Wang L, Bagai J, Artibee KJ, Vaughan DE, Malow BA
(2014) Sleep 37: 359-67
MeSH Terms: Biomarkers, Body Mass Index, Cardiovascular Diseases, Case-Control Studies, Circadian Rhythm, Cross-Sectional Studies, Endothelial Cells, Female, Humans, Male, Middle Aged, Plasminogen Activator Inhibitor 1, Polysomnography, Sleep, Sleep Apnea, Obstructive, Tissue Plasminogen Activator
Show Abstract · Added March 10, 2014
STUDY OBJECTIVES - Obstructive sleep apnea (OSA) is strongly associated with cardiovascular disease, including stroke and acute coronary syndromes. Plasminogen activator inhibitor-1 (PAI-1), the principal inhibitor of tissue-type plasminogen activator (t-PA), has a pronounced circadian rhythm and is elevated in both OSA and cardiovascular disease and may be an important link between the two conditions. Endothelial dysfunction is one of the underlying pathophysiological mechanisms of cardiovascular disease, and may be altered in OSA. Our primary aim was to compare circadian variability of PAI-1 and t-PA in patients with OSA and normal controls by determining the amplitude (peak level) and mesor (rhythm adjusted mean) of PAI-1 and t-PA in serial blood samples over a 24-h period. The secondary aim was to measure markers of endothelial function (brachial and radial artery flow) in patients with OSA compared with normal controls.
SETTING - Cross-sectional cohort study.
PATIENTS OR PARTICIPANTS - Subjects age 18 y or older, with a body mass index of 25-45 kg/m(2), with or without evidence of untreated OSA.
INTERVENTIONS - Plasma samples were collected every 2 h, in OSA patients and matched controls, over a 24-h period. PAI-1 and t-PA antigen and activity were measured. The presence or absence of OSA (apnea-hypopnea index of 5 or greater) was confirmed by overnight polysomnography. Endothelial function was measured via brachial artery flow mediated vasodilatation and computerized arterial pulse waveform analysis.
MEASUREMENTS AND RESULTS - The rhythm-adjusted mean levels of PAI-1 antigen levels in the OSA group (21.8 ng/mL, 95% confidence level [CI], 18 to 25.7) were significantly higher as compared to the non-OSA group (16 ng/mL, 95% CI, 12.2 to 19.8; P = 0.03). The rhythm-adjusted mean levels of PAI-1 activity levels in the OSA group (23.9 IU/mL, 95% CI, 21.4 to 26.5) were also significantly higher than in the non-OSA group (17.2 IU/ mL, 95% CI, 14.6 to 19.9; P < 0.001).There were strong correlations between amplitude of PAI-1 activity and severity of OSA as measured by AHI (P = 0.02), and minimum oxygen levels during sleep (P = 0.04). Endothelial function parameters did not differ significantly between the two groups.
CONCLUSION - The presence of obstructive sleep apnea adversely affects circadian fibrinolytic balance with higher mean plasminogen activator inhibitor-1 activity and antigen, and significantly lower mean tissue-type plasminogen activator activity compared with controls. This perturbation may be an important mechanism for increased cardiovascular events in patients with obstructive sleep apnea. Intermittent hypoxia and changes in circadian clock gene activity in obstructive sleep apnea may be responsible for these findings and warrant further study. Favorable changes in fibrinolytic balance may underlie the reduction in cardiovascular events observed with the treatment of obstructive sleep apnea.
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16 MeSH Terms
Circadian yin-yang regulation and its manipulation to globally reprogram gene expression.
Xu Y, Weyman PD, Umetani M, Xiong J, Qin X, Xu Q, Iwasaki H, Johnson CH
(2013) Curr Biol 23: 2365-74
MeSH Terms: Bacterial Proteins, CLOCK Proteins, Circadian Rhythm, Circadian Rhythm Signaling Peptides and Proteins, Gene Expression, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Hydrogen, Hydrogenase, Multigene Family, Phosphorylation, Promoter Regions, Genetic, Synechococcus, Transcription, Genetic
Show Abstract · Added February 12, 2015
BACKGROUND - The cyanobacterial circadian program exerts genome-wide control of gene expression. KaiC undergoes rhythms of phosphorylation that are regulated by interactions with KaiA and KaiB. The phosphorylation status of KaiC is thought to mediate global transcription via output factors SasA, CikA, LabA, RpaA, and RpaB. Overexpression of kaiC has been reported to globally repress gene expression.
RESULTS - Here, we show that the positive circadian component KaiA upregulates "subjective dusk" genes and that its overexpression deactivates rhythmic gene expression without significantly affecting growth rates in constant light. We analyze the global patterns of expression that are regulated by KaiA versus KaiC and find in contrast to the previous report of KaiC repression that there is a "yin-yang" regulation of gene expression whereby kaiA overexpression activates "dusk genes" and represses "dawn genes," whereas kaiC overexpression complementarily activates dawn genes and represses dusk genes. Moreover, continuous induction of kaiA latched KaiABC-regulated gene expression to provide constitutively increased transcript levels of diverse endogenous and heterologous genes that are expressed in the predominant subjective dusk phase. In addition to analyzing KaiA regulation of endogenous gene expression, we apply these insights to the expression of heterologous proteins whose products are of potential value, namely human proinsulin, foreign luciferase, and exogenous hydrogenase.
CONCLUSIONS - Both KaiC and KaiA complementarily contribute to the regulation of circadian gene expression via yin-yang switching. Circadian patterns can be reprogrammed by overexpression of kaiA or kaiC to constitutively enhance gene expression, and this reprogramming can improve 24/7 production of heterologous proteins that are useful as pharmaceuticals or biofuels.
Copyright © 2013 Elsevier Ltd. All rights reserved.
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14 MeSH Terms