Circadian Rhythms Of Gene Expression Research Articles

Chronic trazodone treatment increases trophic factor and circadian rhythm gene expression in rat brain regions relevant for antidepressant efficacy

Chronic trazodone treatment increases trophic factor and circadian rhythm gene expression in rat brain regions relevant for antidepressant efficacy

Sleep disturbance associated with Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) (OMIM #182290) is a rare genetic disorder with a prevalence of 1 in 25 000 live births. Approximately 90% of SMS patients have harbored a 3.7 Mb interstitial 17p11.2 deletion involving the RAI1 gene, while 10% of cases have carried pathogenic variants of the RAI1 gene. SMS is characterized by sleep disturbance, intellectual impairment, developmental delay, craniofacial and cardiovascular anomalies, obesity, self injury, aggressive and autistic-like behaviors. Most SMS patients have sleep disorders such as short total sleep time, frequent night waking, short sleep onset, and early morning waking. The sleep disturbance may aggravate with age and persist throughout life. Three mechanisms have been delineated. The first concern was the abnormal secretion of melatonin, with high levels during daytime and low levels at night. Evaluation of the integrity of the intrinsically photosensitive retinal ganglion cell (ipRGC)/melanopsin system has found that SMS patients showed dysfunction in the sustained component of the pupillary light responses to blue light. Synchronization of daily melatonin profile and its photoinhibition are dependent on the activation of melanopsin. Dysfunction of the retina-melanin system may be one of the causes of melatonin spectrum disorders. Secondly, dysregulation of circadian rhythm gene expression has also been noted in mice and SMS patients. Finally, there may be association between sleep deprivation symptoms and DNA methylation patterns, which has provided new insights for SMS-associated sleep disorders and symptoms alike. Treatment for SMS-related sleep disorders is administered primarily through medications like melatonin tablets, which can alleviate insomnia-related sleep difficulties, in particular externalizing behavior in children. Researchers are also actively exploring other treatments for SMS currently.

Epigenetic Clock and Circadian Rhythms in Stem Cell Aging and Rejuvenation.

This review summarizes the current understanding of the interaction between circadian rhythms of gene expression and epigenetic clocks characterized by the specific profile of DNA methylation in CpG-islands which mirror the senescence of all somatic cells and stem cells in particular. Basic mechanisms of regulation for circadian genes CLOCK-BMAL1 as well as downstream clock-controlled genes (ССG) are also discussed here. It has been shown that circadian rhythms operate by the finely tuned regulation of transcription and rely on various epigenetic mechanisms including the activation of enhancers/suppressors, acetylation/deacetylation of histones and other proteins as well as DNA methylation. Overall, up to 20% of all genes expressed by the cell are subject to expression oscillations associated with circadian rhythms. Additionally included in the review is a brief list of genes involved in the regulation of circadian rhythms, along with genes important for cell aging, and oncogenesis. Eliminating some of them (for example, Sirt1) accelerates the aging process, while the overexpression of Sirt1, on the contrary, protects against age-related changes. Circadian regulators control a number of genes that activate the cell cycle (Wee1, c-Myc, p20, p21, and Cyclin D1) and regulate histone modification and DNA methylation. Approaches for determining the epigenetic age from methylation profiles across CpG islands in individual cells are described. DNA methylation, which characterizes the function of the epigenetic clock, appears to link together such key biological processes as regeneration and functioning of stem cells, aging and malignant transformation. Finally, the main features of adult stem cell aging in stem cell niches and current possibilities for modulating the epigenetic clock and stem cells rejuvenation as part of antiaging therapy are discussed.

Circadian Synchrony: Sleep, Nutrition, and Physical Activity

The circadian clock in mammals regulates the sleep/wake cycle and many associated behavioral and physiological processes. The cellular clock mechanism involves a transcriptional negative feedback loop that gives rise to circadian rhythms in gene expression with an approximately 24-h periodicity. To maintain system robustness, clocks throughout the body must be synchronized and their functions coordinated. In mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is entrained to the light/dark cycle through photic signal transduction and subsequent induction of core clock gene expression. The SCN in turn relays the time-of-day information to clocks in peripheral tissues. While the SCN is highly responsive to photic cues, peripheral clocks are more sensitive to non-photic resetting cues such as nutrients, body temperature, and neuroendocrine hormones. For example, feeding/fasting and physical activity can entrain peripheral clocks through signaling pathways and subsequent regulation of core clock genes and proteins. As such, timing of food intake and physical activity matters. In an ideal world, the sleep/wake and feeding/fasting cycles are synchronized to the light/dark cycle. However, asynchronous environmental cues, such as those experienced by shift workers and frequent travelers, often lead to misalignment between the master and peripheral clocks. Emerging evidence suggests that the resulting circadian disruption is associated with various diseases and chronic conditions that cause further circadian desynchrony and accelerate disease progression. In this review, we discuss how sleep, nutrition, and physical activity synchronize circadian clocks and how chronomedicine may offer novel strategies for disease intervention.

What if melatonin could help patients with severe COVID-19?

What if melatonin could help patients with severe COVID-19?

The duration of exposure to 50 Hz magnetic fields: Influence on circadian genes and DNA damage responses in murine hematopoietic FDC-P1 cells.

We investigated the effects of 50 Hz extremely low-frequency magnetic fields (MFs) on gene expression related to the circadian rhythm or DNA damage signaling and whether these fields modify DNA damage repair rate after bleomycin treatment. Murine FDC-P1 hematopoietic cells were exposed for different durations (15 min, 2 h, 12 h, and 24 h) to either 200 μT MFs or sham-exposures. Cells were then collected for comet assay or real-time PCR to determine immediate DNA damage level and circadian rhythm gene expression, respectively. To assess DNA-damage signaling and DNA repair rate, the cells were subsequently treated with 20 μg/mL bleomycin for 1 h and then either assayed immediately or allowed to repair their DNA for 1 or 2 h. We found that circadian rhythm-related genes were upregulated after 12 h of MF exposure and downregulated after 24 h of MF exposure, but none of the affected genes were core genes controlling the circadian rhythm. In addition, we found that the repair rate for bleomycin-induced damage was only decreased after MF exposure for 24 h. In conclusion, our findings suggest that the effects of MFs are duration-dependent; they were observed predominantly after long exposures.

Sex and Disease Differences in Circadian Rhythms of Gene Expression in the Human Brain

Abnormal circadian rhythms are endophenotypes of several psychiatric disorders, including schizophrenia (SCZ). Further, there are sex differences in rhythms, both in control subjects and in SCZ. However, little is known about how rhythms differ between men and women at the molecular level or whether there are disease-related rhythm alterations.

Patients with Subarachnoid Hemorrhage Exhibit Disturbed Expression Patterns of the Circadian Rhythm Gene Period-2.

Circadian rhythm gene expression in cerebral pacemaker regions is regulated by a transcriptional-translational feedback loop across the 24-h day-night cycle. In preclinical models of subarachnoid hemorrhage (SAH), cyclic gene expression is disrupted. Stabilization of circadian rhythm gene expression attenuates susceptibility to ischemic damage in both neuronal and myocardial tissues. In this clinical observational study, circadian rhythm gene Period-2 (Per2) mRNA expression levels were determined from blood leukocytes and cerebrospinal fluid (CSF) cells via real-time PCR on days 1, 7 and 14 after aneurysm rupture in 49 patients with spontaneous SAH. CSF Per2 expression was markedly suppressed immediately after SAH and remained suppressed over the course of two weeks of ICU treatment. Short-term mortality as well as occurrence of delirium was associated with greater extent of Per2 suppression on day 1 after SAH. Patients that developed delayed cerebral ischemia exhibited comparatively lower Per2 expression levels on day 7 after SAH, while presence of vasospasm remained unaffected. However, Per2 expression did not differ in patient groups with favourable or non-favourable functional neurological outcome (modified Rankin Scales 1–3 vs. 4–6). While our findings suggest a potential protective effect of stable circadian rhythm gene expression on the extent of ischemic damage, this effect was confined to the early disease course and was not reflected in patients’ functional neurological outcome.

Взаимосвязь инкрементов продолжительности жизни и массы тела Drosophila melanogaster с дифференциаль-ной экспрессией генов циркадных ритмов в условиях культивирования с повышенным содержанием белка

The rhythmic functioning of the molecular circadian clock in various tissues and nutrition has a significant impact on the duration and quality of life, as well as the rate of aging of organisms. It is known that body weight correlates with the expression of various genes and the risk of death at different ages. In this study, an attempt was made to identify patterns in realization of genetic information under the influence of various factors, in particular, the ability of ectopic expression of circadian rhythm genes in the fat body and muscles to influence body weight in conditions when media contain different concentrations of protein. We used transgenic Drosophila melanogaster lines carrying UAS sequences in promoters of circadian rhythm genes (cry, per, tim, clk, cyc), that enhance expression, and lines that allow to induce the expression of tissue-specific GSG-311-2 (muscles) and P {Switch1} 106 (fat body). Drosophila body mass was measured on “Mettler Toledo” analytical scales, and a correlation with lifespan increments in response to overexpression of circadian rhythm genes from pre-viously published data was established. A strong correlation was found between the increments of body weight and lifespan in the case of overexpression of circadian rhythm genes in the fat body against the background of a protein-rich diet; according to Spearman, the corre-lation coefficient was 0.955. Based on the results obtained and data on the high evolutionary conservatism of the signaling pathways involved in the process (human signaling pathways are evolutionarily close to Drosophila cascades), generalizations were made regarding the negative consequences of using high-protein diets to reduce the body weight against the background of circadian rhythm disorders that are widespread in megacities.

Epigallocatechin‑3‑gallate inhibits self‑renewal ability of lung cancer stem‑like cells through inhibition of CLOCK.

Circadian rhythm plays an important role in diverse physiological processes. Abnormal expression of circadian rhythm genes is associated with increased risk of disease, including different types of cancer. The cancer stem cell (CSC) hypothesis suggests that there is a small subset of stem-like cells within tumors that are responsible for tumor initiation. However, the biological effect of circadian rhythm on CSCs remains largely unknown. Studies have highlighted that the circadian rhythm protein CLOCK controls key aspects of various diseases. In the present study, lung cancer stem-like cells were successfully enriched using a sphere formation assay. Next, it was observed that CLOCK mRNA and protein expression levels in the A549 and H1299 sphere cells were notably increased compared with those in the corresponding parental cells. In addition, flow cytometry was performed to isolate CD133+ cells and, consistently, CLOCK expression was also found to be markedly upregulated in CD133+ lung cancer cells. Subsequently, to determine the effect of CLOCK on lung cancer stem cells in detail, CLOCK was knocked down using targeted short inhibiting RNA and the results demonstrated that the sphere-forming ability of the A549 and H1299 cell lines was reduced. In addition, CSC-like properties, including the expression of CD133, CD44, sex determining region Y-box 2, Nanog and octamer-binding transcription factor 4, were markedly decreased in the A549 and H1299 sphere cells following knockdown of CLOCK. Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, has been reported to be a potential anticancer phytochemical. EGCG was found to repress CLOCK expression in A549 and H1299 sphere cells. In addition, EGCG also decreased the ratio of CD133+ cells. The Wnt/β-catenin pathway was notably inactivated by the knockdown of CLOCK in A549 and H1299 sphere cells. Subsequently, using a xenograft model, it was demonstrated that EGCG suppressed the CSC-like characteristics of lung cancer cells by targeting CLOCK. In conclusion, the present study demonstrated that EGCG inhibited the self-renewal ability of lung cancer stem-like cells by targeting CLOCK.

Circadian Gene Expression Rhythms During Critical Illness.

Core clock genes regulate tissue-specific transcriptome oscillations that synchronize physiologic processes throughout the body, held in phase by the central circadian rhythm. The central circadian rhythm rapidly dampens with onset of critical illness, but the effect of critical illness on gene expression oscillations is unknown. The objective of this study was to characterize the rhythmicity and phase coherence of core clock genes and the broader transcriptome after onset of critical illness. Cross-sectional study. ICUs and hospital clinical research unit. Critically ill patients within the first day of presenting from the community and healthy volunteers. Usual care (critically ill patients) and modified constant routine (healthy volunteers). We studied 15 critically ill patients, including 10 with sepsis and five with intracerebral hemorrhage, and 11 healthy controls. The central circadian rhythm and rest-activity rhythms were profiled by continuous wrist actigraphy, and serum melatonin sampled every 2 hours along with whole blood for RNA isolation over 24 hours. The gene expression transcriptome was obtained by RNA sequencing. Core clock genes were analyzed for rhythmicity by cosinor fit. Significant circadian rhythmicity was identified in five of six core clock genes in healthy controls, but none in critically ill patients. TimeSignature, a validated algorithm based on 41 genes, was applied to assess overall transcriptome phase coherence. Median absolute error of TimeSignature was higher in individual critically ill patients than healthy patients (4.90 vs 1.48 hr) and was correlated with encephalopathy severity by Glasgow Coma Scale in critically ill patients (rho, -0.54; p = 0.036). Gene expression rhythms rapidly become abnormal during critical illness. The association between disrupted transcriptome rhythms and encephalopathy suggests a path for future work to elucidate the underlying pathophysiology.

Chemical Perturbation of Chloroplast-Related Processes Affects Circadian Rhythms of Gene Expression in Arabidopsis: Salicylic Acid Application Can Entrain the Clock.

The plant circadian system reciprocally interacts with metabolic processes. To investigate entrainment features in metabolic–circadian interactions, we used a chemical approach to perturb metabolism and monitored the pace of nuclear-driven circadian oscillations. We found that chemicals that alter chloroplast-related functions modified the circadian rhythms. Both vitamin C and paraquat altered the circadian period in a light-quality-dependent manner, whereas rifampicin lengthened the circadian period under darkness. Salicylic acid (SA) increased oscillatory robustness and shortened the period. The latter was attenuated by sucrose addition and was also gated, taking place during the first 3 h of the subjective day. Furthermore, the effect of SA on period length was dependent on light quality and genotype. Period lengthening or shortening by these chemicals was correlated to their inferred impact on photosynthetic electron transport activity and the redox state of plastoquinone (PQ). Based on these data and on previous publications on circadian effects that alter the redox state of PQ, we propose that the photosynthetic electron transport and the redox state of PQ participate in circadian periodicity. Moreover, coupling between chloroplast-derived signals and nuclear oscillations, as observed in our chemical and genetic assays, produces traits that are predicted by previous models. SA signaling or a related process forms a rhythmic input loop to drive robust nuclear oscillations in the context predicted by the zeitnehmer model, which was previously developed for Neurospora. We further discuss the possibility that electron transport chains (ETCs) are part of this mechanism.

0169 Disruption of Sleep Architecture and Circadian Rhythms Following High Frequency Head Impacts

Abstract Introduction Mild Traumatic Brain Injury (mTBI) can cause a broad array of behavioral problems including cognitive and emotional deficits. Sleep disturbances including disrupted sleep latency and efficiency are common amongst human mTBI patients. Crucially, sleep plays a key role in hippocampal learning and memory consolidation, yet the contribution of single and repetitive mTBIs influencing sleep related cognitive outcomes remains unclear. Methods To study the effect of repetitive mTBI on sleep and circadian rhythms, C57Bl/6 mice underwent sham or High Frequency-Head Impact (HF-HI, 30 closed head impacts, 5/per day for 6-days) procedures before brains were assessed at 1d, 1m and 2m using a combination of molecular neurobiology (RNA/protein), EEG/ EMG recordings and behavioral analysis. Results HF-HI induces learning and memory deficits in the Barnes and T-Maze at both 1d and 1m post injury, in the absence of axonal injury, inflammation, or protein deposition. Disruptions in circadian mRNA expression was identified at multiple time points post HF-HI. RNA analysis of mouse cortex, hippocampus, and hypothalamus for core circadian rhythm genes (Bmal1, Clock, Cryptochrome 2, Period1 and Period 2) was conducted at 1d and 1m post HF-HI. We found dysregulated expression of these core biological clock genes in these regions at both time points. Furthermore, we find distinct changes to sleep architecture chronically post injury. Animals were implanted with EEG and EMG for monitoring at 2m post injury. EEG and EMG signals were coded for wake, NREM, and REM. One-month post injury, HFHI injured mice showed dysregulated sleep architecture compared to sham mice, while both groups had the same total sleep time. We also demonstrate that HF-HI alters EEG activity in awake animals. Conclusion Overall, our data shows disruptions in both sleep architecture and expression of circadian rhythm genes following HF-HI. This opens up an important avenue of potential therapeutic intervention following injury. Support If deficits in sleep and circadian rhythms can be rescued after mTBI, it may assist in improving symptoms and chronic outcomes after injury.

Effect of Prenatal Glucocorticoid Exposure on Circadian Rhythm Gene Expression in the Brains of Adult Rat Offspring

Circadian clocks developed in organisms as a way of estimating the time of day. In mammals, the circadian clock is based on molecular oscillators that operate through transcriptional‐translational feedback loops. While normal circadian signaling relies on a ‘master clock’, in the suprachiasmatic nucleus (SCN), to synchronize peripheral oscillators to environmental light, glucocorticoid receptor (GR) signaling has the ability to reset the phase of peripheral clocks. GR is responsive to cortisol and is central to the regulation of genes involved in stress response, immune regulation and metabolism. Phase shifts allow peripheral clocks to become uncoupled from the master clock. The SCN does not express GR and this ensures it stays tied to the light‐dark cycle. It has been shown that maternal exposure to glucocorticoids (GCs) can lead to modification of hypothalamic‐pituitary‐adrenal (HPA) function and impact stress‐related behaviours via GR activation. While exploring the effects of prenatal GC exposure on rat offspring, our lab previously demonstrated altered circadian rhythm signaling in the adrenal glands using whole transcriptomic profiling. Pregnant WKY rats were given daily subcutaneous injections of 0.1 mg/kg/day DEX (Dexamethasone, a synthetic GC), or a saline vehicle throughout the third semester, and offspring sacrificed at 18 weeks of age for tissue collection. Brain regions were isolated through a micropunch technique and RNA extracted. Results from the current study show that prenatal GC exposure affects circadian rhythm gene expression in the molecular oscillators of the amygdala, hippocampus, prefrontal cortex, paraventricular nucleus as well as the main oscillator in the SCN. Transcripts of circadian rhythm genes in these tissues were measured through RT‐qPCR and demonstrated both sex and tissue specific alteration in expression of circadian genes including Bmal1, Clock, Npas2, as well as the Per and Cry genes. This widespread dysregulation of the circadian rhythm system points to a mechanism whereby the dysfunction seen previously in the adrenal gland arises from a programmed dysregulation of the entire circadian system beginning at the master clock in the SCN.Support or Funding InformationSupported by grants from CIHR and NOSMFA Research Development Fund.

Regulation of the Neurospora Circadian Clock by the Spliceosome Component PRP5.

Increasing evidence has pointed to the connection between pre-mRNA splicing and the circadian clock; however, the underlying mechanisms of this connection remain largely elusive. In the filamentous fungus Neurospora crassa, the core circadian clock elements comprise White Collar 1 (WC-1), WC-2 and FREQUENCY (FRQ), which form a negative feedback loop to control the circadian rhythms of gene expression and physiological processes. Previously, we have shown that in Neurospora, the pre-mRNA splicing factors Pre-mRNA-processing ATP-dependent RNA helicase 5 (PRP5), protein arginine methyl transferase 5 (PRMT5) and snRNA gene U4-2 are involved in the regulation of splicing of frq transcripts, which encode the negative component of the circadian clock system. In this work we further demonstrated that repression of spliceosomal component sRNA genes, U5, U4-1, and prp5, affected the circadian conidiation rhythms. In a prp5 knockdown strain, the molecular rhythmicity was dampened. The expression of a set of snRNP genes including prp5 was up-regulated in a mutant strain lacking the clock component wc-2, suggesting that the function of spliceosome might be under the circadian control. Among these snRNP genes, the levels of prp5 RNA and PRP5 protein oscillated. The distribution of PRP5 in cytosol was rhythmic, suggesting a dynamic assembly of PRP5 in the spliceosome complex in a circadian fashion. Silencing of prp5 caused changes in the transcription and splicing of NCU09649, a clock-controlled gene. Moreover, in the clock mutant frq9, the rhythmicity of frq I-6 splicing was abolished. These data shed new lights on the regulation of circadian clock by the pre-RNA splicing, and PRP5 may link the circadian clock and pre-RNA splicing events through mediating the assembly and function of the spliceosome complex.

Abstract 1888: Circadian rhythm modulation of breast cancer gene expression depends on stem cell properties induced in culture

Abstract It is important to know whether breast cancer cells within tumors have functional circadian clocks. If so, they may benefit from the ability provided by the clock to predict when important daily events occur such as nutrient availability in blood following meals or elevated immune cell surveillance at night. If instead the circadian clock is nonfunctional, then clinical treatments could be directed towards activating the clock because evidence indicates circadian rhythm loss leads to more aggressive tumor growth. Here, we examined the role of circadian clocks in metastasis-related events, focusing on epithelial-mesenchymal transition (EMT), including cancer stem cell (CSC) generation, and mesenchymal-epithelial transition (MET). Because of their differing circadian properties two tumor-forming cell lines were compared, MCF-7 human breast cancer and C6 rat glioma cells. C6 monolayer and tumorsphere cultures express distinct circadian rhythms in gene expression. In contrast, monolayer MCF-7 cell cultures are reported to be arrhythmic and so appear to lack a functional circadian clock. Nevertheless, MCF-7 cells may contain inducible circadian oscillators that fail to generate circadian rhythms under standard culture conditions but may function in tumor microenvironments. Tumorspheres simulate the three-dimensional tumor structure and were used here to test for favorable conditions enabling circadian rhythms in cancer cells. Circadian rhythms in EMT, MET, mitosis, migration, and cell death were evaluated through time-lapse imaging over several days. Bioluminescence imaging and quantitative RT-PCR were used to test for circadian rhythms in expression of the core circadian clock gene Per2 in MCF-7 cells. Following treatment with serum-free culture medium designed for stem cells, EMT and CSC-related protein markers of MCF-7 and C6 cells were confirmed by immunofluorescence: MSI1 and CD133 in MCF-7; OCT4, TWIST1, ZEB1, vimentin in C6. Morphometry showed distinct changes in cell shape following EMT as shown by nearly all MCF-7 cells having an average roundness of 0.815 ±0.09 SD and a C6 roundness of 0.855 ±0.029. This medium increased the number of MCF-7 tumorspheres expressing circadian rhythms by 31.5%, and average amplitude of rhythms increased 11.6-fold. MET was then induced by returning cells to serum-containing medium, which produced cells with a flattened cell morphology indicating epithelial or pseudoepithelial differentiation. A circadian clock in C6 cells appeared to gate MET events after the return to serum (95% confidence limit of period: 20.8-26.9 hrs, p<0.05). The circadian timing properties of MCF-7 tumorspheres suggest that the circadian clock may also be present in tumors and that cell-cell interactions or paracrine factors could sustain otherwise poorly performing circadian clocks in breast cancer. Citation Format: Arpan De, Vishal Premdev Sharma, Dilshan Harshajith Beligala, Angelia Marie Lee, Michael Eric Geusz. Circadian rhythm modulation of breast cancer gene expression depends on stem cell properties induced in culture [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1888.

Dysregulation of Circadian Rhythm Gene Expression in Cystic Fibrosis Mice.

Cystic fibrosis (CF) is autosomal recessive disease that affects multiple body systems. CF patients often experience sleep disturbances, altered sleep patterns, and sleep apnea. Sleep in mammals is controlled in part by circadian clock genes, including Clock, Bmal1, Period1, Period2, Cryptochrome1, and Cryptochrome2. The purpose of this study was to gain a better understanding of the biological underpinnings of disordered sleep experienced in CF. To accomplish this, we evaluated circadian clock gene expression profiles in CF and wildtype mice, divided into two subgroups each based on sleep condition. One subgroup of each genotype was permitted to maintain their sleep-wake cycle while the other was deprived of sleep for six hours prior to sacrifice. Brain, skeletal muscle, jejunum, colon, lung and adipose tissues were collected from each mouse. Quantitative polymerase chain reaction (PCR) was used to quantify expression of Clock, Bmal1, Period1, Period2, Cryptochrome1 and Cryptochrome2, and expression levels were compared between study groups. Our comparisons showed distinct differences between the CF groups and the wildtype groups under both sleep conditions. Additionally, we found the CF mice that had been sleep deprived had severely dysregulated expression of all measured genes in the lung apart from Cry1. Our findings suggest that (1) disordered sleep in CF may be caused by circadian system dysregulation and (2) the loss of the cystic fibrosis transmembrane conductance regulator (CFTR) is a causative factor in the dysregulated circadian clock gene expression profiles of CF mice.

Preservation of circadian rhythms by the protein folding chaperone, BiP.

Dysregulation of collagen synthesis is associated with disease progression in cancer and fibrosis. Collagen synthesis is coordinated with the circadian clock, which in cancer cells is, curiously, deregulated by endoplasmic reticulum (ER) stress. We hypothesized interplay between circadian rhythm, collagen synthesis, and ER stress in normal cells. Here we show that fibroblasts with ER stress lack circadian rhythms in gene expression upon clock-synchronizing time cues. Overexpression of binding immunoglobulin protein (BiP) or treatment with chemical chaperones strengthens the oscillation amplitude of circadian rhythms. The significance of these findings was explored in tendon, where we showed that BiP expression is ramped preemptively prior to a surge in collagen synthesis at night, thereby preventing protein misfolding and ER stress. In turn, this forestalls activation of the unfolded protein response in order for circadian rhythms to be maintained. Thus, targeting ER stress could be used to modulate circadian rhythm and restore collagen homeostasis in disease.—Pickard, A., Chang, J., Alachkar, N., Calverley, B., Garva, R., Arvan, P., Meng, Q.-J., Kadler, K. E. Preservation of circadian rhythms by the protein folding chaperone, BiP.

A saturated reaction in repressor synthesis creates a daytime dead zone in circadian clocks.

Negative feedback loops (NFLs) for circadian clocks include light-responsive reactions that allow the clocks to shift their phase depending on the timing of light signals. Phase response curves (PRCs) for light signals in various organisms include a time interval called a dead zone where light signals cause no phase shift during daytime. Although the importance of the dead zone for robust light entrainment is known, how the dead zone arises from the biochemical reactions in an NFL underlying circadian gene expression rhythms remains unclear. In addition, the observation that the light-responsive reactions in the NFL vary between organisms raises the question as to whether the mechanism for dead zone formation is common or distinct between different organisms. Here we reveal by mathematical modeling that the saturation of a biochemical reaction in repressor synthesis in an NFL is a common mechanism of daytime dead zone generation. If light signals increase the degradation of a repressor protein, as in Drosophila, the saturation of repressor mRNA transcription nullifies the effect of light signals, generating a dead zone. In contrast, if light signals induce the transcription of repressor mRNA, as in mammals, the saturation of repressor translation can generate a dead zone by cancelling the influence of excess amount of mRNA induced by light signals. Each of these saturated reactions is located next to the light-responsive reaction in the NFL, suggesting a design principle for daytime dead zone generation.

Impact of adult attention deficit hyperactivity disorder and medication status on sleep/wake behavior and molecular circadian rhythms.

Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric condition that has been strongly associated with changes in sleep and circadian rhythms. Circadian rhythms are near 24-h cycles that are primarily generated by an endogenous circadian timekeeping system, encoded at the molecular level by a panel of clock genes. Stimulant and non-stimulant medication used in the management of ADHD has been shown to potentially impact on circadian processes and their behavioral outputs. In the current study, we have analyzed circadian rhythms in daily activity and sleep, and the circadian gene expression in a cohort of healthy controls (N = 22), ADHD participants not using ADHD-medication (N = 17), and participants with ADHD and current use of ADHD medication (N = 17). Rhythms of sleep/wake behavior were assessed via wrist-worn actigraphy, whilst rhythms of circadian gene expression were assessed ex-vivo in primary human-derived dermal fibroblast cultures. Behavioral data indicate that patients with ADHD using ADHD-medication have lower relative amplitudes of diurnal activity rhythms, lower sleep efficiency, more nocturnal activity but not more nocturnal wakenings than both controls and ADHD participants without medication. At the molecular level, there were alterations in the expression of PER2 and CRY1 between ADHD individuals with no medication compared to medicated ADHD patients or controls, whilst CLOCK expression was altered in patients with ADHD and current medication. Analysis of fibroblasts transfected with a BMAL1:luc reporter showed changes in the timing of the peak expression across the three groups. Taken together, these data support the contention that both ADHD and medication status impact on circadian processes.