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310 results for “Circadian clock”
Data from: Phosphorylation, disorder, and phase separation govern the behavior of Frequency in the fungal circadian clock
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The circadian clock of the bacterium B. subtilis evokes properties of complex, multicellular circadian systems
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Data from: Sporadic feeding regulates robust food entrainable circadian clocks in blind cavefish
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Data from: The bear circadian clock doesn't 'sleep' during winter dormancy
Background: Most biological functions are synchronized to the environmental light:dark cycle via a circadian timekeeping system. Bears exhibit shallow torpor combined with metabolic suppression during winter dormancy. We sought to confirm that free-running circadian rhythms of body temperature (Tb) and activity were expressed in torpid grizzly (brown) bears and that they were functionally responsive to environmental light. We also measured activity and ambient light exposures in denning wild bears to determine if rhythms were evident and what the photic conditions of their natural dens were. Lastly, we used cultured skin fibroblasts obtained from captive torpid bears to assess molecular clock operation in peripheral tissues. Circadian parameters were estimated using robust wavelet transforms and maximum entropy spectral analyses. Results: Captive grizzly bears housed in constant darkness during winter dormancy expressed circadian rhythms of activity and Tb. The rhythm period of juvenile bears was significantly shorter than that of adult bears. However, the period of activity rhythms in adult captive bears was virtually identical to that of adult wild denning bears as was the strength of the activity rhythms. Similar to what has been found in other mammals, a single light exposure during the bear's active period delayed subsequent activity onsets whereas these were advanced when light was applied during the bear's inactive period. Lastly, in vitro studies confirmed the expression of molecular circadian rhythms with a period comparable to the bear's own behavioral rhythms. Conclusions: Based on these findings we conclude that the circadian system is functional in torpid bears and their peripheral tissues even when housed in constant darkness, is responsive to phase-shifting effects of light, and therefore, is a normal facet of torpid bear physiology.
Data from: Developmental exposure to PCB153 (2,2',4,4',5,5'-hexachlorobiphenyl) alters circadian rhythms and the expression of clock and metabolic genes
Polychlorinated biphenyls (PCBs) are highly persistent and ubiquitously distributed environmental pollutants. Based on their chemical structure, PCBs are classified into non-ortho-substituted and ortho-substituted congeners. Ortho-substituted PCBs are structurally similar to dioxin and their toxic effects and mode of action are well established. In contrast, very little is known about the effects of non-ortho-substituted PCBs, particularly during early development. The objective of this study is to investigate the effects of exposure to an environmentally prominent ortho-substituted PCB (2,2',4,4',5,5'-hexachlorobiphenyl; PCB153) on zebrafish embryos. We exposed zebrafish embryos to either DMSO or three different concentrations of PCB153 starting from 4 hours post-fertilization (hpf) to 120 hpf. We quantified gross morphological changes, behavioral phenotypes, gene expression changes and circadian behavior in the larvae. There were no developmental defects during the exposure period, but starting at 7 dpf, we observed spinal deformity in the 10 μM PCB153 treated group. A total of 633, 2227, and 3378 differentially expressed genes were observed in 0.1, 1 and 10 μM PCB153 treated embryos, respectively. Of these, 301 genes were common to all treatment groups. KEGG pathway analysis revealed enrichment of genes related to circadian rhythm, FoxO signaling and insulin resistance pathways. Behavioral analysis revealed that PCB153 exposure significantly alters circadian behavior. Disruption of circadian rhythms has been associated with the development of metabolic and neurological diseases. Thus, understanding the mechanisms of action on environmental chemicals in disrupting circadian regulation of metabolism is essential for preventing or mitigating chemical-induced metabolic disease.
Multiple paths to cold tolerance: the role of environmental cues, morphological traits and the circadian clock gene vrille
<p><strong>Background</strong>: Tracing the association between insect cold tolerance and latitudinally and locally varying environmental conditions, as well as key morphological traits and molecular mechanisms, is essential for understanding the processes involved in adaptation. We explored these issues in two closely-related species, Drosophila montana and Drosophila flavomontana, originating from diverse climatic locations across several latitudes on the coastal and mountainous regions of North America. We also investigated the association between sequence variation in one of the key circadian clock genes, vrille, and cold tolerance in both species. Finally, we studied the impact of vrille on fly cold tolerance and cold acclimation ability by silencing it with RNA interference in D. montana.</p> <p><strong>Results</strong>: We performed a principal component analysis (PCA) on variables representing bioclimatic conditions on the study sites and used latitude as a proxy of photoperiod. PC1 separated the mountainous continental sites from the coastal ones based on temperature variability and precipitation, while PC2 arranged the sites based on summer and annual mean temperatures. Cold tolerance tests showed D. montana to be more cold-tolerant than D. flavomontana and chill coma resistance (CT<sub>min</sub>) of this species showed an association with PC2. Chill coma recovery time (CCRT) of both species improved towards northern latitudes, and in D. flavomontana this trait was also associated with PC1. D. flavomontana flies were darkest in the coast and in the northern mountainous populations, but coloration showed no linkage with cold tolerance. Body size decreased towards cold environments in both species, but only within D. montana populations largest flies showed fastest recovery from cold. Finally, both the sequence analysis and RNAi study on vrille suggested this gene to play an essential role in D. montana cold resistance and acclimation, but not in recovery time.</p> <p><strong>Conclusions</strong>: Our study demonstrates the complexity of insect cold tolerance and emphasizes the need to trace its association with multiple environmental variables and morphological traits to identify potential agents of natural selection. It also shows that a circadian clock gene vrille is essential both for short- and long-term cold acclimation, potentially elucidating the connection between circadian clock system and cold tolerance.</p> <p> </p>
Plant circadian clock control of Medicago truncatula nodulation involving regulation of Nodule Cysteine-Rich genes
<p>Legumes house nitrogen-fixing endosymbiotic rhizobia in specialized polyploid cells within root nodules, which undergo tightly regulated metabolic activity. By carrying out expression analysis of transcripts over time in Medicago truncatula nodules we found that the circadian clock enables coordinated control of metabolic and regulatory processes linked to nitrogen fixation. This involves the circadian clock-associated transcriptional factor LATE ELONGATED HYPOCOTYL (LHY), with lhy mutants being affected in nodulation. Rhythmic transcripts in root nodules include a subset of Nodule-specific Cysteine Rich peptides (NCRs) that have the LHY-bound conserved Evening Element in their promoters. Until now, studies have suggested that NCRs act to regulate bacteroid differentiation and keep the rhizobial population in check. However, these conclusions came from the study of a few members of this very large gene family that has complex diversified spatio-temporal expression. We suggest that rhythmic expression of NCRs may be important for temporal coordination of bacterial activity with the rhythms of the plant host, in order to ensure optimal symbiosis.</p>
Data from: Cyclin dependent kinase 5 (CDK5) regulates the circadian clock
<p>Circadian oscillations emerge from transcriptional and post-translational feedback loops. An important step in generating rhythmicity is the translocation of clock components into the nucleus, which is regulated in many cases by kinases. In mammals, the kinase promoting the nuclear import of the key clock component Period 2 (PER2) is unknown. We observed that the cyclin-dependent kinase 5 (CDK5) regulates the mammalian clock involving phosphorylation of PER2. Knock-down of Cdk5 in the suprachiasmatic nuclei (SCN), the main coordinator site of the mammalian circadian system, shortened the free-running period in mice. CDK5 phosphorylated PER2 at serine 394 (S394) in a diurnal fashion. This facilitated interaction with Cryptochrome 1 (CRY1) and nuclear entry of the PER2-CRY1 complex. Taken together, we found that CDK5 drives nuclear entry of PER2, which is critical for establishing an adequate circadian period of the circadian cycle. Therefore, CDK5 is critically involved in the regulation of the circadian clock.</p>
Hydrobates spp. – Circadian locomotor output cycles kaput (Clock) gene poly-glutamine repeats
<p>Annual cues in the environment result in physiological changes that allow organisms to time reproduction during periods of optimal resource availability. Understanding how circadian rhythm genes sense these environmental cues and stimulate the appropriate physiological changes in response is important for determining the adaptability of species, especially in the advent of changing climate. A first step involves characterizing the environmental correlates of natural variation in these genes. Band-rumped and Leach's storm-petrels (<em>Hydrobates</em> spp.) are pelagic seabirds that breed across a wide range of latitudes. Importantly, some populations have undergone allochronic divergence, in which sympatric populations use the same breeding sites at different times of year. We investigated the relationship between variation in key functional regions of four genes that play an integral role in the cellular clock mechanism – <em>Clock, Bmal1, Cry2 </em>and<em> Per2</em> – with both breeding season and absolute latitude in these two species complexes. We discovered that allele frequencies in two genes, <em>Clock</em> and <em>Bmal1</em>, differed between seasonal populations in one archipelago, and also correlated with absolute latitude of breeding colonies. These results indicate that variation in these circadian rhythm genes may be involved in allochronic speciation, as well as adaptation to photoperiod at breeding locations.</p>
Fig. 9 in Modulation of cellular circadian clocks by triterpenoids
Fig. 9. Early responses of core clock genes in U2OS cells treated with celastrol, pristimerin, and cucurbitacin B.
Fig. 6 in Modulation of cellular circadian clocks by triterpenoids
Fig. 6. Response of PER2-luc reporter in U2OS cells to each compound administration; comparison with celastrol.
Fig. 4 in Modulation of cellular circadian clocks by triterpenoids
Fig. 4. Relationship between the structures of cucurbitacin B and its analogues and clock modulation.
Fig. 8 in Modulation of cellular circadian clocks by triterpenoids
Fig. 8. Celastrol increases the expression of Per2 and shortens the circadian period in NIH3T3 cells.
Exercise Timing and the Circadian Clock in Individuals With Type 2 Diabetes and Those at Risk
ClinicalTrials.gov study NCT06136013. IPD Sharing: Not stated. Countries: 1. Publications: 1.
Study of Circadian Clock Properties in Healthy Subjects, Obese and Type 2 Diabetic Patients.
ClinicalTrials.gov study NCT02384148. IPD Sharing: Not stated. Countries: 1. Publications: 2.
The CLOCK Study - A Human Dietary Intervention Study on Peripheral Circadian Clocks and Energy Metabolism
ClinicalTrials.gov study NCT02487576. IPD Sharing: Not stated. Countries: 1. Publications: 4.
Circadian Clocks and Eating Patterns (Cohort)
ClinicalTrials.gov study NCT04642534. IPD Sharing: NO. Countries: 1. Publications: 1.
Data from: Cyclin dependent kinase 5 (CDK5) regulates the circadian clock
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Multiple paths to cold tolerance: the role of environmental cues, morphological traits and the circadian clock gene vrille
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Plant circadian clock control of Medicago truncatula nodulation involving regulation of Nodule Cysteine-Rich genes
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.