Dataset Information

Dynamics of the Drosophila circadian clock: theoretical anti-jitter network and controlled chaos.

ABSTRACT:

Background

Electronic clocks exhibit undesirable jitter or time variations in periodic signals. The circadian clocks of humans, some animals, and plants consist of oscillating molecular networks with peak-to-peak time of approximately 24 hours. Clockwork orange (CWO) is a transcriptional repressor of Drosophila direct target genes.

Methodology/principal findings

Theory and data from a model of the Drosophila circadian clock support the idea that CWO controls anti-jitter negative circuits that stabilize peak-to-peak time in light-dark cycles (LD). The orbit is confined to chaotic attractors in both LD and dark cycles and is almost periodic in LD; furthermore, CWO diminishes the Euclidean dimension of the chaotic attractor in LD. Light resets the clock each day by restricting each molecular peak to the proximity of a prescribed time.

Conclusions/significance

The theoretical results suggest that chaos plays a central role in the dynamics of the Drosophila circadian clock and that a single molecule, CWO, may sense jitter and repress it by its negative loops.

SUBMITTER: Fathallah-Shaykh HM

PROVIDER: S-EPMC2954144 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Publications

Dynamics of the Drosophila circadian clock: theoretical anti-jitter network and controlled chaos.

Fathallah-Shaykh Hassan M HM

PloS one 20101013 10

<h4>Background</h4>Electronic clocks exhibit undesirable jitter or time variations in periodic signals. The circadian clocks of humans, some animals, and plants consist of oscillating molecular networks with peak-to-peak time of approximately 24 hours. Clockwork orange (CWO) is a transcriptional repressor of Drosophila direct target genes.<h4>Methodology/principal findings</h4>Theory and data from a model of the Drosophila circadian clock support the idea that CWO controls anti-jitter negative c ...[more]

PMID: 20967246

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Project description:Purpose: Alteration in light dark cycle leads to changes in daily behavior in mammals. We have previously demonstrated that different light:dark cycle lengths result in dynamic changes in DNA methylation within the suprachiasmatic nuclei (SCN) that globally alter transcription of both clock genes and non-clock genes. The goal of this study was to re-examine DNA methylation in the SCN separately for dorsal and ventral regions. Method: Six-week-old wild-type mice (C57BL/6Cr1) were entrained to light:dark cycles either 22, 24, or 26 hours in length (T22, T24, or T26) for six weeks. After 6 weeks, we recorded wheel-running behavior in constant darkness. After 3 days in DD, we used Clocklab software to predict time of activity onset for each mouse. Brains were isolated at the circadian time CT4 and then sliced immediately using vibratome, one coronal SCN slice of ~250μM was collected from the middle part of the SCN. Using ophthalmic knife vSCN and dSCN sub-regions were separated. To get enough DNA, a pool of vSCN and dSCN was prepared twice from 5 mice from each T-cycle. Genomic DNA was extracted from SCN slices by overnight Proteinase K digestion, followed by phenol-chloroform and ethanol precipitation. After RNase treatment, genomic DNA was sonicated to generate small fragments (average of 300bp), using a Covaris sonicator (BioRuptor). DNA immunoprecipitation was performed using Epiquik™ MeDIP Ultra Kit (EPIGENTEK™), following manufacturer's instructions. The methylated enriched DNA was then used for library preparation using Accel-NGS™ DNA Library Kits (Swift Biosciences), following manufacturer's instructions. Quality check, library preparation and sequencing were performed by Fasteris (CH). Results: 13-21 x 10^6 reads were obtained from each meDIP library. Quality control was performed on the fasta raw sequence data using FastQC.MeDIP-seq data were aligned to the mm9 mouse genome build using the Burrows-Wheeler Alignment tool (BWA) (Li and Durbin, 2009). Mapped reads were than analyzed using the MEDIPS package (Lienhard et al., 2014). Methylation score was calculated for each region of 500bp across the genome. CpG density-dependent normalization was incorporated. Pairwise correlation analysis of the genome wide coverage profile between MEDIP replicate samples was performed using the MEDIPS.correlation function. Pearson correlation coefficient r varied between 0.85 and 0.92, indicating good reproducibility of MEDIP-seq signal. Differential methylation analysis was performed using MEDIPS in 500bp widows excluding regions with less than 8 unique mapped reads. DMR were than identified by filtering for a widows associated with a p ≤0.001. DMR were than mapped using the web based chip-seq tool “ChIPseek” (Chen et al., 2014). Different sets of genes showed methylation changes in dorsal vs. ventral regions. Interestingly, far greater changes were observed in vSCN than in dSCN.

Project description:The biological master clock, suprachiasmatic nucleus (of rat and mouse), is composed of ~10,000 clock cells which are heterogeneous with respect to their circadian periods. Despite this inhomogeneity, an intact SCN maintains a very good degree of circadian phase (time) coherence which is vital for sustaining various circadian rhythmic activities, and it is supposedly achieved by not just one but a few different cell-to-cell coupling mechanisms, among which action potential (AP)-mediated connectivity is known to be essential. But, due to technical difficulties and limitations in experiments, so far very little information is available about the morphology of the connectivity at a cellular scale. Building upon this limited amount of information, here we exhaustively and systematically explore a large pool (~25,000) of various network morphologies to come up with some plausible network features of SCN networks. All candidates under consideration reflect an experimentally obtained 'indegree distribution' as well as a 'physical range distribution of afferent clock cells.' Then, importantly, with a set of multitude criteria based on the properties of SCN circadian phase waves in extrinsically perturbed as well as in their natural states, we select out appropriate model networks: Some important measures are, 1) level of phase dispersal and direction of wave propagation, 2) phase-resetting ability of the model networks subject to external circadian forcing, and 3) decay rate of perturbation induced "phase-singularities." The successful, realistic networks have several common features: 1) "indegree" and "outdegree" should have a positive correlation; 2) the cells in the SCN ventrolateral region (core) have a much larger total degree than that of the dorsal medial region (shell); 3) The number of intra-core edges is about 7.5 times that of intra-shell edges; and 4) the distance probability density function for the afferent connections fits well to a beta function. We believe that these newly identified network features would be a useful guide for future explorations on the very much unknown AP-mediated clock cell connectome within the SCN.

Dataset Information

Dynamics of the Drosophila circadian clock: theoretical anti-jitter network and controlled chaos.

Background

Methodology/principal findings

Conclusions/significance

Publications

Dynamics of the Drosophila circadian clock: theoretical anti-jitter network and controlled chaos.

Similar Datasets

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