Project description:Dynamic transitions in the epigenome have been associated with regulated patterns of nuclear organization. The accumulating evidence that chromatin remodeling is implicated in circadian function prompted us to explore whether the clock may control nuclear architecture. We applied the chromosome conformation capture on chip technology in mouse embryonic fibroblasts (MEFs) to demonstrate the presence of circadian long-range interactions using the clock-controlled Dbp gene as bait. The circadian genomic interactions with Dbp were highly specific and were absent in MEFs whose clock was disrupted by ablation of the Bmal1 gene (also called Arntl). We establish that the Dbp circadian interactome contains a wide variety of genes and clock-related DNA elements. These findings reveal a previously unappreciated circadian and clock-dependent shaping of the nuclear landscape.
Project description:Our aim is to study the circadian expression of genes to aid in our attempt of modelling the Arabidopsis circadian clock. Circadian microarray data have previously been published for plants after white light (WL)-dark cycles, using the 8k chip (Harmer et al. 2000). We intend to repeat this experiment using the 26k chips and are coordinating with Dr. Harmer, who is pursuing complementary experiments in UC Davis. Plants will be transferred to continuous WL after entrainment to 12h:12h light dark cycles. RNAs will be harvested every 4 hours over two days, with the same accession and sampling intervals used previously by Harmer et al. The two days of sampling provide internal replication. Our experience shows that this is the most economical design: it is easier to identify rhythms over a two-day timecourse than in two replicates of a single day. Hence: 13 RNA samples on 13 chips in total. METHOD: Seed was sown on MS agar plates with 3% sucrose, imbibed at 4 C for 96 hours. Seed was then entrained for 7 days at 22C, in cycles of 12 hours white light, 12 hours darkness. After 7 days they were transferred to constant white light at 22 C: this is time 0h. Tissue harvested at the time points shown after time 0. Experimenter name = Kieron Edwards Experimenter phone = 024 7652 8374 Experimenter fax = 024 7652 3701 Experimenter department = Department of Biological Sciences Experimenter institute = University of Warwick Experimenter address = Department of Biological Sciences Experimenter address = University of Warwick Experimenter address = Gibbet Hill Road Experimenter address = Coventry Experimenter zip/postal_code = CV4 7AL Experimenter country = UK Keywords: time_series_design, growth_condition_design
Project description:Circadian clocks drive ~24 hr rhythms in tissue physiology. They rely on transcriptional/translational feedback loops driven by interacting networks of clock complexes.To gain insights into the role of the mammary clock, circadian time-series microarrays were performed to identify rhythmic genes in vivo. Breast tissues were isolated at 4 hr intervals for two circadian (24 hourly) cycles, from mice kept under constant darkness to avoid any light- or dark-driven genes.
Project description:Life on earth is assumed to have developed in tropical regions that are characterized by regular 24 hr cycles in irradiance and temperature that remain the same throughout the seasons. All organisms developed circadian clocks that predict these environmental cycles and prepare the organisms in advance for them. A central question in chronobiology is how endogenous clocks changed in order to anticipate very different cyclical environmental conditions such as extremely short and long photoperiods existing close to the poles. Flies of the family Drosophilidae can be found all over the world-from the tropics to subarctic regions-making them unprecedented models for studying the evolutionary processes that underlie the adaptation of circadian clocks to different latitudes. This review summarizes our current understanding of these processes. We discuss evolutionary changes in the clock genes and in the clock network in the brain of different Drosophilids that may have caused behavioural adaptations to high latitudes.
Project description:Physiology is regulated by interconnected cell and tissue circadian clocks. Disruption of the rhythms generated by this interconnectedness is associated with metabolic disease. Here we tested the interactions between clocks in two critical components of organismal metabolism – liver and skeletal muscle – by rescuing clock function either in each organ separately, or in both organs simultaneously, in otherwise clock-less mice. Experiments revealed that individual clocks are partially sufficient for tissue glucose metabolism, yet the connections between both tissue clocks coupled with daily feeding rhythms maximizes systemic glucose tolerance. This synergy relies in part on local transcriptional control of the glucose machinery, feeding-responsive signals such as insulin, and metabolic cycles that connect the muscle and liver. We posit that spatiotemporal mechanisms of muscle and liver play an essential role in the maintenance of systemic glucose homeostasis, and that disrupting this diurnal coordination can contribute to the metabolic disease.
Project description:BACKGROUND:Previous studies have implicated a role for circadian clocks in regulating pre-adult development of organisms. Among them two approaches are most notable: 1) use of insects whose clocks have different free-running periods and 2) imposition of artificial selection on either rate of development, timing of emergence or circadian period in laboratory populations. Using these two approaches, influence of clock on rate of development has been elucidated. However, the contribution of circadian clocks in determining time taken for pre-adult development has remained unclear. Here we present results of our studies aimed to understand this influence by examining populations of fruit flies carrying three different alleles of the period gene and hence having different free-running periods. We tried to achieve similarity of genetic background among the three strains while also ensuring that they harbored sufficient variation on loci other than period gene. RESULTS:We find that under constant conditions, flies with long period have slower development whereas in presence of light-dark cycles (LD) of various lengths, the speed of development for each genotype is influenced by whether their eclosion rhythms can entrain to them. Under LD 12:12 (T24), where all three strains entrain, they do not show any difference in time taken for emergence, whereas under LD 10:10 (T20) where long period flies do not entrain and LD 14:14 (T28) where short period flies do not entrain, they have slower and faster pre-adult development, respectively, compared to the controls. We also show that a prior stage in development namely pupation is not rhythmic though time taken for pupation is determined by both the environmental cycle and period allele. CONCLUSION:We discuss how in presence of daily time cues, interaction of the cyclic environmental factors with the clock determines the position and width of the gate available for a fly to emerge (duration of time within a cycle when adult emergence can occur) resulting in an altered developmental duration from that observed under constant conditions. We also discuss the relevance of genetic background influencing this regulation.
Project description:Microarray expression profiling was used to identify genes expressed in developing soybean (Glycine max) seeds that are controlled by the circadian clock. Plants with developing seeds were entrained to 12hour light: 12 hour dark cycles and sampled in constant light conditions.