Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression linked to sleep homeostasis in murine cortex

ABSTRACT: Why we sleep is still one of the most perplexing mysteries in biology. Strong evidence, however, indicates that sleep is necessary for normal brain function and that the need to sleep is a tightly regulated process. Surprisingly molecular mechanisms that determine the need to sleep are incompletely described. Moreover, very little is known about transcriptional changes that specifically accompany the accumulation and discharge of sleep need. In this study we present an integrated 2 cross-laboratory analysis of the effects of sleep deprivation (SD) in gene expression in the mouse cortex. We also evaluate changes in gene expression genome-wide following various lengths of subsequent recovery sleep. (RS). We demonstrate that changes in gene expression specifically linked to SD or RS, and not to technical factors (e.g. the assay used), requires a novel analysis methodology not previously utilized in the field of sleep research. Cortical samples from mice were analyzed, from groups that were sleep deprived, sleep deprived and allowed to recover for 1, 2, 3, or 6 hours, and circadian control animals that were not sleep deprived. The experimental protocol began at lights on (ZT0) with 13 mice: 1 sacrificed, 4 control mice left undisturbed, and 8 mice kept awake with gentle brushing when attempting to sleep. After 5 hours of sleep deprivation the mice were randomly assigned to recovery sleep or continued sleep deprivation, and at fixed intervals the mice were sacrificed, dissected and the left cortex retained. The experimental protocol was repeated 7 times, one animal per timepoint per experimental day, so that 7 independent experiments are represented for each timepoint. All animals were acclimated to the brushing and tapping on cages used during sleep deprivationfor 6 days, and dissections and tissue collection were performed by a single experimenter.

ORGANISM(S): Mus musculus

SUBMITTER: Lucia Peixoto

PROVIDER: E-GEOD-78215 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:To gain insight into the molecular changes of sleep need, this study addresses gene expression changes in a subpopulation of neurons selectively activated by sleep deprivation. Whole brain expression analyses after 6h sleep deprivation clearly indicate that Homer1a is the best index of sleep need, consistently in all mouse strains analyzed. Transgenic mice expressing a FLAG-tagged poly(A)-binding protein (PABP) under the control of Homer1a promoter were generated. Because PABP binds the poly(A) tails of mRNA, affinity purification of FLAG-tagged PABP proteins from whole brain lysates, is expected to co-precipitate all mRNAs from neurons expressing Homer1a. Three other activity-induced genes (Ptgs2, Jph3, and Nptx2) were identified by this technique to be over-expressed after sleep loss. All four genes play a role in recovery from glutamate-induced neuronal hyperactivity. The consistent activation of Homer1a suggests a role for sleep in intracellular calcium homeostasis for protecting and recovering from the neuronal activation imposed by wakefulness. Experiment Overall Design: Experiments were performed on male mice, 12 weeks of age +/- 1 week. Animals were housed in polycarbonate cages (31x18x18cm) in an experimental room with an ambient temperature varying from 23Â° to 25Â°C under a 12:12 hrs light/dark cycle. Food and water were available ad libitum. At light onset mice were either sleep deprived by gentle handling (n=10) or left undisturbed (n=10) for 6 hrs. Animals were then randomly sacrificed by cervical dislocation. Total RNA from the whole brain was isolated for control (n=4) and sleep deprived (n=4) using a commercial RNA extraction kit (RNeasy Lipid Tissue Kit, Quiagen). Specific Homer1a-expressing cells polyA RNAs were immunoprecipitated following the total brain crosslinking (1% formaldehyde perfusion) for sleep deprived (n=6) and control (n=6) animals. The total RNA from the pull-down supernatants were also harvested (n=4). To test for transcriptional changes after sleep deprivation Homer1a-expressing cells, we proceeded in 2 steps: (1) identify probe sets enriched in the pull-down extracts, (2) among those probe sets compare sleep deprivation to control condition in both pull-down (6 vs. 6 chip comparison) and whole-brain (4 vs. 4 chip comparison) extracts. 4728 probe sets were significantly enriched at 5% FDR when pull-downs were compared to both supernatant and whole-brain extracts.

Project description:Although at the organismal level sleep is defined as a behavioral state, at the level of the cerebral cortex sleep has a distinct local and use-dependent aspect. This observation raises the question whether sleep is a functional property of a complex brain or occurs at the level of neuronal assemblies with populations that were active more during wakefulness needing more intense sleep to recover. Here we show that primary cortical cultures have the capacity to change between sleep- and wake-like states that share key signatures with their in vivo counterparts. Cortical cultures initially exhibit random firing activity that is gradually replaced by a M-bM-^@M-^\sleep-likeM-bM-^@M-^] synchronized burst-pause firing activity as neurons mature and make connections. When stimulated with excitatory neurotransmitters, transient tonic firing is observed, followed by the reappearance of a M-bM-^@M-^\sleep-likeM-bM-^@M-^] state. Besides electrophysiological similarities also the transcriptional profile of stimulated cortical cultures greatly resembles that of the cortex of sleep deprived animals. We then used our in vitro model to map the metabolic pathways activated by the M-bM-^@M-^\wake-likeM-bM-^@M-^] state and found evidence for increased lysolipid release, strongly suggesting that sleep plays a role in neuronal membrane homeostasis. With our in vitro model the cellular and molecular consequences of sleep loss and the genetic determinants of disturbed sleep can now be investigated in a dish. Keywords: stress response For the in vivo transcriptome analyses mice were sleep deprived for 6 hours and brain harvested immediately afterwards. For the in vitro analyses, cortical cultures were stimulated with a neurotransmitter cocktail and cells harvested 3 hours afterwards. Control mice were kept undisturbed in their home cage and control cultures were sham stimulated with water. Also, another set of sleep deprived mice as well as stimulated cultures were allowed to recover before being sampled the next day at the time of day at which sleep deprivation or stimulation started the day before).

Project description:These studies address temporal changes in gene expression during spontaneous sleep and extended wakefulness in the mouse cerebral cortex, a neuronal target for processes that control sleep; and the hypothalamus, an important site of sleep regulatory processes. We determined these changes by comparing expression in sleeping animals sacrificed at different times during the lights on period, to that in animals sleep deprived and sacrificed at the same diurnal time. Experiment Overall Design: Experiments were performed on male mice (C57/BL6), 10 weeks of age Â±1 week. Animals were housed in a light/dark cycle of 12 hrs, in a pathogen free, temperature- and humidity-controlled room (22Â°C and 45-55%, respectively) with water available ad libitum. Food was accessible for 12 hrs only during the active period. Animals were subjected to 14 days of acclimatization during which a nighttime feeding pattern was established. This was done to avoid differential food intake between mice that were subsequently sleep deprived during the lights on period and those allowed to sleep. Mice were sacrificed following 3, 6, 9 and 12 hrs of total sleep deprivation (n=5 at each time point). Deprivation was initiated at lights-on, and performed through gentle handling. Sleeping animals, which were left undisturbed, were sacrificed at the same diurnal time points as sleep deprived mice (n=5 at each time point). An additional control group of mice were sacrificed at time zero, i.e., at the time of lights-on (n=5). All mice were behaviorally monitored using the AccuScan infrared monitoring system that detects movement when the mouse crosses electronic beams (Columbus Instruments). Mice were sacrificed by cervical dislocation. Brain sectioning was performed according to the mouse brain atlas of Franklin and Paxinos . The primary and secondary motor areas (M1 and M2) of the cerebral cortex and broadly defined regions and zones of the hypothalamus were sampled. RNA was isolated with Trizol (Invitrogen) and further purified using RNeasy columns (Qiagen) as per the manufacturer's instructions.

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Gene expression linked to sleep homeostasis in murine cortex

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