Project description:The fragile X autosomal homolog 1 (Fxr1) is regulated by lithium and has been GWAS-associated with schizophrenia and insomnia. Homeostatic regulation of synaptic strength is essential for the maintenance of brain functions and involves both cell-autonomous and system-level processes such as sleep. We examined the contribution of Fxr1 to cell-autonomous homeostatic synaptic scaling and neuronal responses to sleep loss, using a combination of gene overexpression and Crispr/Cas9-mediated somatic knockouts to modulate gene expression. Our findings indicate that Fxr1 is downregulated during both scaling and sleep deprivation via a glycogen synthase kinase 3 beta (GSK3β)-dependent mechanism. In both conditions, downregulation of Fxr1 is essential for the homeostatic modulation of surface AMPA receptors and synaptic strength. Preventing the downregulation of Fxr1 during sleep deprivation results in altered EEG signatures. Furthermore, sequencing of neuronal translatomes revealed the contribution of Fxr1 to changes induced by sleep deprivation. These findings uncover a role of Fxr1 as a shared signaling hub between cell-autonomous homeostatic plasticity and system-level responses to sleep loss, with potential implications for neuropsychiatric illnesses and treatments.
Project description:Circadian rhythms are present across almost all species and affect several physiological and behavioral aspects of living organisms. The evolutionary advantage conferred by these rhythms could be their anticipatory properties. In the nervous system, anticipation is particularly interesting due to the spatiotemporal constraints derived by the highly compartmentalized neuronal structure. Previous work has confirmed that 900 genes are expressed in the mouse forebrain in robustly rhythmic fashion, and 180 transcripts are equally robustly circadian at the synapse. Interestingly, mRNAs are found in higher amounts at the end of the dark phase, and decrease exponentially during the first hours of light. This pattern resembles the “sawtooth” pattern of homeostatic sleep pressure. To further characterize this phenotype we propose to compare the synaptic transcriptome of sleep deprived mice to its control base line. This work would shed light into the emerging field of synaptic RNA transport and translation and its regulatory inputs. Hopefully, the results will yield to two different findings: the circadian and activity potential to regulate synaptic transport of RNA and the classification of transcripts deferentially regulated by both processes.
Project description:The circadian clock drives daily changes of physiology, including sleep-wake cycles, by regulating transcription, protein abundance and function. Circadian phosphorylation controls cellular processes in peripheral organs, but little is known about its role in brain function and synaptic activity. We applied advanced quantitative phosphoproteomics to mouse forebrain synaptoneurosomes isolated across 24h, accurately quantifying almost 8,000 phosphopeptides. Remarkably, half of the synaptic phosphoproteins, including numerous kinases, had large-amplitude rhythms peaking at rest-activity and activity-rest transitions. Bioinformatic analyses revealed global temporal control of synaptic function via phosphorylation, including synaptic transmission, cytoskeleton reorganization and excitatory/inhibitory balance. Remarkably, sleep deprivation abolished 98% of all phosphorylation cycles in synaptoneurosomes, indicating that sleep-wake cycles rather than circadian signals are main drivers of synaptic phosphorylation, responding to both sleep and wake pressures.
Project description:In the associated paper FXR1 is shown to package exceptionally long mRNAs in the cytoplasm and organizes them into an mRNP network. We performed iCLIP of FXR-WT and its mutant FXR1-V361P in HeLa cells where we knocked down endogenous FXR1 and replaced it with either GFP-tagged WT or V361P-mutant FXR1. The GFP-tagged proteins were immunoprecipitated using an anti-GFP antibody.
Project description:Every day, we sleep for a third of the day. Sleep is important for cognition, brain waste clearance, metabolism, and immune responses. Homeostatic regulation of sleep is maintained by progressively rising sleep need during wakefulness, which then dissipates during sleep. The molecular mechanisms governing sleep are largely unknown. Here, we used a combination of single-cell RNA sequencing and cell-type specific proteomics to interrogate the molecular and functional underpinnings of sleep. Different cell-types in the brain regions show similar transcriptional response to sleep need whereas sleep deprivation changes overall expression indicative of altered antigen processing, synaptic transmission and cellular metabolism in brainstem, cortex and hypothalamus, respectively. Increased sleep need enhances expression of transcription factor Sox2, Mafb, and Zic1 in brainstem; Hlf, Cebpb and Sox9 in cortex, and Atf3, Fosb and Mef2c in hypothalamus. Results from cell-type proteome analysis suggest that sleep deprivation changes abundance of proteins in cortical neurons indicative of altered synaptic vesicle cycles and glucose metabolism whereas in astrocytes it alters the abundance of proteins associated with fatty acid degradation. Similarly, phosphoproteomics of each cell type demonstrates large shifts in site-specific protein phosphorylation in neurons and astrocytes of sleep deprived mice. Our results indicate that sleep deprivation regulates transcriptional, translational and post-translational responses in a cell-specific manner and advances our understanding of the cellular and molecular mechanisms that govern sleep-wake homeostasis in mammals.
Project description:In Alzheimer’s disease (AD), pathophysiological changes in the hippocampus cause deficits in episodic memory formation, leading to cognitive impairment. Hippocampal hyperactivity and decreased sleep quality are associated with early AD, but their basis is poorly understood. We find that homeostatic mechanisms transiently counteract increased excitatory drive of hippocampal CA1 neurons in AppNL-G-F mice, but fail to stabilize it at control levels. Spatial transcriptomics (ST) analysis identifies the Pmch gene encoding Melanin-Concentrating Hormone (MCH) as part of the adaptive response in AppNL-G-F mice. Hypothalamic MCH peptide is produced in sleep-active lateral hypothalamic neurons that project to CA1 and modulate memory. We show that MCH downregulates synaptic transmission and modulates firing rate homeostasis in hippocampal neurons. Moreover, MCH reverses the increased excitatory drive of CA1 neurons in AppNL-G-F mice. Consistent with our finding that a reduced fraction of MCH-neurons is active in AppNL-G-F mice, these animals spend less time in rapid eye movement (REM) sleep. In addition, MCH-axons projecting to CA1 become progressively impaired in both AppNL-G-F mice and AD patients. Our findings identify the MCH-system as vulnerable in early AD and suggest that impaired MCH-system function contributes to aberrant excitatory drive and sleep defects, which can compromise hippocampal-dependent functions.
Project description: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.
Project description:Sleep supports lifelong brain health and cognition. Sleep loss in early life can drive lasting changes in adult behavior, indicating sleep plays a distinct but poorly understood role supporting brain development. We systematically examined the molecular and behavioral adaptations and synaptic consequences of acute sleep deprivation (SD) in developing and adult mice. Developing mice lack robust adaptations to SD, exacerbating cognitive deficits. Synapse proteome and phosphoproteome analysis revealed profound vulnerability to SD in developing mice, including immediate impacts on synaptogenesis and key aspects of brain development. With maturation, a unified biochemical effect of sleep on synapses emerges, together with robust adaptations and resilience to SD. Our findings show sleep plays a distinct role in early life supporting synapse development, transitioning to homeostatic functions with maturation.