The mammalian circadian clock, expressed throughout the brain and body, controls daily metabolic homeostasis. Clock function in peripheral tissues is required, but not sufficient, for this task. ...Because of the lack of specialized animal models, it is unclear how tissue clocks interact with extrinsic signals to drive molecular oscillations. Here, we isolated the interaction between feeding and the liver clock by reconstituting Bmal1 exclusively in hepatocytes (Liver-RE), in otherwise clock-less mice, and controlling timing of food intake. We found that the cooperative action of BMAL1 and the transcription factor CEBPB regulates daily liver metabolic transcriptional programs. Functionally, the liver clock and feeding rhythm are sufficient to drive temporal carbohydrate homeostasis. By contrast, liver rhythms tied to redox and lipid metabolism required communication with the skeletal muscle clock, demonstrating peripheral clock cross-talk. Our results highlight how the inner workings of the clock system rely on communicating signals to maintain daily metabolism.
Circadian rhythms coordinate biological processes with Earth's 24‐h daily light/dark cycle. In the last years, efforts in the field of chronobiology have sought to understand the ways in which the ...circadian clock controls transcription across tissues and cells. This has been supported by the development of different bioinformatic approaches that allow the identification of 24‐h oscillating transcripts. This workflow aims to describe how to isolate muscle stem cells for RNA sequencing analysis from a typical circadian experiment and introduces bioinformatic tools suitable for the analysis of circadian transcriptomes.
Muscle stem cells, ‘satellite cells’, replenish muscle fibers upon damage, and their function is influenced by circadian clocks. Characterizing circadian rhythms in satellite cells has been challenging in this low abundance cell type with available methodologies. Here, we share a workflow to compare oscillating transcripts in mouse satellite cells starting from cell isolation and ending with bioinformatic analyses.
Molecular Bases of Brain Preconditioning Deryagin, Oleg G; Gavrilova, Svetlana A; Gainutdinov, Khalil L ...
Frontiers in neuroscience,
07/2017, Letnik:
11
Journal Article
Recenzirano
Odprti dostop
Preconditioning of the brain induces tolerance to the damaging effects of ischemia and prevents cell death in ischemic penumbra. The development of this phenomenon is mediated by mitochondrial ...adenosine triphosphate-sensitive potassium (Formula: see text) channels and nitric oxide signaling (NO). The aim of this study was to investigate the dynamics of molecular changes in mitochondria after ischemic preconditioning (IP) and the effect of pharmacological preconditioning (PhP) with the Formula: see text-channels opener diazoxide on NO levels after ischemic stroke in rats. Immunofluorescence-histochemistry and laser-confocal microscopy were applied to evaluate the cortical expression of electron transport chain enzymes, mitochondrial Formula: see text-channels, neuronal and inducible NO-synthases, as well as the dynamics of nitrosylation and nitration of proteins in rats during the early and delayed phases of IP. NO cerebral content was studied with electron paramagnetic resonance (EPR) spectroscopy using spin trapping. We found that 24 h after IP in rats, there is a two-fold decrease in expression of mitochondrial Formula: see text-channels (
= 0.012) in nervous tissue, a comparable increase in expression of cytochrome c oxidase (
= 0.008), and a decrease in intensity of protein S-nitrosylation and nitration (
= 0.0004 and
= 0.001, respectively). PhP led to a 56% reduction of free NO concentration 72 h after ischemic stroke simulation (
= 0.002). We attribute this result to the restructuring of tissue energy metabolism, namely the provision of increased catalytic sites to mitochondria and the increased elimination of NO, which prevents a decrease in cell sensitivity to oxygen during subsequent periods of severe ischemia.
Tissue regeneration requires coordination between resident stem cells and local niche cells
. Here we identify that senescent cells are integral components of the skeletal muscle regenerative niche ...that repress regeneration at all stages of life. The technical limitation of senescent-cell scarcity
was overcome by combining single-cell transcriptomics and a senescent-cell enrichment sorting protocol. We identified and isolated different senescent cell types from damaged muscles of young and old mice. Deeper transcriptome, chromatin and pathway analyses revealed conservation of cell identity traits as well as two universal senescence hallmarks (inflammation and fibrosis) across cell type, regeneration time and ageing. Senescent cells create an aged-like inflamed niche that mirrors inflammation associated with ageing (inflammageing
) and arrests stem cell proliferation and regeneration. Reducing the burden of senescent cells, or reducing their inflammatory secretome through CD36 neutralization, accelerates regeneration in young and old mice. By contrast, transplantation of senescent cells delays regeneration. Our results provide a technique for isolating in vivo senescent cells, define a senescence blueprint for muscle, and uncover unproductive functional interactions between senescent cells and stem cells in regenerative niches that can be overcome. As senescent cells also accumulate in human muscles, our findings open potential paths for improving muscle repair throughout life.
A molecular clock network is crucial for daily physiology and maintaining organismal health. We examined the interactions and importance of intratissue clock networks in muscle tissue maintenance. In ...arrhythmic mice showing premature aging, we created a basic clock module involving a central and a peripheral (muscle) clock. Reconstituting the brain-muscle clock network is sufficient to preserve fundamental daily homeostatic functions and prevent premature muscle aging. However, achieving whole muscle physiology requires contributions from other peripheral clocks. Mechanistically, the muscle peripheral clock acts as a gatekeeper, selectively suppressing detrimental signals from the central clock while integrating important muscle homeostatic functions. Our research reveals the interplay between the central and peripheral clocks in daily muscle function and underscores the impact of eating patterns on these interactions.
In mammals, the circadian clock network drives daily rhythms of tissue-specific homeostasis. To dissect daily inter-tissue communication, we constructed a mouse minimal clock network comprising only ...two nodes: the peripheral epidermal clock and the central brain clock. By transcriptomic and functional characterization of this isolated connection, we identified a gatekeeping function of the peripheral tissue clock with respect to systemic inputs. The epidermal clock concurrently integrates and subverts brain signals to ensure timely execution of epidermal daily physiology. Timely cell-cycle termination in the epidermal stem cell compartment depends upon incorporation of clock-driven signals originating from the brain. In contrast, the epidermal clock corrects or outcompetes potentially disruptive feeding-related signals to ensure the optimal timing of DNA replication. Together, we present an approach for cataloging the systemic dependencies of daily temporal organization in a tissue and identify an essential gate-keeping function of peripheral circadian clocks that guarantees tissue homeostasis.
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•Brain:epidermal circadian clock communication was isolated in vivo•Circadian systemic inputs to the epidermis were defined•Peripheral clock inputs are required for full-epidermal daily physiology•The epidermal clock gates brain clock signals to ensure tissue health
Circadian clocks are present throughout the body and act in a coordinated manner to maintain organismal health. By circadian profiling of isolated brain:epidermal clock communication, Mortimer and colleagues define the circadian systemic inputs to the epidermis and a phase-shifting function for the epidermal clock toward systemic signals.
Physiology is regulated by interconnected cell and tissue circadian clocks. Disruption of the rhythms generated by the concerted activity of these clocks 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 showed that individual clocks are partially sufficient for tissue glucose metabolism, yet the connections between both tissue clocks coupled to daily feeding rhythms support 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 metabolic disease.
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•Muscle Bmal1 is partially sufficient to drive local glucose metabolism•Diurnal transcriptomes of liver and muscle are largely independent•Even in combination, liver and muscle clocks do not impart systemic glucose tolerance•Synergy between feeding rhythms and liver and muscle clocks enables glucose tolerance
Smith et al. rescued circadian clock function in liver and muscle in otherwise clock-less mice, finding that glucose tolerance is achieved only when feeding rhythms and Bmal1 function in liver and muscle are engaged simultaneously. The authors posit that disruption of this spatiotemporal mechanism contributes to circadian-disruption-induced metabolic disease.
Most cellular phenotypes are genetically complex. Identifying the set of genes that are most closely associated with a specific cellular state is still an open question in many cases. Here we study ...the transcriptional profile of cellular senescence using a combination of network-based approaches, which include eigenvector centrality feature selection and community detection. We apply our method to cell-type-resolved RNA sequencing data obtained from injured muscle tissue in mice. The analysis identifies some genetic markers consistent with previous findings, and other previously unidentified ones, which are validated with previously published single-cell RNA sequencing data in a different type of tissue. The key identified genes, both those previously known and the newly identified ones, are transcriptional targets of factors known to be associated with established hallmarks of senescence, and can thus be interpreted as molecular correlates of such hallmarks. The method proposed here could be applied to any complex cellular phenotype even when only bulk RNA sequencing is available, provided the data is resolved by cell type.
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