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Effects of sleep and wake on astrocytes: clues from molecular and ultrastructural studies.

Bellesi M, de Vivo L, Tononi G, Cirelli C - BMC Biol. (2015)

Bottom Line: Yet, little is known about the effects of sleep and wake on astrocytes.Wake-related changes likely reflect an increased need for glutamate clearance, and are consistent with an overall increase in synaptic strength when sleep is prevented.The reduced astrocytic coverage during sleep, instead, may favor glutamate spillover, thus promoting neuronal synchronization during non-rapid eye movement sleep.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Blvd, Madison, WI, 53719, USA. bellesi@wisc.edu.

ABSTRACT

Background: Astrocytes can mediate neurovascular coupling, modulate neuronal excitability, and promote synaptic maturation and remodeling. All these functions are likely to be modulated by the sleep/wake cycle, because brain metabolism, neuronal activity and synaptic turnover change as a function of behavioral state. Yet, little is known about the effects of sleep and wake on astrocytes.

Results: Here we show that sleep and wake strongly affect both astrocytic gene expression and ultrastructure in the mouse brain. Using translating ribosome affinity purification technology and microarrays, we find that 1.4 % of all astrocytic transcripts in the forebrain are dependent on state (three groups, sleep, wake, short sleep deprivation; six mice per group). Sleep upregulates a few select genes, like Cirp and Uba1, whereas wake upregulates many genes related to metabolism, the extracellular matrix and cytoskeleton, including Trio, Synj2 and Gem, which are involved in the elongation of peripheral astrocytic processes. Using serial block face scanning electron microscopy (three groups, sleep, short sleep deprivation, chronic sleep restriction; three mice per group, >100 spines per mouse, 3D), we find that a few hours of wake are sufficient to bring astrocytic processes closer to the synaptic cleft, while chronic sleep restriction also extends the overall astrocytic coverage of the synapse, including at the axon-spine interface, and increases the available astrocytic surface in the neuropil.

Conclusions: Wake-related changes likely reflect an increased need for glutamate clearance, and are consistent with an overall increase in synaptic strength when sleep is prevented. The reduced astrocytic coverage during sleep, instead, may favor glutamate spillover, thus promoting neuronal synchronization during non-rapid eye movement sleep.

No MeSH data available.


Related in: MedlinePlus

Functional characterization of genes differentially expressed in sleep (S) and wake (W + SD). Top: Heat diagrams show the probeset intensity for each individual animal in the three experimental conditions. Bottom: Functional annotation analysis (DAVID default settings, except for kappa = 4, similarly threshold = 0.7) for S (n = 55) and W + SD (n = 396) genes. The top eight functional annotation clusters in order of enrichment score are shown for S (left) and W + SD (right)
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Fig4: Functional characterization of genes differentially expressed in sleep (S) and wake (W + SD). Top: Heat diagrams show the probeset intensity for each individual animal in the three experimental conditions. Bottom: Functional annotation analysis (DAVID default settings, except for kappa = 4, similarly threshold = 0.7) for S (n = 55) and W + SD (n = 396) genes. The top eight functional annotation clusters in order of enrichment score are shown for S (left) and W + SD (right)

Mentions: The vast majority of genes (396, representing 1.3 % of all analyzed probesets) that changed their expression because of behavioral state were wake genes, while only 55 genes (0.1 % of all analyzed probesets) were sleep genes. A statistical approach using gene annotation enrichment analysis (DAVID) was carried out, together with an extensive analysis of the literature, to elucidate the biological processes, molecular functions and cellular components associated with sleep and wake in astrocytes (Fig. 4, Additional file 5: Table S5 and Additional file 6: Table S6). Despite the short list of sleep genes, we found enrichment of genes involved in cell development and proliferation (Pax3, Pax7, Rab38, Tsnaxip1, Spata4, Sphk2 and Pik3ca) and biosynthesis (Fbp1 and Pigs). Other sleep genes included Slc16a1, which codes for the MCT1 transporter involved in the astrocyte–neuron lactate shuttle [28, 29] and whose activity in the hippocampus is essential for long-term memory formation [30]. By contrast, the functional categories enriched during wake included cell metabolism (Adcy10, Foxf2, Cox8a, Cox19 and Ppp1r3c), nucleotide binding (Gem, Pak3, Rhoh, Trio, Kif15 and Ttl), anatomical structure development (Klf4, Cdh6, Ptp4a1, Uhrf1, Trp53, Eif2b5 and Hoxc6), endocytosis (Mrc2, Ehd2, Hip1 and Mertk), and ion binding (Kcnmb2, Kcnh5, Kcnj1 and Cacna1a). Overall, a large category of astrocytic genes modulated by behavioral state was related to the extracellular matrix and/or the cytoskeleton, including sleep genes Arap3 (involved in actin cytoskeleton remodeling), collagen type IV alpha 4 (Col4a4), Ceacam1, the actinin-associated LIM protein Pdlim3, and actin gamma (Actg1). Wake genes included Trio, Gem and Synj2, all of which have been involved in cytoskeleton modifications and the elongation of astrocytic processes, as well as genes coding for integrins (Itgal, Itgb6 and Itgb1) and other extracellular matrix proteins (Efemp2, Emilin3 and Emid2), the mannose receptor C2 that binds and internalizes collagen (Mrc2), the proteoglycan syndecan 4 (Sdc4), the endoglycosidase heparanase (Hpse), and others (Mitd1, Ptp4a1, Ehd2, Nrap and Smagp).Fig. 4


Effects of sleep and wake on astrocytes: clues from molecular and ultrastructural studies.

Bellesi M, de Vivo L, Tononi G, Cirelli C - BMC Biol. (2015)

Functional characterization of genes differentially expressed in sleep (S) and wake (W + SD). Top: Heat diagrams show the probeset intensity for each individual animal in the three experimental conditions. Bottom: Functional annotation analysis (DAVID default settings, except for kappa = 4, similarly threshold = 0.7) for S (n = 55) and W + SD (n = 396) genes. The top eight functional annotation clusters in order of enrichment score are shown for S (left) and W + SD (right)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4548305&req=5

Fig4: Functional characterization of genes differentially expressed in sleep (S) and wake (W + SD). Top: Heat diagrams show the probeset intensity for each individual animal in the three experimental conditions. Bottom: Functional annotation analysis (DAVID default settings, except for kappa = 4, similarly threshold = 0.7) for S (n = 55) and W + SD (n = 396) genes. The top eight functional annotation clusters in order of enrichment score are shown for S (left) and W + SD (right)
Mentions: The vast majority of genes (396, representing 1.3 % of all analyzed probesets) that changed their expression because of behavioral state were wake genes, while only 55 genes (0.1 % of all analyzed probesets) were sleep genes. A statistical approach using gene annotation enrichment analysis (DAVID) was carried out, together with an extensive analysis of the literature, to elucidate the biological processes, molecular functions and cellular components associated with sleep and wake in astrocytes (Fig. 4, Additional file 5: Table S5 and Additional file 6: Table S6). Despite the short list of sleep genes, we found enrichment of genes involved in cell development and proliferation (Pax3, Pax7, Rab38, Tsnaxip1, Spata4, Sphk2 and Pik3ca) and biosynthesis (Fbp1 and Pigs). Other sleep genes included Slc16a1, which codes for the MCT1 transporter involved in the astrocyte–neuron lactate shuttle [28, 29] and whose activity in the hippocampus is essential for long-term memory formation [30]. By contrast, the functional categories enriched during wake included cell metabolism (Adcy10, Foxf2, Cox8a, Cox19 and Ppp1r3c), nucleotide binding (Gem, Pak3, Rhoh, Trio, Kif15 and Ttl), anatomical structure development (Klf4, Cdh6, Ptp4a1, Uhrf1, Trp53, Eif2b5 and Hoxc6), endocytosis (Mrc2, Ehd2, Hip1 and Mertk), and ion binding (Kcnmb2, Kcnh5, Kcnj1 and Cacna1a). Overall, a large category of astrocytic genes modulated by behavioral state was related to the extracellular matrix and/or the cytoskeleton, including sleep genes Arap3 (involved in actin cytoskeleton remodeling), collagen type IV alpha 4 (Col4a4), Ceacam1, the actinin-associated LIM protein Pdlim3, and actin gamma (Actg1). Wake genes included Trio, Gem and Synj2, all of which have been involved in cytoskeleton modifications and the elongation of astrocytic processes, as well as genes coding for integrins (Itgal, Itgb6 and Itgb1) and other extracellular matrix proteins (Efemp2, Emilin3 and Emid2), the mannose receptor C2 that binds and internalizes collagen (Mrc2), the proteoglycan syndecan 4 (Sdc4), the endoglycosidase heparanase (Hpse), and others (Mitd1, Ptp4a1, Ehd2, Nrap and Smagp).Fig. 4

Bottom Line: Yet, little is known about the effects of sleep and wake on astrocytes.Wake-related changes likely reflect an increased need for glutamate clearance, and are consistent with an overall increase in synaptic strength when sleep is prevented.The reduced astrocytic coverage during sleep, instead, may favor glutamate spillover, thus promoting neuronal synchronization during non-rapid eye movement sleep.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Blvd, Madison, WI, 53719, USA. bellesi@wisc.edu.

ABSTRACT

Background: Astrocytes can mediate neurovascular coupling, modulate neuronal excitability, and promote synaptic maturation and remodeling. All these functions are likely to be modulated by the sleep/wake cycle, because brain metabolism, neuronal activity and synaptic turnover change as a function of behavioral state. Yet, little is known about the effects of sleep and wake on astrocytes.

Results: Here we show that sleep and wake strongly affect both astrocytic gene expression and ultrastructure in the mouse brain. Using translating ribosome affinity purification technology and microarrays, we find that 1.4 % of all astrocytic transcripts in the forebrain are dependent on state (three groups, sleep, wake, short sleep deprivation; six mice per group). Sleep upregulates a few select genes, like Cirp and Uba1, whereas wake upregulates many genes related to metabolism, the extracellular matrix and cytoskeleton, including Trio, Synj2 and Gem, which are involved in the elongation of peripheral astrocytic processes. Using serial block face scanning electron microscopy (three groups, sleep, short sleep deprivation, chronic sleep restriction; three mice per group, >100 spines per mouse, 3D), we find that a few hours of wake are sufficient to bring astrocytic processes closer to the synaptic cleft, while chronic sleep restriction also extends the overall astrocytic coverage of the synapse, including at the axon-spine interface, and increases the available astrocytic surface in the neuropil.

Conclusions: Wake-related changes likely reflect an increased need for glutamate clearance, and are consistent with an overall increase in synaptic strength when sleep is prevented. The reduced astrocytic coverage during sleep, instead, may favor glutamate spillover, thus promoting neuronal synchronization during non-rapid eye movement sleep.

No MeSH data available.


Related in: MedlinePlus