Extensive and Divergent Effects of Sleep and Wakefulness on Brain Gene Expression

Abstract

Sleep is present in all species where it has been studied, but its functions remain unknown. To investigate what benefits sleep may bring at the cellular level, we profiled gene expression in awake and sleeping rats by using high-density microarrays. We find that approximately 10% of the transcripts in the cerebral cortex change their expression between day and night and demonstrate that half of them are modulated by sleep and wakefulness independent of time of day. We also show that molecular correlates of sleep are found in the cerebellum, a structure not known for generating sleep rhythms. Finally, we show that different functional categories of genes are selectively associated with sleep and wakefulness. The approximately 100 known genes whose expression increases during sleep provide molecular support for the proposed involvement of sleep in protein synthesis and neural plasticity and point to a novel role for sleep in membrane trafficking and maintenance.

Rapid alterations in cortical protein profiles underlie spontaneous sleep and wake bouts

“…The detection of unique spots in each of the experimental groups provides the first evidence that alterations in protein profiles underlie spontaneous sleep-wake bouts. In addition, the percentages of state-related SYPRO Ruby expression were comparable to those reported for cortical mRNA profiles from rats sacrificed after several hours of spontaneous sleep [albeit, in the same portion of the lights-on period as our studies; Cirelli et al, 2004], suggesting that the intracellular response to sleep and waking impacts small subsets of both total cellular protein and mRNA. The analysis of phosphorylated spots suggested that cellular activities also varied across spontaneous sleep-wake states (Fig.…”

“…More recent microarray analyses showed that a small percentage of genes (i.e., 1-5%) were differentially expressed across sleep and waking states, independent of the time of day (TOD) or the brain region studied [Cirelli et al, 2004;Terao et al, 2006]. These patterns were conserved across rodent species [Terao et al, 2006] and encoded proteins associated with a variety of housekeeping functions, including energy metabolism, synaptic plasticity, membrane trafficking and maintenance, and cholesterol biosynthesis [Cirelli et al, 2004;Terao et al, 2006].…”

“…Spontaneous sleep-wakefulness or natural sleep is less well studied, based on the short, rapid cycling of sleep-wake bouts in rodents, the requirement to dissociate circadian and homeostatic influences, and the possible effects on cellular activities resulting from the practical difficulty of sacrificing a sleeping animal without first waking him up. Such technical considerations further elaborate the complexities involved in studies designed to understand the intracellular response to sleep.More recent microarray analyses showed that a small percentage of genes (i.e., 1-5%) were differentially expressed across sleep and waking states, independent of the time of day (TOD) or the brain region studied [Cirelli et al, 2004;Terao et al, 2006]. These patterns were conserved across rodent species [Terao et al, 2006] and encoded proteins associated with a variety of housekeeping functions, including energy metabolism, synaptic plasticity, membrane trafficking and maintenance, and cholesterol biosynthesis [Cirelli et al, 2004;Terao et al, 2006].…”

“…To confirm the 2DE results and begin examination of cellular mechanisms associated with sleep, the expression of two sleep-related proteins was monitored following SD by mRNA and Western analyses. Frontal cortex tissue was analyzed, as this region exhibits the electrical activities characteristic of spontaneous sleep-wakefulness [Steriade and Timofeev, 2003] and SD [Borbely and Achermann, 1999], mediates some of the cognitive deficits associated with SD [Rogers et al, 2003;Van Dongen et al, 2003] and shows alterations in mRNA profiles after periods of spontaneous sleep-wakefulness [Cirelli et al, 2004] and SD [Cirelli et al, 2004;Terao et al, 2006]. …”

“…The failure to maintain the cellular oxidation state has been proposed to account for some of the deleterious effects of SD [D'Almeida et al, 1998;Ramanathan et al, 2002] and has long been associated with the detrimental effects of aging [Zhu et al, 2006]. It is interesting to note that an increase in gst pi 2 subunit mRNA was also reported following spontaneous sleep [Cirelli et al, 2004]. Sleep may therefore play a role in the maintenance of the cellular redox state through the differential expression of proteins/mRNAs involved in the clearance of reactive oxygen species.…”