Age Attenuates the Transcriptional Changes that Occur with Sleep in the Medial Prefrontal Cortex

Sleep abnormalities are common with aging. Studies show that sleep plays important roles in brain functions, and loss of sleep is associated with increased risks for neurological diseases. In this study, we used next generation RNA-sequencing to explore effects of age on transcriptome changes between sleep and sleep deprivation in medial prefrontal cortex. Old mice showed a 30% reduction in the number of genes significantly altered between sleep/wake, and, in general, had smaller magnitudes of changes in differentially expressed genes compared to young. Gene ontology analysis revealed differential age-effects on certain pathways. Compared to young mice, many of the wake-active functions were similarly induced by sleep deprivation in old mice, whereas many of the sleep-active pathways were attenuated in old mice. We found similar magnitude of changes in a number of synaptic homeostasis genes (Fos, Arc, and Bdnf) induced by sleep deprivation, suggesting intact synaptic upscaling during extended wakefulness with aging. However, sleep-activated processes, such as DNA repair, synaptogenesis, and axon guidance, were sensitive to the effect of aging. Old mice expressed elevated levels of immune-related genes  when compared to young mice, and enrichment analysis using cell-type specific markers indicated up-regulation of microglia and oligodendrocyte genes in old mice. Moreover, gene sets of the two cell types showed age-specific sleep/wake regulation. This study indicates alteration of molecular changes with sleep in old mice. Medial prefrontal cortex of spontaneous sleep (SS) and sleep deprived (SD) young (2-4month) and old (18-20month) mice; SD were performed for 3, 6, 9, 12 hours since lights-on (7am) and compared to time-matched SS mice slept for >=75% of last hour before sacrifice. Mice were also randomly selected at ZT0 (baseline).