Loss of MeCP2 leads to sleep deficits that are time-of-day dependent and worsen with sleep deprivation

Rett syndrome (RTT) is a severe, progressive neurodevelopmental disorder caused by mutations in the X-linked gene encoding methyl-CpG-binding protein 2 (<i>MECP2</i>). Sleep problems are frequently reported in Rett Syndrome, but the exact nature remains relatively unexplored. Currently there is limited understanding of MECP2's role in sleep architecture and regulation. In this study, we employed longitudinal electroencephalographic (EEG) and electromyographic (EMG) recordings to investigate sleep architecture during baseline conditions as well as the homeostatic response to sleep deprivation (SD) in <i>Mecp</i>2^-/y male mice. At baseline, <i>Mecp</i>2^-/y mice have more non-rapid-eye-movement (NREM) sleep and less rapid-eye-movement (REM) sleep than their wildtype littermates during the light period. However, <i>Mecp</i>2^-/y mice display altered sleep timing during the dark period, spending more time in both NREM and REM during the first half and less time during the second half. <i>Mecp</i>2^-/y mice also have lower EEG spectral power during wake and NREM at higher frequencies and higher power at lower frequencies during REM in compared to wildtype mice. In response to SD, <i>Mecp</i>2^-/y mice can accumulate and discharge sleep pressure normally and show a sleep rebound. However, baseline differences in sleep architecture are heightened after SD. Overall, our findings show that RTT mice exhibit distinct sleep patterns compared to wildtype mice, with time-of-day-dependent variations in NREM and REM sleep, as well as altered EEG spectral properties, that become more pronounced following SD. Future research should explore the molecular mechanisms through which MECP2 regulates sleep architecture to develop targeted therapeutics for sleep disturbances in RTT patients.