Circadian rhythm disruption in a mouse model of Rett syndrome circadian disruption in RTT

• Sleep and circadian rhythms were disrupted in a model of RTT (Mecp2−/y mice).
• Mutant SCN showed reduced numbers of VIP + neurons.
• Neural activity rhythms were compromised at the level of the SCN.
• The molecular clockwork was disrupted throughout the organism.
• Chronic jet lag accelerated mortality in the mutants.

Disturbances in the sleep/wake cycle are prevalent in patients with Rett syndrome (RTT). We sought to determine whether the circadian system is disrupted in a RTT model, Mecp2−/y mice. We found that MeCP2 mutants showed decreased strength and precision of daily rhythms of activity coupled with extremely fragmented sleep. The central circadian clock (suprachiasmatic nucleus) exhibited significant reduction in the number of neurons expressing vasoactive intestinal peptide (VIP) as well as compromised spontaneous neural activity. The molecular clockwork was disrupted both centrally in the SCN and in peripheral organs, indicating a general disorganization of the circadian system. Disruption of the molecular clockwork was observed in fibroblasts of RTT patients. Finally, MeCP2 mutant mice were vulnerable to circadian disruption as chronic jet lag accelerated mortality. Our finds suggest an integral role of MeCP2 in the circadian timing system and provides a possible mechanistic explanation for the sleep/wake distrubances observed in RTT patients. The work raises the possibility that RTT patients may benefit from a temporally structured environment.