Tingting Lou’s research while affiliated with University of Tsukuba and other places

Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is an X-linked rare neurodevelopmental disorder associated with severe sleep disturbances. However, little is known about the mechanisms underlying sleep disturbances in CDD patients. Here, we employed the electroencephalogram (EEG) recording to characterize sleep–wake behaviors and EEG activity in male CDKL5-deficient mice. We found that young adult and middle-aged Cdkl5 knockout (KO) mice recapitulated sleep phenotypes in patients with CDD, including difficulties in initiating and maintaining sleep, reduction in total sleep time, and frequent night awakenings. Cdkl5 KO mice exhibited pre-sleep arousal, but normal circadian rhythm and homeostatic sleep response. Conditional knockout (cKO) of Cdkl5 in glutamatergic neurons resulted in reduced sleep time and difficulty in sleep maintenance. Further, the rate of age-associated decline in sleep and EEG activity in Cdkl5 KO mice was comparable to that of wild-type littermates. Together, these results confirm a causative role for CDKL5 deficiency in sleep disturbances observed in CDD patients and establish an animal model for translational research of sleep treatment in CDD. Moreover, our results provide valuable information for developing therapeutic strategies and identifying sleep and EEG parameters as potential biomarkers for facilitating preclinical and clinical trials in CDD.

Sleep disturbances have been recognized as a core symptom of post-traumatic stress disorders (PTSD). However, the neural basis of PTSD-related sleep disturbances remains unclear. It has been challenging to establish the causality link between a specific brain region and traumatic stress-induced sleep abnormalities. Here, we found that single prolonged stress (SPS) could induce acute changes in sleep/wake duration as well as short- and long-term electroencephalogram (EEG) alterations in the isogenic mouse model. Moreover, the medial prefrontal cortex (mPFC) showed persistent high number of c-fos expressing neurons, of which more than 95% are excitatory neurons, during and immediately after SPS. Chemogenetic inhibition of the prelimbic region of mPFC during SPS could specifically reverse the SPS-induced acute suppression of delta power (1–4 Hz EEG) of non-rapid-eye-movement sleep (NREMS) as well as most of long-term EEG abnormalities. These findings suggest a causality link between hyper-activation of mPFC neurons and traumatic stress-induced specific sleep–wake EEG disturbances.

Sleep and wake have global effects on brain physiology, from molecular changes1-4 and neuronal activities to synaptic plasticity3-7. Sleep-wake homeostasis is maintained by the generation of a sleep need that accumulates during waking and dissipates during sleep8-11. Here we investigate the molecular basis of sleep need using quantitative phosphoproteomic analysis of the sleep-deprived and Sleepy mouse models of increased sleep need. Sleep deprivation induces cumulative phosphorylation of the brain proteome, which dissipates during sleep. Sleepy mice, owing to a gain-of-function mutation in the Sik3 gene 12 , have a constitutively high sleep need despite increased sleep amount. The brain proteome of these mice exhibits hyperphosphorylation, similar to that seen in the brain of sleep-deprived mice. Comparison of the two models identifies 80 mostly synaptic sleep-need-index phosphoproteins (SNIPPs), in which phosphorylation states closely parallel changes of sleep need. SLEEPY, the mutant SIK3 protein, preferentially associates with and phosphorylates SNIPPs. Inhibition of SIK3 activity reduces phosphorylation of SNIPPs and slow wave activity during non-rapid-eye-movement sleep, the best known measurable index of sleep need, in both Sleepy mice and sleep-deprived wild-type mice. Our results suggest that phosphorylation of SNIPPs accumulates and dissipates in relation to sleep need, and therefore SNIPP phosphorylation is a molecular signature of sleep need. Whereas waking encodes memories by potentiating synapses, sleep consolidates memories and restores synaptic homeostasis by globally downscaling excitatory synapses4-6. Thus, the phosphorylation-dephosphorylation cycle of SNIPPs may represent a major regulatory mechanism that underlies both synaptic homeostasis and sleep-wake homeostasis.