Circadian Rhythms and Sleep Are Dependent Upon Expression Levels of Key Ubiquitin Ligase Ube3a

Sleep disturbance in Angelman syndrome patients

Angelman syndrome (AS) is a neurodevelopmental disorder caused by abnormal expression of the maternal ubiquitin protein ligase E3A gene (UBE3A). As one of the most challenging symptoms and important focuses of new treatment, sleep disturbance is reported to occur in 70-80% of patients with AS and has a serious impact on the lives of patients and their families. Although clinical studies and animal model studies have provided some clues, recent research into sleep disorders in the context of AS is still very limited. It is generally accepted that there is an interaction between neurodevelopment and sleep; however, there is no recognized mechanism for sleep disorders in AS patients. Accordingly, there are no aetiologically specific clinical treatments for AS-related sleep disorders. The most common approaches involve ameliorating symptoms through methods such as behavioural therapy and symptomatic pharmacotherapy. In recent years, preclinical and clinical studies on the targeted treatment of AS have emerged. Although precision therapy for restoring the UBE3A level and the function of its signalling pathways is inevitably hindered by many remaining obstacles, this approach has the potential to address AS-related sleep disturbance.

Reanalysis of primate brain circadian transcriptomics reveals connectivity-related oscillations

Research shows that brain circuits controlling vital physiological processes are closely linked with endogenous time-keeping systems. In this study, we aimed to examine oscillatory gene expression patterns of well-characterized neuronal circuits by reanalyzing publicly available transcriptomic data from a spatiotemporal gene expression atlas of a non-human primate. Unexpectedly, brain structures known for regulating circadian processes (e.g., hypothalamic nuclei) did not exhibit robust cycling expression. In contrast, basal ganglia nuclei, not typically associated with circadian physiology, displayed the most dynamic cycling behavior of its genes marked by sharp temporally defined expression peaks. Intriguingly, the mammillary bodies, considered hypothalamic nuclei, exhibited gene expression patterns resembling the basal ganglia, prompting reevaluation of their classification. Our results emphasize the potential for high throughput circadian gene expression analysis to deepen our understanding of the functional synchronization across brain structures that influence physiological processes and resulting complex behaviors.

Adolescent sleep defects and dopaminergic hyperactivity in mice with a schizophrenia-linked Shank3 mutation

Shank3 is a shared risk gene for autism spectrum disorders and schizophrenia. Sleep defects have been characterized for autism models with Shank3 mutations; however, evidence has been lacking for the potential sleep defects caused by Shank3 mutation associated with schizophrenia and how early in development these defects may occur. Here we characterized the sleep architecture of adolescent mice carrying a schizophrenia-linked, R1117X mutation in Shank3. We further employed GRABDA dopamine sensor and fiber photometry to record dopamine release in the nucleus accumbens during sleep/wake states. Our results show that homozygous mutant R1117X mice have significantly reduced sleep in the dark phase during adolescence, altered electroencephalogram power, especially during the rapid-eye-movement sleep, and dopamine hyperactivity during sleep but not during wakefulness. Further analyses suggest that these adolescent defects in sleep architecture and dopaminergic neuromodulation tightly correlate with the social novelty preference later in adulthood and predict adult social performance during same-sex social interactions. Our results provide novel insights into the sleep phenotypes in mouse models of schizophrenia and the potential use of developmental sleep as a predictive metric for adult social symptoms. Together with recent studies in other Shank3 models, our work underscores the idea that Shank3-involved circuit disruptions may be one of the shared pathologies in certain types of schizophrenia and autism. Future research is needed to establish the causal relationship among adolescent sleep defects, dopaminergic dysregulation, and adult behavioral changes in Shank3 mutation animals and other models.

Sleep problems in children with Angelman Syndrome: The effect of a behavioral intervention program

BACKGROUND & AIMS

The aim of this study was to investigate the effect of a behavioral intervention on sleep problems, which are significant and an unmet clinical need in children with Angelman Syndrome (AS).

METHODS & PROCEDURES

Children (2-18 years) with AS and sleep problems were randomized to a behavioral intervention program or a control group. Intervention consisted of a standardized program including home visits, psycho-education, feedback based on direct observation of bedtime routine and video footage of the night and behavioral treatment techniques by a behavioral therapist. Change in sleep duration (primary) and parental sleep, nighttime visits, sleep hygiene, daytime behavior, parental stress and quality of life (secondary) were assessed post-intervention and at follow-up using questionnaires, diary, actigraphy and videosomnography.

OUTCOMES & RESULTS

The groups, 9 children in each, did not differ at baseline. We found a significant effect of intervention on wake after sleep onset with classical statistical analysis (videosomnography). With single case analysis we found a positive effect on total sleep time (diary and actigraphy) and wake after sleep onset (diary) with a persistent effect on total sleep time (actigraphy) and wake after sleep onset (diary). On secondary outcome there was a significant and persistent effect on sleep hygiene and several quality of life domains.

CONCLUSIONS & IMPLICATIONS

Behavioral intervention has a positive and persistent effect on sleep problems in children with AS. We advise psycho-education for all parents and use of videosomnography for both evaluation of and feedback on sleep behavior patterns, individual behavioral advice and specific behavioral techniques for children with sleep problems.

Antisense oligonucleotide therapy rescues disturbed brain rhythms and sleep in juvenile and adult mouse models of Angelman syndrome

UBE3A encodes ubiquitin protein ligase E3A, and in neurons its expression from the paternal allele is repressed by the UBE3A antisense transcript (UBE3A-ATS). This leaves neurons susceptible to loss-of-function of maternal UBE3A. Indeed, Angelman syndrome, a severe neurodevelopmental disorder, is caused by maternal UBE3A deficiency. A promising therapeutic approach to treating Angelman syndrome is to reactivate the intact paternal UBE3A by suppressing UBE3A-ATS. Prior studies show that many neurological phenotypes of maternal Ube3a knockout mice can only be rescued by reinstating Ube3a expression in early development, indicating a restricted therapeutic window for Angelman syndrome. Here, we report that reducing Ube3a-ATS by antisense oligonucleotides in juvenile or adult maternal Ube3a knockout mice rescues the abnormal electroencephalogram (EEG) rhythms and sleep disturbance, two prominent clinical features of Angelman syndrome. Importantly, the degree of phenotypic improvement correlates with the increase of Ube3a protein levels. These results indicate that the therapeutic window of genetic therapies for Angelman syndrome is broader than previously thought, and EEG power spectrum and sleep architecture should be used to evaluate the clinical efficacy of therapies.

Death of a Protein: The Role of E3 Ubiquitin Ligases in Circadian Rhythms of Mice and Flies

Circadian clocks evolved to enable organisms to anticipate and prepare for periodic environmental changes driven by the day–night cycle. This internal timekeeping mechanism is built on autoregulatory transcription–translation feedback loops that control the rhythmic expression of core clock genes and their protein products. The levels of clock proteins rise and ebb throughout a 24-h period through their rhythmic synthesis and destruction. In the ubiquitin–proteasome system, the process of polyubiquitination, or the covalent attachment of a ubiquitin chain, marks a protein for degradation by the 26S proteasome. The process is regulated by E3 ubiquitin ligases, which recognize specific substrates for ubiquitination. In this review, we summarize the roles that known E3 ubiquitin ligases play in the circadian clocks of two popular model organisms: mice and fruit flies. We also discuss emerging evidence that implicates the N-degron pathway, an alternative proteolytic system, in the regulation of circadian rhythms. We conclude the review with our perspectives on the potential for the proteolytic and non-proteolytic functions of E3 ubiquitin ligases within the circadian clock system.