Angelman Research Articles

Variance in the pathophysiological impact of the hemizygosity of gamma-aminobutyric acid type A receptor subunit genes between Prader-Willi syndrome and Angelman syndrome

IntroductionAngelman syndrome (AS) and Prader-Willi syndrome (PWS) are neurodevelopmental disorders caused by loss of function of maternally expressed UBE3A and paternally expressed contiguous genes on chromosome 15q11-13, respectively. A majority of these syndromes suffer from a large deletion of the relevant chromosome (AS Del or PWS Del), which includes biallelically expressed gamma-aminobutyric acid type A receptor subunit (GABAaR) genes, while remaining individuals present without the deletion (AS non-Del or PWS non-Del). We previously reported that AS Del, but not AS non-Del individuals, show aberrantly desynchronized somatosensory-evoked magnetic fields (SEFs) and speculated that it might reflect GABAergic dysfunction due to the hemizygosity of GABAaR genes. To verify its pathophysiological impact on PWS and AS, we analyzed the SEFs of PWS individuals. MethodSEFs were recorded from eight PWS Del and two PWS non-Del individuals. The latency and strength of the first peak (N1m) were compared with those of AS Del/non-Del individuals and controls, most of which were obtained earlier. ResultsIn contrast to AS, both PWS Del and PWS non-Del showed normal SEF waveforms. Desynchronized response with delayed N1m peak latency was exclusively indicated in AS Del. N1m strength was statistically higher in AS Del and AS non-Del, but not in PWS Del and PWS non-Del. ConclusionsOur results indicate that the pathophysiological impact of the hemizygosity of GABAaR genes is lower in PWS than AS. UBE3A deficiency and the hemizygosity of GABAaR genes could synergistically deteriorate neuronal function, resulting in aberrant SEFs in AS Del.

Development of an adapted Clinical Global Impression scale for use in Angelman syndrome

BackgroundThe Clinical Global Impression-Severity (CGI-S) and CGI-Improvement (CGI-I) scales are widely accepted tools that measure overall disease severity and change, synthesizing the clinician’s impression of the global state of an individual. Frequently employed in clinical trials for neuropsychiatric disorders, the CGI scales are typically used in conjunction with disease-specific rating scales. When no disease-specific rating scale is available, the CGI scales can be adapted to reflect the specific symptom domains that are relevant to the disorder. Angelman syndrome (AS) is a rare, clinically heterogeneous condition for which there is no disease-specific rating scale. This paper describes efforts to develop standardized, adapted CGI scales specific to AS for use in clinical trials.MethodsIn order to develop adapted CGI scales specific to AS, we (1) reviewed literature and interviewed caregivers and clinicians to determine the most impactful symptoms, (2) engaged expert panels to define and operationalize the symptom domains identified, (3) developed detailed rating anchors for each domain and for global severity and improvement ratings, (4) reviewed the anchors with expert clinicians and established minimally clinically meaningful change for each symptom domain, and (5) generated mock patient vignettes to test the reliability of the resulting scales and to standardize rater training. This systematic approach to developing, validating, and training raters on a standardized, adapted CGI scale specifically for AS is described herein.ResultsThe resulting CGI-S/I-AS scales capture six critical domains (behavior, gross and fine motor function, expressive and receptive communication, and sleep) defined by caregivers and expert clinicians as the most challenging for patients with AS and their families.ConclusionsRigorous training and careful calibration for clinicians will allow the CGI-S/-I-AS scales to be reliable in the context of randomized controlled trials. The CGI-S/-I-AS scales are being utilized in a Phase 3 trial of gaboxadol for the treatment of AS.

Flurothyl-induced seizure paradigm revealed higher seizure susceptibility in middle-aged Angelman syndrome mouse model

IntroductionEpilepsy is one of the main clinical problems in Angelman syndrome (AS). Seizures typically start in early childhood then decrease or are often alleviated by young adulthood. Several studies using AS model mice showed comparable seizure susceptibility during young adulthood. In contrast, the course of epilepsy post young adulthood differs from persistently relieved to rerising among reports. To elucidate this, we evaluated the seizure susceptibility of AS model mice of two different ages. MethodsMice lacking maternal Ube3a gene (Ube3am–/p+) of C57BL/6 background or their littermate wild type (WT) were divided into two groups by age, 2 to 3 months (2–3 M) and 6 to 12 months (6–12 M), corresponding to adolescent to young adult aged and middle aged humans, respectively. Seizure susceptibility was evaluated by flurothyl inhalation or intraperitoneal injection of pentylenetetrazole (PTZ IP)-induced acute seizure protocol. ResultsIn the flurothyl-induced seizure paradigm, the latency to seizure occurrence had a significant interaction with genotype and age. Post-hoc analysis revealed that the latency was significantly shorter at 6–12 M than at 2–3 M in Ube3am-/p+ mice, and in Ube3am-/p+ mice than in WT mice at 6–12 M. No significant interaction or difference was observed by PTZ IP. ConclusionThe flurothyl-induced seizure paradigm revealed that seizure susceptibility of Ube3am-/p+ mice increased with age, similar to clinical studies reporting the reappearance of epilepsy in older age. The flurothyl-induced seizure paradigm applied to middle-aged Ube3am–/p+ mice could be a suitable protocol for screening drugs against seizures in AS.

Kliničke i kognitivne karakteristike Angelmanovog sindroma

Introduction. Angelman syndrome, as a rare genetic and neurodevelopmental disorder characterized by severe intellectual deficit and falling behind in psychomotor development, represents a challenge for adequate and correct creation of individual (rehabilitation procedure. More precise determination of cognitive and speech profile is difficult due to integrative hypermotor behavior and attention and speech deficits. Objective. The aim of this paper was to analyze and summarize empirical data on clinical, cognitive and speech characteristics of Angelman syndrome. Methods. A systematic review of the literature published in peer-reviewed publications, from 2001 to June 5, 2021, was performed by searching electronic databases available through the service of the Serbian Library Consortium for Coordinated Acquisition - KOBSON. A "hand search" (Research Gate and Google Scholar) was also used. Results. The analyzed results of the research indicate that the presence of sensorimotor schemes that represent cognitive structures of the earliest childhood is characteristic for Angelman syndrome. Receptive speech skills are more developed than expressive ones, which usually do not exist. Supportive therapy, which includes interventions in early childhood, speech therapy and occupational programs, is very important for treatment within this clinical picture. Conclusion. It is necessary to improve the process of assessing cognitive and speech skills due to the targeted creation of an individual cognitive-speech developmental profile. It is also crucial to identify urgent areas that require treatment and in which individual and family support should be provided.

Angelman Syndrome in a Filipino Child

Angelman syndrome (AS) is a distinct condition that presents with severe developmental delay. This condition also presents with speech impairment, ataxia/tremor, and inappropriate laughter. Some other features in most patients include microcephaly, seizures, tongue protrusion, wide mouth, and hypopigmentation. This case aims to emphasize the value of diagnosis in a patient with developmental delay. The diagnosis allows anticipation of the development of other possible problems and guides appropriate management. This report also aims to increase awareness regarding the condition. Here we present a 71-month-old Filipino male with developmental delay at six months, seizures at 10 months with a note of an overall happy demeanor and frequent inappropriate bouts of laughter at one year old. The patient also presented with severe stunting, microcephaly, wide mouth and ataxic gait. Through pattern recognition and the updated consensus of its diagnostic criteria, and confirmation via fluorescence in situ hybridization (FISH), which revealed a deletion in chromosome 15q11, the diagnosis of AS was made. This case re-emphasizes the role of clinical recognition of this condition and its confirmation via cytogenetic techniques like FISH, which will aid appropriate management and counseling for the patient and their families.

One-shot gene therapy for Angelman syndrome shows promise in mice

One-shot gene therapy for Angelman syndrome shows promise in mice

Paused Angelman syndrome trial to restart

Paused Angelman syndrome trial to restart

Emerging Therapies and challenges for individuals with Angelman syndrome.

This review describes current understandings in the search for therapies to support children with Angelman syndrome. There is a rapid progression in particular in genetic therapies in this disorder supported by the Angelman community. Recent papers shed light on the timing of therapies and novel genetic therapies coming to trial as well as potential therapies still in preclinical phases. Further understanding of UBE3A and its role in neuronal development and plasticity as well as other mechanisms contributing to the Angelman phenotype is offering an opportunity for novel therapeutics. Greater understanding of the pathophysiology of the different phenotypes will offer an opportunity for novel therapeutics and may well change the course of this disorder over time where previously there has been minimal ability to intervene.

Structural validity of the Child Behavior Checklist (CBCL) for preschoolers with neurogenetic syndromes

BackgroundPsychologists routinely use the Child Behavior Checklist for Ages 1½–5 (CBCL) to assess challenging behaviors of preschoolers with developmental disabilities. However, the CBCL has not been thoroughly validated in neurogenetic syndromes (NGS). AimWe investigated the structural validity of the CBCL in NGS. MethodsBased on 152 preschoolers with Angelman, fragile X, Prader-Willi, and Williams syndromes, we employed confirmatory factor analysis (CFA) to evaluate the goodness-of-fit of CBCL narrowband, broadband, and DSM-oriented scales. ResultsCFA models largely supported the unidimensionality of most narrowband scales and the two-factor structure of internalizing and externalizing broadband scales. However, there was limited evidence for the unidimensionality of most DSM-oriented scales. ConclusionsPsychologists may consider using the CBCL as a psychometrically sound narrowband and broadband measure of challenging behaviors but should exercise caution when interpreting DSM-oriented scales for preschoolers with NGS. Our findings underscore a continued need to enhance assessment measures for identifying early precursors of child psychopathology in pediatric populations with atypical developmental trajectories.

The STARS Phase 2 Study: A Randomized Controlled Trial of Gaboxadol in Angelman Syndrome.

ObjectiveTo evaluate safety and tolerability and exploratory efficacy end points for gaboxadol (OV101) compared with placebo in individuals with Angelman syndrome (AS).MethodsGaboxadol is a highly selective orthosteric agonist that activates δ-subunit–containing extrasynaptic γ-aminobutyric acid type A (GABAA) receptors. In a multicenter, double-blind, placebo-controlled, parallel-group trial, adolescent and adult individuals with a molecular diagnosis of AS were randomized (1:1:1) to 1 of 3 dosing regimens for a duration of 12 weeks: placebo morning dose and gaboxadol 15 mg evening dose (qd), gaboxadol 10 mg morning dose and 15 mg evening dose (bid), or placebo morning and evening dose. Safety and tolerability were monitored throughout the study. Prespecified exploratory efficacy end points included adapted Clinical Global Impression–Severity and Clinical Global Impression–Improvement (CGI-I) scales, which documented the clinical severity at baseline and change after treatment, respectively.ResultsEighty-eight individuals were randomized. Of 87 individuals (aged 13–45 years) who received at least 1 dose of study drug, 78 (90%) completed the study. Most adverse events (AEs) were mild to moderate, and no life-threatening AEs were reported. Efficacy of gaboxadol, as measured by CGI-I improvement in an exploratory analysis, was observed in gaboxadol qd vs placebo (p = 0.0006).ConclusionAfter 12 weeks of treatment, gaboxadol was found to be generally well-tolerated with a favorable safety profile. The efficacy as measured by the AS-adapted CGI-I scale warrants further studies.Clinicaltrials.gov IdentifierNCT02996305.Classification of EvidenceThis study provides Class I evidence that, for individuals with AS, gaboxadol is generally safe and well-tolerated.

Short-latency somatosensory-evoked potentials demonstrate cortical dysfunction in patients with Angelman syndrome.

BackgroundAngelman syndrome (AS) is neurodevelopmental disorder, causal gene of which is maternally expressed UBE3A. A majority of patients results from the large deletion of relevant chromosome which includes GABAA receptor subunit genes (GABARs) as well as UBE3A (AS Del). We previously reported aberrantly desynchronized primary somatosensory response in AS Del by using magnetoencephalography. The purpose of this study is to estimate cortical and subcortical involvement in the deficit of primary somatosensory processing in AS.MethodsWe analyzed short-latency somatosensory-evoked potentials (SSEPs) in 8 patients with AS Del. SSEPs were recorded on a 4-channel system comprising of two cortical electrodes which were placed on the frontal and centro-parietal areas. The peak and onset latency of each component were measured to compare latency and interval times.ResultsThe first-cortical peak latency (N20, P20), and N13-N20 peak interval times were significantly prolonged in AS Del compared to healthy controls. In contrast, there was no difference in latencies between subcortical components up to N20 onset or for N11-N20 onset interval times.ConclusionHighly desynchronized first-cortical SSEP components and normal latencies of subcortical components indicated cortical dysfunction rather than impairment of afferent pathways in AS Del patients, which might be attributed to GABAergic dysfunction due to loss of UBE3A function and heterozygosity of GABARs

Chronic α1-Na/K-ATPase inhibition reverses the elongation of the axon initial segment of the hippocampal CA1 pyramidal neurons in Angelman syndrome model mice.

Angelman syndrome (AS) is a neurodevelopmental disorder caused by the loss of function of the maternal UBE3A gene. The hippocampus is one of the most prominently affected brain regions in AS model mice, manifesting in severe hippocampal-dependent memory and plasticity deficits. Previous studies in AS mice reported an elongated axon initial segment (AIS) in pyramidal neurons (PNs) of the hippocampal CA1 region. These were the first reports in mammals to show AIS elongation in vivo. Correspondingly, this AIS elongation was linked to enhanced expression of the α1 subunit of Na+/K+-ATPase (α1-NaKA). Recently, it was shown that selective pharmacological inhibition of α1-NaKA by marinobufagenin (MBG) in adult AS mice rescued the hippocampal-dependent deficits via normalizing their compromised activity-dependent calcium (Ca+2) dynamics. In the herein study, we showed that achronic selective α1-NaKA inhibition reversed the AIS elongation in hippocampal CA1 PNs of adult AS mice, and differentially altered their excitability and intrinsic properties. Taken together, our study is the first to demonstrate in vivo structural plasticity of the AIS in a mammalian model, and further elaborates on the modulatory effects of elevated α1-NaKA levels in the hippocampus of AS mice.

Quantitative EEG Analysis in Angelman Syndrome: Candidate Method for Assessing Therapeutics.

The goal of these studies was to use quantitative (q)EEG techniques on data from children with Angelman syndrome (AS) using spectral power analysis, and to evaluate this as a potential biomarker and quantitative method to evaluate therapeutics. Although characteristic patterns are evident in visual inspection, using qEEG techniques has the potential to provide quantitative evidence of treatment efficacy. We first assessed spectral power from baseline EEG recordings collected from children with AS compared to age-matched neurotypical controls, which corroborated the previously reported finding of increased total power driven by elevated delta power in children with AS. We then retrospectively analyzed data collected during a clinical trial evaluating the safety and tolerability of minocycline (3 mg/kg/d) to compare pretreatment recordings from children with AS (4-12 years of age) to EEG activity at the end of treatment and following washout for EEG spectral power and epileptiform events. At baseline and during minocycline treatment, the AS subjects demonstrated increased delta power; however, following washout from minocycline treatment the AS subjects had significantly reduced EEG spectral power and epileptiform activity. Our findings support the use of qEEG analysis in evaluating AS and suggest that this technique may be useful to evaluate therapeutic efficacy in AS. Normalizing EEG power in AS therefore may become an important metric in screening therapeutics to gauge overall efficacy. As therapeutics transition from preclinical to clinical studies, it is vital to establish outcome measures that can quantitatively evaluate putative treatments for AS and neurological disorders with distinctive EEG patterns.

Bioinformatics analyses show dysregulation of calcium-related genes in Angelman syndrome mouse model

BackgroundAngelman syndrome (AS) is a genetic neurodevelopmental disorder caused by the loss of function of the UBE3A protein in the brain. In a previous study, we showed that activity-dependent calcium dynamics in hippocampal CA1 pyramidal neurons of AS mice is compromised, and its normalization rescues the hippocampal-dependent deficits. Therefore, we expected that the expression profiles of calcium-related genes would be altered in AS mice hippocampi. MethodsWe analyzed mRNA sequencing data from AS model mice and WT controls in light of the newly published CaGeDB database of calcium-related genes. We validated our results in two independent RNA sequencing datasets from two additional different AS models: first one, a human neuroblastoma cell line where UBE3A expression was knocked down by siRNA, and the second, an iPSC-derived neurons from AS patient and healthy donor control. FindingsWe found signatures of dysregulated calcium-related genes in AS mouse model hippocampus. Additionally, we show that these calcium-related genes function as signatures for AS in other human cellular models of AS, thus strengthening our findings. InterpretationOur findings suggest the downstream implications and significance of the compromised calcium signaling in Angelman syndrome. Moreover, since AS share similar features with other autism spectrum disorders, we believe that these findings entail meaningful data and approach for other neurodevelopmental disorders, especially those with known alterations of calcium signaling. FundingThis work was supported by the Angelman Syndrome Foundation and by the Israel Science Foundation, Grant Number 248/20.

LRSAM1 E3 ubiquitin ligase promotes proteasomal clearance of E6-AP protein

Numerous proteins participate and actively contribute to the various cellular mechanisms, where several of them are crucial for regular metabolism, including survival. Thus, to maintain optimal cellular physiology, cells govern protein quality control functions with the assistance of comprehensive actions of molecular chaperones, the ubiquitin-proteasome system, and autophagy. In the ubiquitin-proteasome pathway, few quality control E3 ubiquitin ligases actively participate against misfolded protein aggregation generated via stress conditions. But how these quality control E3s active expression levels returned to basal levels when cells achieved re-establishment of proteostasis is still poorly understood. Our current study demonstrated that LRSAM1 E3 ubiquitin ligase promotes the proteasomal degradation of quality control E3 ubiquitin ligase E6-AP. We have observed the co-localization and recruitment of LRSAM1 with E6-AP protein and noticed that LRSAM1 induces the endogenous turnover of E6-AP. Partial depletion of LRSAM1 elevates the levels of E6-AP and affects overall cell cycle regulatory proteins (p53 and p27) expression, including the rate of cellular proliferation. The current finding also provides an excellent opportunity to better understand the basis of the E6-AP associated pathomechanism of Angelman Syndrome disorder. Additionally, this study touches upon the novel potential molecular strategy to regulate the levels of one quality control E3 ubiquitin ligase with another E3 ubiquitin ligase and restore proteostasis and provide a possible therapeutic approach against abnormal protein aggregation diseases.

Strabismus surgery in Angelman syndrome: More than ocular alignment.

PurposeTo report and evaluate strabismus surgery in children with Angelman syndrome, in order to optimize and standardize surgical approach. Other purposes are to understand the possible relation between ocular findings and motor ability, and between improvement in ocular alignment and changes in motor skills in this population.DesignObservational cross-sectional study.MethodsMedical records of pediatric patients with Angelman syndrome, who underwent strabismus surgery, were investigated. Collected data included: genotype, gender, age at the time of surgery, refractive error, pre-operative strabismus, surgical procedure, surgical outcome, gross and fine motor development assessment pre- and post-operatively.ResultsSeventeen subjects, aged 3–15 years, were investigated. Fourteen patients were exotropic, three esotropic. Most patients presented astigmatism. Considering the exaggerated response to standard amounts of surgery and the risk of consecutive strabismus on long term follow-up reported by previous studies in children with developmental delay, a reduction of the amount of strabismus surgery was applied. Post-operatively, all patients presented with a significative reduction of the baseline deviation angle, with all esotropic patients and 7 exotropic patients (59%) achieving orthotropia. The surgical outcomes were variable according to the type and the amount of baseline strabismus, but no case presented with exaggerated surgical response. At baseline, patients showed important delays in all motor abilities, and, post-operatively, presented a significant improvement in walking and fine motor tasks. Pre- and post-operative motor abilities were negatively correlated to astigmatism, anisometropia, and amount of deviation.ConclusionsAccording to our data, the standard nomograms for strabismus surgery may be successfully applied in subjects with Angelman syndrome and exotropia. Our data suggest that the reduction of the deviation angle improves motor skills in strabismic pediatric patients with Angelman syndrome.

Strabismus surgery in Angelman syndrome: More than ocular alignment

Strabismus surgery in Angelman syndrome: More than ocular alignment

Molecular Evolution, Neurodevelopmental Roles and Clinical Significance of HECT-Type UBE3 E3 Ubiquitin Ligases.

Protein ubiquitination belongs to the best characterized pathways of protein degradation in the cell; however, our current knowledge on its physiological consequences is just the tip of an iceberg. The divergence of enzymatic executors of ubiquitination led to some 600–700 E3 ubiquitin ligases embedded in the human genome. Notably, mutations in around 13% of these genes are causative of severe neurological diseases. Despite this, molecular and cellular context of ubiquitination remains poorly characterized, especially in the developing brain. In this review article, we summarize recent findings on brain-expressed HECT-type E3 UBE3 ligases and their murine orthologues, comprising Angelman syndrome UBE3A, Kaufman oculocerebrofacial syndrome UBE3B and autism spectrum disorder-associated UBE3C. We summarize evolutionary emergence of three UBE3 genes, the biochemistry of UBE3 enzymes, their biology and clinical relevance in brain disorders. Particularly, we highlight that uninterrupted action of UBE3 ligases is a sine qua non for cortical circuit assembly and higher cognitive functions of the neocortex.

Communication-related assessments in an Angelman syndrome mouse model.

IntroductionAngelman syndrome (AS) is a neurodevelopmental disorder characterized by motor deficits, seizures, some autistic‐like behaviors, and severe impairment of speech. A dysfunction of the maternally imprinted UBE3A gene, coupled with a functional yet silenced paternal copy, results in AS. Although studies of transgenic mouse models have revealed a great deal about neural populations and rescue timeframes for specific features of AS, these studies have largely failed to examine intermediate phenotypes that contribute to the profound communicative disabilities associated with AS.MethodsHere, we use a variety of tasks, including assessments of rapid auditory processing and social communication. Expressive vocalizations were directly assessed and correlated against other core behavioral measures (motor, social, acoustic perception) to model putative influences on communication.ResultsAS mice displayed the characteristic phenotypes associated with Angelman syndrome (i.e., social and motor deficits), as well as marginal enhancements in rapid auditory processing ability. Our characterization of adult ultrasonic vocalizations further showed that AS mice produce fewer vocalizations and vocalized for a shorter amount of time when compared to controls. Additionally, a strong correlation between motor indices and ultrasonic vocalization output was shown, suggesting that the motor impairments in AS may contribute heavily to communication impairments.ConclusionIn summary, the combination of motor deficits, social impairment, marginal rapid auditory enhancements, and altered ultrasonic vocalizations reported in a mouse model of AS clearly parallel the human symptoms of the disorder. This mouse model offers a novel route to interrogate the underlying genetic, physiologic, and behavioral influences on the under‐studied topic of impaired communication in AS.

Imprinting disorders in humans: a review.

Mammals have two complete sets of chromosomes, one from each parent with equal autosomal gene expression. Less than one percentage of human genes are imprinted or show expression from only one parent without changing gene structure, usually by DNA methylation, but reversible in gametogenesis. Many imprinted genes affect fetal growth and development accounting for several human disorders reviewed in this report. Disorders include Prader-Willi and Angelman syndromes, the first examples of imprinting errors in humans, chromosome 15q11.2-q13.3 duplication, Silver-Russell syndrome, Beckwith-Weidemann syndrome, GNAS gene-related inactivation disorders (e.g. Albright hereditary osteodystrophy), uniparental chromosome 14 disomy, chromosome 6q24-related transient neonatal diabetes mellitus, parent of origin effects in 15q11.2 BP1-BP2 deletion (Burnside-Butler) syndrome and 15q11-q13 single gene imprinted disorders. Periconceptional and intrauterine life can be influenced by environmental factors and nutrition impacting DNA methylation. This process not only alters development of the fetus, but pregnancy complications may result from large fetal size. Epigenetic processes control imprinted gene functions and regulation with susceptibility to diseases as described. A better understanding of these processes will impact on care and treatment of affected individuals.