A neurodevelopmental survey of Angelman syndrome with genotype-phenotype correlations

Parental stress and family quality of life in families of individuals living with Angelman syndrome

Background

Angelman syndrome (AS) is a developmental disorder caused by one of four molecular etiologies. Affected individuals have intellectual disability (ID), limited speech, seizures, and sleep problems. Parents of individuals with AS exhibit elevated stress compared to parents of individuals with other IDs. We examined parental stress and family quality of life (FQOL) over time in families of individuals living with AS.

Methods

Data were collected in a natural history study of AS. The Parenting Stress Index, Third Edition (PSI) and the Beach Center FQOL scale assessed parent stress and FQOL. Stress and FQOL were examined across AS molecular subtypes, and predictors were analyzed using a generalised linear model. Relationships between parental stress and FQOL were examined using Pearson correlations and a stepwise mixed-linear model approach.

Results

Our sample consisted of 231 families of individuals living with AS. Parental stress was clinically elevated and was highest in families of individuals with UBE3A mutations, while FQOL did not differ across subtype in most domains. Increasing age predicted a decrease in parental stress but did not predict FQOL. Elevated parental stress was additionally predicted by maladaptive behaviours and child male sex, while lower FQOL was predicted by child male sex, parent marital status, and family income. Parental stress had a small negative impact on FQOL.

Conclusions

Stress is elevated in parents of individuals with AS across subtypes and has a small negative impact on family quality of life. Interventions to reduce stress have potential to improve individual and family well-being.

Developing Meaningful Score Differences for the Bayley-4 and Vineland-3 in Angelman Syndrome using a Delphi Panel

Objectives

To develop within-patient meaningful score differences (MSDs) on the Bayley Scales of Infant Development, Fourth Edition (Bayley-4), and the Vineland Adaptive Behavior Scales, Third Edition (Vineland-3), for individuals with Angelman syndrome (AS).

Methods

A Delphi method, involving a panel of 19 caregivers of individuals with AS, was used to establish MSDs for Bayley-4 and Vineland-3 Growth Scale Values. MSD was defined as the smallest change that would noticeably impact the daily functioning of an individual with AS or family quality of life in a way that was important to the individual with AS or their family. For each subscale of the Bayley-4 and Vineland-3, the panel was presented with 2 to 4 vignettes describing varying levels of baseline functioning and asked to select a MSD from a range of potential values. An iterative process involving three rounds of ratings and two rounds of discussion was used to build consensus. The median caregiver rating from round 3 was retained as the final recommended MSD value for each vignette.

Results

Final MSD ratings for the five subscales of Bayley-4 and 10 subscales of the Vineland-3 had an agreement rate of 70% or higher. MSD thresholds for each subscale were not single cut-offs, but rather reflected a range of MSD values dependent on level of baseline functioning.

Conclusions

The Delphi Panel method incorporates the caregiver perspective to provide preliminary estimates of what constitutes meaningful within person change on the Bayley-4 and Vineland-3 in individuals with AS with various levels of baseline functioning.

Highlights

⍰ To acquire regulatory approval in drug development, sponsors must demonstrate both statistical significance and clinical meaningfulness of a treatment effect.While several clinical trials are underway in AS, within person meaningful score difference thresholds are not yet established for the most commonly used outcome measures, namely the Bayley and Vineland.⍰ Aligning with FDA guidance, we have developed an innovative qualitative approach using a Delphi panel to incorporate caregiver perspectives in defining meaningful change and generated preliminary patient-informed meaningful score differences (MSDs) for individuals with Angelman Syndrome.⍰ What caregivers of individuals with AS consider to be a MSD on the measures depends primarily on the baseline severity of their child's presentation.

Age-Related Trajectories of Autistic Traits in Children With Angelman Syndrome

Angelman syndrome (AS) is a rare neurogenetic disorder. Previous studies indicate a high prevalence of autism spectrum disorder (ASD) with considerable variability. Little is known regarding the longitudinal trajectory of autistic traits. We aim to investigate autistic traits, the effect of age on these traits, and associated features in AS children. This (partly) longitudinal clinical record study at the ENCORE Expertise Center involved 107 AS children aged 2-18 with one (N = 107), two (N = 49), or three (N = 14) measurements. Autistic traits and sensory processing issues were assessed using various instruments, and DSM classifications were used descriptively. Covariates were genotype, gender, and epilepsy. Results indicate a high prevalence of autistic traits and sensory processing issues. Children with the deletion genotype exhibited more autistic traits. Autism Diagnostic Observation Schedule (ADOS) classifications indicated higher rates of ASD compared to clinician DSM classifications. Autistic traits generally remained stable over time, except that ADOS scores significantly decreased for children with the UBE3A mutation genotype, and in the social affect domain for the entire group. In conclusion, incorporating the assessment of autistic traits and sensory processing into clinical practice for AS is important to inform adaptations of the environment to meet the child's needs. Additionally, clinicians and researchers should be mindful of the potential for overestimating ASD traits in AS when relying on the ADOS. ASD diagnosis in AS should integrate multiple diagnostic instruments, diverse hetero-anamnestic sources, and multidisciplinary expert opinions.

Cullin-RING Ubiquitin Ligases in Neurodevelopment and Neurodevelopmental Disorders

Ubiquitination is a dynamic and tightly regulated post-translational modification essential for modulating protein stability, trafficking, and function to preserve cellular homeostasis. This process is orchestrated through a hierarchical enzymatic cascade involving three key enzymes: the E1 ubiquitin-activating enzyme, the E2 ubiquitin-conjugating enzyme, and the E3 ubiquitin ligase. The final step of ubiquitination is catalyzed by the E3 ubiquitin ligase, which facilitates the transfer of ubiquitin from the E2 enzyme to the substrate, thereby dictating which proteins undergo ubiquitination. Emerging evidence underscores the critical roles of ubiquitin ligases in neurodevelopment, regulating fundamental processes such as neuronal polarization, axonal outgrowth, synaptogenesis, and synaptic function. Mutations in genes encoding ubiquitin ligases and the consequent dysregulation of these pathways have been increasingly implicated in a spectrum of neurodevelopmental disorders, including autism spectrum disorder, intellectual disability, and attention-deficit/hyperactivity disorder. This review synthesizes current knowledge on the molecular mechanisms underlying neurodevelopment regulated by Cullin-RING ubiquitin ligases-the largest subclass of ubiquitin ligases-and their involvement in the pathophysiology of neurodevelopmental disorders. A deeper understanding of these mechanisms holds significant promise for informing novel therapeutic strategies, ultimately advancing clinical outcomes for individuals affected by neurodevelopmental disorders.

Association between sleep disturbances and challenging behavior in children and adolescents with Angelman syndrome

Angelman Syndrome (AS) is a neurodevelopmental disorder with severe symptoms and associated comorbidities. It is caused by the inactivity or lack of the UBE3a gene. Symptoms of the syndrome include intellectual disability and developmental delay. The current study investigated sleep disturbances (SD) in children and adolescents with AS, associations between SD and possible predictors of SD. Variables examined included age, gender, newborn and infancy history, challenging behavior, type of therapy received, genetic type of AS, and seizures. The sample included data from 109 participants with a mean age of 8.21, accessed via the Global Angelman Syndrome Registry. Chi-square tests were carried out to assess the associations between the variables and a logistical regression was carried out to assess the possible predictors of SD. Associations were found between SD and certain repetitive behaviors: slapping walls, focal hand movements, and agitation at new situations. From these associations, a regression formed a predictive model for sleep disturbances. The findings of this research demonstrated the importance of investigating the relationship between sleep disturbances and challenging behavior in children and adolescents with AS and the need for further research in this area.

Genotype-phenotype correlation over time in Angelman syndrome: Researching 134 patients

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by the loss of function of maternal UBE3A. The major cause of AS is a maternal deletion in 15q11.2-q13, and the minor causes are a UBE3A mutation, uniparental disomy (UPD), and imprinting defect (ID). Previous reports suggest that all patients with AS exhibit developmental delay, movement or balance disorders, behavioral characteristics, and speech impairment. In contrast, a substantial number of AS patients with a UBE3A mutation, UPD, or ID were reported not to show these consistent features and to show age-dependent changes in their features. In this study, we investigated 134 patients with AS, including 57 patients with a UBE3A mutation and 48 patients with UPD or ID. Although developmental delay was present in all patients, 20% of patients with AS caused by UPD or ID did not exhibit movement or balance disorders. Differences were also seen in hypopigmentation and seizures, depending on the causes. Moreover, patients with a UBE3A mutation, UPD, or ID tended to show fewer of the specific phenotypes depending on their age. In particular, in patients with UPD or ID, easily provoked laughter and hyperactivity tended to become more pronounced as they aged. Therefore, the clinical features of AS based on cause and age should be understood, and genetic testing should not be limited to patients with the typical clinical features of AS.

Adaptive Skills of Individuals with Angelman Syndrome Assessed Using the Vineland Adaptive Behavior Scales, 2nd Edition

In the current study, we examined adaptive skills and trajectories over time in 257 individuals with Angelman syndrome (AS) using the Vineland Adaptive Behavior Scales, 2nd Edition. Multilevel linear models were used to examine differences between molecular subtypes over time, from one year to 13 years of age, in the adaptive domains of communication, daily living skills, socialization and motor skills. Individuals with non-deletion subtypes typically demonstrated a higher level of adaptive skills compared to those with deletion subtypes. Statistically significant growth was observed in all adaptive domains through at least early adolescence. Individuals with AS should continue to receive developmental services and educational supports through adolescence and into adulthood given the slow rates of growth being observed across adaptive domains.

Exploring the Clinical and Genetic Landscape of Angelman Syndrome: Patient-Reported Insights from an Italian Registry

Background: The Angelman Syndrome Registry (RISA) was developed as a retrospective study with the following objectives: to evaluate the clinical history of individuals with Angelman Syndrome (AS) in Italy and compare it with the existing literature; to investigate the feasibility of gathering data by directly involving participants in the data collection process; and to explore the relationship between different symptoms and genotypes. Methods: Established in 2018, RISA enrolled a total of 82 participants, with 62 (75.6%) providing complete data. Demographic, clinical, and genetic information was collected using electronic case report forms. Descriptive statistics characterized the sample, while associations between genotype and clinical characteristics were examined. Results: Descriptive analysis revealed a median participant age of 8.0 years, with males comprising 48.8% of the sample. Deletion (58.1%) was the most common genotype. The majority (82.2%) experienced epilepsy, with seizures typically onset before 3 years of age. Most patients (86.2%) required multiple anti-epileptic drugs for control, with generalized tonic-clonic seizures and atypical absence seizures being most prevalent. The deletion group exhibited more severe developmental delays and a trend towards higher seizure severity. Sleep problems affected 69.4% of participants, characterized by difficulties in sleep onset and maintenance. Conclusions: This study offers valuable insights into the clinical history and genetic characteristics of AS in Italy, consistent with the prior literature. Additionally, it underscores the efficacy of patient registries in capturing comprehensive data on rare diseases such as AS, highlighting their potential to advance research and enhance patient care.

Developmental milestones and daily living skills in individuals with Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a neurodevelopmental disorder associated with severe global developmental delay. However, the ages at which different developmental skills are achieved in these individuals remain unclear. We seek to determine the probability and the age of acquisition of specific developmental milestones and daily living skills in individuals with AS across the different molecular subtypes, viz. class I deletion, class II deletion, uniparental disomy, imprinting defect, and UBE3A variants.

METHODS

Caregivers participating in a longitudinal multicenter Angelman Syndrome Natural History Study completed a questionnaire regarding the age at which their children achieved specific developmental milestones and daily living skills. The Cox Proportional Hazard model was applied to analyze differences in the probability of achievement of skills at various ages among five molecular subtypes of AS.

RESULTS

Almost all individuals, regardless of molecular subtype, were able to walk with support by five years of age. By age 15, those with a deletion had at least a 50% probability of acquiring 17 out of 30 skills compared to 25 out of 30 skills among those without a deletion. Overall, fine and gross motor skills such as holding and reaching for small objects, sitting, and walking with support were achieved within a fairly narrow range of ages, while toileting, feeding, and hygiene skills tend to have greater variability in the ages at which these skills were achieved. Those without a deletion had a higher probability (25-92%) of achieving daily living skills such as independently toileting and dressing compared to those with a deletion (0-13%). Across all molecular subtypes, there was a low probability of achieving independence in bathing and brushing teeth.

CONCLUSION

Individuals with AS without a deletion are more likely to achieve developmental milestones and daily living skills at an earlier age than those with a deletion. Many individuals with AS are unable to achieve daily living skills necessary for independent self-care.

Factors associated with sleep disturbances in children and adolescents with Angelman Syndrome

BACKGROUND

Angelman Syndrome (AS) is a rare genetic disorder characterised by hyperactivity, overexcitability, developmental delays, and lack of speech.

METHODS

This study used secondary data analysis to investigate sleep disturbances in children and adolescents (n = 212) who are enrolled in the Global Angelman Syndrome Registry. Participants were divided into two groups based on the presence or absence of sleep disturbance. The cut-off score of 40 on the Sleep Disturbance Scale for Children was used to indicate the presence or absence of sleep disturbances. Sleep disturbances and their association with co-occurring conditions were examined regarding challenging behaviour, language and communication, infancy history, gastrointestinal symptoms, and epilepsy. Multiple regression was then conducted to investigate possible predictors for sleep disturbances.

RESULTS

Children and adolescents with AS, with and without sleep disturbances, differed considerably regarding anxiety. Sleep disturbances were significantly associated with an ability to use spoken words and computerised communication devices, and anxiety was a predictor of sleep disturbances.

CONCLUSION

Future research is necessary to replicate this novel research, and to advance the clinical treatment of sleep disturbances in children and adolescents with AS.

Child characteristics associated with child quality of life and parenting stress in Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterised by severe intellectual disability, movement disorder, epilepsy, sleeping problems, and behavioural issues. Little is known on child health-related quality of life (HRQoL) in AS. AS family studies have reported elevated parenting stress and a high impact of the child's syndrome on the parent. It is unclear which factors influence child HRQoL and parenting stress/impact in AS.

METHODS

We collected data prospectively through standardised clinical assessments of children with AS at the ENCORE Expertise centre for Angelman Syndrome at the Erasmus MC Sophia Children's Hospital. A linear regression analysis was conducted for the following outcome variables: (1) child HRQoL (Infant and Toddler Quality of Life Questionnaire); (2) the impact of the child's syndrome on the parent (Infant and Toddler Quality of Life Questionnaire); and (3) parenting stress (Parenting Stress Index). Predictor variables were child genotype, epilepsy, sleeping problems (Sleep Disturbance Scale for Children), cognitive developmental level (Bayley Cognition Scale), autistic features (Autism Diagnostic Observation Schedule) and emotional/behavioural problems (Child Behaviour Checklist). Covariates were sex, age and socio-economic status.

RESULTS

The study sample consisted of 73 children with AS, mean age = 9.1 years, range = 2-18 years. Emotional/behavioural problems were the strongest significant predictor of lowered child HRQoL. Internalising problems were driving this effect. In addition, having the deletion genotype and higher age was related to lower child HRQoL. Sleeping problems were related to a higher impact of the child's syndrome on the parent. Finally, emotional/behavioural problems were associated with higher parenting stress. Cognitive developmental level, autistic features and epilepsy were not a significant predictor of child HRQoL and parenting stress/impact.

CONCLUSIONS

These results suggest that interventions aimed at increasing child HRQoL and decreasing parenting stress/impact in AS should focus on child emotional/behavioural problems and sleeping problems, using a family-centred approach.

Age of diagnosis for children with chromosome 15q syndromes

OBJECTIVE

The objective of this study was to identify the age of diagnosis for children with one of three neurogenetic conditions resulting from changes in chromosome 15 (Angelman syndrome [AS], Prader-Willi syndrome [PWS], and duplication 15q syndrome [Dup15q]).

METHODS

Data about the diagnostic process for each condition were contributed by the advocacy organizations. Median and interquartile ranges were calculated for each condition by molecular subtype and year. Comparison tests were run to explore group differences.

RESULTS

The median age of diagnosis was 1.8 years for both AS and Dup15q. PWS was diagnosed significantly younger at a median age of 1 month. Deletion subtypes for both PWS and AS were diagnosed earlier than nondeletion subtypes, and children with isodicentric duplications in Dup15q were diagnosed earlier than those with interstitial duplications.

CONCLUSION

Understanding variability in the age of diagnosis for chromosome 15 disorders is an important step in reducing the diagnostic odyssey and improving access to interventions for these populations. Results from this study provide a baseline by which to evaluate efforts to reduce the age of diagnosis for individuals with these conditions.

Stem cell models of Angelman syndrome

Angelman syndrome (AS) is an imprinted neurodevelopmental disorder that lacks a cure, characterized by developmental delay, intellectual impairment, seizures, ataxia, and paroxysmal laughter. The condition arises due to the loss of the maternally inherited copy of the UBE3A gene in neurons. The paternally inherited UBE3A allele is unable to compensate because it is silenced by the expression of an antisense transcript (UBE3A-ATS) on the paternal chromosome. UBE3A, encoding enigmatic E3 ubiquitin ligase variants, regulates target proteins by either modifying their properties/functions or leading them to degradation through the proteasome. Over time, animal models, particularly the Ube3a mat-/pat+ Knock-Out (KO) mice, have significantly contributed to our understanding of the molecular mechanisms underlying AS. However, a shift toward human pluripotent stem cell models (PSCs), such as human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), has gained momentum. These stem cell models accurately capture human genetic and cellular characteristics, offering an alternative or a complement to animal experimentation. Human stem cells possess the remarkable ability to recapitulate neurogenesis and generate "brain-in-a-dish" models, making them valuable tools for studying neurodevelopmental disorders like AS. In this review, we provide an overview of the current state-of-the-art human stem cell models of AS and explore their potential to become the preclinical models of choice for drug screening and development, thus propelling AS therapeutic advancements and improving the lives of affected individuals.

Ubiquitin-protein ligase E3A (UBE3A) mediation of viral infection and human diseases

The Ubiquitin-protein ligase E3A, UBE3A, also known as E6-associated protein (E6-AP), is known to play an essential role in regulating the degradation of various proteins by transferring Ub from E2 Ub conjugating enzymes to the substrate proteins. Several studies indicate that UBE3A regulates the stabilities of key viral proteins in the virus-infected cells and, thereby, the infected virus-mediated diseases, even if it were reported that UBE3A participates in non-viral-related human diseases. Furthermore, mutations such as deletions and duplications in the maternally inherited gene in the brain cause human neurodevelopmental disorders such as Angelman syndrome (AS) and autism. It is also known that UBE3A functions as a transcriptional coactivator for the expression of steroid hormone receptors. These reports establish that UBE3A is distinguished by its multitudinous functions that are paramount to viral pathology and human diseases. This review is focused on molecular mechanisms for such intensive participation of UBE3A in disease formation and virus regulation.

Qualitative Insights into Key Angelman Syndrome Motor Related Concepts Reported by Caregivers-A Thematic Analysis of Semi-Structured Interviews

Previous patient-centered concept models of Angelman syndrome (AS) are integral in developing our understanding of the symptoms and impact of this condition with a holistic perspective and have highlighted the importance of motor function. We aimed to develop the motor and movement aspects of the concept models, to support research regarding motor-related digital outcomes aligned with patients' and caregivers' perspectives. We conducted a qualitative analysis of semi-structured interviews of 24 caregivers to explore AS motor-related features, factors influencing them and their impact on patients and caregivers.The most impacted motor features were gait, walking and stair-climbing. Half of caregivers ranked motor symptoms as one of the most burdensome symptoms of AS. Caregivers frequently reported physical therapy, motivation, medical management and age as factors influencing motor function in AS and reported that impaired motor function affected both patients and caregivers. Measures of lower-limb motor function were identified as relevant to monitor drug effectiveness in AS. Caregivers discussed expected benefits of a digital outcome and potential issues with wearable technology in the context of AS. We propose a new motor function patient-centered concept model, providing insights for the development of relevant, motor-related, digital outcomes in AS.

Enabling endpoint development for interventional clinical trials in individuals with Angelman syndrome: a prospective, longitudinal, observational clinical study (FREESIAS)

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by the absence of a functional UBE3A gene, which causes developmental, behavioral, and medical challenges. While currently untreatable, comprehensive data could help identify appropriate endpoints assessing meaningful improvements in clinical trials. Herein are reported the results from the FREESIAS study assessing the feasibility and utility of in-clinic and at-home measures of key AS symptoms.

METHODS

Fifty-five individuals with AS (aged < 5 years: n = 16, 5-12 years: n = 27, ≥ 18 years: n = 12; deletion genotype: n = 40, nondeletion genotype: n = 15) and 20 typically developing children (aged 1-12 years) were enrolled across six USA sites. Several clinical outcome assessments and digital health technologies were tested, together with overnight 19-lead electroencephalography (EEG) and additional polysomnography (PSG) sensors. Participants were assessed at baseline (Clinic Visit 1), 12 months later (Clinic Visit 2), and during intermittent home visits.

RESULTS

The participants achieved high completion rates for the clinical outcome assessments (adherence: 89-100% [Clinic Visit 1]; 76-91% [Clinic Visit 2]) and varied feasibility of and adherence to digital health technologies. The coronavirus disease 2019 (COVID-19) pandemic impacted participants' uptake of and/or adherence to some measures. It also potentially impacted the at-home PSG/EEG recordings, which were otherwise feasible. Participants achieved Bayley-III results comparable to the available natural history data, showing similar scores between individuals aged ≥ 18 and 5-12 years. Also, participants without a deletion generally scored higher on most clinical outcome assessments than participants with a deletion. Furthermore, the observed AS EEG phenotype of excess delta-band power was consistent with prior reports.

CONCLUSIONS

Although feasible clinical outcome assessments and digital health technologies are reported herein, further improved assessments of meaningful AS change are needed. Despite the COVID-19 pandemic, remote assessments facilitated high adherence levels and the results suggested that at-home PSG/EEG might be a feasible alternative to the in-clinic EEG assessments. Taken altogether, the combination of in-clinic/at-home clinical outcome assessments, digital health technologies, and PSG/EEG may improve protocol adherence, reduce patient burden, and optimize study outcomes in AS and other rare disease populations.

Drosophila UBE3A regulates satiety signaling through the Piezo mechanosensitive ion channel

Angelman syndrome (AS) is a rare neurogenetic disorder characterized by developmental delays, speech impairments, ataxic movements, and in some cases, hyperphagic feeding behavior. Loss of function mutations, loss of expression from the maternal allele or absence of maternal UBE3A result in AS. Recent studies have established a connection between UBE3A and the mechanosensitive ion channel PIEZO2, suggesting the potential role of UBE3A in the regulation of PIEZO channels. In this study, we investigated the role of Drosophila UBE3A (Dube3a) in Piezo associated hyperphagic feeding behavior. We developed a novel assay using green fluorescent protein (GFP) expressing yeast to quantify gut distention in flies with Piezo and Dube3a mutations. We confirmed that Dube3a15b loss of function flies displayed gut distention to almost identical levels as PiezoKO flies. Further analysis using deficiency (Df) lines encompassing the Dube3a locus provided proof for a role of Dube3a in satiety signaling. We also investigated endogenous Piezo expression across the fly midgut and tracheal system. Piezo protein could be detected in both neurons and trachea of the midgut. Overexpression of Dube3a driven by the Piezo promoter resulted in distinct tracheal remodeling within the midgut. These findings suggest that Dube3a plays a key role in the regulation of Piezo and that subsequent dysregulation of these ion channels may explain the hyperphagic behavior observed in 32% of cases of AS. Further investigation will be needed to identify the intermediate protein(s) interacting between the Dube3a ubiquitin ligase and Piezo channels, as Piezo does not appear to be a direct ubiquitin substrate for UBE3A in mice and humans.

Quantitative measures of motor development in Angelman syndrome

Angelman Syndrome is a rare neurodevelopmental disorder characterized by developmental delay, lack of speech, seizures, intellectual disability, characteristic behavior, and movement disorders. Clinical gait analysis provides the opportunity for movement quantification to investigate an observed maladaptive change in gait pattern and offers an objective outcome of change. Pressure-sensor-based technology, inertial and activity monitoring, and instrumented gait analysis (IGA) were employed to define motor abnormalities in Angelman syndrome. Temporal-spatial gait parameters of persons with Angelman Syndrome (pwAS) show deficiencies in gait performance through walking speed, step length, step width, and walk ratio. pwAS walk with reduced step lengths, increased step width, and greater variability. Three-dimensional motion kinematics showed increased anterior pelvic tilt, hip flexion, and knee flexion. PwAS have a walk ratio more than two standard deviations below controls. Dynamic electromyography showed prolonged activation of knee extensors, which was associated with a decreased range of motion and the presence of hip flexion contractures. Use of multiple gait tracking modalities revealed that pwAS exhibit a change in gait pattern to a flexed knee gait pattern.  Cross-sectional studies of individuals with AS show a regression toward this maladaptive gait pattern over development in pwAS ages 4-11. PwAS unexpectedly did not have spasticity associated with change in gait pattern. Multiple quantitative measures of motor patterning may offer early biomarkers of gait decline consistent with critical periods of intervention, insight into appropriate management strategies, objective primary outcomes, and early indicators of adverse events.

Systematic Review: Emotion Dysregulation in Syndromic Causes of Intellectual and Developmental Disabilities

OBJECTIVE

To summarize the current state of the literature regarding emotion dysregulation (ED) in syndromic intellectual disabilities (S-IDs) in 6 of the most common forms of S-IDs-Down syndrome, fragile X syndrome (FXS), tuberous sclerosis complex, Williams syndrome, Prader-Willi syndrome, and Angelman syndrome-and to determine future research directions for identification and treatment of ED.

METHOD

PubMed bibliographic database was searched from date of inception to May 2021. PRISMA 2020 guidelines were followed with the flowchart, table of included studies, list of excluded studies, and checklist provided. Filters applied included human research and English. Only original research articles were included in the final set, but review articles were used to identify secondary citations of primary studies. All articles were reviewed for appropriateness by 2 authors and summarized. Inclusion criteria were met by 145 articles (Down syndrome = 29, FXS = 55, tuberous sclerosis complex = 11, Williams syndrome = 18, Prader-Willi syndrome = 24, Angelman syndrome = 8).

RESULTS

Each syndrome review was summarized separately and further subdivided into articles related to underlying neurobiology, behaviors associated with ED, assessment, and targeted intervention. FXS had the most thorough research base, followed by Down syndrome and Prader-Willi syndrome, with the other syndromes having more limited available research. Very limited research was available regarding intervention for all disorders except FXS.

CONCLUSION

Core underlying characteristics of S-IDs appear to place youth at higher risk for ED, but further research is needed to better assess and treat ED in S-IDs. Future studies should have a standard assessment measure of ED, such as the Emotion Dysregulation Inventory, and explore adapting established curricula for ED from the neurotypical and autism spectrum disorder fields.

Developmental Skills of Individuals with Angelman Syndrome Assessed Using the Bayley-III

We describe the development of 236 children with Angelman syndrome (AS) using the Bayley Scales of Infant and Toddler Development, Third Edition. Multilevel linear mixed modeling approaches were used to explore differences between molecular subtypes and over time. Individuals with AS continue to make slow gains in development through at least age 12 years of age at about 1-2 months/year based on age equivalent score and 1-16 growth score points/year depending on molecular subtype and domain. Children with a deletion have lower scores at baseline and slower rate of gaining skills while children with UBE3A variant subtype demonstrated higher scores as well as greater rates of skill attainment in all domains. The developmental profiles of UPD and ImpD were similar.

Typical and atypical neural mechanisms support spoken word processing in Angelman syndrome

Angelman syndrome (AS) is known to affect expressive and receptive communication abilities. This study examined individual differences in neural mechanisms underlying speech processing in children with AS (n = 24, M age = 10.01 years) and typical development (n = 30, M age = 10.82 years) using auditory event-related potentials during passive listening to common English words and novel pseudowords. A group of adults with AS (n = 7, M = 31.78 years) provided data about the upper developmental range. The typically developing group demonstrated the expected more negative amplitudes in response to words than pseudowords within 250-500 ms after stimulus onset at the left temporal scalp region. Children and adults with AS exhibited a similar left-lateralized pattern of word-pseudoword differentiation at temporal and parietal regions, but not the midline parietal memory response for known words observed in the typically developing group, suggesting typical-like word-pseudoword differentiation along with possible alterations in the automatic recall of word meaning. These results have important implications for understanding receptive and expressive communication processes in AS and support the use of auditory neural responses for characterizing individual differences in neurodevelopmental disorders with limited speech.

The Hippocampal Response to Acute Corticosterone Elevation Is Altered in a Mouse Model for Angelman Syndrome

Angelman Syndrome (AS) is a severe neurodevelopmental disorder, caused by the neuronal absence of the ubiquitin protein ligase E3A (UBE3A). UBE3A promotes ubiquitin-mediated protein degradation and functions as a transcriptional coregulator of nuclear hormone receptors, including the glucocorticoid receptor (GR). Previous studies showed anxiety-like behavior and hippocampal-dependent memory disturbances in AS mouse models. Hippocampal GR is an important regulator of the stress response and memory formation, and we therefore investigated whether the absence of UBE3A in AS mice disrupted GR signaling in the hippocampus. We first established a strong cortisol-dependent interaction between the GR ligand binding domain and a UBE3A nuclear receptor box in a high-throughput interaction screen. In vivo, we found that UBE3A-deficient AS mice displayed significantly more variation in circulating corticosterone levels throughout the day compared to wildtypes (WT), with low to undetectable levels of corticosterone at the trough of the circadian cycle. Additionally, we observed an enhanced transcriptomic response in the AS hippocampus following acute corticosterone treatment. Surprisingly, chronic corticosterone treatment showed less contrast between AS and WT mice in the hippocampus and liver transcriptomic responses. This suggests that UBE3A limits the acute stimulation of GR signaling, likely as a member of the GR transcriptional complex. Altogether, these data indicate that AS mice are more sensitive to acute glucocorticoid exposure in the brain compared to WT mice. This suggests that stress responsiveness is altered in AS which could lead to anxiety symptoms.

Rodent Models of Audiogenic Epilepsy: Genetic Aspects, Advantages, Current Problems and Perspectives

Animal models of epilepsy are of great importance in epileptology. They are used to study the mechanisms of epileptogenesis, and search for new genes and regulatory pathways involved in the development of epilepsy as well as screening new antiepileptic drugs. Today, many methods of modeling epilepsy in animals are used, including electroconvulsive, pharmacological in intact animals, and genetic, with the predisposition for spontaneous or refractory epileptic seizures. Due to the simplicity of manipulation and universality, genetic models of audiogenic epilepsy in rodents stand out among this diversity. We tried to combine data on the genetics of audiogenic epilepsy in rodents, the relevance of various models of audiogenic epilepsy to certain epileptic syndromes in humans, and the advantages of using of rodent strains predisposed to audiogenic epilepsy in current epileptology.

Association between early and current gastro-intestinal symptoms and co-morbidities in children and adolescents with Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a neurogenetic disorder that causes severe intellectual disability, expressive language deficits, motor impairment, ataxia, sleep problems, epileptic seizures and a happy disposition. People with AS frequently experience gastrointestinal (GI) symptoms.

METHOD

This study used data from the Global Angelman Syndrome Registry to explore the relationship between early and current GI symptoms and co-morbidity in children and adolescents with AS (n = 173). Two groups that experienced a high (n = 91) and a low (n = 82) frequency of GI symptoms were examined in relation to feeding and GI history in infancy, sleep and toileting problems, levels of language and communication and challenging behaviours. Predictors of GI symptoms were then investigated using a series of logistic regressions.

RESULTS

This analysis found that constipation and gastroesophageal reflux affected 84% and 64%, of the sample, respectively. The high frequency of GI symptoms were significantly associated with: 'refusal to nurse', 'vomiting', 'arching', 'difficulty gaining weight', gastroesophageal reflux, 'solid food transition', frequency of night-time urinary continence and sleep hyperhidrosis during infancy. GI symptoms were not significantly associated with sleep, toileting, language or challenging behaviours. Significant predictors of high frequency GI symptoms were gastroesophageal reflux and sleep hyperhidrosis.

CONCLUSIONS

Future research needs to investigate the association between AS and GI co-morbidity in adults with AS.

Spoken language comprehension in children and adults with Angelman Syndrome

INTRODUCTION

Objective evaluation of receptive communication abilities in nonspeaking individuals using standardized behavioral measures can be complicated by co-occurring intellectual disabilities and motor difficulties. Eye tracking during listening may offer an informative complementary approach to directly evaluate receptive language skills.

METHOD

This study examined feasibility of eye gaze measures as an index of spoken language comprehension in nonspeaking children and adults with Angelman syndrome (AS; n = 23) using a looking-while-listening procedure. Typically developing children (n = 34) provided a reference data set. Primary caregivers of participants with AS completed standardized informant reports (MacArthur-Bates Communicative Development Inventory: Words and Gestures; Vineland Adaptive Behavior Scales-3; Aberrant Behavior Checklist-2) to characterize communicative skills and general adaptive functioning.

RESULTS

Gaze data in participants with AS, particularly in the individuals reported by caregivers to have larger receptive vocabularies and stronger adaptive communicative functioning, demonstrated the expected pattern of comprehension reflected by the increased probability of looks to the target images after vs. before they were named in a spoken sentence. However, processing speed (gaze reaction time) was significantly slower in participants with AS than in the typically developing group.

CONCLUSIONS

Gaze-based paradigms could be an informative measure of receptive communication processes in participants who are unable to complete traditional standardized behavioral assessments.

Laryngotracheal separation surgery in a patient with severe Angelman syndrome involving a 19.3 Mb deletion on 15q11.2-q14

A severe Angelman syndrome (AS) patient with a very large deletion (19.3 Mb) at 15q11.2-q14 required laryngotracheal separation, which is not a common surgery in AS. Comparative genomic hybridization-based microarrays can be useful to confirm deletion size and clinical severity.

Therapeutic approach to neurological manifestations of Angelman syndrome

INTRODUCTION

Angelman syndrome (AS) is a neurogenetic disorder due to deficient expression of the maternal copy of the UBE3A gene, which encodes ubiquitin ligase E3A protein. Severe developmental delay, seizures and other neurological disorders characterize AS.

AREAS COVERED

In this review, we focus on a comprehensive therapeutic approach to the most disabling neurological manifestations of AS: epilepsy, sleep disturbances, behavioral and movement disorders. Articles were identified through PubMed and Google Scholar up to October 2021.

EXPERT OPINION

Evidence for the treatment of neurological manifestations in AS mainly derives from poor quality studies (case reports, small case series, expert opinions). Seizures can be polymorphic and includes atypical absences, myoclonic, generalized tonic-clonic, unilateral clonic, or atonic attacks. Sodium valproate, levetiracetam, and benzodiazepines are the most commonly used anti-seizure medications. Melatonin or mirtazapine seem to improve sleep quality. Antipsychotics, antidepressants, and anxiolytics have been proposed for the treatment of behavioral manifestations, but no evidence-based studies are available. Non-pharmacological approach may also be useful. Mild dystonia is common but usually does not significantly impact patients' motor performances. Well-conducted clinical trials aimed to evaluate treatment of neurological complications of AS are warranted. Gene and molecular precision therapies represent a fascinating area of research in the future.

Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism

Our study reviewed abnormalities in spontaneous, as well as event-related, brain activity in syndromes with a known genetic underpinning that are associated with autistic symptomatology. Based on behavioral and neurophysiological evidence, we tentatively subdivided the syndromes on primarily hyper-sensitive (Fragile X, Angelman) and hypo-sensitive (Phelan-McDermid, Rett, Tuberous Sclerosis, Neurofibromatosis 1), pointing to the way of segregation of heterogeneous idiopathic ASD, that includes both hyper-sensitive and hypo-sensitive individuals. This segmentation links abnormalities in different genes, such as FMR1, UBE3A, GABRB3, GABRA5, GABRG3, SHANK3, MECP2, TSC1, TSC2, and NF1, that are causative to the above-mentioned syndromes and associated with synaptic transmission and cell growth, as well as with translational and transcriptional regulation and with sensory sensitivity. Excitation/inhibition imbalance related to GABAergic signaling, and the interplay of tonic and phasic inhibition in different brain regions might underlie this relationship. However, more research is needed. As most genetic syndromes are very rare, future investigations in this field will benefit from multi-site collaboration with a common protocol for electrophysiological and event-related potential (EEG/ERP) research that should include an investigation into all modalities and stages of sensory processing, as well as potential biomarkers of GABAergic signaling (such as 40-Hz ASSR).

A novel variant in UBE3A in a family with multigenerational intellectual disability and developmental delay

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder and is characterized by severe cognitive disability, motor dysfunction, speech impairment, hyperactivity, and frequent seizures. Although the maternal chromosomal region 15q11.2-q13 deletion is the most common mechanism of AS, ~10% of individuals with AS are caused by the intragenic variants in the maternally inherited UBE3A, which encodes an E3 ubiquitin ligase.

METHODS

Clinical diagnoses were based on detailed clinical findings. Trio-based exome sequencing was performed on the proband and her parents to identify the underlying genetic variants. The candidate variants were confirmed by Sanger sequencing following PCR amplification. In silico analyses were conducted to predict the effect of the identified variant on the function of UBE3A protein.

RESULTS

We identified a novel variant c.2029G>C (p. Gly677Arg) in UBE3A as the most promising candidate. In silico analyses showed that p.Gly677Arg in the UBE3A affects a highly conserved residue. Her mother had the variant at this locus. Sanger sequencing results showed that II-2, II-5, II-7, IV-1, III-5, III-7, III-8, and III-9 have the variant c.2029G>C, and all patients inherited maternally variant in UBE3A, while the offsprings of the male carrier were unaffected.

CONCLUSIONS

We identified a novel variant (c.2029G>C) in the UBE3A in a Chinese family with multigenerational intellectual disability and developmental delay. Our findings expanded the genotypic spectrum of AS and provided important information for genetic counseling.

Gait as a quantitative translational outcome measure in Angelman syndrome

Angelman syndrome (AS) is a genetic neurodevelopmental disorder characterized by developmental delay, lack of speech, seizures, intellectual disability, hypotonia, and motor coordination deficits. Motor abilities are an important outcome measure in AS as they comprise a broad repertoire of metrics including ataxia, hypotonia, delayed ambulation, crouched gait, and poor posture, and motor dysfunction affects nearly every individual with AS. Guided by collaborative work with AS clinicians studying gait, the goal of this study was to perform an in‐depth gait analysis using the automated treadmill assay, DigiGait. Our hypothesis is that gait presents a strong opportunity for a reliable, quantitative, and translational metric that can serve to evaluate novel pharmacological, dietary, and genetic therapies. In this study, we used an automated gait analysis system, in addition to standard motor behavioral assays, to evaluate components of motor, exploration, coordination, balance, and gait impairments across the lifespan in an AS mouse model. Our study demonstrated marked global motoric deficits in AS mice, corroborating previous reports. Uniquely, this is the first report of nuanced aberrations in quantitative spatial and temporal components of gait in AS mice compared to sex‐ and age‐matched wildtype littermates followed longitudinally using metrics that are analogous in AS individuals. Our findings contribute evidence toward the use of nuanced motor outcomes (i.e., gait) as valuable and translationally powerful metrics for therapeutic development for AS, as well as other genetic neurodevelopmental syndromes.

A multidisciplinary approach and consensus statement to establish standards of care for Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurogenetic disorder present in approximately 1/12,000 individuals and characterized by developmental delay, cognitive impairment, motor dysfunction, seizures, gastrointestinal concerns, and abnormal electroencephalographic background. AS is caused by absent expression of the paternally imprinted gene UBE3A in the central nervous system. Disparities in the management of AS are a major problem in preparing for precision therapies and occur even in patients with access to experts and recognized clinics. AS patients receive care based on collective provider experience due to limited evidence-based literature. We present a consensus statement and comprehensive literature review that proposes a standard of care practices for the management of AS at a critical time when therapeutics to alter the natural history of the disease are on the horizon.

METHODS

We compiled the key recognized clinical features of AS based on consensus from a team of specialists managing patients with AS. Working groups were established to address each focus area with committees comprised of providers who manage >5 individuals. Committees developed management guidelines for their area of expertise. These were compiled into a final document to provide a framework for standardizing management. Evidence from the medical literature was also comprehensively reviewed.

RESULTS

Areas covered by working groups in the consensus document include genetics, developmental medicine, psychology, general health concerns, neurology (including movement disorders), sleep, psychiatry, orthopedics, ophthalmology, communication, early intervention and therapies, and caregiver health. Working groups created frameworks, including flowcharts and tables, to help with quick access for providers. Data from the literature were incorporated to ensure providers had review of experiential versus evidence-based care guidelines.

CONCLUSION

Standards of care in the management of AS are keys to ensure optimal care at a critical time when new disease-modifying therapies are emerging. This document is a framework for providers of all familiarity levels.

Anxiety in Angelman Syndrome

Angelman Syndrome (AS) is a neurodevelopmental disorder most commonly caused by the impaired expression of the maternal UBE3A gene on chromosome 15. Though anxiety has been identified as a frequently present characteristic in AS, there are limited studies examining anxiety in this population. Studies of anxiety in other neurodevelopmental disorders have found disorder specific symptoms of anxiety and age specific displays of anxiety symptoms. However, there is a consistent challenge in identifying anxiety in people with neurodevelopmental disorders given the lack of measurement instruments specifically designed for this population. Given the limited information about AS and anxiety, the aims of the current project were to (a) examine symptoms of anxiety in children with AS and (b) determine the correlates of anxiety in children with AS. Participants included 42 adult caregivers of youth with AS in the AS Natural History study who completed the Developmental Behavior Checklist (DBC). The results found that 26% of the sample demonstrated elevated symptoms of anxiety and established a relationship between elevated anxiety in youth with AS and higher levels of irritability, hyperactivity, self-absorbed behaviors, and disruptive/antisocial behaviors. Findings from this research provide a foundation for tailoring evidence-based assessments and treatments for youth with AS and anxiety.

Epilepsy and Molecular Phenotype Affect the Neurodevelopment of Pediatric Angelman Syndrome Patients in China

OBJECTIVE

This study investigated the mental development of children with Angelman syndrome (AS) in China and evaluated the relationship between neurodevelopment and molecular subtype, age, epilepsy, and sex using the Chinese version of the Griffith Mental Development Scale (GMDS-C) to provide detailed baseline data regarding neurodevelopment with AS in China.

METHODS

Participants were recruited from the AS Natural History Study. The GMDS-C was used to evaluate all participants' mental age and developmental quotients. The general quotient (GQ) and quotients of five subscales (sports, personal-social, auditory language, eye-hand coordination, and comprehensive performance) were calculated.

RESULTS

A total of 119 children (average age: 42.12 months; range, 7.5-95.5 months) with a genetic diagnosis of AS were enrolled. The median GQ score of the GMDS was 29.6 points (95% confidence interval, 28.6-33.25). The children had relatively good locomotor and personal-social skills but poor language skills. Overall, 89% (106/119) had mental ages younger than 24 months for all five subscales. The non-deletion group (i.e., without deletion in chromosome 15q11-13) had higher GQs and locomotor, personal-social, and performance subscale quotients. The GQ was significantly different among the three age subgroups and significantly correlated with age. Compared with the non-epilepsy group, the epilepsy group had lower GQs and lower quotients for the locomotor, personal-social, speech, language, and eye-hand coordination subscales.

CONCLUSION

Children with AS in China experience severe neurodevelopmental deterioration. In addition to age, molecular subtypes and the onset of seizures may also correlate with these patients' intellectual development. The GMDS-C is an accurate tool that can assess the clinical characteristics of AS. The data of this study can be used as baseline data for clinical trials performed to evaluate drug development or other AS treatment development.

Electrophysiological Abnormalities in Angelman Syndrome Correlate With Symptom Severity

Background

Angelman syndrome (AS) is a rare neurodevelopmental disorder caused by the absence of functional UBE3A in neurons. Excess low-frequency oscillations as measured with electroencephalography (EEG) have been identified as a characteristic finding, but the relationship of this EEG finding to the symptomatology of AS and its significance in the pathophysiology of AS remain unknown.

Methods

We used correlations and machine learning to investigate the cross-sectional and longitudinal relationship between EEG spectral power and motor, cognitive, and language skills (Bayley Scales of Infant and Toddler Development, Third Edition); adaptive behavior (Vineland Adaptive Behavior Scales, Second Edition); AS-specific symptoms (AS Clinical Severity Scale); and the age of epilepsy onset in a large sample of children (age: 1–18 years) with AS due to a chromosomal deletion of 15q11-q13 (45 individuals with 72 visits).

Results

We found that after accounting for age differences, participants with stronger EEG delta-band abnormality had earlier onset of epilepsy and lower performance scores across symptom domains including cognitive, motor, and communication. Combing spatial and spectral information beyond the delta frequency band increased the cross-sectional association with clinical severity on average by approximately 45%. Furthermore, we found evidence for longitudinal correlations of EEG delta-band power within several performance domains, including the mean across Bayley Scales of Infant and Toddler Development, Third Edition, scores.

Conclusions

Our results show an association between EEG abnormalities and symptom severity in AS, underlining the significance of the former in the pathophysiology of AS. Furthermore, our work strengthens the rationale for using EEG as a biomarker in the development of treatments for AS, a concept that may apply more generally to neurodevelopmental disorders.

Neuropsychological and ASD phenotypes in rare genetic syndromes: A critical review of the literature

OBJECTIVE

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by core deficits in social communication and restricted and repetitive behaviors and interests. Recent advances in clinical genetics have improved our understanding of genetic syndromes associated with ASD, which has helped clarify distinct etiologies of ASD and document syndrome-specific profiles of neurocognitive strengths and weaknesses. Pediatric neuropsychologists have the potential to be impactful members of the care team for children with genetic syndromes and their families.

METHOD

We provide a critical review of the current literature related to the neuropsychological profiles of children with four genetic syndromes associated with ASD, including Tuberous Sclerosis Complex (TSC), fragile X syndrome (FXS), 22q11.2 deletion syndrome, and Angelman syndrome. Recommendations for assessment, intervention, and future directions are provided.

RESULTS

There is vast heterogeneity in terms of the cognitive, language, and developmental abilities of these populations. The within- and across-syndrome variability characteristic of genetic syndromes should be carefully considered during clinical evaluations, including possible measurement limitations, presence of intellectual disability, and important qualitative differences in the ASD-phenotypes across groups.

CONCLUSIONS

Individuals with genetic disorders pose challenging diagnostic and assessment questions. Pediatric neuropsychologists with expertise in neurodevelopmental processes are well suited to address these questions and identify profiles of neurocognitive strengths and weaknesses, tailor individualized recommendations, and provide diagnostic clarification.

PACS1-Neurodevelopmental disorder: clinical features and trial readiness

Background

PACS1-Neurodevelopmental Disorder (PACS1-NDD) is an ultra-rare condition due to a recurrent mutation in the PACS1 gene. Little systematically collected data exist about the functional abilities and neurodevelopmental morbidities in children with PACS1-NDD

Methods

Parents of individuals with PACS1-NDD completed an on-line survey designed collaboratively by researchers, parents, and clinicians. Analyses focused on those with a confirmed R203W variant.

Results

Of 35 individuals with confirmed variants, 18 (51%) were female. The median age was 8 years (interquartile range 4.5–15). Seventeen (49%) had a diagnosis of epilepsy. Twelve (40%, of 30 responding to the question) reported autism and (N = 11/30, 37%) reported features of autism. Most children walked independently (N = 29/32, 91%), had a pincer grasp (N = 23/32, 72%), could feed themselves independently (N = 15/32, 47%), and used speech (N = 23/32, 72%). Sixteen of twenty-nine (55%) had simple pre-academic skills. Neither epilepsy nor autism was associated with functional abilities or other clinical features (all P > 0.05).

Conclusions

PACS1-NDD is a moderately-severe intellectual disability syndrome in which seizures occur but are not a defining or primary feature. Successful precision medicine clinical trials for this ultra-rare disorder must target important core features of this disorder and utilize assessment tools commensurate with the level of function in this clinical population.

Hyperactive behaviour in Angelman syndrome: the association with sleep problems and age of epilepsy onset

BACKGROUND

Sleep problems are common in many neurodevelopmental disorders, but little is known about how sleep is related to behavioural symptoms in Angelman syndrome (AS) or other genetic disorders. Hyperactive behaviour, sleep problems and epilepsy seem to be more common in AS than in other genetic conditions associated with severe intellectual disability. We hypothesised that both more sleep problems and earlier onset of epileptic seizures would predict more symptoms of hyperactivity. Hence, the aim of the project was to explore the association between hyperactive behaviour, sleep problems and age of epilepsy onset in individuals with AS.

METHOD

All known parents/guardians (n = 115) of individuals with AS in Norway were invited to participate in this descriptive correlational study. Fifty-six individuals (49%) responded, and 42 people (25 male and 17 female; mean age 18.5 years, range 2-57 years) with genetically verified AS were included. Scores for 'hyperactivity' and 'sleep problems' were derived from questionnaire data. Information on epilepsy was obtained from medical records.

RESULTS

'Hyperactivity' was positively correlated with 'total sleep problems' (r = 0.46, P = 0.002) and negatively correlated with 'age of epilepsy onset' (r = -0.47, P = 0.01). 'Age of epilepsy onset' was not correlated with 'total sleep problems'. An overall multiple regression model with 'hyperactivity' as the dependent variable and 'age of epilepsy onset' and 'total sleep problems' as covariates was significant (R²  = 0.39, F = 8.16, P = 0.002). Hence, hyperactivity in AS could be predicted from both age of epilepsy onset and current sleep problems.

CONCLUSIONS

Sleep problems may increase hyperactivity symptoms in individuals with AS. The association between hyperactivity and sleep problems in AS indicates that both should be investigated together as part of routine clinical assessment and intervention for either area of difficulty. Younger age of epilepsy onset was associated with more hyperactivity in AS, which may be related to encephalopathic effects of seizures and epilepsy.

Genotype-Phenotype Correlations in Angelman Syndrome

Angelman syndrome (AS) is a rare neurodevelopmental disease that is caused by the loss of function of the maternal copy of ubiquitin-protein ligase E3A (UBE3A) on the chromosome 15q11-13 region. AS is characterized by global developmental delay, severe intellectual disability, lack of speech, happy disposition, ataxia, epilepsy, and distinct behavioral profile. There are four molecular mechanisms of etiology: maternal deletion of chromosome 15q11-q13, paternal uniparental disomy of chromosome 15q11-q13, imprinting defects, and maternally inherited UBE3A mutations. Different genetic types may show different phenotypes in performance, seizure, behavior, sleep, and other aspects. AS caused by maternal deletion of 15q11-13 appears to have worse development, cognitive skills, albinism, ataxia, and more autistic features than those of other genotypes. Children with a UBE3A mutation have less severe phenotypes and a nearly normal development quotient. In this review, we proposed to review genotype-phenotype correlations based on different genotypes. Understanding the pathophysiology of the different genotypes and the genotype-phenotype correlations will offer an opportunity for individualized treatment and genetic counseling. Genotype-phenotype correlations based on larger data should be carried out for identifying new treatment modalities.

The adaptive functioning profile of Pitt-Hopkins syndrome

BACKGROUND

There are few cohort studies describing the adaptive functioning profile for Pitt-Hopkins syndrome (PTHS). In this study we examine the adaptive functioning profile for PTHS and compare it to Angelman syndrome (AS).

METHOD

Caregivers of 14 individuals with PTHS, 33 with deletion AS and 23 with non-deletion AS, completed the Vineland Adaptive Behavior Scales-II.

RESULTS

The profile of adaptive functioning in PTHS was characterised by strengths in socialisation, followed by motor skills, communication then daily living skills. The PTHS group scored significantly lower than the non-deletion AS group on all domains except socialisation and significantly lower than the deletion AS group, for motor skills only.

CONCLUSIONS

An uneven adaptive behavior profile for individuals with PTHS mirrors that of AS, with implications for assessment and intervention.

Delta power robustly predicts cognitive function in Angelman syndrome

Objective

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by loss of function of the maternally inherited UBE3A gene in neurons. Promising disease‐modifying treatments to reinstate UBE3A expression are under development and an early measure of treatment response is critical to their deployment in clinical trials. Increased delta power in EEG recordings, reflecting abnormal neuronal synchrony, occurs in AS across species and correlates with genotype. Whether delta power provides a reliable biomarker for clinical symptoms remains unknown.

Methods

We analyzed combined EEG recordings and developmental assessments in a large cohort of individuals with AS (N = 82 subjects, 133 combined EEG and cognitive assessments, 1.08–28.16 years; 32F) and evaluated delta power as a biomarker for cognitive function, as measured by the Bayley Cognitive Score. We examined the robustness of this biomarker to varying states of consciousness, recording techniques and analysis procedures.

Results

Delta power predicted the Bayley Scale cognitive score (P < 10⁻⁵, R² = 0.9374) after controlling for age (P < 10⁻²⁴), genotype:age (P < 10⁻¹¹), and repeat assessments (P < 10⁻⁸), with the excellent fit on cross validation (R² = 0.95). There were no differences in model performance across states of consciousness or bipolar versus average montages (ΔAIC < 2). Models using raw data excluding frontal channels outperformed other models (ΔAIC > 4) and predicted performance in expressive (P = 0.0209) and receptive communication (P < 10⁻³) and fine motor skills (P < 10⁻⁴).

Interpretation

Delta power is a simple, direct measure of neuronal activity that reliably correlates with cognitive function in AS. This electrophysiological biomarker offers an objective, clinically relevant endpoint for treatment response in emerging clinical trials.

The multi-domain responder index: a novel analysis tool to capture a broader assessment of clinical benefit in heterogeneous complex rare diseases

In traditional clinical trial design, efficacy is typically assessed using a single primary endpoint in a randomized controlled trial to detect an expected treatment effect of a therapy in a narrowly selected patient population. This accepted paradigm is based on clinical evaluations that may not actually capture the breadth of the impact of a disease, which is especially true in the setting of complex, multisystem, rare diseases with small, extremely heterogeneous patient populations. The multi-domain responder index (MDRI) is a novel approach that accommodates complex and heterogeneous disease manifestations and evaluates a broad array of clinical disease without impairing the power or rigor of a study to fully understand a treatment. The MDRI sums the scores corresponding to clinically significant thresholds of change for each component domain in each individual patient, capturing the mean clinically meaningful change across multiple domains within individuals. This novel approach combines and then sums the results of independent domain endpoint responder analyses into one responder score to provide a broad basis for the assessment of efficacy. The impact of a treatment across multiple, physiologically independent domains, can be assessed clinically, reducing the adverse impact of heterogeneity on trial outcomes and allowing eligibility criteria to enroll a wider range of patients, ultimately resulting in efficacy and safety assessments of a therapy across a broad group of heterogeneous patients in rare disease programs.

Trial registration The following studies are referenced within this manuscript (CLINICALTRIALS.GOV registration numbers): NCT00912925; NCT00146770; NCT00067470; NCT00104234; NCT00069641; NCT02230566; NCT02377921; NCT02432144.

Refining the Behavioral Phenotype of Angelman Syndrome: Examining Differences in Motivation for Social Contact Between Genetic Subgroups

Angelman syndrome (AS) is caused by loss of information from the 15q11.2-13 region on the maternal chromosome with striking phenotypic difference from Prader–Willi syndrome in which information is lost from the same region on the paternal chromosome. Motivation for social contact and sensory seeking behaviors are often noted as characteristics of the phenotype of AS and it has been argued that the strong drive for social contact supports a kinship theory interpretation of genomic imprinting. In this study we developed an experimental paradigm for quantifying the motivation for social contact in AS and examined differences across the genetic subtypes that cause AS [deletion, imprinting centre defect (ICD), uniparental disomy and UBE3A mutation]. Using single case experimental designs we examined the rate of acquisition of behavioral responses using operant learning paradigms for 21 children with AS whilst systematically varying the nature of social and sensory reinforcement. Variability in rates of acquisition was influenced by the nature of rewarding stimuli. Across the total sample both sensory stimuli and social contact could increase the rate of rewarded behavior with difference between children in the most effective reward. A striking difference in the rewarding properties of social contact across genetic subtypes was evidenced by non-deletion genetic causes of AS showing significantly higher rates of responding than the deletion cause in the social reinforcement paradigm. The results indicate that reinforcer assessment can beneficially inform behavioral interventions and that within syndrome variability in the behavioral phenotype of AS is likely driven by genetic difference. The non-deletion cause of AS, and particularly the ICD group, may be the optimal group for further study of genomic imprinting.

Angelman syndrome genotypes manifest varying degrees of clinical severity and developmental impairment

Angelman Syndrome (AS) is a severe neurodevelopmental disorder due to impaired expression of UBE3A in neurons. There are several genetic mechanisms that impair UBE3A expression, but they differ in how neighboring genes on chromosome 15 at 15q11-q13 are affected. There is evidence that different genetic subtypes present with different clinical severity, but a systematic quantitative investigation is lacking. Here we analyze natural history data on a large sample of individuals with AS (n = 250, 848 assessments), including clinical scales that quantify development of motor, cognitive, and language skills (Bayley Scales of Infant Development, Third Edition; Preschool Language Scale, Fourth Edition), adaptive behavior (Vineland Adaptive Behavioral Scales, Second Edition), and AS-specific symptoms (AS Clinical Severity Scale). We found that clinical severity, as captured by these scales, differs between genetic subtypes: individuals with UBE3A pathogenic variants and imprinting defects (IPD) are less affected than individuals with uniparental paternal disomy (UPD); of those with UBE3A pathogenic variants, individuals with truncating mutations are more impaired than those with missense mutations. Individuals with a deletion that encompasses UBE3A and other genes are most impaired, but in contrast to previous work, we found little evidence for an influence of deletion length (class I vs. II) on severity of manifestations. The results of this systematic analysis highlight the relevance of genomic regions beyond UBE3A as contributing factors in the AS phenotype, and provide important information for the development of new therapies for AS. More generally, this work exemplifies how increasing genetic irregularities are reflected in clinical severity.

Strabismus surgery in Angelman syndrome: More than ocular alignment

PURPOSE

To 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.

DESIGN

Observational cross-sectional study.

METHODS

Medical 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.

RESULTS

Seventeen 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.

CONCLUSIONS

According 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.

Angelman syndrome and melatonin: What can they teach us about sleep regulation

In 1965, Dr Harry Angelman reported a neurodevelopmental disorder affecting three unrelated children who had similar symptoms: brachycephaly, mental retardation, ataxia, seizures, protruding tongues, and remarkable paroxysms of laughter. Over the past 50 years, the disorder became Angelman's namesake and symptomology was expanded to include hyper-activity, stereotypies, and severe sleep disturbances. The sleep disorders in many Angelman syndrome (AS) patients are broadly characterized by difficulty falling and staying asleep at night. Some of these patients sleep less than 4 hours a night and, in most cases, do not make up this lost sleep during the day-leading to the speculation that AS patients may "need" less sleep. Most AS patients also have severely reduced levels of melatonin, a hormone produced by the pineal gland exclusively at night. This nightly pattern of melatonin production is thought to help synchronize internal circadian rhythms and promote nighttime sleep in humans and other diurnal species. It has been proposed that reduced melatonin levels contribute to the sleep problems in AS patients. Indeed, emerging evidence suggests melatonin replacement therapy can improve sleep in many AS patients. However, AS mice show sleep problems that are arguably similar to those in humans despite being on genetic backgrounds that do not make melatonin. This suggests the hypothesis that the change in nighttime melatonin may be a secondary factor rather than the root cause of the sleeping disorder. The goals of this review article are to revisit the sleep and melatonin findings in both AS patients and animal models of AS and discuss what AS may tell us about the underlying mechanisms of, and interplay between, melatonin and sleep.

Comprehensive Assessment of Individuals With Significant Levels of Intellectual Disability: Challenges, Strategies, and Future Directions

The variety and extent of impairments in individuals with severe-profound levels of intellectual disability (ID) impact their ability to complete valid behavioral assessments. Although standardized assessment is crucial for objectively evaluating patients, many individuals with severe-profound levels of ID perform at the floor of most assessments designed for their chronological age. Additionally, the presence of language and motor impairments may influence the individual's ability to perform a task, even when that task is meant to measure an unrelated construct leading to an underestimation of their true ability. This article provides an overview of the assessment protocols used by multiple groups working with individuals with severe-profound levels of ID, discusses considerations for obtaining high-quality assessment results, and suggests guidelines for standardizing these protocols across the field.

Properties of beta oscillations in Dup15q syndrome

Background

Duplications of 15q11.2-q13.1 (Dup15q syndrome) are highly penetrant for autism, intellectual disability, hypotonia, and epilepsy. The 15q region harbors genes critical for brain development, particularly UBE3A and a cluster of gamma-aminobutyric acid type A receptor (GABA_AR) genes. We recently described an electrophysiological biomarker of the syndrome, characterized by excessive beta oscillations (12–30 Hz), resembling electroencephalogram (EEG) changes induced by allosteric modulation of GABA_ARs. In this follow-up study, we tested a larger cohort of children with Dup15q syndrome to comprehensively examine properties of this EEG biomarker that would inform its use in future clinical trials, specifically, its (1) relation to basic clinical features, such as age, duplication type, and epilepsy; (2) relation to behavioral characteristics, such as cognition and adaptive function; (3) stability over time; and (4) reproducibility of the signal in clinical EEG recordings.

Methods

We computed EEG power and beta peak frequency (BPF) in a cohort of children with Dup15q syndrome (N = 41, age range 9–189 months). To relate EEG parameters to clinical (study 1) and behavioral features (study 2), we examined age, duplication type, epilepsy, cognition, and daily living skills (DLS) as predictors of beta power and BPF. To evaluate stability over time (study 3), we derived the intraclass correlation coefficients (ICC) from beta power and BPF computed from children with multiple EEG recordings (N = 10, age range 18–161 months). To evaluate reproducibility in a clinical setting (study 4), we derived ICCs from beta power computed from children (N = 8, age range 19–96 months), who had undergone both research EEG and clinical EEG.

Results

The most promising relationships between EEG and clinical traits were found using BPF. BPF was predicted both by epilepsy status (R² = 0.11, p = 0.038) and the DLS component of the Vineland Adaptive Behavior Scale (R² = 0.17, p = 0.01). Beta power and peak frequency showed high stability across repeated visits (beta power ICC = 0.93, BPF ICC = 0.92). A reproducibility analysis revealed that beta power estimates are comparable between research and clinical EEG (ICC = 0.94).

Conclusions

In this era of precision health, with pharmacological and neuromodulatory therapies being developed and tested for specific genetic etiologies of neurodevelopmental disorders, quantification and examination of mechanistic biomarkers can greatly improve clinical trials. To this end, the robust beta oscillations evident in Dup15q syndrome are clinically reproducible and stable over time. With future preclinical and computational studies that will help disentangle the underlying mechanism, it is possible that this biomarker could serve as a robust measure of drug target engagement or a proximal outcome measure in future disease modifying intervention trials.

High-voltage, diffuse delta rhythms coincide with wakeful consciousness and complexity in Angelman syndrome

Abundant evidence from slow wave sleep, anesthesia, coma, and epileptic seizures links high-voltage, slow electroencephalogram (EEG) activity to loss of consciousness. This well-established correlation is challenged by the observation that children with Angelman syndrome (AS), while fully awake and displaying volitional behavior, display a hypersynchronous delta (1–4 Hz) frequency EEG phenotype typical of unconsciousness. Because the trough of the delta oscillation is associated with down-states in which cortical neurons are silenced, the presence of volitional behavior and wakefulness in AS amidst diffuse delta rhythms presents a paradox. Moreover, high-voltage, slow EEG activity is generally assumed to lack complexity, yet many theories view functional brain complexity as necessary for consciousness. Here, we use abnormal cortical dynamics in AS to assess whether EEG complexity may scale with the relative level of consciousness despite a background of hypersynchronous delta activity. As characterized by multiscale metrics, EEGs from 35 children with AS feature significantly greater complexity during wakefulness compared with sleep, even when comparing the most pathological segments of wakeful EEG to the segments of sleep EEG least likely to contain conscious mentation and when factoring out delta power differences across states. These findings (i) warn against reverse inferring an absence of consciousness solely on the basis of high-amplitude EEG delta oscillations, (ii) corroborate rare observations of preserved consciousness under hypersynchronization in other conditions, (iii) identify biomarkers of consciousness that have been validated under conditions of abnormal cortical dynamics, and (iv) lend credence to theories linking consciousness with complexity.

Differentiating molecular etiologies of Angelman syndrome through facial phenotyping using deep learning

Angelman syndrome (AS) is caused by several genetic mechanisms that impair the expression of maternally-inherited UBE3A through deletions, paternal uniparental disomy (UPD), UBE3A pathogenic variants, or imprinting defects. Current methods of differentiating the etiology require molecular testing, which is sometimes difficult to obtain. Recently, computer-based facial analysis systems have been used to assist in identifying genetic conditions based on facial phenotypes. We sought to understand if the facial-recognition system DeepGestalt could find differences in phenotype between molecular subtypes of AS. Images and molecular data on 261 individuals with AS ranging from 10 months through 32 years were analyzed by DeepGestalt in a cross-validation model with receiver operating characteristic (ROC) curves generated. The area under the curve (AUC) of the ROC for each molecular subtype was compared and ranked from least to greatest differentiable phenotype. We determined that DeepGestalt demonstrated a high degree of discrimination between the deletion subtype and UPD or imprinting defects, and a lower degree of discrimination with the UBE3A pathogenic variants subtype. Our findings suggest that DeepGestalt can recognize subclinical differences in phenotype based on etiology and may provide decision support for testing.