Genotype-Phenotype Correlations in Angelman Syndrome

Generation of three iPSC lines with inducible systems to be used in Angelman syndrome research

The neurodevelopmental disorder Angelman syndrome (AS) has an incidence of 1:15.000 live births and is caused by absence of UBE3A protein, showing imprinted gene expression in the brain. Imprinted genes are controlled by differentially methylated regions resulting in parent-of-origin dependent gene expression. Two iPS cell lines derived from patients with AS and one healthy control iPSC line were used to integrate a 3rd generation reverse tetracycline transactivator protein (rtTA3) into the AAVS1 locus on chromosome 19. The rtTA allows tetracycline-dependent activation of an inducible promoter that can be introduced at a position of interest in the cell lines described here.

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.

Exploring an objective measure of overactivity in children with rare genetic syndromes

BACKGROUND

Overactivity is prevalent in several rare genetic neurodevelopmental syndromes, including Smith-Magenis syndrome, Angelman syndrome, and tuberous sclerosis complex, although has been predominantly assessed using questionnaire techniques. Threats to the precision and validity of questionnaire data may undermine existing insights into this behaviour. Previous research indicates objective measures, namely actigraphy, can effectively differentiate non-overactive children from those with attention-deficit hyperactivity disorder. This study is the first to examine the sensitivity of actigraphy to overactivity across rare genetic syndromes associated with intellectual disability, through comparisons with typically-developing peers and questionnaire overactivity estimates.

METHODS

A secondary analysis of actigraphy data and overactivity estimates from The Activity Questionnaire (TAQ) was conducted for children aged 4-15 years with Smith-Magenis syndrome (N=20), Angelman syndrome (N=26), tuberous sclerosis complex (N=16), and typically-developing children (N=61). Actigraphy data were summarized using the M10 non-parametric circadian rhythm variable, and 24-hour activity profiles were modelled via functional linear modelling. Associations between actigraphy data and TAQ overactivity estimates were explored. Differences in actigraphy-defined activity were also examined between syndrome and typically-developing groups, and between children with high and low TAQ overactivity scores within syndromes.

RESULTS

M10 and TAQ overactivity scores were strongly positively correlated for children with Angelman syndrome and Smith-Magenis syndrome. M10 did not substantially differ between the syndrome and typically-developing groups. Higher early morning activity and lower evening activity was observed across all syndrome groups relative to typically-developing peers. High and low TAQ group comparisons revealed syndrome-specific profiles of overactivity, persisting throughout the day in Angelman syndrome, occurring during the early morning and early afternoon in Smith-Magenis syndrome, and manifesting briefly in the evening in tuberous sclerosis complex.

DISCUSSION

These findings provide some support for the sensitivity of actigraphy to overactivity in children with rare genetic syndromes, and offer syndrome-specific temporal descriptions of overactivity. The findings advance existing descriptions of overactivity, provided by questionnaire techniques, in children with rare genetic syndromes and have implications for the measurement of overactivity. Future studies should examine the impact of syndrome-related characteristics on actigraphy-defined activity and overactivity estimates from actigraphy and questionnaire techniques.

Behavioral and Psychiatric Disorders in Syndromic Autism

Syndromic autism refers to autism spectrum disorder diagnosed in the context of a known genetic syndrome. The specific manifestations of any one of these syndromic autisms are related to a clinically defined genetic syndrome that can be traced to certain genes and variants, genetic deletions, or duplications at the chromosome level. The genetic mutations or defects in single genes associated with these genetic disorders result in a significant elevation of risk for developing autism relative to the general population and are related to recurrence with inheritance patterns. Additionally, these syndromes are associated with typical behavioral characteristics or phenotypes as well as an increased risk for specific behavioral or psychiatric disorders and clinical findings. Knowledge of these associations helps guide clinicians in identifying potentially treatable conditions that can help to improve the lives of affected patients and their families.

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.

Short Stature and Distinct Growth Characteristics in Angelman Syndrome

Objectives - Angelman syndrome (AS) is a rare, genetic, neurodevelopmental disorder characterized by severe impairments in speech, cognition and motor skills accompanied by unique behaviors, distinct facial features and high prevalence of epilepsy and sleep problems. Despite some reports of short stature among AS patients, this feature is not included in the clinical criteria defined in 2005. We investigated growth patterns among AS patients with respect to mutation type, growth periods, family history and endocrine abnormalities. Methods - Data was collected from patients' medical files in AS national clinic. Mutation subtypes were divided to deletion and non-deletion. Four growth periods were defined: preschool, childhood, peak-height velocity, and final-height. Results - The cohort included 88 individuals (46 males), with 54 (61.4%) carrying deletion subtype. A median of 3 observations per individual , produced 280 data points. Final-height-SDS was significantly lower compared to general population (-1.23±1.26, p<0.001), and in deletion group vs. non-deletion (-1.67±1.3 vs. -0.65±0.96, p=0.03). Final-height-SDS was significantly lower compared to height-SDS in preschool period (-1.32 vs -0.47, p=0.007). Patient's final-height-SDS was significantly lower than the parents' (∆final-height-SDS=0.94±0.99, p=0.002). IGF1-SDS was significantly decreased compared to general population (-0.55±1.61, p=0.04), with lower values among deletion group (-0.70±1.44, p=0.01) Conclusions - AS patients demonstrate specific growth pattern with deceleration during childhood and adolescence resulting in significantly decreased final height compared to normal population, and even lower among deletion subgroup, which could be attributed to reduced IGF1 levels. We propose adding short stature to the clinical criteria and developing adjusted growth curves for AS population.

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.

Angelman syndrome in two siblings: clinical case

Background. Angelman syndrome (AS) is rare genetic disease characterized by severe mental retardation, gross developmental speech delay, facial dysmorphia, disorders of motor activity, behavior and sleep, epileptic seizures manifestation. Pathology refers to diseases of genomic imprinting. There are four possible mechanisms of pathology development in Angelman syndrome: 15q11.2-q13 deletion on the chromosome 15 of maternal origin, mutation of the ubiquitin ligase (UBE3A) gene at the 15q11.2 locus on the chromosome 15 of maternal origin, uniparental disomy of the 15q11.2-q13 region of paternal origin, imprinting center defect.

Clinical case description. Clinical picture of Angelman syndrome in two twin sibs (boy E., girl V.) observed in Children’s City Clinical Hospital № 1 in Nizhny Novgorod is presented. Children from consecutive pregnancy with dichorionic-diamniotic twins; preterm birth at 30 weeks. There was burdened obstetric-biological and perinatal history due to the threatened miscarriage during this pregnancy and due to asphyxia of both children during delivery. The disease has classical course in both patients: static functions development delay, gross developmental speech and intellectual delay, behavioral and motor disorders (stereotypy, tremor, ataxia, episodes of unmotivated laughter, sleep disorders), presence of typical facial dysmorphia. This diagnosis was confirmed by the molecular genetic study (boy — mutation in exon 7 of the UBE3A gene, girl — mutations in exons 6 and 7 of the UBE3A gene). Features of epileptic seizure therapy in both patients are presented.

Conclusion. The presented clinical case demonstrates typical clinical picture of AS in two sibs confirmed by molecular genetic study. The therapy of this syndrome is very complicated. The described patients require constant anticonvulsant therapy, observation of neurologist, psychotherapist, working with speech pathologist. Complete correction of this syndrome is impossible. 

Transition from Animal-Based to Human Induced Pluripotent Stem Cells (iPSCs)-Based Models of Neurodevelopmental Disorders: Opportunities and Challenges

Neurodevelopmental disorders (NDDs) arise from the disruption of highly coordinated mechanisms underlying brain development, which results in impaired sensory, motor and/or cognitive functions. Although rodent models have offered very relevant insights to the field, the translation of findings to clinics, particularly regarding therapeutic approaches for these diseases, remains challenging. Part of the explanation for this failure may be the genetic differences-some targets not being conserved between species-and, most importantly, the differences in regulation of gene expression. This prompts the use of human-derived models to study NDDS. The generation of human induced pluripotent stem cells (hIPSCs) added a new suitable alternative to overcome species limitations, allowing for the study of human neuronal development while maintaining the genetic background of the donor patient. Several hIPSC models of NDDs already proved their worth by mimicking several pathological phenotypes found in humans. In this review, we highlight the utility of hIPSCs to pave new paths for NDD research and development of new therapeutic tools, summarize the challenges and advances of hIPSC-culture and neuronal differentiation protocols and discuss the best way to take advantage of these models, illustrating this with examples of success for some NDDs.

Pathophysiology of Nociception and Rare Genetic Disorders with Increased Pain Threshold or Pain Insensitivity

Pain and nociception are different phenomena. Nociception is the result of complex activity in sensory pathways. On the other hand, pain is the effect of interactions between nociceptive processes, and cognition, emotions, as well as the social context of the individual. Alterations in the nociceptive route can have different genesis and affect the entire sensorial process. Genetic problems in nociception, clinically characterized by reduced or absent pain sensitivity, compose an important chapter within pain medicine. This chapter encompasses a wide range of very rare diseases. Several genes have been identified. These genes encode the Nav channels 1.7 and 1.9 (SCN9A, and SCN11A genes, respectively), NGFβ and its receptor tyrosine receptor kinase A, as well as the transcription factor PRDM12, and autophagy controllers (TECPR2). Monogenic disorders provoke hereditary sensory and autonomic neuropathies. Their clinical pictures are extremely variable, and a precise classification has yet to be established. Additionally, pain insensitivity is described in diverse numerical and structural chromosomal abnormalities, such as Angelman syndrome, Prader Willy syndrome, Chromosome 15q duplication syndrome, and Chromosome 4 interstitial deletion. Studying these conditions could be a practical strategy to better understand the mechanisms of nociception and investigate potential therapeutic targets against pain.

Improving Gene Therapy for Angelman Syndrome with Secreted Human UBE3A

The rare genetic neurodevelopmental disease Angelman syndrome (AS) is caused by the loss of function of UBE3A, a ubiquitin ligase. The disease results in a lifetime of severe symptoms, including intellectual disability and motor impairments for which there are no effective treatments. One avenue of treatment for AS is the use of gene therapy to reintroduce a functional copy of the UBE3A gene. Our group had previously shown that recombinant adeno-associated virus (rAAV) expressing mouse Ube3a could rescue deficits in a mouse model of AS. Here, we expand on this work and show that this approach could be successfully replicated in a second AS model using the human UBE3A gene. Furthermore, we address the challenge of limited vector distribution in the brain by developing a novel modified form of UBE3A. This modified protein, termed STUB, was designed with a secretion signal and a cell-penetrating peptide. This allowed transduced cells to act as factories for the production of UBE3A protein that could be taken up by neighboring non-transduced cells, thus increasing the number of neurons receiving the therapeutic protein. Combining this construct with intracerebroventricular injections to maximize rAAV distribution within the brain, we demonstrate that this novel approach improves the recovery of behavioral and electrophysiological deficits in the AS rat model. More importantly, a comparison of rAAV-STUB to a rAAV expressing the normal human UBE3A gene showed that STUB was a more effective therapeutic. These data suggest that rAAV-STUB is a new potential approach for the treatment of AS.

The role of whole exome sequencing in the UBE3A point mutation of Angelman Syndrome: A case report

INTRODUCTION

Angelman Syndrome (AS) is a rare disorder with a relatively well-defined phenotype caused by lack of expression of the maternally inherited ubiquitin-protein ligase E3A (UBE3A) gene in the brain. This article describes the role of genetic testing using whole-exome sequencing (WES) in detecting rare AS variants, a point mutation in the UBE3A gene.

CASE PRESENTATION

We describe a rarely reported clinical presentation of AS in a two year and ten months old girl with severe developmental delay, movement and balance disorder, frequent smiling, apparent happy demeanor, speech impairment, absence of seizure, lack of sleep, and abnormal food-related behavior. Physical examination showed microcephaly, with facial characteristics of AS, ataxia gait, and truncal hypotonia. The electroencephalogram showed medium amplitude rhythmic 2-3c/s. Brain Magnetic Resonance Imaging revealed microcephaly, corpus callosum dysgenesis, and heterotopia grey matter on the bilateral lateral ventricle. WES was conducted to search pathogenic variants and showed a heterozygous mutation in exon 9 of the UBE3A gene, c.1513C > T (p.Arg505Ter).

CONCLUSION

Angelman syndrome is a neurodevelopmental disorder that has several underlying genetic etiologies. WES could detect a rare variant of Angelman syndrome, identified as the point mutation of the UBE3A gene, which cannot be seen with other modalities.

Case Report: An Atypical Angelman Syndrome Case With Obesity and Fulfilled Autism Spectrum Disorder Identified by Microarray

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders which are etiologically heterogeneous. Chromosomal microarray is now recommended as the first-tier clinical diagnostic test for ASD. We performed chromosomal microarray in 16 Thai patients with ASD using an Illumina HumanCytoSNP-12 v2.1 array and found one case with uniparental disomy (UPD) of chromosome 15. Methylation-specific PCR showed abnormal methylation of the maternal SNRPN allele. Haplotype analysis revealed that the patient had received both chromosomes 15 from his father. These results were consistent with Angelman syndrome. However, his clinical features had no clinical significance for classic Angelman syndrome. He had first presented at the pediatric clinic with no speech, poor social interaction skills and repetitive behaviors consistent with ASD based on the DSM-IV criteria at 2 years of age and later confirmed by ADOS at 5 years of age. He was strikingly overweight but had no dysmorphic facies, seizures nor ataxia and was diagnosed as non-syndromic ASD, a diagnosis which was believed until at 10 years of age, his DNA was included for analysis in this current cohort study. Our findings suggest that ASD patients with unknown etiology should be considered for methylation-specific PCR testing for Angelman syndrome where chromosomal microarray is not available. In the study, we also review the clinical features of Angelman syndrome caused by UPD and the frequency of ASD in individuals with Angelman syndrome.