Distinct phenotypes distinguish the molecular classes of Angelman syndrome

IPSC Models of Chromosome 15Q Imprinting Disorders: From Disease Modeling to Therapeutic Strategies

The chromosome 15q11-q13 region of the human genome is regulated by genomic imprinting, an epigenetic phenomenon in which genes are expressed exclusively from one parental allele. Several genes within the 15q11-q13 region are expressed exclusively from the paternally inherited chromosome 15. At least one gene UBE3A, shows exclusive expression of the maternal allele, but this allele-specific expression is restricted to neurons. The appropriate regulation of imprinted gene expression across chromosome 15q11-q13 has important implications for human disease. Three different neurodevelopmental disorders result from aberrant expression of imprinted genes in this region: Prader-Willi syndrome (PWS), Angelman syndrome (AS), and 15q duplication syndrome.

Towards an understanding of Angelman syndrome in mice studies

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by severe mental retardation, absence of speech, abnormal motor coordination, abnormal EEG, and spontaneous seizure. AS is caused by a deficiency in the ubiquitin ligase E3A (Ube3a) gene product, known to play a dual role as both ubiquitin ligase and transcription coactivator. In AS animal models, multiple Ube3a substrates are accumulated in neurons. So far, studies in mouse models have either aimed at re-expressing Ube3a or manipulating downstream signaling pathways. Reintroducing Ube3a in AS mice showed promising results but may have two caveats. First, it may cause an overdosage in the Ube3a expression, which in turn is known to contribute to autism spectrum disorders. Second, in mutation cases, the exogenous Ube3a may have to compete with the mutated endogenous form. Such two caveats left spaces for developing therapies or interventions directed to targets downstream Ube3a. Notably, Ube3a expression is dynamically regulated by neuronal activity and plays a crucial role in synaptic plasticity. The abnormal synaptic plasticity uncovered in AS mice has been frequently rescued, but circuits symptoms like seizure are resistant to treatment. Future investigations are needed to further clarify the function (s) of Ube3a during development. Here I reviewed the recently identified major Ube3a substrates and signaling pathways involved in AS pathology, the Ube3a expression, imprinting and evolution, the AS mouse models that have been generated and inspired therapeutic potentials, and finally proposed some future explorations to better understand the AS pathology.

Ocular findings and strabismus surgery outcomes in Chinese children with Angelman syndrome: Three case reports

RATIONALE

Angelman syndrome (AS) is an uncommon genetic disease characterized as serious retarded mental development and ocular abnormality.

PATIENT CONCERNS

This report aims to present the ophthalmological features, and identify the diagnosis and outcomes of strabismus surgery in AS patients.

DIAGNOSIS

Three children with exotropia were diagnosed with AS based on their typical clinical features.

INTERVENTIONS

All patients underwent multiplex ligation-dependent probe amplification (MLPA) analysis and accepted lateral rectus recession surgery with the assistance of intravenous combined inhalation anesthesia.

OUTCOMES

The maternal heritage deletion of chromosome 15q11.2-q13 was verified in all patients by MLPA. All patients with strabismus could not cooperate during the vision test, and had astigmatism. The strabismus type of AS patients was horizontal exotropia, and no vertical strabismus was found. One of these patients was combined with high myopia. The hypopigmentation on the hair and iris was ubiquitous. However, retina pigmentation was normal. After different degrees of lateral rectus recession, the exotropia was significantly relieved, and the surgical effects were stable postoperatively.

LESSONS

Horizontal exotropia is the major strabismus type. Severe intellectual disability, hyperactivity, and speech impairment are the common characteristics of AS children. Its examination and operation design remains challenging. Thus, repeated examinations and intelligence rehabilitation are essential.

Multi-Method Assessment of Sleep in Children With Angelman Syndrome: A Case-Controlled Study

Objectives: To assess sleep quality and timing in children with Angelman syndrome (AS) with sleep problems using questionnaires and actigraphy and contrast sleep parameters to those of typically developing (TD) children matched for age and sex. Methods: Week-long actigraphy assessments were undertaken with children with AS (n = 20) with parent-reported sleep difficulties and compared with age and sex matched TD controls. The presence of severe sleep problems was assessed using the modified Simonds and Parraga sleep questionnaire. Sleep hygiene was measured using the Family Inventory of Sleep Habits. Results: Actigraphy and parent-completed sleep diary data indicated that children with AS had significantly earlier bedtimes (p = .003, Cohen d = .47) and poorer sleep efficiency (78%, p = .04, d = .33) than TD children (84%). No significant differences in total sleep time, sleep onset latency or wake after sleep onset were found between the two groups. The expected relationship between later bedtimes and increasing age found for the TD group (p < .001, β.78) was not evidenced for the AS group (p = .09, β.39). Considerable inter-individual and night to night variation in actigraphy assessed total sleep time and wake after sleep onset was found for children with AS compared to TD children. Parent report indicated that a greater proportion of children with AS had severe night waking problems compared to TD children (81 versus 5%). No significant differences in sleep hygiene and excessive daytime sleepiness were found between the two groups (p > .05). Conclusions: This study reports the largest objective dataset of sleep quality parameters in children with AS. Sleep quality in this group was characterised by poor efficiency and significant intra- and inter-individual variability that warrants further investigation. This variability should inform assessment and intervention for sleep in children with AS, as averages of total sleep, even across a 7 day period may not capture the difficulties with night waking highlighted by parental questionnaire report.

An overview of health issues and development in a large clinical cohort of children with Angelman syndrome

This study presents a broad overview of health issues and psychomotor development of 100 children with Angelman syndrome (AS), seen at the ENCORE Expertise Center for AS in Rotterdam, the Netherlands. We aimed to further delineate the phenotype of AS, to evaluate the association of the phenotype with genotype and other determinants such as epilepsy and to get insight in possible targets for intervention. We confirmed the presence of a more severe phenotype in the 15q11.2‐q13 deletion subtype. Novel findings were an association of (early onset of) epilepsy with a negative effect on development, a high occurrence of nonconvulsive status epilepticus, a high rate of crouch gait in the older children with risk of deterioration of mobility, a relatively low occurrence of microcephaly, a higher mean weight for height in all genetic subtypes with a significant higher mean in the nondeletion children, and a high occurrence of hyperphagia across all genetic subtypes. Natural history data are needed to design future trials. With this large clinical cohort with structured prospective and multidisciplinary follow‐up, we provide unbiased data on AS to support further intervention studies to optimize outcome and quality of life of children with AS and their family.

Early Diagnosis in Prader-Willi Syndrome Reduces Obesity and Associated Co-Morbidities

Prader–Willi syndrome (PWS) is an imprinting genetic disorder characterized by lack of expression of genes on the paternal chromosome 15q11–q13 region. Growth hormone (GH) replacement positively influences stature and body composition in PWS. Our hypothesis was that early diagnosis delays onset of obesity in PWS. We studied 352 subjects with PWS, recruited from the NIH Rare Disease Clinical Research Network, to determine if age at diagnosis, ethnicity, gender, and PWS molecular class influenced the age they first become heavy, as determined by their primary care providers, and the age they first developed an increased appetite and began seeking food. The median ages that children with PWS became heavy were 10 years, 6 years and 4 years for age at diagnosis < 1 year, between 1 and 3 years, and greater than 3 years of age, respectively. The age of diagnosis and ethnicity were significant factors influencing when PWS children first became heavy (p < 0.01), however gender and the PWS molecular class had no influence. Early diagnosis delayed the onset of becoming heavy in individuals with PWS, permitting early GH and other treatment, thus reducing the risk of obesity-associated co-morbidities. Non-white individuals had an earlier onset of becoming heavy.

An observational study of pediatric healthcare burden in Angelman syndrome: results from a real-world study

BACKGROUND

The objective of this study is to describe variations in the healthcare resource utilization (HRU) among individuals with Angelman syndrome (AS) over the first 12 years of life. Data for this study were drawn from the AS Natural History study (ASNHS), which is an observational study on the developmental progress, behavior, and medical morbidity of individuals with AS conducted over eight years. Caregiver-reported information on hospitalization, surgery, and medication utilization was used to assess HRU. Repeated measures mixed effect models were used to assess the relationship between age and probability of hospitalization, surgery, and prescription medication utilization.

RESULTS

Mean age at study enrollment was 6 years of age and both sexes were equally represented. The mean number of visits per participant was three. Results from this study suggest that individuals with AS have a high HRU burden. Hospitalization and surgery burden were highest in the first year of life. Use of medications for seizures and sleep disturbance increased over time.

CONCLUSIONS

The study highlights the significant healthcare burden among individuals with AS. Future studies that estimate cost and caregiver burden associated with AS are needed to assess the lifelong economic impact of AS on families and healthcare system.

Communication in Angelman syndrome: a scoping review

AIM

A scoping review was conducted to examine and evaluate empirical data on the communication profile of Angelman syndrome beyond the described dissociation between receptive language and speech.

METHOD

Three databases (PsycINFO, Embase, and Web of Science) were searched to retrieve articles investigating communication in Angelman syndrome. Seventeen articles investigating the broader communication profile were found; their methodology was evaluated against quality criteria.

RESULTS

Despite the absence of speech, individuals with Angelman syndrome have a wide repertoire of non-verbal communicative behaviours, mainly characterized by gestures, although advanced forms such as symbolic communication are used by some individuals. The use of communicative forms differs between the genetic aetiologies of Angelman syndrome; individuals with non-deletion aetiologies typically have greater communicative abilities.

INTERPRETATION

The broader communication profile of Angelman syndrome is characterized by diverse and multimodal abilities, including some use of symbolic forms of communication that appears atypical given the absence of speech. This is suggestive of a probable dissociation between speech and other expressive forms of communication, indicating an isolated speech production impairment. This highlights a need in this population for alternative communication and specific input from services tailored to support the nuances of the communication profile of Angelman syndrome.

WHAT THIS PAPER ADDS

Although absent speech is near universal, a diverse profile of other communicative abilities has been reported. Parental reporting has been predominantly used to assess the communication profile of Angelman syndrome. Literature that investigates the specificities and possible dissociations in such a communication profile is limited.

A placebo-controlled trial of folic acid and betaine in identical twins with Angelman syndrome

Background

Angelman syndrome (AS) is a neurodevelopmental disorder that is caused by maternal genetic deficiency of a gene that encodes E6-AP ubiquitin-protein ligase (gene symbol UBE3A) mapping to chromosome 15q11-q13. AS leads to stiff and jerky gait, excess laughter, seizures, and severe intellectual disability. In some parts of the brain, the paternally inherited UBE3A gene is subject to genomic imprinting by the action of the UBE3A-antisense transcript (UBE3A-ATS) on the paternally inherited allele. Consequently, only the maternally inherited UBE3A gene is expressed in mature neurons. AS occurs due to deletions of the maternal 15q11 − 13 region, paternal uniparental disomy (UPD), imprinting center defects, mutations in the maternal UBE3A gene, or other unknown genetic malfunctions that result in a silenced maternal UBE3A gene in the specific imprinted regions of the brain.

Results

A potential treatment strategy for AS is to increase methylation of UBE3A-ATS to promote expression of the paternal UBE3A gene and thus ameliorate the clinical phenotypes of AS. We treated two sets of male identical twins with class I deletions with a 1 year treatment trial of either betaine and folic acid versus placebo. We found no statistically significant changes in the clinical parameters tested at the end of the 1 year trial, nor did we find any significant adverse events.

Conclusions

This study tested the hypothesis that by increasing the methylation of the UBE3A-antisense transcript in Angelman syndrome to promote expression of the silenced paternal UBE3A gene we may ameliorate the clinical phenotypes of AS. We treated two sets of identical twins with placebo versus betaine and folic acid. Although this study represented a novel approach to treating Angelman syndrome, the differences in the developmental testing results was not significant. This paper also discusses the value of monozygotic twin studies in minimizing confounding variables and its utility in conducting small treatment studies.

Trial registration

NCT00348933. Registered 6 July 2006.

Preserved expressive language as a phenotypic determinant of Mosaic Angelman Syndrome

Background

Angelman Syndrome (AS) is a neurodevelopmental disorder with core features of intellectual disability, speech impairment, movement disorders, and a unique behavioral profile. Typically, AS results from absent maternal expression of UBE3A, but some individuals have imprinting defects in a portion of their cells. These individuals are mosaic for normal and defective UBE3A expression, resulting in mosaic AS (mAS) with a partial loss of gene expression.

Methods

This study aims to contrast the mAS phenotype to that of AS. Clinical characteristics of mAS were obtained from a parental survey of 22 mAS patients and from the Angelman Natural History study. These were contrasted with those of AS using historical data.

Results

Developmental delay was present in nearly all mAS patients, whereas the core features of AS were reported in less than 40%. While language and ability to manage activities of daily living were markedly improved over that expected in AS, mAS patients demonstrated a high incidence of behavioral challenges.

Conclusion

Clinical work‐up of an individual with developmental delay, hyperactivity, anxiety, and an uncharacteristically happy demeanor should prompt methylation studies to rule out mAS. We expand the phenotypic spectrum of AS to include features that overlap with Prader‐Willi such as hyperphagia.

Mechanisms underlying the EEG biomarker in Dup15q syndrome

Background

Duplications of 15q11.2-q13.1 (Dup15q syndrome), including the paternally imprinted gene UBE3A and three nonimprinted gamma-aminobutyric acid type-A (GABAA) receptor genes, are highly penetrant for neurodevelopmental disorders such as autism spectrum disorder (ASD). To guide targeted treatments of Dup15q syndrome and other forms of ASD, biomarkers are needed that reflect molecular mechanisms of pathology. We recently described a beta EEG phenotype of Dup15q syndrome, but it remains unknown which specific genes drive this phenotype.

Methods

To test the hypothesis that UBE3A overexpression is not necessary for the beta EEG phenotype, we compared EEG from a reference cohort of children with Dup15q syndrome (n = 27) to (1) the pharmacological effects of the GABAA modulator midazolam (n = 12) on EEG from healthy adults, (2) EEG from typically developing (TD) children (n = 14), and (3) EEG from two children with duplications of paternal 15q (i.e., the UBE3A-silenced allele).

Results

Peak beta power was significantly increased in the reference cohort relative to TD controls. Midazolam administration recapitulated the beta EEG phenotype in healthy adults with a similar peak frequency in central channels (f = 23.0 Hz) as Dup15q syndrome (f = 23.1 Hz). Both paternal Dup15q syndrome cases displayed beta power comparable to the reference cohort.

Conclusions

Our results suggest a critical role for GABAergic transmission in the Dup15q syndrome beta EEG phenotype, which cannot be explained by UBE3A dysfunction alone. If this mechanism is confirmed, the phenotype may be used as a marker of GABAergic pathology in clinical trials for Dup15q syndrome.

A mouse model of Angelman syndrome imprinting defects

Angelman syndrome, Prader-Will syndrome and Dup15q syndrome map to a cluster of imprinted genes located at 15q11-q13. Imprinting at this domain is regulated by an imprinting control region consisting of two distinct elements, the Angelman syndrome imprinting center (AS-IC) and the Prader-Willi syndrome imprinting center (PWS-IC). Individuals inheriting deletions of the AS-IC exhibit reduced expression of the maternally expressed UBE3A gene and biallelic expression of paternal-only genes. We have previously demonstrated that AS-IC activity partly consists of providing transcription across the PWS-IC in oocytes, and that these transcripts are necessary for maternal imprinting of Snrpn. Here we report a novel mouse mutation that truncates transcripts prior to transiting the PWS-IC and results in a domain-wide imprinting defect. These results confirm a transcription-based model for imprint setting at this domain. The imprinting defect can be preempted by removal of the transcriptional block in oocytes, but not by its removal in early embryos. Imprinting defect mice exhibit several traits often found in individuals with Angelman syndrome imprinting defects.

The use of iPSC technology for modeling Autism Spectrum Disorders

Autism Spectrum Disorders (ASDs) are a group of neurodevelopmental disorders that influence social skills, involving communication, interaction, and behavior, usually with repetitive and restrictive manners. Due to the variety of genes involved in ASDs and several possible environmental factors influence, there is still no answer to what really causes syndromic and non-syndromic types of ASDs, usually affecting each individual in a unique way. However, we know that the mechanism underlying ASDs involves brain functioning. The human brain is a complex structure composed of close to 100 billion cells, which is a big challenge to study counting just with post mortem tissue investigation or genetic approaches. Therefore, human induced pluripotent stem cells (iPSC) technology has been used as a tool to produce viable cells for understanding a working brain. Taking advantage of patient-derived stem cells, researchers are now able to generate neurons, glial cells and brain organoids in vitro to model ASDs. In this review we report data from different studies showing how iPSCs have been a critical tool to study the different phenotypes of ASDs.

Healthcare burden among individuals with Angelman syndrome: Findings from the Angelman Syndrome Natural History Study

Background

The objective of this study is to describe healthcare resource utilization (HRU) and supportive therapy utilization (STU) among individuals with Angelman syndrome (AS), and to compare such usage by molecular etiology.

Methods

Participants were categorized into deletion and non‐deletion genotypes. Statistical differences were assessed using an independent samples t test.

Results

Data were available on 302 individuals. Mean age of participants was 5.5 years, 92% of whom were less than 13 years, and 71% had the deletion etiology. About 68% of participants had at least one hospitalization since birth to enrollment in the study; the average number of hospitalizations during that time period was 2.3 and average length of stay was 4.5 days. The most common reasons for hospitalization were seizures, lower respiratory infections, and surgery. The most common reasons for surgery were myringotomy, strabismus surgery, tonsillectomy or adenoidectomy, and gastrostomy tube insertion/fundoplication. Anticonvulsants, gastroesophageal reflux disease, sleep, and behavioral medications were the most commonly prescribed drugs. STU was high among individuals with AS.

Conclusions

This study shows that individuals with AS have high HRU/STU, and apart from a few differences, HRU/STU was similar across molecular etiology. These results reflect usage in younger individuals and studies that describe HRU/STU in older individuals are needed.

Electrophysiological Phenotype in Angelman Syndrome Differs Between Genotypes

BACKGROUND

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by either disruptions of the gene UBE3A or deletion of chromosome 15 at 15q11-q13, which encompasses UBE3A and several other genes, including GABRB3, GABRA5, GABRG3, encoding gamma-aminobutyric acid type A receptor subunits (β3, α5, γ3). Individuals with deletions are generally more impaired than those with other genotypes, but the underlying pathophysiology remains largely unknown. Here, we used electroencephalography (EEG) to test the hypothesis that genes other than UBE3A located on 15q11-q13 cause differences in pathophysiology between AS genotypes.

METHODS

We compared spectral power of clinical EEG recordings from children (1-18 years of age) with a deletion genotype (n = 37) or a nondeletion genotype (n = 21) and typically developing children without Angelman syndrome (n = 48).

RESULTS

We found elevated theta power (peak frequency: 5.3 Hz) and diminished beta power (peak frequency: 23 Hz) in the deletion genotype compared with the nondeletion genotype as well as excess broadband EEG power (1-32 Hz) peaking in the delta frequency range (peak frequency: 2.8 Hz), shared by both genotypes but stronger for the deletion genotype at younger ages.

CONCLUSIONS

Our results provide strong evidence for the contribution of non-UBE3A neuronal pathophysiology in deletion AS and suggest that hemizygosity of the GABRB3-GABRA5-GABRG3 gene cluster causes abnormal theta and beta EEG oscillations that may underlie the more severe clinical phenotype. Our work improves the understanding of AS pathophysiology and has direct implications for the development of AS treatments and biomarkers.

The Autism and Angelman Syndrome Protein Ube3A/E6AP: The Gene, E3 Ligase Ubiquitination Targets and Neurobiological Functions

UBE3A is a gene implicated in neurodevelopmental disorders. The protein product of UBE3A is the E3 ligase E6-associated protein (E6AP), and its expression in the brain is uniquely regulated via genetic imprinting. Loss of E6AP expression leads to the development of Angelman syndrome (AS), clinically characterized by lack of speech, abnormal motor development, and the presence of seizures. Conversely, copy number variations (CNVs) that result in the overexpression of E6AP are strongly associated with the development of autism spectrum disorders (ASDs), defined by decreased communication, impaired social interest, and increased repetitive behavior. In this review article, we focus on the neurobiological function of Ube3A/E6AP. As an E3 ligase, many functional target proteins of E6AP have been discovered, including p53, Arc, Ephexin5, and SK2. On a neuronal level, E6AP is widely expressed within the cell, including dendritic arbors, spines, and the nucleus. E6AP regulates neuronal morphological maturation and plays an important role in synaptic plasticity and cortical development. These molecular findings provide insight into our understanding of the molecular events underlying AS and ASDs.

UBE3A and Its Link With Autism

UBE3A is a dual function protein consisting of ubiquitin ligase as well as transcriptional co-activator function. UBE3A gene is imprinted in the brain with preferential maternal-specific expression particularly in the neuron and loss of activity of the maternally inherited UBE3A causes Angelman syndrome (AS), characterized by severe mental retardation, lack of speech, seizures and autistic features. Interestingly, duplication, triplication, or gain-of-function mutations in the UBE3A gene are also linked with autism clinically distinguished by social impairments and stereotyped behaviors. These findings indicate that the expression and activity of UBE3A must be tightly regulated during brain development and UBE3A might be playing a crucial role in controlling synaptic function and plasticity through proteasome-mediated degradation as well as transcriptional regulation of its target proteins. In fact, several recent reports demonstrated the role of UBE3A in the modulation of synaptic function and plasticity. This review focuses on the critical role of UBE3A in regulating the synaptic function and how its altered activity is associated with autism.

Angelman syndrome-associated point mutations in the Zn2+-binding N-terminal (AZUL) domain of UBE3A ubiquitin ligase inhibit binding to the proteasome

Deregulation of the HECT ubiquitin ligase UBE3A/E6AP has been implicated in Angelman syndrome as well as autism spectrum disorders. We and others have previously identified the 26S proteasome as one of the major UBE3A-interacting protein complexes. Here, we characterize the interaction of UBE3A and the proteasomal subunit PSMD4 (Rpn10/S5a). We map the interaction to the highly conserved Zn2+-binding N-terminal (AZUL) domain of UBE3A, the integrity of which is crucial for binding to PSMD4. Interestingly, two Angelman syndrome point mutations that affect the AZUL domain show an impaired ability to bind PSMD4. Although not affecting the ubiquitin ligase or the estrogen receptor α-mediated transcriptional regulation activities, these AZUL domain mutations prevent UBE3A from stimulating the Wnt/β-catenin signaling pathway. Taken together, our data indicate that impaired binding to the 26S proteasome and consequential deregulation of Wnt/β-catenin signaling might contribute to the functional defect of these mutants in Angelman syndrome.

A randomized placebo controlled clinical trial to evaluate the efficacy and safety of minocycline in patients with Angelman syndrome (A-MANECE study)

BACKGROUND

Minocycline is an old tetracycline antibiotic that has shown antiinflammatory and antiapoptotic properties in different neurological disease mouse models. Previous single arm study in humans demonstrated benefits in individuals with Angelman Syndrome (AS); however, its efficacy in patients with Angelman Syndrome has not been assessed in a controlled trial. This was a randomized, double-blind, placebo-controlled, crossover trial in individuals with AS, aged 6 years to 30 years (n = 32, mean age 12 [SD 6·29] years). Participants were randomized to minocycline or placebo for 8 weeks and then switched to the other treatment (a subset of 22 patients) or to receive minocycline for up to 16 weeks (10 patients). After week 16, all patients entered a wash-out 8-week follow-up period.

RESULTS

Thirty-six subjects were screened and 34 were randomized. Thirty two subjects (94·1%) completed at least the first period and all of them completed the full trial. Intention-to-treat analysis demonstrated the lack of significantly greater improvements in the primary outcome, mean changes in age equivalent of the development index of the Merrill-Palmer Revised Scale after minocycline compared with placebo (1·90 ± 3·16 and 2·00 ± 3·28, respectively, p = 0·937). Longer treatment duration up to 16 weeks did not result in better treatment outcomes (1·86 ± 3·35 for 8 weeks treatment vs 1·20 ± 5·53 for 16 weeks treatment, p = 0·667). Side effects were not significantly different during minocycline and placebo treatments. No serious adverse events occurred on minocycline.

CONCLUSIONS

Minocycline treatment for up to 16 weeks in children and young adults with AS resulted in lack of significant improvements in development indexes compared to placebo treatment. Treatment with minocycline appears safe and well tolerated; even if it cannot be completely ruled out that longer trials might be required for a potential minocycline effect to be expressed, available results and lack of knowledge on the actual mechanism of action do not support this hypothesis.

TRIAL REGISTRATION

European Clinical Trial database ( EudraCT 2013-002154-67 ), registered 16th September 2013; US Clinical trials database ( NCT02056665 ), registered 6th February 2014.

Research protocol: The initiation, design and establishment of the Global Angelman Syndrome Registry

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder affecting between 1 in 15 000 and 1 in 24 000 individuals. The condition results in severe developmental and expressive language delays, motor impairments and a unique behavioural phenotype consisting of excessive laughter, smiling and sociability. While many studies have contributed knowledge about the causes and natural history of the syndrome, large scale longitudinal studies are required to advance research and therapeutics for this rare syndrome.

METHOD

This article describes the protocol for the Global Angelman Syndrome Registry, and some initial findings. Due to the rarity of AS and the variability in symptom presentation, the registry team will strive for complete case ascertainment. Parents and caregivers will submit data to the registry via a secure internet connection. The registry consists of 10 modules that cover patient demographics; developmental, diagnostic, medical and surgical history, behaviour and development, epilepsy, medications and interventions and sleep.

RESULTS

Since its launch at https://angelmanregistry.info in September 2016, almost 470 individuals with AS have been signed up to the registry worldwide: 59% are from North and South America, 23% are from Europe, 17% are from the Asia Pacific region and 1% are from the Middle East or Africa. The majority of registrants are children, with only 16% aged over 20 years. Most participants indicated a chromosome deletion (76%), with fewer participants indicating a mutation, uniparental disomy or imprinting defect (20%).

CONCLUSION

Findings indicate a need to consider recruitment strategies that target caregivers of older children and adults, and parents and caregivers from non-English speaking backgrounds.

Angelman syndrome in adolescence and adulthood: A retrospective chart review of 53 cases

Angelman syndrome is a neurogenetic disorder with varying clinical presentations and symptoms as the individual ages. The goal of this study was to characterize changes over time in the natural history of this syndrome in a large population. We reviewed the medical records of the 53 patients who were born prior to 2000 and seen at the Angelman Syndrome Clinic at Massachusetts General Hospital to assess neurological, sleep, behavioral, gastrointestinal, orthopedic, and ophthalmologic functioning. The average age of this cohort was 24 years. Active seizures were present in 35%, nonepileptic myoclonus in 42%, and clinically significant tremors in 55%. Anxiety was present in 57%, increasing to 71% in those ages 26-43 years. In terms of sleep, 56% reported 8 hr of sleep or more, although 43% reported frequent nocturnal awakenings. Gastrointestinal issues remain problematic with 81% having constipation and 53% gastroesophageal reflux. The majority lived in a parent's home and remained independently mobile, though scoliosis was reportedly present in 30%, and 20% had reported low bone density/osteoporosis. The results of this study suggest that the prevalence of active seizures may decrease in adulthood but that the prevalence of movement disorders such as tremor and nonepileptic myoclonus may increase. Anxiety increases significantly as individuals age while defiant behaviors appear to decrease. Sleep dysfunction typically improves as compared to childhood but remains a significant issue for many adults. Other areas that require monitoring into adulthood include gastrointestinal dysfunction, and orthopedic/mobility issues, such as reported scoliosis and bone density, and ophthalmologic disorders.

Integration of CpG-free DNA induces de novo methylation of CpG islands in pluripotent stem cells

CpG islands (CGIs) are primarily promoter-associated genomic regions and are mostly unmethylated within highly methylated mammalian genomes. The mechanisms by which CGIs are protected from de novo methylation remain elusive. Here we show that insertion of CpG-free DNA into targeted CGIs induces de novo methylation of the entire CGI in human pluripotent stem cells (PSCs). The methylation status is stably maintained even after CpG-free DNA removal, extensive passaging, and differentiation. By targeting the DNA mismatch repair gene MLH1 CGI, we could generate a PSC model of a cancer-related epimutation. Furthermore, we successfully corrected aberrant imprinting in induced PSCs derived from an Angelman syndrome patient. Our results provide insights into how CpG-free DNA induces de novo CGI methylation and broaden the application of targeted epigenome editing for a better understanding of human development and disease.

Melatonin and Angelman Syndrome: Implications and Mathematical Model of Diurnal Secretion

The main aim of the study was to compare the melatonin rhythms in subjects with Angelman syndrome (n = 9) and in children with (n = 80) and without (n = 40) epilepsy (nonepileptic patients diagnosed with peripheral nerve palsies, myopathy, and back pain) using our mathematical model of melatonin circadian secretion. The characteristics describing the diurnal hormone secretion such as minimum melatonin concentration, release amplitude, phase shift of melatonin release, and sleep duration as well as the dim light melatonin onset (DLMO) of melatonin secretion and the γ shape parameter allow analyzing the fit and deducing about how much the measured melatonin profile differs from a physiological bell-shaped secretion. The estimated sleep duration and phase shift of melatonin release as well as the DMLO offsets at 25% and 50% relative thresholds are the key characteristic of Angelman syndrome children. As revealed from the γ shape parameter, the melatonin secretion profiles are disturbed in majority of the AG subjects revealing rather a triangular course instead of the bell-like one.

Novel intragenic deletions within the UBE3A gene in two unrelated patients with Angelman syndrome: case report and review of the literature

BACKGROUND

Patients with Angelman syndrome (AS) are affected by severe intellectual disability with absence of speech, distinctive dysmorphic craniofacial features, ataxia and a characteristic behavioral phenotype. AS is caused by the lack of expression in neurons of the UBE3A gene, which is located in the 15q11.2-q13 imprinted region. Functional loss of UBE3A is due to 15q11.2-q13 deletion, mutations in the UBE3A gene, paternal uniparental disomy and genomic imprinting defects.

CASE PRESENTATION

We report here two patients with clinical features of AS referred to our hospital for clinical follow-up and genetic diagnosis. Methylation Specific-Multiplex Ligation-Dependent Probe Amplification (MS-MLPA) of the 15q11.2-q13 region was carried out in our laboratory as the first diagnostic tool detecting two novel UBE3A intragenic deletions. Subsequently, the MLPA P336-A2 kit was used to confirm and determine the size of the UBE3A deletion in the two patients. A review of the clinical features of previously reported patients with whole UBE3A gene or partial intragenic deletions is presented here together with these two new patients.

CONCLUSION

Although rare, UBE3A intragenic deletions may represent a small fraction of AS patients without a genetic diagnosis. Testing for UBE3A intragenic exonic deletions should be performed in those AS patients with a normal methylation pattern and no mutations in the UBE3A gene.

Atypical Angelman syndrome due to a mosaic imprinting defect: Case reports and review of the literature

Angelman syndrome (AS) is characterized by severe intellectual disability, limited, or absent speech and a generally happy demeanor. The four known etiological mechanisms; deletions, uniparental disomy, imprinting defects, and UBE3A mutation all affect expression of the UBE3A gene at 15q11-q13. An atypical phenotype is seen in individuals who are mosaic for a chromosome 15q11-q13 imprinting defect on the maternal allele. These patients present with a milder phenotype, often with hyperphagia and obesity or non-specific intellectual disability. Unlike typical AS syndrome, they can have a vocabulary up to 100 words and speak in sentences. Ataxia and seizures may not be present, and the majority of individuals do not have microcephaly. Here we review the current literature and present three individuals with atypical AS caused by a mosaic imprinting defect to demonstrate why DNA methylation analysis at the SNRPN locus needs to be considered in a broader clinical context. © 2017 Wiley Periodicals, Inc.

Unmet clinical needs and burden in Angelman syndrome: a review of the literature

Background

Angelman syndrome (AS) is a rare disorder with a relatively well-defined phenotype. Despite this, very little is known regarding the unmet clinical needs and burden of this condition, especially with regard to some of the most prevalent clinical features—movement disorders, communication impairments, behavior, and sleep.

Main text

A targeted literature review using electronic medical databases (e.g., PubMed) was conducted to identify recent studies focused on specific areas of the AS phenotype (motor, communication, behavior, sleep) as well as epidemiology, diagnostic processes, treatment, and burden. 142 articles were reviewed and summarized. Findings suggest significant impairment across the life span in all areas of function. While some issues may resolve as individuals get older (e.g., hyperactivity), others become worse (e.g., movement disorders, aggression, anxiety). There are no treatments focused on the underlying etiology, and the symptom-based therapies currently prescribed do not have much, if any, empirical support.

Conclusions

The lack of standardized treatment protocols or approved therapies, combined with the severity of the condition, results in high unmet clinical needs in the areas of motor functioning, communication, behavior, and sleep for individuals with AS and their families.

Epilepsy and sleep disorders improve in adolescents and adults with Angelman syndrome: A multicenter study on 46 patients

OBJECTIVE

Actual knowledge on evolution of Angelman syndrome (AS) relies on questionnaire-based cohort studies, phone interviews, or small retrospective cohort studies focused on specific clinical-genetic features. These reports provide conflicting results. The aim of this study was to assess the long-term outcome of epilepsy, sleep disorders, and EEG in a vast series of AS subjects.

METHODS

We collected patients with genetically confirmed AS, aged ≥14years, followed in three tertiary epilepsy Centers or attending the meetings of the Italian Organization for AS (OrSA). Retrospective clinical and EEG data were retrieved from hospital archives or family documents. At index evaluation (IE) (last visit at tertiary Centers or single visit during OrSA meetings), caregivers were interviewed about anamnestic data and filled questionnaires on sleep disorders and daily-living skills. Patients underwent general and neurologic evaluation, and video-EEG recordings. All available EEGs were analyzed to compare evolution of spike-wave index (SWI) over the years.

RESULTS

Forty-six subjects aged 14-45years were included: 24 from tertiary Centers, 22 from OrSA meetings. During childhood, 42/46 (91.3%) had seizures, which improved over the years in all subjects. Among patients with epilepsy, 27(64%) became seizure-free at a median age of 10years and 4 remained seizure-free even after antiepileptic withdrawal. During childhood, 39/46 (84.8%) had sleep disorders, which improved in 27/39 (69%) over the years. At IE, daily-living skills corresponded to age≤1.6years in 29/46 (63%). Electroencephalogram showed typical AS patterns in 35/46 (76.1%). In EEGs recorded from 10 patients, SWI was not significantly different between infancy/childhood and adolescence/adulthood.

CONCLUSION

Improvement of epilepsy or sleep disorders should not disregard the clinical suspicion of AS in adolescent or adult patients with suggestive features. Drug withdrawal might be considered in the management of epilepsy despite the persistence of epileptiform abnormalities.

In silico modeling of the cryptic E2∼ubiquitin-binding site of E6-associated protein (E6AP)/UBE3A reveals the mechanism of polyubiquitin chain assembly

To understand the mechanism for assembly of Lys⁴⁸-linked polyubiquitin degradation signals, we previously demonstrated that the E6AP/UBE3A ligase harbors two functionally distinct E2∼ubiquitin-binding sites: a high-affinity Site 1 required for E6AP Cys⁸²⁰∼ubiquitin thioester formation and a canonical Site 2 responsible for subsequent chain elongation. Ordered binding to Sites 1 and 2 is here revealed by observation of UbcH7∼ubiquitin-dependent substrate inhibition of chain formation at micromolar concentrations. To understand substrate inhibition, we exploited the PatchDock algorithm to model in silico UbcH7∼ubiquitin bound to Site 1, validated by chain assembly kinetics of selected point mutants. The predicted structure buries an extensive solvent-excluded surface bringing the UbcH7∼ubiquitin thioester bond within 6 Å of the Cys⁸²⁰ nucleophile. Modeling onto the active E6AP trimer suggests that substrate inhibition arises from steric hindrance between Sites 1 and 2 of adjacent subunits. Confirmation that Sites 1 and 2 function in trans was demonstrated by examining the effect of E6APC820A on wild-type activity and single-turnover pulse-chase kinetics. A cyclic proximal indexation model proposes that Sites 1 and 2 function in tandem to assemble thioester-linked polyubiquitin chains from the proximal end attached to Cys⁸²⁰ before stochastic en bloc transfer to the target protein. Non-reducing SDS-PAGE confirms assembly of the predicted Cys⁸²⁰-linked ¹²⁵I-polyubiquitin thioester intermediate. Other studies suggest that Glu⁵⁵⁰ serves as a general base to generate the Cys⁸²⁰ thiolate within the low dielectric binding interface and Arg⁵⁰⁶ functions to orient Glu⁵⁵⁰ and to stabilize the incipient anionic transition state during thioester exchange.

Autism spectrum disorders and disease modeling using stem cells

Autism spectrum disorders (ASD) represent a variety of disorders characterized as complex lifelong neurodevelopment disabilities, which may affect the ability of communication and socialization, including typical comportments like repetitive and stereotyped behavior. Other comorbidities are usually present, such as echolalia, hypotonia, intellectual disability and difficulties in processing figured speech. Furthermore, some ASD individuals may present certain abilities, such as eidetic memory, outstanding musical or painting talents and special mathematical skills, among others. Considering the variability of the clinical symptoms, one autistic individual can be severely affected in communication while others can speak perfectly, sometimes having a vocabulary above average in early childhood. The same variability can be seen in other clinical symptoms, thus the "spectrum" can vary from severe to mild. Induced pluripotent stem cell technology has been used to model several neurological diseases, including syndromic and non-syndromic autism. We discuss how modeling the central nervous system cells in a dish may help to reach a better understanding of ASD pathology and variability, as well as personalize their treatment.

Prevalence of gastrointestinal symptoms in Angelman syndrome

Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability, expressive speech impairment, movement disorder, epilepsy, and a happy demeanor. Children with AS are frequently reported to be poor feeders during infancy and as having gastrointestinal issues such as constipation, reflux, and abnormal food related behaviors throughout their lifetime. To assess the prevalence of gastrointestinal disorders in individuals with AS, we retrospectively analyzed medical records of 120 individuals seen at the Angelman Syndrome Clinic at Massachusetts General Hospital and 43 individuals seen at the University of North Carolina Comprehensive Angelman Clinic. The majority of patients' medical records indicated at least one symptom of gastrointestinal dysfunction, with constipation and gastroesophageal reflux disease (GERD) the most common. Other gastrointestinal issues reported were cyclic vomiting episodes, difficulty swallowing, excessive swallowing, and eosinophilic esophagitis. Upper gastrointestinal symptoms such as GERD, swallowing difficulties, cyclic vomiting, and eosinophilic esophagitis were more common in those with deletions and uniparental disomy, likely related to the involvement of multiple genes and subsequent hypotonia. The frequency of constipation is consistent among all genetic subtypes while early feeding issues appear to mainly affect those with deletions. Caregivers and healthcare providers should be aware of the high prevalence of these issues, as proper treatment may improve not only gastrointestinal dysfunction but also sleep and behavioral issues.

Strain-dependence of the Angelman Syndrome phenotypes in Ube3a maternal deficiency mice

Angelman syndrome (AS) is a genetic neurodevelopmental disorder, most commonly caused by deletion or mutation of the maternal allele of the UBE3A gene, with behavioral phenotypes and seizures as key features. Currently no treatment is available, and therapeutics are often ineffective in controlling AS-associated seizures. Previous publications using the Ube3a maternal deletion model have shown behavioral and seizure susceptibility phenotypes, however findings have been variable and merit characterization of electroencephalographic (EEG) activity. In this study, we extend previous studies comparing the effect of genetic background on the AS phenotype by investigating the behavioral profile, EEG activity, and seizure threshold. AS C57BL/6J mice displayed robust behavioral impairments, spontaneous EEG polyspikes, and increased cortical and hippocampal power primarily driven by delta and theta frequencies. AS 129 mice performed poorly on wire hang and contextual fear conditioning and exhibited a lower seizure threshold and altered spectral power. AS F1 hybrid mice (C57BL/6J × 129) showed milder behavioral impairments, infrequent EEG polyspikes, and fewer spectral power alterations. These findings indicate the effect of common genetic backgrounds on the Ube3a maternal deletion behavioral, EEG, and seizure threshold phenotypes. Our results will inform future studies on the optimal strain for evaluating therapeutics with different AS-like phenotypes.

Exploring Expressive Communication Skills in a Cross-Sectional Sample of Children and Young Adults With Angelman Syndrome

PURPOSE

This study explores data on expressive communication skills of 300 individuals aged 0.0-21.11 years with Angelman syndrome (AS). These data provide a composite portrait of communication skills in a large sample of children and young adults with this rare disorder, specifying new detailed information about expressive communication.

METHOD

The database associated with the Communication Matrix assessment (Rowland, 2004, 2011; Rowland & Fried-Oken, 2010) was mined for data regarding individuals with AS. We extracted data on the reasons for communicating, level of communication achieved, and use of various expressive communication modes to convey 24 specific messages. The performance of children and young adults in 5 age groups in the cross-sectional sample were contrasted.

RESULTS

Results confirmed earlier studies showing that few individuals with AS use natural speech. However, in addition to using presymbolic modes, many children used alternative symbolic modes such as picture symbols, object symbols, and manual signs. Assessment scores increased slightly with age, F(4, 295) = 2.416, p = .049.

CONCLUSIONS

Aggregating data on a large sample of individuals with AS provides a reference point for practitioners and family members and a basis for future investigations.

Disrupted neuronal maturation in Angelman syndrome-derived induced pluripotent stem cells

Angelman syndrome (AS) is a neurogenetic disorder caused by deletion of the maternally inherited UBE3A allele and is characterized by developmental delay, intellectual disability, ataxia, seizures and a happy affect. Here, we explored the underlying pathophysiology using induced pluripotent stem cell-derived neurons from AS patients and unaffected controls. AS-derived neurons showed impaired maturation of resting membrane potential and action potential firing, decreased synaptic activity and reduced synaptic plasticity. These patient-specific differences were mimicked by knocking out UBE3A using CRISPR/Cas9 or by knocking down UBE3A using antisense oligonucleotides. Importantly, these phenotypes could be rescued by pharmacologically unsilencing paternal UBE3A expression. Moreover, selective effects of UBE3A disruption at late stages of in vitro development suggest that changes in action potential firing and synaptic activity may be secondary to altered resting membrane potential. Our findings provide a cellular phenotype for investigating pathogenic mechanisms underlying AS and identifying novel therapeutic strategies.

Effects of the synthetic neurosteroid ganaxolone on seizure activity and behavioral deficits in an Angelman syndrome mouse model

Angelman syndrome (AS) is a rare neurogenetic disorder characterized by severe developmental delay, motor impairments, and epilepsy. GABAergic dysfunction is believed to contribute to many of the phenotypic deficits seen in AS. We hypothesized that restoration of inhibitory tone mediated by extrasynaptic GABA_A receptors could provide therapeutic benefit. Here, we report that ganaxolone, a synthetic neurosteroid that acts as a positive allosteric modulator of synaptic and extrasynaptic GABA_A receptors, was anxiolytic, anticonvulsant, and improved motor deficits in the Ube3a-deficient mouse model of AS when administered by implanted mini-pump for 3 days or 4 weeks. Treatment for 4 weeks also led to recovery of spatial working memory and hippocampal synaptic plasticity deficits. This study demonstrates that ganaxolone ameliorates many of the behavioral abnormalities in the adult AS mouse, and tolerance did not occur to the therapeutic effects of the drug. The results support clinical studies to investigate ganaxolone as a symptomatic treatment for AS.

From Cortical and Subcortical Grey Matter Abnormalities to Neurobehavioral Phenotype of Angelman Syndrome: A Voxel-Based Morphometry Study

Angelman syndrome (AS) is a rare neurogenetic disorder due to loss of expression of maternal ubiquitin-protein ligase E3A (UBE3A) gene. It is characterized by severe developmental delay, speech impairment, movement or balance disorder and typical behavioral uniqueness. Affected individuals show normal magnetic resonance imaging (MRI) findings, although mild dysmyelination may be observed. In this study, we adopted a quantitative MRI analysis with voxel-based morphometry (FSL-VBM) method to investigate disease-related changes in the cortical/subcortical grey matter (GM) structures. Since 2006 to 2013 twenty-six AS patients were assessed by our multidisciplinary team. From those, sixteen AS children with confirmed maternal 15q11-q13 deletions (mean age 7.7 ± 3.6 years) and twenty-one age-matched controls were recruited. The developmental delay and motor dysfunction were assessed using Bayley III and Gross Motor Function Measure (GMFM). Principal component analysis (PCA) was applied to the clinical and neuropsychological datasets. High-resolution T1-weighted images were acquired and FSL-VBM approach was applied to investigate differences in the local GM volume and to correlate clinical and neuropsychological changes in the regional distribution of GM. We found bilateral GM volume loss in AS compared to control children in the striatum, limbic structures, insular and orbitofrontal cortices. Voxel-wise correlation analysis with the principal components of the PCA output revealed a strong relationship with GM volume in the superior parietal lobule and precuneus on the left hemisphere. The anatomical distribution of cortical/subcortical GM changes plausibly related to several clinical features of the disease and may provide an important morphological underpinning for clinical and neurobehavioral symptoms in children with AS.

Autism in Angelman Syndrome

The aim was to explore the comorbidity between Angelman syndrome and autism spectrum disorders (ASDs). Identification of autism in children with Angelman syndrome presents a diagnostic challenge. In the present study, 16 children with Angelman syndrome, all with a 15q11-13 deletion, were examined for ASDs. Thirteen children with Angelman syndrome received an ADOS-G algorithm classification of ASD; the remaining three were outside the autistic spectrum. Ten fulfilled the criteria for autism, and three for PDD-NOS. The 10 children with Angelman syndrome and comorbid autism were compared with eight children with only autism regarding their social and communicative skills. The results indicated that Angelman syndrome is better understood in terms of developmental delay, and autism in terms of developmental deviance. It is concluded that autism might have been overdiagnosed due to the extremely low mental age of the children with Angelman syndrome.

RBFOX1 and RBFOX2 are dispensable in iPSCs and iPSC-derived neurons and do not contribute to neural-specific paternal UBE3A silencing

Angelman Syndrome (AS) is a rare neurodevelopmental disorder caused by loss of function of the maternally inherited copy of UBE3A, an imprinted gene expressed biallelically in most tissues, but expressed exclusively from the maternal allele in neurons. Active transcription of the neuron-specific long non-coding RNA (lncRNA), UBE3A-ATS, has been shown to silence paternal UBE3A. We hypothesized that alternative splicing factors RBFOX2 and RBFOX1 might mediate splicing changes and result in the transcription of UBE3A-ATS in neurons. We found that RBFOX2 and RBFOX1 both bind to UBE3A-ATS transcript in neurons, but are not required for gene expression and/or neuron-specific processing in the SNURF/SNRPN-UBE3A region. However, we found that depletion of RBFOX2 causes a proliferation phenotype in immature neural cultures, suggesting that RBFOX2 is involved in division versus differentiation decisions in iPSC-derived neural progenitors. Absence of RBFOX2 also altered the expression of some genes that are important for glutamatergic neocortical development and Wnt-Frizzled signalling in mature neuronal cultures. Our data show that while RBFOX1 and RBFOX2 do not mediate neuron-specific processing of UBE3A-ATS, these proteins play important roles in developing neurons and are not completely functionally redundant.

Mitochondrial Superoxide Contributes to Hippocampal Synaptic Dysfunction and Memory Deficits in Angelman Syndrome Model Mice

Angelman syndrome (AS) is a neurodevelopmental disorder associated with developmental delay, lack of speech, motor dysfunction, and epilepsy. In the majority of the patients, AS is caused by the deletion of small portions of maternal chromosome 15 harboring the UBE3A gene. This results in a lack of expression of the UBE3A gene because the paternal allele is genetically imprinted. The UBE3A gene encodes an enzyme termed ubiquitin ligase E3A (E6-AP) that targets proteins for degradation by the 26S proteasome. Because neurodegenerative disease and other neurodevelopmental disorders have been linked to oxidative stress, we asked whether mitochondrial reactive oxygen species (ROS) played a role in impaired synaptic plasticity and memory deficits exhibited by AS model mice. We discovered that AS mice have increased levels of superoxide in area CA1 of the hippocampus that is reduced by MitoQ 10-methanesuflonate (MitoQ), a mitochondria-specific antioxidant. In addition, we found that MitoQ rescued impairments in hippocampal synaptic plasticity and deficits in contextual fear memory exhibited by AS model mice. Our findings suggest that mitochondria-derived oxidative stress contributes to hippocampal pathophysiology in AS model mice and that targeting mitochondrial ROS pharmacologically could benefit individuals with AS.

SIGNIFICANCE STATEMENT

Oxidative stress has been hypothesized to contribute to the pathophysiology of neurodevelopmental disorders, including autism spectrum disorders and Angelman syndrome (AS). Herein, we report that AS model mice exhibit elevated levels of mitochondria-derived reactive oxygen species in pyramidal neurons in hippocampal area CA1. Moreover, we demonstrate that the administration of MitoQ (MitoQ 10-methanesuflonate), a mitochondria-specific antioxidant, to AS model mice normalizes synaptic plasticity and restores memory. Finally, our findings suggest that antioxidants that target the mitochondria could be used therapeutically to ameliorate synaptic and cognitive deficits in individuals with AS.

Translating RNA sequencing into clinical diagnostics: opportunities and challenges

RNA-based measurements have the potential for application across diverse areas of human health, including disease diagnosis, prognosis and therapeutic selection. Current clinical applications include infectious diseases, cancer, transplant medicine and fetal monitoring.

RNA sequencing (RNA-seq) allows for the detection of a wide variety of RNA species, including mRNA, non-coding RNA, pathogen RNA, chimeric gene fusions, transcript isoforms and splice variants, and provides the capability to quantify known, pre-defined RNA species and rare RNA transcript variants within a sample. In addition to differential expression and detection of novel transcripts, RNA-seq also supports the detection of mutations and germline variation for hundreds to thousands of expressed genetic variants, facilitating assessment of allele-specific expression of these variants.

Circulating RNAs and small regulatory RNAs, such as microRNAs, are very stable. These RNA species are vigorously being tested for their potential as biomarkers. However, there are currently few agreed upon methods for isolation or quantitative measurements and a current lack of quality controls that can be used to test platform accuracy and sample preparation quality.

Analytical, bioinformatic and regulatory challenges exist, and ongoing efforts toward the establishment of benchmark standards, assay optimization for clinical conditions and demonstration of assay reproducibility are required to expand the clinical utility of RNA-seq.

RNA sequencing (RNA-seq) is a powerful approach for comprehensive analyses of transcriptomes. This Review describes the widespread potential applications of RNA-seq in clinical medicine, such as detecting disease-associated mutations and gene expression disruptions, as well as characteristic non-coding RNAs, circulating extracellular RNAs or pathogen RNAs. The authors also highlight the challenges in adopting RNA-seq routinely into clinical practice.

With the emergence of RNA sequencing (RNA-seq) technologies, RNA-based biomolecules hold expanded promise for their diagnostic, prognostic and therapeutic applicability in various diseases, including cancers and infectious diseases. Detection of gene fusions and differential expression of known disease-causing transcripts by RNA-seq represent some of the most immediate opportunities. However, it is the diversity of RNA species detected through RNA-seq that holds new promise for the multi-faceted clinical applicability of RNA-based measures, including the potential of extracellular RNAs as non-invasive diagnostic indicators of disease. Ongoing efforts towards the establishment of benchmark standards, assay optimization for clinical conditions and demonstration of assay reproducibility are required to expand the clinical utility of RNA-seq.

Potential therapeutic approaches for Angelman syndrome

INTRODUCTION

Angelman syndrome (AS) is a neurodevelopmental disorder caused by deficiency of maternally inherited UBE3A, an ubiquitin E3 ligase. Despite recent progress in understanding the mechanism underlying UBE3A imprinting, there is no effective treatment. Further investigation of the roles played by UBE3A in the central nervous system (CNS) is needed for developing effective therapies.

AREA COVERED

This review covers the literature related to genetic classifications of AS, recent discoveries regarding the regulation of UBE3A imprinting, alterations in cell signaling in various brain regions and potential therapeutic approaches. Since a large proportion of AS patients exhibit comorbid autism spectrum disorder (ASD), potential common molecular bases are discussed.

EXPERT OPINION

Advances in understanding UBE3A imprinting provide a unique opportunity to induce paternal UBE3A expression, thus targeting the syndrome at its 'root.' However, such efforts have yielded less-than-expected rescue effects in AS mouse models, raising the concern that activation of paternal UBE3A after a critical period cannot correct all the CNS defects that developed in a UBE3A-deficient environment. On the other hand, targeting abnormal downstream cell signaling pathways has provided promising rescue effects in preclinical research. Thus, combined reinstatement of paternal UBE3A expression with targeting abnormal signaling pathways should provide better therapeutic effects.

Selective multifaceted E3 ubiquitin ligases barricade extreme defense: Potential therapeutic targets for neurodegeneration and ageing

Efficient and regular performance of Ubiquitin Proteasome System and Autophagy continuously eliminate deleterious accumulation of nonnative protiens. In cellular quality control system, E3 ubiquitin ligases are significant employees for defense mechanism against abnormal toxic proteins. Few findings indicate that lack of functions of E3 ubiquitin ligases can be a causative factor of neurodevelopmental disorders, neurodegeneration, cancer and ageing. However, the detailed molecular pathomechanism implying E3 ubiquitin ligases in cellular functions in multifactorial disease conditions are not well understood. This article systematically represents the unique characteristics, molecular nature, and recent developments in the knowledge of neurobiological functions of few crucial E3 ubiquitin ligases. Here, we review recent literature on the roles of E6-AP, HRD1 and ITCH E3 ubiquitin ligases in the neuro-pathobiological mechanisms, with precise focus on the processes of neurodegeneration, and thereby propose new lines of potential targets for therapeutic interventions.

Angelman syndrome: A review highlighting musculoskeletal and anatomical aberrations

Angelman's syndrome (AS) is a genetic neurodevelopment disorder. The cause is a known abnormality involving the maternal inherited ubiquitin-protein ligase (UBE3A) gene. Clinical characteristics universal to the disorder are well documented in the literature and include developmental delay, seizures, ataxia, altered tone, severely impaired speech and intellect, as well as an overall happy demeanor, frequent bouts of laughter, and hypermotoric behavior. Associated with this disorder are several musculoskeletal aberrations. To date, a review of case studies reporting on these musculoskeletal changes has not been carried out. Thus, the purpose of this paper was to provide an overview of the musculoskeletal changes present in individuals with AS. In our review of 21 case reports from 1965-2013, the most consistently reported anatomical changes were of the craniofacial region. These include microcephaly, brachycephaly, a palpable occipital groove, prognathism, and wide spaced teeth. Other musculoskeletal abnormalities less frequently reported in the literature include scoliosis, excessive lumbar lordosis, and pes planus. Given that the majority of the case reports reviewed was of young children, the possibility of underreporting musculoskeletal changes which may manifest in the later years of life may be present. Early diagnosis and interventions to minimize secondary complications are crucial to maintain quality of life. An overall multidisciplinary approach is emphasized to maximize developmental potential for these individuals. Future prospective studies that follow patients into adulthood are needed to better understand the prevalence and development of secondary musculoskeletal changes, which in turn can inform intervention techniques and preventative measures. Clin. Anat. 29:561-567, 2016. © 2015 Wiley Periodicals, Inc.

Parent stress across molecular subtypes of children with Angelman syndrome

BACKGROUND

Parenting stress has been consistently reported among parents of children with developmental disabilities. However, to date, no studies have investigated the impact of a molecular subtype of Angelman syndrome (AS) on parent stress, despite distinct phenotypic differences among subtypes.

METHOD

Data for 124 families of children with three subtypes of AS: class I and II deletions (n = 99), imprinting centre defects (IC defects; n = 11) and paternal uniparental disomy (UPD; n = 14) were drawn from the AS Rare Diseases Clinical Research Network (RDCRN) database and collected from five research sites across the Unites States. The AS study at the RDCRN gathered health information to understand how the syndrome develops and how to treat it. Parents completed questionnaires on their perceived psychological stress, the severity of children's aberrant behaviour and children's sleep patterns. Children's adaptive functioning and developmental levels were clinically evaluated.

RESULTS

Child-related stress reached clinical levels for 40% of parents of children with deletions, 100% for IC defects and 64.3% for UPD. Sleep difficulties were similar and elevated across subtypes. There were no differences between molecular subtypes for overall child and parent-related stress. However, results showed greater isolation and lack of perceived parenting skills for parents of children with UPD compared with deletions. Better overall cognition for children with deletions was significantly related to more child-related stress while their poorer adaptive functioning was associated with more child-related stress. For all three groups, the severity of children's inappropriate behaviour was positively related to different aspects of stress.

CONCLUSIONS

How parents react to stress depends, in part, on children's AS molecular subtype. Despite falling under the larger umbrella term of AS, it is important to acknowledge the unique aspects associated with children's molecular subtype. Identifying these factors can lead to tailored interventions that fit the particular needs of families of children with different AS subtypes.