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

Relationships between challenging behavior and gastrointestinal symptoms, sleep problems, and internalizing and externalizing symptoms in children and adolescents with Angelman syndrome

BACKGROUND

Angelman syndrome (AS), is a rare genetic disorder. This study investigated the relationship between parent-reported comorbid symptoms including gastrointestinal symptoms, sleep problems, internalizing symptoms, and behavior problems in children and adolescents with AS.

METHOD

Parents of 98 children and adolescents with AS completed the Gastrointestinal Symptom Inventory, Children's Sleep Habits Questionnaire, Child Behavior Checklist, Social Communication Questionnaire, and the Behavior Problem Inventory-Short Form. Data were analyzed using descriptive statistics, Pearson's correlation coefficients, and hierarchical multiple regressions.

RESULTS

There was a high frequency of GI symptoms (99%), sleep problems (95.9%), challenging behavior (98%), internalizing symptoms (38%), and 72.4% of children and adolescents presented with ASD symptoms. Self-injurious behavior (SIB), aggressive/destructive behavior, and the frequency of stereotyped behavior positively correlated with GI symptoms and sleep problems and it was moderately negatively associated with age. Internalizing symptoms and age were positively associated with SIB. Aggression was significantly related to gender, but not the presence of ASD symptoms.

CONCLUSIONS

Findings highlight the relationships between comorbid conditions. They may lead to a deeper understanding of how comorbidities present in children and adolescents with Angelman Syndrome.

Two infants with mild, atypical clinical features of Kagami-Ogata syndrome caused by epimutation

Kagami-Ogata syndrome (KOS) is an imprinting disorder characterized by polyhydramnios, bell-shaped thorax with coat-hanger appearance (curved ribs), respiratory distress, abdominal wall defects, and distinct facial features, together with intellectual developmental delay with special needs. Abnormal expression of the imprinted genes on chromosome 14q32.2 causes KOS. Epimutation with aberrant hypermethylation of the MEG3/DLK1: intergenic differentially methylated region (MEG3/DLK1:IG-DMR) and the MEG3:TSS-DMR is one of the etiologies of KOS. We report two infants with KOS caused by epimutation presenting with some characteristic clinical features, mild clinical course, and almost normal motor and intellectual development. Methylation analysis for ten DMRs related to major imprinting disorders using pyrosequencing with genomic DNA (gDNA) extracted from leukocytes showed abnormally increased methylation levels of the MEG3/DLK1:IG-DMR and MEG3:TSS-DMR in both patients, but lower than those in patients with paternal uniparental disomy chromosome 14 (upd(14)pat). The methylation levels in the DMRs other than both DMRs were within normal range. We also conducted methylation analysis for the MEG3/DLK1:IG-DMR and MEG3:TSS-DMR with gDNA extracted from nails and buccal cells of both patients. Methylation levels in the MEG3:TSS-DMR, particularly in buccal cells, were closer to normal range compared to those in leukocytes. Microsatellite analysis for chromosome 14 and array comparative hybridization analysis showed no upd(14)pat or microdeletion involving the 14q32.2 imprinted region in either patient. A differential mosaic ratio of cells with aberrant methylation of DMRs at the 14q32.2 imprinted region among tissues (connective tissue, lung, and brain) might have led to their atypical clinical features. Further studies of patients with epimutation should further expand the phenotypic spectrum of KOS.

Atypical presentation of Angelman syndrome with intact expressive language due to low-level mosaicism

BACKGROUND

Angelman syndrome (AS) occurs due to a lack of expression or function of the maternally inherited UBE3A gene. Individuals with AS typically have significant developmental delay, severe speech impairment with absent to minimal verbal language, gait abnormalities including ataxia, and an incongruous happy demeanor. The majority of individuals with AS also have seizures and microcephaly. Some individuals with mosaic AS have been reported to have expressive language and milder levels of developmental delay.

CASE REPORT

We report a male patient presenting with mild to moderate intellectual disability, hyperphagia, obesity, and the ability to communicate verbally. His phenotype was suggestive of Prader-Willi syndrome. However, methylation testing was positive for Angelman syndrome and additional methylation specific multiplex ligation-dependent amplification (MS-MLPA) study revealed low-level mosaicism for AS.

CONCLUSION

A broader phenotypic spectrum should be considered for AS as patients with atypical presentations may otherwise elude diagnosis.

Methylation analysis and developmental profile of two individuals with Angelman syndrome due to mosaic imprinting defects

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by loss of expression of the maternally-inherited UBE3A on chromosome 15q11.2. In AS due to a chromosomal deletion that encompasses UBE3A, paternal uniparental disomy of chromosome 15, or imprinting defects (ImpD), the SNRPN locus is unmethylated, while in neurotypical individuals, it is ∼50% methylated. We present the developmental profile of two adults with mild AS assessed using standardized behavioral and neurodevelopmental measures. Both had intellectual disability with unusually advanced verbal communication skills compared to other individuals with AS. Methylation of the SNRPN locus was examined using Methylation Specific Quantitative Melt Analysis (MS-QMA) in different tissues at one time point for participant A (22 years) and two time points for participant B (T1: 22 years, T2: 25 years), and these levels were compared to a typical AS cohort. While participant A showed methylation levels comparable to the typical AS cohort, participant B showed methylation mosaicism in all tissues at both time points and changes in methylation levels from T1 to T2. AS should be considered in individuals with intellectual disability and verbal speech who may not have the typical symptoms of AS.

Clinical Characterization of Epilepsy in Children With Angelman Syndrome

BACKGROUND

Epilepsy is highly prevalent in children with Angelman syndrome (AS), and its detailed characterization and relationship to the genotype (deletion vs nondeletion) is important both for medical practice and for clinical trial design.

METHODS AND MATERIALS

We retrospectively analyzed the main clinical features of epilepsy in 265 children with AS who were enrolled in the AS Natural History Study, a multicenter, observational study conducted at six centers in the United States. Participants were prospectively followed up and classified by genotype.

RESULTS

Epilepsy was reported in a greater proportion of individuals with a deletion than a nondeletion genotype (171 of 187 [91%] vs. 48 of 78 [61%], P < 0.001). Compared with participants with a nondeletion genotype, those with deletions were younger at the time of the first seizure (age: median [95% confidence interval]: 24 [21-24] months vs. 57 [36-85] months, P < 0.001) and had a higher prevalence of generalized motor seizures. Hospitalization following a seizure was reported in more children with a deletion than a nondeletion genotype (92 of 171 [54%] vs. 17 of 48 [36%], P = 0.04). The overall prevalence of absence seizures was not significantly different between genotype groups. Forty-six percent (102/219) of the individuals reporting epilepsy were diagnosed with AS concurrently or after their first seizure.

CONCLUSIONS

Significant differences exist in the clinical expression of epilepsy in AS according to the underlying genotype, with earlier age of onset and more severe epilepsy in individuals with AS due to a chromosome 15 deletion.

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.

DNA methylation analysis for screening and diagnostic testing in neurodevelopmental disorders

DNA methylation (mDNA) plays an important role in the pathogenesis of neurodevelopmental disorders (NDDs), however its use in diagnostic testing has been largely restricted to a handful of methods for locus-specific analysis in monogenic syndromes. Recent studies employing genome-wide methylation analysis (GWMA) have explored utility of a single array-based test to detect methylation changes in probands negative by exome sequencing, and to diagnose different monogenic NDDs with defined epigenetic signatures. While this may be a more efficient approach, several significant barriers remain. These include non-uniform and low coverage of regulatory regions that may have CG-rich sequences, and lower analytical sensitivity as compared with locus-specific analyses that may result in methylation mosaicism not being detected. A major challenge associated with the above technologies, regardless of whether the analysis is locus specific or genome wide, is the technical bias introduced by indirect analysis of methylation. This review summarizes evidence from the most recent studies in this field and discusses future directions, including direct analysis of methylation using long-read technologies and detection of 5-methylcytosine (5-mC or total mDNA) and 5-hydroxymethylacytosine (5-hmC) as biomarkers of NDDs.

Chromosome 15 Imprinting Disorders: Genetic Laboratory Methodology and Approaches

Chromosome 15 imprinting disorders include Prader-Willi (PWS) and Angelman (AS) syndromes, which are caused by absent expression from the paternal and maternal alleles in the chromosome 15q11. 2-q13 region, respectively. In addition, chromosome 15q duplication caused by the presence of at least one additional maternally derived copy of the 15q11.2-q13 region can lead to seizures, cognitive and behavioral problems. We focus on PWS and AS in the report, and expand the discussion of clinical care and description with genetic testing to include high-resolution studies to more specifically characterize the molecular mechanisms of disease. The importance of early diagnosis with the necessity for accurate molecular characterization through a step-wise algorithm is emphasized in an era of targeted therapeutic interventions. We present a flowchart to aid in ordering specialized genetic testing as several methods are available for patients presenting with features of PWS and/or AS.

Prenatal treatment path for angelman syndrome and other neurodevelopmental disorders

Angelman syndrome (AS) is a rare neurodevelopmental disorder caused by mutation or deletion of the maternally inherited UBE3A allele. These pathogenic mutations lead to loss of maternal UBE3A expression in neurons. Antisense oligonucleotides and gene therapies are in development, which activate the intact but epigenetically silenced paternal UBE3A allele. Preclinical studies indicate that treating during the prenatal period could greatly reduce the severity of symptoms or prevent AS from developing. Genetic tests can detect the chromosome 15q11-q13 deletion that is the most common cause of AS. New, highly sensitive noninvasive prenatal tests that take advantage of single-cell genome sequencing technologies are expected to enter the clinic in the coming years and make early genetic diagnosis of AS more common. Efforts are needed to identify fetuses and newborns with maternal 15q11-q13 deletions and to phenotype these babies relative to neurotypical controls. Clinical and parent observations suggest AS symptoms are detectable in infants, including reports of problems with feeding and motor function. Quantitative phenotypes in the 0- to 1-year age range will permit a more rapid assessment of efficacy when future treatments are administered prenatally or shortly after birth. Although prenatal therapies are currently not available for AS, prenatal testing combined with prenatal treatment has the potential to revolutionize how clinicians detect and treat babies before they are symptomatic. This pioneering prenatal treatment path for AS will lay the foundation for treating other syndromic neurodevelopmental disorders. Autism Res 2020, 13: 11-17. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Prenatal treatment could benefit expectant parents whose babies test positive for the chromosome microdeletion that causes Angelman syndrome (AS). Prenatal treatment is predicted to have better outcomes than treating after symptoms develop and may even prevent AS altogether. This approach could generally be applied to the treatment of other syndromic neurodevelopmental disorders.

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.

UBA6 and Its Bispecific Pathways for Ubiquitin and FAT10

Questions have been raised since the discovery of UBA6 and its significant coexistence with UBE1 in the ubiquitin–proteasome system (UPS). The facts that UBA6 has the dedicated E2 enzyme USE1 and the E1–E2 cascade can activate and transfer both ubiquitin and ubiquitin-like protein FAT10 have attracted a great deal of attention to the regulational mechanisms of the UBA6–USE1 cascade and to how FAT10 and ubiquitin differentiate with each other. This review recapitulates the latest advances in UBA6 and its bispecific UBA6–USE1 pathways for both ubiquitin and FAT10. The intricate networks of UBA6 and its interplays with ubiquitin and FAT10 are briefly reviewed, as are their individual and collective functions in diverse physiological conditions.

Linguagem, neurodesenvolvimento e comportamento na Síndrome de Angelman: relato de caso

RESUMO Objetivo O objetivo deste estudo é apresentar achados de linguagem, comportamento e neurodesenvolvimento de uma menina com diagnóstico da Síndrome de Angelman, avaliada aos três e aos oito anos. Método Os instrumentos de avaliação foram Observação do Comportamento Comunicativo, Early Language Milestone Scale (ELM) e Teste de Screening de Desenvolvimento DENVER-II (TSDD-II). Resultados No caso apresentado, verifica-se a presença dos sinais fenotípicos da SA, tais como boca larga, dentes espaçados, língua protuberante, estrabismo, fissuras palpebrais ascendentes e sialorreia. Na avaliação de linguagem, foram verificados déficits expressivos e receptivos, com ausência de oralidade e prejuízos na compreensão. O TSDD-II e a ELMS indicaram grave comprometimento de todas as habilidades avaliadas aos três e aos oito anos. O desempenho encontrado, nas duas avaliações, foi muito semelhante em todas as áreas do desenvolvimento infantil. Ao longo dos anos, verificou-se pouca evolução, apesar do grande investimento terapêutico e educacional. Conclusão A presença de um quadro complexo como a SA demanda necessidades clínicas de alta complexidade, situação agravada frente à escassez de recursos terapêuticos que possam minimizar os impactos deletérios da síndrome, culminando em comprometimento da qualidade de vida da população com a SA, bem como de suas famílias.

Two Angelman families with unusually advanced neurodevelopment carry a start codon variant in the most highly expressed UBE3A isoform

We present three children from two unrelated families with Angelman syndrome (AS) whose developmental skills are far more advanced than any other non-mosaic AS individual ever reported. All have normal gait and use syntactic language spontaneously to express their needs. All of them have a c.2T > C (p.Met1Thr) variant in UBE3A, which abrogates the start codon of isoform 1, but not of isoforms 2 and 3. This variant was maternally inherited in one set of siblings, but de novo in the other child from the unrelated family. This report underscores the importance of considering AS in the differential diagnosis even in the presence of syntactic speech.