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PubMed2026

Emerging Therapies for Angelman Syndrome.

Angelman syndrome (AS) is a complex neurogenetic disorder characterized by severe global developmental delay, motor dysfunction, and epilepsy, primarily resulting from the lack of functional ubiquitin protein ligase E3A (UBE3A) protein expression in neurons. While current management remains largely symptomatic, the therapeutic landscape for AS is rapidly evolving. Emerging strategies aim to restore UBE3A function through upstream interventions, such as gene replacement therapy or unsilencing of the imprinted paternal allele, which is present but transcriptionally silenced in neurons due to genomic imprinting. This imprinting is mediated by the distal portion of a long non-coding RNA known as the UBE3A-antisense transcript (UBE3A-ATS). This UBE3A-ATS has become a key therapeutic target, with several approaches developed to unsilence the paternal allele, including antisense oligonucleotides (ASOs), CRISPR-based editing, synthetic microRNA, and other modalities. To date, three ASO programs have demonstrated promising signals in early clinical development, with reported improvements in clinical outcomes and electroencephalography (EEG) biomarkers. Given the potential for improved outcomes with early intervention, the inclusion of AS in broader genomic newborn screening programs is currently being explored. An early-intervention approach, or combination of approaches, holds significant promise for transforming the lives of individuals affected by AS with outcomes dependent on their age or genotype.

Humans↗
PubMed2006

Psychological consequences of prenatal diagnosis in a case of familial Angelman syndrome.

Angelman Syndrome (AS), characterized by mental retardation, absence of speech, seizures and motor dysfunction, is caused by genetic defects leading to loss of expression of the maternal copy of the chromosome 15q11-13 imprinted region. Most cases are sporadic, being caused by de novo deletion of maternal chromosome 15q11-13 (75%) or by paternal uniparental disomy (3-4%). Familial cases can occur, due to mutations in the UBE3A gene or in the imprinting center. We describe the case of a pregnant woman having two nephews with AS caused by a UBE3A mutation; lack of communication within the family led the woman to be completely unaware of the risk of disease recurrence until 15 weeks of gestation. UBE3A genetic testing revealed she carried the familial mutation 892-893delCT. Prenatal diagnosis was performed on amniotic fluid and demonstrated that the fetus had inherited the mutation. The unexpected diagnosis and the subsequent termination of the pregnancy caused the woman to undergo acute psychological distress showing relevant psychopathological symptoms. Nevertheless, at 2-year follow-up, adverse consequences were minimized, and the couple was planning a new pregnancy. Factors affecting the psychological outcome of abortion and the role of psychological support in reducing the risk of long-term unfavorable consequences are discussed.

Abortion, Induced↗
PubMed1997

De novo truncating mutations in E6-AP ubiquitin-protein ligase gene (UBE3A) in Angelman syndrome.

Angelman syndrome (AS) is associated with maternal deletions of human chromosome 15q11-q13 and with paternal uniparental disomy for this region indicating that deficiency of an imprinted, maternally expressed gene within the critical interval is the likely cause of the syndrome. Although the gene for E6-AP ubiquitin-protein ligase (UBE3A) was mapped to the critical region for AS, evidence of expression from both parental alleles initially suggested that it was an unlikely candidate gene for this disorder. Because attempts to identify any novel maternally expressed transcripts were unsuccessful and because the UBE3A gene remained within a narrowed AS critical region, we searched for mutations in UBE3A in 11 AS patients without known molecular defects (large deletion, uniparental disomy, or imprinting mutation). This analysis tested the possibility that deficiency of an undefined, maternally expressed transcript or isoform of the UBE3A gene could cause AS. Four mutations were identified including a de novo frameshift mutation and a de novo nonsense mutation in exon 3 and two missense mutations of less certain significance. The de novo truncating mutations indicate that UBE3A is the AS gene and suggest the possibility of a maternally expressed gene product in addition to the biallelically expressed transcript. Intragenic mutation of UBE3A in AS is the first example of a genetic disorder of the ubiquitin-dependent proteolytic pathway in mammals. It may represent an example of a human genetic disorder associated with a locus producing functionally distinct imprinted and biallelically expressed gene products.

Angelman Syndrome↗
PubMed1996

Cortical myoclonus in Angelman syndrome.

Angelman syndrome (AS) results from lack of genetic contribution from maternal chromosome 15q11-13. This region encompasses three GABAA receptor subunit genes (beta3, alpha5, and gamma3). The characteristic phenotype of AS is severe mental retardation, ataxic gait, tremulousness, and jerky movements. We studied the movement disorder in 11 AS patients, aged 3 to 28 years. Two patients had paternal uniparental disomy for chromosome 15, 8 had a >3 Mb deletion, and 1 had a microdeletion involving loci D15S10, D15S113, and GABRB3. All patients exhibited quasicontinuous rhythmic myoclonus mainly involving hands and face, accompanied by rhythmic 5- to 10-Hz electroencephalographic (EEG) activity. Electromyographic bursts lasted 35 +/- 13 msec and had a frequency of 11 +/- 2.4 Hz. Burst-locked EEG averaging in 5 patients, generated a premyoclonus transient preceding the burst by 19 +/- 5 msec. A cortical spread pattern of myoclonic cortical activity was observed. Seven patients also demonstrated myoclonic seizures. No giant somatosensory evoked potentials or C-reflex were observed. The silent period following motor evoked potentials was shortened by 70%, indicating motor cortex hyperexcitability. Treatment with piracetam in 5 patients significantly improved myoclonus. We conclude that spontaneous, rhythmic, fast-bursting cortical myoclonus is a prominent feature of AS.

Adolescent↗
PubMed2006

Atypical cases of Angelman syndrome.

Angelman syndrome (AS) is a profound disorder notable for mental retardation and severe language deficits that results from lack of function of the maternally inherited copy of the UBE3A gene. Chromosome deletions of 15q11q13, paternal uniparental disomy (UPD), UBE3A gene mutations, and imprinting center defects are all commonly recognized mechanisms that disrupt the function of the maternal copy of the UBE3A gene. We report here two patients with different atypical etiologies of AS. The first patient is a 3-year-old boy with global developmental delay, severe speech deficits, seizures, and very happy disposition. Southern blot analysis for the maternal and paternal chromosome 15 methylation products showed a mosaic methylation pattern, suggesting an imprinting center defect. The second patient is a 4(1/2)-year-old boy with global developmental delay, no expressive language, microcephaly, seizures, and ataxic gait. Array-based comparative genomic hybridization (CGH) demonstrated a loss in copy number for two overlapping clones encompassing the UBE3A gene, indicating a partial deletion within UBE3A. His mother, who was adopted, had an identical pattern, suggesting that her deletion was probably on her paternally imprinted allele. These patients illustrate the expanding spectrum of molecular findings in AS, reinforce the need to maintain suspicion when clinical features suggest AS but initial testing is normal, and show the power of CGH as a tool to uncover partial UBE3A deletions.

Angelman Syndrome↗
PubMed2026

A dual-reporter mouse for therapeutic discovery in Angelman syndrome.

Angelman syndrome is a neurodevelopmental disorder caused by loss of the maternal UBE3A allele, the sole source of UBE3A in mature neurons owing to epigenetic silencing of the paternal allele. Although emerging therapies are being developed to restore UBE3A expression by activating the dormant paternal UBE3A allele, existing mouse models for such preclinical studies have limited throughput and utility, creating bottlenecks for both in vitro therapeutic screening and in vivo characterization. To address this, we developed the Ube3a-INSG dual-reporter knockin mouse, in which an IRES-Nanoluciferase-T2A-Sun1-sfGFP (INSG) cassette was inserted downstream of the endogenous Ube3a stop codon. The INSG model preserves UBE3A protein levels and function while enabling 2 complementary allele-specific readouts: Sun1-sfGFP and Nanoluciferase. We show that Sun1-sfGFP, a nuclear envelope-localized reporter, enables single-cell fluorescence analysis, whole-brain light-sheet imaging, and nuclear quantification by flow cytometry. Further, Nanoluciferase supports high-throughput luminescence assays for sensitive pharmacological profiling in cultured neurons and noninvasive in vivo bioluminescence imaging for pharmacodynamic assessment. By combining scalable screening, cellular analysis, and real-time in vivo monitoring in a single model, the Ube3a-INSG dual-reporter mouse provides a powerful platform to accelerate therapeutic development centered on UBE3A.

Animals↗
PubMed1992

Linkage analysis with chromosome 15q11-13 markers shows genomic imprinting in familial Angelman syndrome.

Angelman syndrome (AS) and Prader-Willi syndrome (PWS) have become the classical examples of genomic imprinting in man, as completely different phenotypes are generated by the absence of maternal (AS) or paternal (PWS) contributions to the q11-13 region of chromosome 15 as a result of deletion or uniparental disomy. Apparently, most patients are sporadic cases. The genetic mechanism underlying familial AS has remained enigmatic for a long time. Recently, evidence has been emerging suggesting autosomal dominant inheritance of a detectable or undetectable defect in a gene or genes at 15q11-13, subject to genomic imprinting. The present report describes an unusually large pedigree with segregation of AS through maternal inheritance and apparent asymptomatic transmission through several male ancestors. Deletion and paternal disomy at 15q11-13 were excluded. However, the genetic defect is still located in this region, as we obtained a maximum lod score of 5.40 for linkage to the GABA receptor locus GABRB3 and the anonymous DNA marker D15S10, which have been mapped within or adjacent to the AS critical region at 15q11-13. The size of the pedigree allowed calculation of an odds ratio in favour of genomic imprinting of 9.25 x 10(5). This family illustrates the necessity of extensive pedigree analysis when considering recurrence risks for relatives of AS patients, those without detectable deletion or disomy in particular.

Angelman Syndrome↗
PubMed1997

Different mechanisms and recurrence risks of imprinting defects in Angelman syndrome.

Angelman syndrome (AS) is a neurogenetic disorder that appears to be caused by the loss of function of an imprinted gene expressed from maternal chromosome 15 only. Approximately 6% of patients have a paternal imprint on the maternal chromosome. In the few cases, this is due to an inherited microdeletion, in the 15q11-q13 imprinting center (IC), that blocks the paternal-->maternal imprint switch in the maternal germ line. We have determined the segregation of 15q11-q13 haplotypes in nine families with AS and with an imprinting defect. One family, with two affected siblings, has a microdeletion affecting the IC transcript. In the other eight patients, no mutation was found at this locus. In two families, the patient and a healthy sibling share the same maternal alleles. In one of these families and in two others, grandparental DNA samples were available, and the chromosomes with the imprinting defect were found to be of grandmaternal origin. These findings suggest that germ-line mosaicism or de novo mutations account for a significant fraction of imprinting defects, among patients who have an as-yet-undetected mutation in a cis-acting element. Alternatively, these data may indicate that some imprinting defects are caused by a failure to maintain or to reestablish the maternal imprint in the maternal germ line or by a failure to replicate the imprint postzygotically. Depending on the underlying cause of the imprinting defect, different recurrence risks need to be considered.

Angelman Syndrome↗
PubMed1997

UBE3A/E6-AP mutations cause Angelman syndrome.

Angelman syndrome (AS), characterized by mental retardation, seizures, frequent smiling and laughter, and abnormal gait, is one of the best examples of human disease in which genetic imprinting plays a role. In about 70% of cases, AS is caused by de novo maternal deletions at 15q11-q13 (ref. 2). Approximately 2% of AS cases are caused by paternal uniparental disomy (UPD) of chromosome 15 (ref. 3) and 2-3% are caused by "imprinting mutations'. In the remaining 25% of AS cases, no deletion, uniparental disomy (UPD), or methylation abnormality is detectable, and these cases, unlike deletions or UPD, can be familial. These cases are likely to result from mutations in a gene that is expressed either exclusively or preferentially from the maternal chromosome 15. We have found that a 15q inversion inherited by an AS child from her normal mother disrupts the 5' end of the UBE3A (E6-AP) gene, the product of which functions in protein ubiquitination. We have looked for novel UBE3A mutations in nondeletion/non-UPD/non-imprinting mutation (NDUI) AS patients and have found one patient who is heterozygous for a 5-bp de novo tandem duplication. We have also found in two brothers a heterozygous mutation, an A to G transition that creates a new 3' splice junction 7 bp upstream from the normal splice junction. Both mutations are predicted to cause a frameshift and premature termination of translation. Our results demonstrate that UBE3A mutations are one cause of AS and indicate a possible abnormality in ubiquitin-mediated protein degradation during brain development in this disease.

Amino Acid Sequence↗
PubMed1999

The spectrum of mutations in UBE3A causing Angelman syndrome.

Angelman syndrome (AS) is characterized by mental retardation, absence of speech, seizures and motor dysfunction. AS is caused by maternal deletions for chromosome 15q11-q13, paternal uniparental disomy (UPD), imprinting defects or loss-of-function mutations in the UBE3A locus which encodes E6-AP ubiquitin-protein ligase. The UBE3A gene is imprinted with paternal silencing in human brain and similar silencing of the Ube3a locus in Purkinje cells and hippocampal neurons in the mouse. We have sequenced the major coding exons for UBE3A in 56 index patients with a clinical diagnosis of AS and a normal DNA methylation pattern. The analysis identified disease-causing mutations in 17 of 56 patients (30%) including 13 truncating mutations, two missense mutations, one single amino acid deletion and one stop codon mutation predicting an elongated protein. Mutations were identified in six of eight families (75%) with more than one affected case, and in 11 of 47 isolated cases (23%); no mutation was found in one family with two siblings, one with a typical and one with an atypical phenotype. Mutations were de novo in nine of the 11 isolated cases. An amino acid polymorphism of threonine substituted for alanine at codon 178 was identified, and a 3 bp length polymorphism was found in the intron upstream of exon 8. In all informative cases, phenotypic expression was consistent with imprinting with a normal phenotype when a mutation was on the paternal chromosome and an AS phenotype when a mutation was on the maternal chromosome. Laboratory diagnosis and genetic counseling for AS are complex, and mutation analysis is valuable in clinically typical AS patients with a normal methylation analysis.

Angelman Syndrome↗
PubMed2005

Evolution of seizures and electroencephalographical findings in 23 cases of deletion type Angelman syndrome.

Angelman syndrome (AS) is a genetic disorder with characteristic clinical and EEG findings. We report here the results of long-term follow-up studies on the epileptic seizures and EEG findings of 23 cases of deletion type AS confirmed by FISH analysis, including seven cases previously reported by Matsumoto et al. in 1992. The age at last follow-up in 23 patients was from 1 to 37 years of age (average: 18.0 years), with 10 patients (43.5%) in their 20s, and five over 30. Epileptic seizures were seen in all patients, and the age at seizure onset ranged from 3 to 50 months (average: 21.7 months). Status epilepticus was seen in 11 patients (47.8%). The percentages of cases seizure-free for more than 3 years were 25% (4/16) at 10 years of age, 70% (7/10) at 20, and 80% (4/5) at 30. The EEG findings were classified into six patterns according to the previous report: N (no spike, including focal slow waves), HVS (diffuse high-voltage slow bursts with or without spikes), F (focal spikes or multifocal spikes), S (diffuse spike and waves), C (continuous diffuse spike and waves), Hy (hypsarrythmia or hypsarrhythmia like waves). Hy was noted at ages 0-2 years in two cases. C was observed from the ages 2 to 15 years, being most frequently noted at 3-6 years of age, and it was never seen after 16 years of age. S was observed from ages 1 to 21 years. F was seen from 2 to 21 years of age, and most frequently during the ages of 2-7 years. HVS was seen from 0 years, and still remained after the age of 20. After 22 years of age, all patients showed N pattern including focal slow waves. One of the two patients who had bilateral frontal dominant delta slow waves in their 30s, had a recent seizure. Even if the spikes disappear with age, when bi-frontal focal slow waves remain, seizures may occur even in patients over 30.

Adolescent↗
PubMed2006

Quantitative analysis of SNRPN(correction of SRNPN) gene methylation by pyrosequencing as a diagnostic test for Prader-Willi syndrome and Angelman syndrome.

BACKGROUND: Angelman syndrome (AS) and Prader-Willi syndrome (PWS) are 2 distinct neurodevelopmental disorders caused primarily by deficiency of specific parental contributions at an imprinted domain within the chromosomal region 15q11.2-13. In most cases, lack of paternal contribution leads to PWS either by paternal deletion (approximately 70%) or maternal uniparental disomy (UPD; approximately 30%). Most cases of AS result from the lack of a maternal contribution from this same region by maternal deletion (approximately 70%) or by paternal UPD (approximately 5%). Analysis of allelic methylation differences at the small nuclear ribonucleoprotein polypeptide N (SNRPN) locus can differentiate the maternally and paternally inherited chromosome 15 and can be used as a diagnostic test for AS and PWS. METHODS: Sodium bisulfite-treated genomic DNA was PCR-amplified for the SNRPN gene. We used pyrosequencing to individually quantify the resulting artificial C/T sequence variation at CpG sites. Anonymized DNA samples from PWS patients (n = 40), AS patients (n = 31), and controls (n = 81) were analyzed in a blinded fashion with 2 PCR and 3 pyrosequencing reactions. We compared results from the pyrosequencing assays with those obtained with a commonly used methylation-specific PCR (MS-PCR) diagnostic protocol. RESULTS: The pyrosequencing assays had a sensitivity and specificity of 100% and provided quantification of methylation at 12 CpG sites within the SNRPN locus. The resulting diagnoses were 100% concordant with those obtained from the MS-PCR protocol. CONCLUSIONS: Pyrosequencing is a rapid and robust method for quantitative methylation analysis of the SNRPN locus and can be used as a diagnostic test for PWS and AS.

Angelman Syndrome↗
PubMed1999

Psychosocial problems, coping strategies, and the need for information of parents of children with Prader-Willi syndrome and Angelman syndrome.

The aim of the present study was to identify the psychosocial problems of parents of a child with Prader-Willi syndrome or a child with Angelman syndrome. In addition, the strategies these parents apply to cope with these problems as well as their need for information are described. To assess these topics, parents filled in a self-report questionnaire. Both parent groups were found to have a high need for information, high feelings of loss of control, relatively high depressive feelings, particularly in mothers in both syndrome groups. Differences due to the type of syndrome were found on the fear factor. Parents of a child with Angelman syndrome had greater feelings of fear for the negative consequences for themselves, whereas parents of Prader-Willi children were more concerned about the consequences for the child. In general, coping strategies were not found to be different between the parent groups of children who had either type of syndrome.

Adaptation, Psychological↗
PubMed1992

Paternal uniparental disomy of chromosome 15 in a child with Angelman syndrome.

Angelman and Prader-Willi syndromes are clinically distinct neurobehavioral disorders most commonly resulting from large deletions of chromosome 15q11-q13. The deletions arise differentially during maternal or paternal gametogenesis, respectively. A subgroup of patients with either syndrome have no apparent deletion, and because many such patients with Prader-Willi syndrome display inheritance of two copies of chromosome 15 from the mother only (uniparental disomy; UPD), we suggested that paternal UPD might be found in patients with Angelman syndrome. We report here clinical, cytogenetic, and molecular evidence on the 1 patient with paternal UPD for chromosome 15 who was found in our study population. This represents, to our knowledge, the first patient with paternal UPD to be studied with DNA probes from the chromosome 15q11-q13 critical region. In contrast to our findings for patients with Prader-Willi syndrome, in which maternal UPD was common, our data demonstrate that paternal UPD is infrequent in patients with Angelman syndrome.

Angelman Syndrome↗
PubMed1992

A combined behavioral/pharmacological treatment of sleep-wake schedule disorder in Angelman syndrome.

Angelman syndrome (AS) is a genetic disorder associated with a deletion on chromosome 15. Behavior problems among children with AS include sleep difficulties. Data are presented on the successful treatment of a sleep-wake schedule disorder (SWSD) in a 9-year-old boy with AS. The treatment program included behavioral and pharmacological components. During baseline, the child slept a mean of 1.9 hours per night and 1.3 hours during the day; night sleep was increased to a mean of 8.3 hours and day sleep was reduced to a mean of .08 hours after introduction of the full-treatment program. Medication was discontinued subsequently, and the child slept a mean of 7.8 hours during the night and .07 hours during the day. At 45-day follow-up, night sleep was maintained at 7.1 hours and day sleep remained stable at .29 hours. This is the first known report of an effective treatment of a SWSD in a child with AS.

Behavior Therapy↗
PubMedDate not supplied

Diagnostic testing for Prader-Willi syndrome and Angelman syndrome: a cost comparison.

PURPOSE: Considering cost as a factor, the authors evaluated three approaches to the diagnostic testing of Prader-Willi syndrome (PWS) and Angelman syndrome (AS). METHODS: The approaches evaluated were (1) DNA methylation studies followed by fluorescence in situ hybridization (FISH) for any positive DNA result, (2) FISH analysis followed by DNA testing for any negative result, and (3) simultaneous DNA testing and FISH analysis. RESULTS: Of 136 samples submitted for chromosome analysis and DNA methylation analysis for PWS or AS, 114 had a normal chromosome analysis and methylation studies, 9 were positive for AS, 3 were positive for PWS, and 7 had an abnormal chromosome analysis, but not deletion 15q11.2-q13, and normal methylation studies. On the basis of these results, the authors compared the cost of each testing strategy. CONCLUSION: DNA methylation studies followed by confirmation with FISH for any positive result yields a significant cost savings compared with the other approaches.

Angelman Syndrome↗
PubMed1994

Comparison of high resolution chromosome banding and fluorescence in situ hybridization (FISH) for the laboratory evaluation of Prader-Willi syndrome and Angelman syndrome.

The development of probes containing segments of DNA from chromosome region 15q11-q13 provides the opportunity to confirm the diagnosis of Prader-Willi syndrome (PWS) and Angelman syndrome (AS) by fluorescence in situ hybridization (FISH). We have evaluated FISH studies and high resolution chromosome banding studies in 14 patients referred to confirm or rule out PWS and five patients referred to confirm or rule out AS. In four patients (three from the PWS category and 1 from the AS group) chromosome analysis suggested that a deletion was present but FISH failed to confirm the finding. In one AS group patient, FISH identified a deletion not detectable by high resolution banding. Review of the clinical findings in the discrepant cases suggested that the FISH results were correct and high resolution findings were erroneous. Studies with a chromosome 15 alpha satellite probe (D15Z) on both normal and abnormal individuals suggested that incorrect interpretation of chromosome banding may occasionally be attributable to alpha satellite polymorphism but other variation of 15q11-q13 chromosome bands also contributes to misinterpretation. We conclude that patients who have been reported to have a cytogenetic deletion of 15q11-q13 and who have clinical findings inconsistent with PWS and AS should be re-evaluated by molecular genetic techniques.

Angelman Syndrome↗
PubMed2000

Identification of novel imprinted transcripts in the Prader-Willi syndrome and Angelman syndrome deletion region: further evidence for regional imprinting control.

Deletions and other abnormalities of human chromosome 15q11-q13 are associated with two developmental disorders, Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Loss of expression of imprinted, paternally expressed genes has been implicated in PWS. However, the number of imprinted genes that contribute to PWS, and the range over which the imprinting signal acts to silence one copy of the gene in a parent-of-origin-specific manner, are unknown. To identify additional imprinted genes that could contribute to the PWS phenotype and to understand the regional control of imprinting in 15q11-q13, we have constructed an imprinted transcript map of the PWS-AS deletion interval. The imprinting status of 22 expressed sequence tags derived from the radiation-hybrid human transcript maps or physical maps was determined in a reverse transcriptase-PCR assay and correlated with the position of the transcripts on the physical map. Seven new paternally expressed transcripts localize to an approximately 1.5-Mb domain surrounding the SNRPN-associated imprinting center, which already includes four imprinted, paternally expressed genes. All other tested new transcripts in the deletion region were expressed from both alleles. A domain of exclusive paternal expression surrounding the imprinting center suggests strong regional control of the imprinting process. This study provides the means for further investigation of additional genes that cause or modify the phenotypes associated with rearrangements of 15q11-q13.

Alleles↗