Angelman Research Articles

1H-NMR-based metabolomics reveals metabolic alterations in early development of a mouse model of Angelman syndrome

BackgroundAngelman syndrome (AS) is a rare neurodevelopmental genetic disorder caused by the loss of function of the ubiquitin ligase E3A (UBE3A) gene, affecting approximately 1:15,000 live births. We have recently shown that mitochondrial function in AS is altered during mid to late embryonic brain development leading to increased oxidative stress and enhanced apoptosis of neural precursor cells. However, the overall alterations of metabolic processes are still unknown. Hence, as a follow-up, we aim to investigate the metabolic profiles of wild-type (WT) and AS littermates and to identify which metabolic processes are aberrant in the brain of AS model mice during embryonic development.MethodsWe collected brain tissue samples from mice embryos at E16.5 and performed metabolomic analyses using proton nuclear magnetic resonance (1H-NMR) spectroscopy. Multivariate and Univariate analyses were performed to determine the significantly altered metabolites in AS mice. Pathways associated with the altered metabolites were identified using metabolite set enrichment analysis.ResultsOur analysis showed that overall, the metabolomic fingerprint of AS embryonic brains differed from those of their WT littermates. Moreover, we revealed a significant elevation of distinct metabolites, such as acetate, lactate, and succinate in the AS samples compared to the WT samples. The elevated metabolites were significantly associated with the pyruvate metabolism and glycolytic pathways.LimitationsOnly 14 metabolites were successfully identified and investigated in the present study. The effect of unidentified metabolites and their unresolved peaks was not determined. Additionally, we conducted the metabolomic study on whole brain tissue samples. Employing high-resolution NMR studies on different brain regions could further expand our knowledge regarding metabolic alterations in the AS brain. Furthermore, increasing the sample size could reveal the involvement of more significantly altered metabolites in the pathophysiology of the AS brain.ConclusionsUbe3a loss of function alters bioenergy-related metabolism in the AS brain during embryonic development. Furthermore, these neurochemical changes could be linked to the mitochondrial reactive oxygen species and oxidative stress that occurs during the AS embryonic development.

Epigenetics in rare neurological diseases.

Rare neurological diseases include a vast group of heterogenous syndromes with primary impairment(s) in the peripheral and/or central nervous systems. Such rare disorders may have overlapping phenotypes, despite their distinct genetic etiology. One unique aspect of rare neurological diseases is their potential common association with altered epigenetic mechanisms. Epigenetic mechanisms include regulatory processes that control gene expression and cellular phenotype without changing the composition of the corresponding DNA sequences. Epigenetic factors include three types of proteins, the "readers, writers, and erasers" of DNA and DNA-bound proteins. Thus, epigenetic impairments of many neurological diseases may contribute to their pathology and manifested phenotypes. Here, we aim to provide a comprehensive review on the general etiology of selected rare neurological diseases, that include Rett Syndrome, Prader-Willi Syndrome, Rubinstein-Taybi Syndrome, Huntington's disease, and Angelman syndrome, with respect to their associated aberrant epigenetic mechanisms.

Ube3a unsilencer for the potential treatment of Angelman syndrome

Deletion of the maternal UBE3A allele causes Angelman syndrome (AS); because paternal UBE3A is epigenetically silenced by a long non-coding antisense (UBE3A-ATS) in neurons, this nearly eliminates UBE3A protein in the brain. Reactivating paternal UBE3A holds promise for treating AS. We previously showed topoisomerase inhibitors can reactivate paternal UBE3A, but their therapeutic challenges prompted our search for small molecule unsilencers with a different mechanism of action. Here, we found that (S)-PHA533533 acts through a novel mechanism to significantly increase paternal Ube3a mRNA and UBE3A protein levels while downregulating Ube3a-ATS in primary neurons derived from AS model mice. Furthermore, peripheral delivery of (S)-PHA533533 in AS model mice induces widespread neuronal UBE3A expression. Finally, we show that (S)-PHA533533 unsilences paternal UBE3A in AS patient-derived neurons, highlighting its translational potential. Our findings provide a lead for developing a small molecule treatment for AS that could be safe, non-invasively delivered, and capable of brain-wide unsilencing of paternal UBE3A.

Mechanism of EHMT2-mediated genomic imprinting associated with Prader-Willi syndrome.

Prader-Willi Syndrome (PWS) is caused by loss of expression of paternally expressed genes in the human 15q11.2-q13 imprinting domain. A set of imprinted genes that are active on the paternal but silenced on the maternal chromosome are intricately regulated by a bipartite imprinting center (PWS-IC) located in the PWS imprinting domain. In past work, we discovered that euchromatic histone lysine N-methyltransferase-2 (EHMT2/G9a) inhibitors were capable of un-silencing PWS-associated genes by restoring their expression from the maternal chromosome. Here, in mice lacking the Ehmt2 gene, we document un-silencing of the imprinted Snrpn/Snhg14 gene on the maternal chromosome in the late embryonic and postnatal brain. Using PWS and Angelman syndrome patient derived cells with either paternal or maternal deletion of 15q11-q13, we have found that chromatin of maternal PWS-IC is closed and has compact 3D folding confirmation. We further show that a new and distinct noncoding RNA preferentially transcribed from upstream of the PWS-IC interacts with EHMT2 and forms a heterochromatin complex to silence gene expression of SNRPN in CIS on maternal chromosome. Taken together, these findings demonstrate that allele-specific recruitment of EHMT2 is required to maintain the maternal imprints. Our findings provide novel mechanistic insights and support a new model for imprinting maintenance of the PWS imprinted domain.

Neurodevelopmental Disorders Associated with Gut Microbiome Dysbiosis in Children.

The formation of the human gut microbiome initiates in utero, and its maturation is established during the first 2-3 years of life. Numerous factors alter the composition of the gut microbiome and its functions, including mode of delivery, early onset of breastfeeding, exposure to antibiotics and chemicals, and maternal stress, among others. The gut microbiome-brain axis refers to the interconnection of biological networks that allow bidirectional communication between the gut microbiome and the brain, involving the nervous, endocrine, and immune systems. Evidence suggests that the gut microbiome and its metabolic byproducts are actively implicated in the regulation of the early brain development. Any disturbance during this stage may adversely affect brain functions, resulting in a variety of neurodevelopmental disorders (NDDs). In the present study, we reviewed recent evidence regarding the impact of the gut microbiome on early brain development, alongside its correlation with significant NDDs, such as autism spectrum disorder, attention-deficit/hyperactivity disorder, Tourette syndrome, cerebral palsy, fetal alcohol spectrum disorders, and genetic NDDs (Rett, Down, Angelman, and Turner syndromes). Understanding changes in the gut microbiome in NDDs may provide new chances for their treatment in the future.

Approximating facial expression effects on diagnostic accuracy via generative AI in medical genetics.

Artificial intelligence (AI) is increasingly used in genomics research and practice, and generative AI has garnered significant recent attention. In clinical applications of generative AI, aspects of the underlying datasets can impact results, and confounders should be studied and mitigated. One example involves the facial expressions of people with genetic conditions. Stereotypically, Williams (WS) and Angelman (AS) syndromes are associated with a "happy" demeanor, including a smiling expression. Clinical geneticists may be more likely to identify these conditions in images of smiling individuals. To study the impact of facial expression, we analyzed publicly available facial images of approximately 3500 individuals with genetic conditions. Using a deep learning (DL) image classifier, we found that WS and AS images with non-smiling expressions had significantly lower prediction probabilities for the correct syndrome labels than those with smiling expressions. This was not seen for 22q11.2 deletion and Noonan syndromes, which are not associated with a smiling expression. To further explore the effect of facial expressions, we computationally altered the facial expressions for these images. We trained HyperStyle, a GAN-inversion technique compatible with StyleGAN2, to determine the vector representations of our images. Then, following the concept of InterfaceGAN, we edited these vectors to recreate the original images in a phenotypically accurate way but with a different facial expression. Through online surveys and an eye-tracking experiment, we examined how altered facial expressions affect the performance of human experts. We overall found that facial expression is associated with diagnostic accuracy variably in different genetic conditions.

Variables asociadas a las características de comunicación y lenguaje de las personas con síndrome de Angelman en una muestra de la península Ibérica

IntroductionAngelman syndrome (AS) is a rare condition with low prevalence associated with severe global developmental delay, behavioral phenotype of happy appearance and social interaction, moderate to severe intellectual disability with minimal or absent oral language associated with molecular etiology and featuring clinical variables. ObjectivesTo describe communication and language abilities in a sample of individuals with AS from Spain and Portugal, explore the influence of molecular etiology, age and use of Augmentative and Alternative Communication (AAC). Materials and methodsThe sample comprised 40 individuals diagnosed with AS, from the Iberian Peninsula, assessed using the MacArthur Communicative Development Inventories. ResultsA characteristic profile is shown with a predominance of gestures and receptive language over expressive. Differences are noted by molecular subtype, age, use of AAC and the origin in the Iberian Peninsula. ConclusionsThe linguistic phenotype for Angelman Syndrome is consistent with findings from other studies, however associated variables such as molecular etiology and use of AAC should be considered.

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

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

Developmental milestones and daily living skills in individuals with Angelman syndrome

BackgroundAngelman syndrome (AS) is a neurodevelopmental disorder associated with severe global developmental delay. However, the ages at which different developmental skills are achieved in these individuals remain unclear. We seek to determine the probability and the age of acquisition of specific developmental milestones and daily living skills in individuals with AS across the different molecular subtypes, viz. class I deletion, class II deletion, uniparental disomy, imprinting defect, and UBE3A variants.MethodsCaregivers participating in a longitudinal multicenter Angelman Syndrome Natural History Study completed a questionnaire regarding the age at which their children achieved specific developmental milestones and daily living skills. The Cox Proportional Hazard model was applied to analyze differences in the probability of achievement of skills at various ages among five molecular subtypes of AS.ResultsAlmost all individuals, regardless of molecular subtype, were able to walk with support by five years of age. By age 15, those with a deletion had at least a 50% probability of acquiring 17 out of 30 skills compared to 25 out of 30 skills among those without a deletion. Overall, fine and gross motor skills such as holding and reaching for small objects, sitting, and walking with support were achieved within a fairly narrow range of ages, while toileting, feeding, and hygiene skills tend to have greater variability in the ages at which these skills were achieved. Those without a deletion had a higher probability (25–92%) of achieving daily living skills such as independently toileting and dressing compared to those with a deletion (0–13%). Across all molecular subtypes, there was a low probability of achieving independence in bathing and brushing teeth.ConclusionIndividuals with AS without a deletion are more likely to achieve developmental milestones and daily living skills at an earlier age than those with a deletion. Many individuals with AS are unable to achieve daily living skills necessary for independent self-care.

Peptidomimetic inhibitors targeting TrkB/PSD-95 signaling improves cognition and seizure outcomes in an Angelman Syndrome mouse model.

Angelman syndrome (AS) is a rare genetic neurodevelopmental disorder with profoundly debilitating symptoms with no FDA-approved cure or therapeutic. Brain-derived neurotrophic factor (BDNF), and its receptor TrkB, have a well-established role as regulators of synaptic plasticity, dendritic outgrowth, dendritic spine formation and maintenance. Previously, we reported that the association of PSD-95 with TrkB is critical for intact BDNF signaling in the AS mouse model, as illustrated by attenuated PLCγ and PI3K signaling and intact MAPK pathway signaling. These data suggest that drugs tailored to enhance the TrkB-PSD-95 interaction may provide a novel approach for the treatment of AS and a variety of NDDs. To evaluate this critical interaction, we synthesized a class of high-affinity PSD-95 ligands that bind specifically to the PDZ3 domain of PSD-95, denoted as Syn3 peptidomimetic ligands. We evaluated Syn3 and its analog D-Syn3 (engineered using dextrorotary (D)-amino acids) in vivo using the Ube3a exon 2 deletion mouse model of AS. Following systemic administration of Syn3 and D-Syn3, we demonstrated improvement in the seizure domain of AS. Learning and memory using the novel object recognition assay also illustrated improved cognition following Syn3 and D-Syn3, along with restored long-term potentiation. Finally, D-Syn3 treated mice showed a partial rescue in motor learning. Neither Syn3 nor D-Syn3 improved gross exploratory locomotion deficits, nor gait impairments that have been well documented in the AS rodent models. These findings highlight the need for further investigation of this compound class as a potential therapeutic for AS and other genetic NDDs.

Epilepsy, EEG and chromosomal rearrangements.

Chromosomal abnormalities are associated with a broad spectrum of clinical manifestations, one of the more commonly observed of which is epilepsy. The frequency, severity, and type of epileptic seizures vary according to the macro- and microrearrangements present. Even within a single chromosomal anomaly, we most often deal with a phenotypic spectrum. The aim of the study was to look for chromosomal rearrangements with a characteristic electroencephalographic pattern. Only a few disorders have peculiar electroclinical abnormalities: 1p36, 4p16, 6q terminal or trisomy 12p, Angelman syndrome, inv dup 15, 15q13.3 deletions, ring 20, Down syndrome, or Xp11.22-11.23 duplication. We also reviewed studies on epileptic seizures and typical electroencephalographic patterns described in certain chromosomal rearrangements, focusing on the quest for potential electroclinical biomarkers. The comprehensive review concludes with clinical presentations of the most common micro and macro chromosomal rearrangements, such as 17q21.31 microdeletion, 6q terminal deletion, 15q inv dup syndrome, 2q24.4 deletion, Xp11.22-11.23 duplication, 15q13.3 microdeletion, 1p36 terminal deletion, 5q14.3 microdeletion, and Xq28 duplication. The papers reviewed did not identify any specific interictal electroencephalographic patterns that were unique and significant biomarkers for a given chromosomal microrearrangement. The types of seizures described varied, with both generalized and focal seizures of various morphologies being reported. Patients with chromosomal anomalies may also meet the criteria for specific epileptic syndromes such as Infantile Epilepsy Spasms Syndrome (IESS, West syndrome): 16p13.11, 15q13.3 and 17q21.31 microdeletions, 5q inv dup. syndrome; Dravet syndrome (2q24.4 deletion), Lennox-Gastaut syndrome (15q11 duplication. 1q13.3, 5q inv dup.); or Self-Limited Epilepsy with Autonomic Features (SeLEAS, Panayiotopoulos syndrome: terminal deletion of 6q.n), Self-Limited Epilepsy with Centrotemporal Spikes (SeLECT): fragile X syndrome. It is essential to better characterize groups of patients to more accurately define patterns of epilepsy and EEG abnormalities. This could lead to new treatment strategies. Future research is required to better understand epileptic syndromes and chromosomal rearrangements. PLAIN LANGUAGE SUMMARY: This paper presents EEG recording abnormalities in patients with various gene abnormalities that can cause epilepsy. The authors summarize these EEG variations based on a literature review to see if they occur frequently enough in other chromosomal abnormalities (in addition to those already known) to be a clue for further diagnosis.

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

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

Association Between Challenging Behaviour and Sleep Problems in Adults Enrolled in the Global Angelman Syndrome Registry.

Angelman Syndrome (AS) is a rare genetic disorder that impacts 1:20,000 people. Challenging behaviour, such as severe injurious behaviour, aggression and frequent unprovoked episodes of laughter are a significant problem among adults with AS that adversely impacts an individual's quality of life. This study, for the first time, aims understand the characteristic of challenging behaviour, its frequency, and the factors associated with it in adults with AS. Data from participants with AS (N = 37; aged 18-46 years) registered with the Global Angelman Registry, were divided into challenging behaviour and non-challenging behaviour groups based on the presence or absence of 50% of the behaviours recorded in the registry. Descriptive statistics, chi-squared and t-test analysis were conducted to assess the impact of variables on challenging behaviour. Multiple regressions were conducted to investigate the predictors of challenging behaviour. 56% of the sample presented with challenging behaviour. Disorders of arousal, self-injury, behaviour dysregulation, repetitive behaviour, and the lack of physical therapy accounted for 59% of the variance of challenging behaviour in this population. It was found that challenging behaviour was very common in this population. A significant association was found between challenging behaviour and both sleep arousal and the lack of physical therapy. Sleep arousal and the lack of physical therapy were the key factors associated with challenging behaviour in this study. Targeted interventions are needed to decrease challenging behaviour and future research should focus on sleep interventions and increased opportunities for physical therapy.

Establishing a Standardized DNA Extraction Method Using NaCl from Oral Mucosa Cells for Its Application in Imprinting Diseases Such as Prader-Willi and Angelman Syndromes: A Preliminary Investigation.

Diagnosing imprinting defects in neonates and young children presents challenges, often necessitating molecular analysis for a conclusive diagnosis. The isolation of genetic material from oral swabs becomes crucial, especially in settings where blood sample collection is impractical or for vulnerable populations like newborns, who possess limited blood volumes and are often too fragile for invasive procedures. Oral swab samples emerge as an excellent source of DNA, effectively overcoming obstacles associated with rare diseases. In our study, we specifically addressed the determination of the quality and quantity of DNA extracted from oral swab samples using NaCl procedures. We compared these results with extractions performed using a commercial kit. Subsequently, the obtained material underwent MS-HRM analysis for loci associated with imprinting diseases such as Prader-Willi and Angelman syndromes. Our study emphasizes the significance of oral swab samples as a reliable source for obtaining DNA for MS-HRM analysis. NaCl extraction stands out as a practical and cost-effective method for genetic studies, contributing to a molecular diagnosis that proves particularly beneficial for patients facing delays in characterization, ultimately influencing their treatment.

Prevalence threshold and positive predictive value of noninvasive prenatal testing.

Noninvasive prenatal testing (NIPT) has increased the number of conditions that can be screened. However, the prevalence of conditions assessed by NIPT has remained stable. The "prevalence threshold," a novel epidemiological concept, uses a test's sensitivity and specificity to determine the prevalence below which a test's positive predictive value declines most sharply relative to disease prevalence. In this article, we calculated the prevalence threshold for common conditions assessed through NIPT and compared the value with the actual prevalence of each condition to best ascertain the reliability of NIPT results. Six databases and PubMed were searched from January 2010 to March 2023 for sensitivity and specificity parameters of common conditions tested through NIPT. Using an equation previously derived by the authors of the current paper, the prevalence threshold for each condition was calculated. The theoretical number of test iterations required to reach the prevalence threshold was also reported. None of the conditions tested through the NIPT had a prevalence rate that met or exceeded the calculated prevalence threshold. Trisomy 21 had the greatest concordance between the prevalence rate and the prevalence threshold. In contrast, Angelman, Cri-du-chat, and Prader-Willi syndromes had the most significant discordance. Apart from trisomy 21 and XXY, all remaining conditions required more than one test iteration to reach their respective prevalence threshold. We conclude that at the current prevalence levels, the positive predictive value of NIPT remains low, with the prevalence of disease levels significantly lower than the prevalence threshold for each condition tested.

Understanding reliability of the observer-reported communication ability measure within Angelman syndrome through the lens of generalizability theory

AimsCaregivers rate improved communication ability as one of the most desired outcomes for successful interventions for individuals with Angelman syndrome (AS). When measuring communication ability in clinical trials, the reliability of such measures is critical for detecting significant changes over time. This study examined the reliability of the Observed-Reported Communication Ability (ORCA) measure completed by caregivers of individuals with AS.MethodsThe ORCA measure was completed by 249 caregivers with 170 caregivers completing the ORCA measure again after 5–12 days. Generalizability theory was used to examine the following sources of measurement error in ORCA scores: concepts, subdomains, assessment points, and the interactions among those facets and the object of measurement: communication ability. Three generalizability studies were conducted to understand the reliability of the ORCA measure for different measurement designs. Decision studies were carried out to demonstrate the optimization of measurement procedures of the ORCA measure.ResultsG and Phi coefficients of the original measurement design exceeded the 0.80 threshold considered sufficiently reliable to make relative and absolute decisions about the communication ability of individuals with AS based on their caregivers’ observed scores. The optimization procedures indicated that increasing the number of communication concepts and/or assessment points leads to more reliable estimates of communication.ConclusionThe ORCA measure was able to reliably distinguish different levels of communication ability among individuals with AS. Multiple assessment points and or more concepts would provide more precise estimates of an individual’s communication ability but at the cost of survey fatigue.

Behavioral Sleep Interventions for Children with Rare Genetic Neurodevelopmental Conditions: A Retrospective Analysis of Overall Outcomes for 26 Cases

Abstract Objectives Sleep difficulties are highly prevalent among children with rare genetic neurodevelopmental conditions (RGNC) such as Angelman and Smith-Magenis syndromes. Behavioral interventions are commonly used in the treatment of sleep difficulties in children; however, research is limited in children with RGNC. This study evaluated the overall effectiveness and acceptability of function-based behavioral sleep interventions for children with RGNC. Methods Data was collated from a series of experimental single-case research studies with 26 children (18 months to 19 years of age) with a range of RGNC, who received a behavioral sleep intervention. Intervention strategies included circadian (e.g., sleep/wake rescheduling), antecedent (e.g., sleep hygiene), and/or consequence (e.g., positive reinforcement of sleep-conducive behavior and modified extinction) modifications implemented by parents. Clinicians provided support for parents mostly via telehealth methods. Overall outcomes were examined using modified Brinley plots and effect size estimates. The effect of age, gender, and a range of psychological variables on intervention response was also examined. Results Improvements in sleep problem severity were observed for 24/26 participants, and gains were maintained at long-term follow-up for 13/16. Interestingly, 50% of the children achieved clinically significant change with less restrictive strategies (e.g., circadian, antecedent and positive reinforcement strategies), suggesting extinction procedures may be used as the last option in a sequence of interventions. Parents generally perceived interventions to be acceptable. There was minimal evidence of any differential response to intervention as a function of age, gender, or psychological variables. Conclusions Results suggest function-based behavioral interventions offer an effective and socially valid method for treating sleep disturbance in children with RGNC.

Cobalamins Function as Allosteric Activators of an Angelman Syndrome-Associated UBE3A/E6AP Variant.

Genetic aberrations of the maternal UBE3A allele, which encodes the E3 ubiquitin ligase E6AP, are the cause of Angelman syndrome (AS), an imprinting disorder. In most cases, the maternal UBE3A allele is not expressed. Yet, approximately 10 percent of AS individuals harbor distinct point mutations in the maternal allele resulting in the expression of full-length E6AP variants that frequently display compromised ligase activity. In a high-throughput screen, we identified cyanocobalamin, a vitamin B12-derivative, and several alloxazine derivatives as activators of the AS-linked E6AP-F583S variant. Furthermore, we show by cross-linking coupled to mass spectrometry that cobalamins affect the structural dynamics of E6AP-F583S and apply limited proteolysis coupled to mass spectrometry to obtain information about the regions of E6AP that are involved in, or are affected by binding cobalamins and alloxazine derivatives. Our data suggest that dietary supplementation with vitamin B12 can be beneficial for AS individuals.

A Case with Angelman Syndrome Carried de novo der(15q;15q) By de novo Paternal Uniparental Disomy

Angelman syndrome (AS; OMIM 105830) is a congenital neurodevelopmental disorder typically caused by maternal chromosome 15q11.2-q13 deletion, Ubiquitin-protein ligase E3A (UBE3A) gene mutations, paternal uniparental disomy (UPD), or imprinting center mutations. The rate of sporadic Angelman syndrome carrying UPD is known to be 2-3%. Paternal UPD has been detected in approximately 2-3% of AS patients. Many reports have suggested that patients with UPD-associated AS cases are heterodisomic. We reported a case of a 4-year-old patient diagnosed with AS. She presented with dysmorphic features, including a wide mouth with protruding tongue, flexion of both fingers, drooling with mental retardation, absence of speech, disrupted sleep, without self-injuring behavior. Although electroencephalogram (EEG) findings are important to diagnosing AS, specific EEG and also magnetic resonance imaging (MRI) findings were not detected in our case. In the diagnostic process, which began with conventional cytogenetics, genetic analysis was completed using the next-generation sequencing method. A Robertsonian-type translocation of two long arms in derivative chromosome 15 was detected, defining the patient's karyotype as 45,XX,der(15;15)(q10;q10)dn. Haplotype analysis confirmed the presence of paternal uniparental disomy, indicating that the case carried a de novo rob(15q;15q) translocation. The literature, suggests that AS cases with UPD may exhibit milder clinical features compared to those with microdeletion. Consequently, AS cases involving UPD of chromosome 15 can sometimes be overlooked. Therefore, the case presented here serves as an example highlighting the need to evaluate individuals with translocations involving der(15;15) identified through conventional cytogenetics for potential UPD.

Structural insights into the functional mechanism of the ubiquitin ligase E6AP

E6AP dysfunction is associated with Angelman syndrome and Autism spectrum disorder. Additionally, the host E6AP is hijacked by the high-risk HPV E6 to aberrantly ubiquitinate the tumor suppressor p53, which is linked with development of multiple types of cancer, including most cervical cancers. Here we show that E6AP and the E6AP/E6 complex exist, respectively, as a monomer and a dimer of the E6AP/E6 protomer. The short α1-helix of E6AP transforms into a longer helical structure when in complex with E6. The extended α1-helices of the dimer intersect symmetrically and contribute to the dimerization. The two protomers sway around the crossed region of the two α1-helices to promote the attachment and detachment of substrates to the catalytic C-lobe of E6AP, thus facilitating ubiquitin transfer. These findings, complemented by mutagenesis analysis, suggest that the α1-helix, through conformational transformations, controls the transition between the inactive monomer and the active dimer of E6AP.