UBE3A Research Articles

Novel UBE3A pathogenic variant in a large Georgian family produces non-convulsive status epilepticus responsive to ketogenic diet

PurposeTo report the effect of the ketogenic diet (KD) on non-convulsive status epilepticus (NCSE) due to Angelman syndrome (AS) in two members of a large Georgian family affected by a novel frameshift variant in the UBE3A gene (NM_000462.3). MethodsWe evaluated two members of this family who were affected with clinical and EEG features of AS. Clinical history with special emphasis on development, seizure type, frequency, and treatment was reviewed. Routine and long-term video EEG monitoring were conducted, particularly during NCSE. A non-fasting inpatient KD protocol was implemented using blended food orally with full administration of 4:1 (fat to non-fat) ratio. Urine ketone bodies (KBs), measured with urine ketone acetone strips readings, reached 150 mg/dL in both patients. ResultsPatients had characteristic signs of AS and presented with epilepsy between the age of 2–4 years. As methylation tests were negative, next generation sequencing disclosed a c.2365del variant. For both, NCSE was revealed by cognitive deterioration and did not respond to anti-seizure medication. As recommended, IV pyridoxine, benzodiazepines, and valproic acid were administered, but without success. For both patients, NCSE resolved on the second-third day of KD initiation, before the appearance of ketonuria and resulting in improved communication, mood and sleep. ConclusionKD is safe and effective for the treatment of NCSE due to AS. Resolution before the appearance of ketone bodies points to a possible mechanism of action of KD.

Mowat-Wilson syndrome: literature review and case series

Mowat-Wilson syndrome (MWS) is a rare genetic disorder characterized by a combination of the following signs: 1) facial dysmorphism (wide nose, broad medial eyebrows, pronounced chin, and open mouth); 2) mental retardation; 3) abnormalities of internal organs (congenital heart defects, Hirschsprung's disease, hypospadias/cryptorchidism). The disease is associated with a heterozygous pathogenic mutation in the ZEB2 gene. More than 80 % of MWS patients are diagnosed with epilepsy, the onset of which is usually observed in infancy. Patents have focal motor seizures, atypical absence seizures, generalized convulsive seizures. Epileptic seizures are often triggered by fever; some children are resistant to therapy. MWS patients have a specific phenotype (blue eyes, fair hair, wide-based gait, frequent laughter, limited or absent expressive language) that requires differential diagnosis with Angelman syndrome (caused by a mutation in the UBE3A gene). MWS was described in 1998, but there have been no case reports in the Russian literature yet. We report 4 cases of MWS in children aged 2 to 13 years treated in the Svt. Luka's Institute of Neurology and Epilepsy. In all of these patients, we identified a heterozygous de novo deletion in the ZEB2 gene. Epilepsy was observed in all patients. Mean age at onset was 13 months. All children had focal motor seizures and atypical absence seizures. None of them had tonic-clonic seizures or status epilepticus. The analysis of electroencephalograms showed that patients with a lower index of epileptiform activity tend to have better development and vice versa: children with a high index of epileptiform activity during sleep had more severe developmental delay.

Deleting a UBE3A substrate rescues impaired hippocampal physiology and learning in Angelman syndrome mice

In humans, loss-of-function mutations in the UBE3A gene lead to the neurodevelopmental disorder Angelman syndrome (AS). AS patients have severe impairments in speech, learning and memory, and motor coordination, for which there is currently no treatment. In addition, UBE3A is duplicated in > 1–2% of patients with autism spectrum disorders—a further indication of the significant role it plays in brain development. Altered expression of UBE3A, an E3 ubiquitin ligase, is hypothesized to lead to impaired levels of its target proteins, but identifying the contribution of individual UBE3A targets to UBE3A-dependent deficits remains of critical importance. Ephexin5 is a putative UBE3A substrate that has restricted expression early in development, regulates synapse formation during hippocampal development, and is abnormally elevated in AS mice, modeled by maternally-derived Ube3a gene deletion. Here, we report that Ephexin5 can be directly ubiquitylated by UBE3A. Furthermore, removing Ephexin5 from AS mice specifically rescued hippocampus-dependent behaviors, CA1 physiology, and deficits in dendritic spine number. Our findings identify Ephexin5 as a key driver of hippocampal dysfunction and related behavioral deficits in AS mouse models. These results demonstrate the exciting potential of targeting Ephexin5, and possibly other UBE3A substrates, to improve symptoms of AS and other UBE3A-related developmental disorders.

Identification of Novel UBE3A Mutation Causing Angelman Syndrome

The Angelman Syndrome (AS) is neurodevelopmental disease associated with maternal disruption of the UBE3A gene and is mainly characterized by global developmental delay, sever mental retardation with absence of speech, seizures, dysmorphic facial features, and distinct behavioral profile. In this study a pedigree with one affected member with neurodevelopmental disease who was a result of an unconsanguineous marriage were investigated by Whole Exome Sequencing (WES). DNA was extracted from whole blood and library was prepared using Agilent V6 capturing system. WES was performed on Illumina HiSeq 4000 platform. Genome Analysis Toolkit (GATK) was used for variant calling. Classification of selected variants was done based on ACMG guideline for variant interpretation 2015. WES revealed that the proband has previously unreported nonsense variant (c.2459T>G) in UBE3A gene that causes the substitution of Leu (TTA) with stop codon (TGA), confirming the diagnosis of Angelman syndrome. The patient had delayed motor development, speech impairment, an attention deficit, and an abnormal electroencephalogram (EEG), but no seizures by the age of 2 years. This study emphasis the role of WES in the early diagnosis and better management for AS patient.

Insulin-like growth factor-2 does not improve behavioral deficits in mouse and rat models of Angelman Syndrome

BackgroundAngelman Syndrome (AS) is a rare neurodevelopmental disorder for which there is currently no cure or effective therapeutic. Since the genetic cause of AS is known to be dysfunctional expression of the maternal allele of ubiquitin protein ligase E3A (UBE3A), several genetic animal models of AS have been developed. Both the Ube3a maternal deletion mouse and rat models of AS reliably demonstrate behavioral phenotypes of relevance to AS and therefore offer suitable in vivo systems in which to test potential therapeutics. One promising candidate treatment is insulin-like growth factor-2 (IGF-2), which has recently been shown to ameliorate behavioral deficits in the mouse model of AS and improve cognitive abilities across model systems.MethodsWe used both the Ube3a maternal deletion mouse and rat models of AS to evaluate the ability of IGF-2 to improve electrophysiological and behavioral outcomes.ResultsAcute systemic administration of IGF-2 had an effect on electrophysiological activity in the brain and on a metric of motor ability; however the effects were not enduring or extensive. Additional metrics of motor behavior, learning, ambulation, and coordination were unaffected and IGF-2 did not improve social communication, seizure threshold, or cognition.LimitationsThe generalizability of these results to humans is difficult to predict and it remains possible that dosing schemes (i.e., chronic or subchronic dosing), routes, and/or post-treatment intervals other than that used herein may show more efficacy.ConclusionsDespite a few observed effects of IGF-2, our results taken together indicate that IGF-2 treatment does not profoundly improve behavioral deficits in mouse or rat models of AS. These findings shed cautionary light on the potential utility of acute systemic IGF-2 administration in the treatment of AS.

Electrophysiological Characterization of Regular and Burst Firing Pyramidal Neurons of the Dorsal Subiculum in an Angelman Syndrome Mouse Model

Angelman syndrome (AS) is a debilitating neurogenetic disorder characterized by severe developmental delay, speech impairment, gait ataxia, sleep disturbances, epilepsy, and a unique behavioral phenotype. AS is caused by a microdeletion or mutation in the maternal 15q11-q13 chromosome region containing UBE3A gene. The hippocampus is one of the important brain regions affected in AS mice leading to substantial hippocampal-dependent cognitive and behavioral deficits. Recent studies have suggested an abnormal increase in the α1-Na/K-ATPase (α1-NaKA) in AS mice as the precipitating factor leading to the hippocampal deficits. A subsequent study showed that the hippocampal-dependent behavioral deficits occur as a result of altered calcium (Ca+2) dynamics in the CA1 pyramidal neurons (PNs) caused by the elevated α1-NaKA expression levels in the AS mice. Nonetheless, a causal link between hippocampal deficits and major behavioral phenotypes in AS is still obscure. Subiculum, a region adjacent to the hippocampal CA1 is the major output source of the hippocampus and plays an important role in the transfer of information from the CA1 region to the cortical areas. However, in spite of the robust hippocampal deficits and several known electrophysiological alterations in multiple brain regions in AS mice, the neuronal properties of the subicular neurons were never investigated in these mice. Additionally, subicular function is also implied in many neuropsychiatric disorders such as autism, schizophrenia, Alzheimer’s disease, and epilepsy that share some common features with AS. Therefore, given the importance of the subiculum in these neuropsychiatric disorders and the altered electrophysiological properties of the hippocampal CA1 PNs projecting to the subiculum, we sought to examine the subicular PNs. We performed whole-cell recordings from dorsal subiculum of both WT and AS mice and found three distinct populations of PNs based on their ability to fire bursts or single action potentials following somatic current injection: strong bursting, weak bursting, and regular firing neurons. We found no overall differences in the distribution of these different subicular PN populations among AS and WT controls. However, the different cell types showed distinct alterations in their intrinsic membrane properties. Further, none of these populations were altered in their excitatory synaptic properties. Altogether, our study characterized the different subtypes of PNs in the subicular region of an AS mouse model.

Analysis of clinical phenotype and genetic variants in a Chinese pedigree affected with Angelman syndrome

To explore the genetic etiology for a Chinese pedigree affected with Angelman syndrome (AS). The proband with phenotypes suggestive of AS was subjected to copy number variation sequencing (CNV-seq), methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and high-throughput next generation sequencing (NGS). Variant of the UBE3A gene was verified among family members by Sanger sequencing and bioinformatic analysis. NGS revealed that the proband has carried a heterozygous variant of the UBE3A gene, namely c.1517G>A (p.R506H). The variant has co-segregated with the disease in the pedigree. Multiple amino acid sequence alignment showed that the site of mutant residue is conserved among nine homologous species. The variant was predicted to be deleterious by bioinformatic analysis. A novel variant of the UBE3A gene has been identified in a Chinese pedigree affected with AS. Above finding has further expanded the spectrum of UBE3A gene variants and phenotypes of AS, which also facilitated molecular diagnosis and genetic counseling for the family.

Antisense oligonucleotide treatment rescues UBE3A expression and multiple phenotypes of an Angelman syndrome mouse model

Angelman syndrome (AS) is a severe neurodevelopmental disorder for which only symptomatic treatment with limited benefits is available. AS is caused by mutations affecting the maternally inherited ubiquitin protein ligase E3A (UBE3A) gene. Previous studies showed that the silenced paternal Ube3a gene can be activated by targeting the antisense Ube3a-ATS transcript. We investigated antisense oligonucleotide–induced (ASO-induced) Ube3a-ATS degradation and its ability to induce UBE3A reinstatement and rescue of AS phenotypes in an established Ube3a mouse model. We found that a single intracerebroventricular injection of ASOs at postnatal day 1 (P1) or P21 in AS mice resulted in potent and specific UBE3A reinstatement in the brain, with levels up to 74% of WT levels in the cortex and a full rescue of sensitivity to audiogenic seizures. AS mice treated with ASO at P1 also showed rescue of established AS phenotypes, such as open field and forced swim test behaviors, and significant improvement on the reversed rotarod. Hippocampal plasticity of treated AS mice was comparable to WT but not significantly different from PBS-treated AS mice. No rescue was observed for the marble burying and nest building phenotypes. Our findings highlight the promise of ASO-mediated reactivation of UBE3A as a disease-modifying treatment for AS.

Secreted retrovirus-like GAG-domain-containing protein PEG10 is regulated by UBE3A and is involved in Angelman syndrome pathophysiology

SummaryAngelman syndrome (AS) is a neurodevelopmental disorder caused by the loss of maternal UBE3A, a ubiquitin protein ligase E3A. Here, we study neurons derived from patients with AS and neurotypical individuals, and reciprocally modulate UBE3A using antisense oligonucleotides. Unbiased proteomics reveal proteins that are regulated by UBE3A in a disease-specific manner, including PEG10, a retrotransposon-derived GAG protein. PEG10 protein increase, but not RNA, is dependent on UBE3A and proteasome function. PEG10 binds to both RNA and ataxia-associated proteins (ATXN2 and ATXN10), localizes to stress granules, and is secreted in extracellular vesicles, modulating vesicle content. Rescue of AS patient-derived neurons by UBE3A reinstatement or PEG10 reduction reveals similarity in transcriptome changes. Overexpression of PEG10 during mouse brain development alters neuronal migration, suggesting that it can affect brain development. These findings imply that PEG10 is a secreted human UBE3A target involved in AS pathophysiology.

EEG findings in patients with angelman syndrome. Notched slow waves and age-specific characteristics of the main EEG patterns

Angelman syndrome (AS) is a genetic disorder caused by a mutation in the maternal copy of the UBE3A gene and characterized by typical clinical manifestations (such as mental retardation, difficulty walking, and laughter) and specific changes on the electroencephalogram (EEG).The aim of this study was to analyze age-specific characteristics of the main EEG patterns, including high-amplitude frontal delta activity with spikes, slow-wave delta-theta activity with spikes in the posterior regions, and diffuse continuous rhythmic theta activity. In addition to that, we assessed the frequency of a rare and highly specific for AS EEG pattern: notched slow waves.We have identified and described additional criteria for EEG during sleep: high index of pathological slow-wave activity and the ratio of pathological slow-wave activity index to epileptiform activity index during sleep. We also analyzed all EEG patterns at the age most significant for the detection of this syndrome (up to 3 years) and their age-specific dynamics.We covered the frequency and characteristics of EEG patterns rare in AS patients, such as three-phase bifrontal delta waves, reactive pathological activity in the posterior areas, EEG patterns of focal seizures originating from the posterior areas, benign epileptiform discharges of childhood, and migrating continuous slow-wave activity.We analyzed the differences between main EEG patterns in AS and frontal and occipital intermittent rhythmic delta activity (fIRDA and OIRDA patterns).

Emerging Gene and Small Molecule Therapies for the Neurodevelopmental Disorder Angelman Syndrome

Angelman syndrome (AS) is a rare (~1:15,000) neurodevelopmental disorder characterized by severe developmental delay and intellectual disability, impaired communication skills, and a high prevalence of seizures, sleep disturbances, ataxia, motor deficits, and microcephaly. AS is caused by loss-of-function of the maternally inherited UBE3A gene. UBE3A is located on chromosome 15q11–13 and is biallelically expressed throughout the body but only maternally expressed in the brain due to an RNA antisense transcript that silences the paternal copy. There is currently no cure for AS, but advancements in small molecule drugs and gene therapies offer a promising approach for the treatment of the disorder. Here, we review AS and how loss-of-function of the maternal UBE3A contributes to the disorder. We also discuss the strengths and limitations of current animal models of AS. Furthermore, we examine potential small molecule drug and gene therapies for the treatment of AS and associated challenges faced by the therapeutic design. Finally, gene therapy offers the opportunity for precision medicine in AS and advancements in the treatment of this disorder can serve as a foundation for other single-gene neurodevelopmental disorders.

Genotype-Phenotype Correlations in Angelman Syndrome.

Angelman syndrome (AS) is a rare neurodevelopmental disease that is caused by the loss of function of the maternal copy of ubiquitin–protein ligase E3A (UBE3A) on the chromosome 15q11–13 region. AS is characterized by global developmental delay, severe intellectual disability, lack of speech, happy disposition, ataxia, epilepsy, and distinct behavioral profile. There are four molecular mechanisms of etiology: maternal deletion of chromosome 15q11–q13, paternal uniparental disomy of chromosome 15q11–q13, imprinting defects, and maternally inherited UBE3A mutations. Different genetic types may show different phenotypes in performance, seizure, behavior, sleep, and other aspects. AS caused by maternal deletion of 15q11–13 appears to have worse development, cognitive skills, albinism, ataxia, and more autistic features than those of other genotypes. Children with a UBE3A mutation have less severe phenotypes and a nearly normal development quotient. In this review, we proposed to review genotype–phenotype correlations based on different genotypes. Understanding the pathophysiology of the different genotypes and the genotype–phenotype correlations will offer an opportunity for individualized treatment and genetic counseling. Genotype–phenotype correlations based on larger data should be carried out for identifying new treatment modalities.

Is Spontaneous Hypoglycemia a Feature of XLID Type Nascimento?

Introduction: X-linked intellectual disability (XLID) type Nascimento is a rare, under-diagnosed genetic disorder caused by intragenic mutations in the UBE2A gene. The syndrome was first described in 2006 by Nascimento et el. It is characterized by intellectual disability, dysmorphic facial features, skin anomalies, hypotonia, impaired speech, and seizures. To date, there is no literature to suggest that it affects glucose homeostasis.Case: A 63-year-old male with a history of XLID (mutation in UBE2A pL112P variant), seizures, dementia, stage II CKD, polycystic kidneys, and hyperkalemia presented to the emergency department with altered mental status and blood glucose (BG) of 22 mg/dL. Mental status improved after correction of hypoglycemia.He had multiple admissions for hypoglycemia, however, no history of diabetes mellitus, or use of hypoglycemia inducing medications. Home medications included Patiromer for hyperkalemia. Family history was remarkable for XLID type Nascimento in his brother and sister’s son. Imaging and laboratory studies conducted on prior admissions were inconclusive. Abdominal CT scan showed a 6mm cyst in the head of the pancreas, but no mass. A 72-hour fast after holding dextrose infusion did not yield a clear biochemical differential. BG 51 mg/dL, Insulin <0.5 (3.0–25 mU/L), C-peptide 0.6 (1.1–4.4 ng/mL), pro-insulin 3.2 (0.0–10.0 pmol/L), β-hydroxybutyrate 0.2 (<0.6 mmol/L). BG increased to greater than 25 mg/dL with 1 mg IV glucagon. Insulin antibody was negative (<5 uU/ml). IGF-1, IGF-2 were low at 17 (49–188 ng/mL) and 142 (333-967ng/mL) respectively. Thyroid function and ACTH stimulation test were within normal limits. Aldosterone <0.1(0.0–30 ng/dL), renin 0.195 (0.167–5.38 ng/mL/hr). Urine metabolic screen, urine amino acid screen, plasma amino acid screen and white cell lysosomal enzymes were normal for the nephew and not performed in our patient. The patient’s family requested not pursuing a repeat 72-hour fast, additional imaging or invasive procedures. Dexamethasone 0.5mg orally at bedtime was started which improved blood sugars and patient was discharged. He presented 2 weeks later with recurrent hypoglycemia. Dexamethasone was titrated to 1.5 mg with no improvement. Diazoxide 3mg/kg/day was subsequently started while dexamethasone was tapered and discontinued. Hypoglycemia did not recur.Conclusion: This is the first case report describing spontaneous hypoglycemia in an individual with XLID type Nascimento. Our patient also had hyporeninemic hypoaldosteronism which raises the question of endocrine abnormalities as a manifestation of XLID type Nascimento and if hypoglycemia is an inborn error of metabolism in this patient.

796 Quantitative EEG Analysis in Angelman Syndrome

Abstract Introduction Angelman syndrome (AS) is a neurodevelopmental disorder resulting from decreased expression of the maternal copy of the imprinted UBE3A gene on chromosome 15. This disorder is characterized by intellectual disability, impaired speech and motor skills, and sleep abnormalities but currently lacks any treatment. However, mouse models have shown that un-silencing the dormant paternal copy of UBE3A has been an effective mechanism to restore the functionality of the UBE3A protein, thus clinical trials using this approach are on the near horizon. Developing biomarkers is essential for assessing responses to treatment when clinical trials begin, and quantitative EEG analysis has shown great promise as a biomarker for AS. Methods Here, we sought to define EEG biomarkers directly linked to sleep impairments seen in up to 90% of individuals with AS (Trickett). We analyzed nine overnight sleep studies from patients with AS with age and sex matched Down syndrome and neurotypical controls. We specifically examined low-frequency delta rhythms and sleep spindles during NREM sleep. Results We confirmed that low- delta rhythms are increased during overnight sleep in AS, and that this biomarker appears more reliable than possible changes in sleep spindles. Conclusion Our results suggest that quantitative measurement of delta rhythms during sleep can be used as a potential biomarker for treatments in Angelman syndrome clinical trials. Support (if any):

UBE3A Enzyme Hyperactivity as a Driver of Neurodevelopmental Disease

UBE3A is a HECT (homologous to E6AP C-terminus) domain E3 ubiquitin ligase that targets substrate proteins for degradation through the ubiquitin-proteasome pathway. Deletion or null mutation of the maternal UBE3A gene causes Angelman syndrome, a severe intellectual disability disorder also characterized by epilepsy, motor deficits, and an unusually happy disposition. Hundreds of single amino acid variants of UBE3A have been reported in the literature, but the biological significance for most these variants are unknown. Here, we devised a high-throughput assay to screen the functional consequence of UBE3A missense variants to identify precise mutations that drive disease. We screened over 150 UBE3A variants and identified distinct functional classes of UBE3A mutants, including over a dozen gain-of-function variants previously not known to exist. Mice carrying a specific hyperactivating mutation in UBE3A exhibited aberrant motor and communication deficits, and analysis of patient data showed that UBE3A hyperactivation causes a neurodevelopmental disorder that is distinct from Angelman syndrome. Finally, our detailed structure-function analysis revealed a novel allosteric regulatory site in UBE3A that is perturbed by both gain and loss-of-function mutations. Altogether, our study demonstrates that functional variant analysis can delineate disease subtypes and provide deep structure-functional data to uncover disease-relevant regulatory mechanisms.

Epilepsy-Associated UBE3A Deficiency Downregulates Retinoic Acid Signalling Pathway.

Ubiquitin-protein ligase E3A (UBE3A) has dual functions as a E3 ubiquitin-protein ligase and coactivator of nuclear hormone receptors. Mutations or deletions of the maternally inherited UBE3A gene cause Angelman syndrome. Here, we performed transcriptome profiling in the hippocampus of Ube3am+/p+ and Ube3am–/p+ mice, and determined that the expression of the retinoic acid (RA) signalling pathway was downregulated in Ube3a-deficient mice compared to WT mice. Furthermore, we demonstrated that UBE3A directly interacts with RARα and may function as a coactivator of the nuclear receptor RARα to participate in the regulation of gene expression. Loss of UBE3A expression caused the downregulation of the expression of RA-related genes, including Erbb4, Dpysl3, Calb1, Pten, and Arhgap5 in Ube3am–/p+ mice brain tissues. This work revealed a new role for UBE3A in regulating retinoic acid (RA) signalling downstream genes and hopefully to shed light on the potential drug target of AS.

Evaluation of UBE3A antibodies in mice and human cerebral organoids

UBE3A is an E3 ubiquitin ligase encoded by the neurally imprinted UBE3A gene. The abundance and subcellular distribution of UBE3A has been the topic of many previous studies as its dosage and localization has been linked to neurodevelopmental disorders including Autism, Dup15q syndrome, and Angelman syndrome. While commercially available antibodies have been widely employed to determine UBE3A localization, an extensive analysis and comparison of the performance of different UBE3A antibodies has not been conducted. Here we evaluated the specificities of seven commercial UBE3A antibodies in two of the major experimental models used in UBE3A research, mouse and human pluripotent stem cell-derived neural cells and tissues. We tested these antibodies in their two most common assays, immunofluorescence and western blot. In addition, we also assessed the ability of these antibodies to capture dynamic spatiotemporal changes of UBE3A by utilizing human cerebral organoid models. Our results reveal that among the seven antibodies tested, three antibodies demonstrated substantial nonspecific immunoreactivity. While four antibodies show specific localization patterns in both mouse brain sections and human cerebral organoids, these antibodies varied significantly in background signals and staining patterns in undifferentiated human pluripotent stem cells.

CRISPR/Cas9 directed to the Ube3a antisense transcript improves Angelman syndrome phenotype in mice.

Gene editing holds the potential to correct mutations and cure devastating genetic disorders. The technology has not yet proven efficacious for therapeutic use in CNS diseases with ubiquitous neuronal defects. Angelman syndrome (AS), a severe neurodevelopmental disorder, is caused by a lack of maternal expression of the UBE3A gene. Because of genomic imprinting, only neurons are affected. One therapeutic approach focuses on the intact paternal UBE3A copy in patients with AS that is silenced by an antisense transcript (UBE3A-ATS). We show here that gene editing of Ube3a-ATS in the mouse brain resulted in the formation of base pair insertions/deletions (indels) in neurons and the subsequent unsilencing of the paternal Ube3a allele in neurons, which partially corrected the behavioral phenotype of a murine AS model. This study provides compelling evidence to further investigate editing of the homologous region of the human UBE3A-ATS because this may provide a lasting therapeutic effect for patients with AS.

UBE3A reinstatement as a disease-modifying therapy for Angelman syndrome.

Half a century ago, Harry Angelman reported three patients with overlapping clinical features, now well known as Angelman syndrome. Angelman syndrome is caused by mutations affecting the maternally inherited UBE3A gene, which encodes an E3‐ubiquitin ligase that is critical for typical postnatal brain development. Emerging evidence indicates that UBE3A plays a particularly important role in the nucleus. However, the critical substrates that are controlled by UBE3A remain elusive, which hinders the search for effective treatments. Moreover, given the multitude of signalling mechanisms that are derailed, it is unlikely that targeting a single pathway is going to be very effective. Therefore, expectations are very high for approaches that aim to restore UBE3A protein levels. A particular promising strategy is an antisense oligonucleotide approach, which activates the silenced paternal UBE3A gene. When successful, such treatments potentially offer a disease‐modifying therapy for Angelman syndrome and several other neurodevelopmental disorders. What this paper adds Loss of UBE3A affects multiple signalling pathways in the brain.Emerging evidence suggests that UBE3A plays a critical role in the cell nucleus.Trials using antisense oligonucleotides to restore UBE3A levels are continuing.

Early Developmental EEG and Seizure Phenotypes in a Full Gene Deletion of Ubiquitin Protein Ligase E3A Rat Model of Angelman Syndrome.

Angelman syndrome (AS) is a neurodevelopmental disorder with unique behavioral phenotypes, seizures, and distinctive electroencephalographic (EEG) patterns. Recent studies identified motor, social communication, and learning and memory deficits in a CRISPR engineered rat model with a complete maternal deletion of the Ube3a gene. It is unknown whether this model recapitulates other aspects of the clinical disorder. We report here the effect of Ube3a maternal deletion in the rat on epileptiform activity, seizure threshold, and quantitative EEG. Using video-synchronized EEG (vEEG) monitoring, we assessed spectral power and epileptiform activity early postnatally through adulthood. While EEG power was similar to wild-type (WT) at 1.5 weeks postnatally, at all other ages analyzed, our findings were similar to the AS phenotype in mice and humans with significantly increased δ power. Analysis of epileptiform activity in juvenile and adult rats showed increased time spent in epileptiform activity in AS compared with WT rats. We evaluated seizure threshold using pentylenetetrazol (PTZ), audiogenic stimulus, and hyperthermia to provoke febrile seizures (FSs). Behavioral seizure scoring following PTZ induction revealed no difference in seizure threshold in AS rats, however behavioral recovery from the PTZ-induced seizure was longer in the adult group with significantly increased hippocampal epileptiform activity during this phase. When exposed to hyperthermia, AS rat pups showed a significantly lower temperature threshold to first seizure than WT. Our findings highlight an age-dependence for the EEG and epileptiform phenotypes in a preclinical model of AS, and support the use of quantitative EEG and increased δ power as a potential biomarker of AS.