Mutations in the UBE3A gene are responsible for neurodevelopmental disorders (NDDs), including Angelman syndrome (AS), which is characterized by developmental delays, impaired motor coordination, and cognitive disabilities. In recent years, UBE3A mutations have also been linked to autism spectrum disorders (ASD), due to their significant role in synaptic plasticity and cognitive function. Although substantial research has utilized mammalian models, the zebrafish (Danio rerio) provides unique opportunities to investigate gene functions owing to their transparent embryos, rapid development, and suitability for large-scale genetic and behavioral studies. In this study, we characterized a zebrafish model harboring a point mutation (T > A) in exon 3 of the zebrafish ube3a gene, which induces a stop codon resulting in a truncated protein. We performed comprehensive developmental, behavioral, and molecular analyses to investigate the impact of Ube3a dysfunction at both larval and adult stages. We observed alterations in embryonic development, significant locomotor deficits, including stereotypic movements, and reduced social preference and aggressiveness. Furthermore, RNA sequencing analysis of both larvae and adults revealed dysregulation in chromatin, nucleosome, protein-DNA, and primary cilia-related genes. Our findings provide a functional characterization of the ube3a mutation in zebrafish at both larval and adult stages. This zebrafish model offers new insights into the roles of UBE3A in neurodevelopment and behavior, expanding our understanding of its dysfunction in NDDs.

Angelman syndrome is a rare neurodevelopmental disorder caused by mutations affecting the chromosomal 15q11-13 region, either by contiguous gene deletions, imprinting defects, uniparental disomy, or mutations in the UBE3A gene itself. Phenotypic abnormalities are driven primarily, but not exclusively (especially in 15q11-13 deletion cases) by loss of expression of the maternally inherited UBE3A gene expression. The disorder was first described in 1965 by the English pediatrician Harry Angelman. Since that first description of three children with Angelman syndrome, there has been extensive research into the genetic, molecular and phenotypic aspects of the disorder. In the last decade, this has resulted in over 100 publications per year. Collectively, this research has led the field to a pivotal point in which restoring UBE3A function by genetic therapies is currently explored in several clinical trials. In this study, we employed a bibliometric approach to review and visualize the development of Angelman syndrome research over the last 50 years. We look into different parameters shaping the progress of the Angelman syndrome research field, including source of funding, publishing journals and international collaborations between research groups. Using a network approach, we map the focus of the research field and how that shifted over time. This overview helps understand the shift of research focus in the field and can provide a comprehensive handbook of Angelman syndrome research development.

Angelman Syndrome (AS) is a rare disorder with a relatively well-defined phenotype caused by lack of expression of the maternally inherited ubiquitin-protein ligase E3A (UBE3A) gene in the brain. This article describes the role of genetic testing using whole-exome sequencing (WES) in detecting rare AS variants, a point mutation in the UBE3A gene. We describe a rarely reported clinical presentation of AS in a two year and ten months old girl with severe developmental delay, movement and balance disorder, frequent smiling, apparent happy demeanor, speech impairment, absence of seizure, lack of sleep, and abnormal food-related behavior. Physical examination showed microcephaly, with facial characteristics of AS, ataxia gait, and truncal hypotonia. The electroencephalogram showed medium amplitude rhythmic 2-3c/s. Brain Magnetic Resonance Imaging revealed microcephaly, corpus callosum dysgenesis, and heterotopia grey matter on the bilateral lateral ventricle. WES was conducted to search pathogenic variants and showed a heterozygous mutation in exon 9 of the UBE3A gene, c.1513C > T (p.Arg505Ter). Angelman syndrome is a neurodevelopmental disorder that has several underlying genetic etiologies. WES could detect a rare variant of Angelman syndrome, identified as the point mutation of the UBE3A gene, which cannot be seen with other modalities.

Genetic aberrations of the UBE3A gene encoding the E3 ubiquitin ligase E6AP underlie the development of Angelman syndrome (AS). Approximately 10% of AS individuals harbor UBE3A genes with point mutations, frequently resulting in the expression of full-length E6AP variants with defective E3 activity. Since E6AP exists in two states, an inactive and an active one, we hypothesized that distinct small molecules can stabilize the active state and that such molecules may rescue the E3 activity of AS-derived E6AP variants. Therefore, we established an assay that allows identifying modulators of E6AP in a high-throughput format. We identified several compounds that not only stimulate wild-type E6AP but also rescue the E3 activity of certain E6AP variants. Moreover, by chemical cross-linking coupled to mass spectrometry we provide evidence that the compounds stabilize an active conformation of E6AP. Thus, these compounds represent potential lead structures for the design of drugs for AS treatment.

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family. E6AP catalyzes the posttranslational attachment of ubiquitin via its HECT domain onto various intracellular target proteins to regulate DNA repair and cell cycle progression. The HECT domain consists of an N-lobe, required for E2~ubiquitin recruitment, while the C-lobe contains the conserved catalytic cysteine required for ubiquitin transfer. Previous genetic studies of AS patients have identified point mutations in UBE3A that result in amino acid substitutions or premature termination during translation. An AS transversion mutation (codon change from ATA to AAA) within the region of the gene that codes for the catalytic HECT domain of E6AP has been annotated (I827K), but the molecular basis for this loss of function substitution remained elusive. Here, we demonstrate that the I827K substitution destabilizes the 3D fold causing protein aggregation of the C-terminal lobe of E6AP using a combination of spectropolarimetry and nuclear magnetic resonance (NMR) spectroscopy. Our fluorescent ubiquitin activity assays with E6AP-I827K show decreased ubiquitin thiolester formation and ubiquitin discharge. Using 3D models in combination with our biochemical and biophysical results, we rationalize why the I827K disrupts E6AP-dependent ubiquitylation. This work provides new insight into the E6AP mechanism and how its malfunction can be linked to the AS phenotype.