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1. Abundance and localization of human UBE3A protein isoforms

   https://doi.org/10.1093/hmg/ddaa191  

   Sirois, Carissa L; Bloom, Judy E; Fink, James J; Gorka, Dea; Keller, Steffen; Germain, Noelle D; Levine, Eric S; Chamberlain, Stormy J (August 2020, Human Molecular Genetics)

   null (Ed.)

   Abstract Loss of UBE3A expression, a gene regulated by genomic imprinting, causes Angelman syndrome (AS), a rare neurodevelopmental disorder. The UBE3A gene encodes an E3 ubiquitin ligase with three known protein isoforms in humans. Studies in mouse suggest that the human isoforms may have differences in localization and neuronal function. A recent case study reported mild AS phenotypes in individuals lacking one specific isoform. Here we have used CRISPR/Cas9 to generate isogenic human embryonic stem cells (hESCs) that lack the individual protein isoforms. We demonstrate that isoform 1 accounts for the majority of UBE3A protein in hESCs and neurons. We also show that UBE3A predominantly localizes to the cytoplasm in both wild type and isoform-null cells. Finally, we show that neurons lacking isoform 1 display a less severe electrophysiological AS phenotype. 

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2. Evaluation of UBE3A antibodies in mice and human cerebral organoids

   https://doi.org/10.1038/s41598-021-85923-x  

   Sen, Dilara; Drobna, Zuzana; Keung, Albert J. (December 2021, Scientific Reports)

   null (Ed.)

   Abstract 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. 

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3. Human Cerebral Organoids Reveal Early Spatiotemporal Dynamics and Pharmacological Responses of UBE3A

   https://doi.org/10.1016/j.stemcr.2020.08.006  

   Sen, Dilara; Voulgaropoulos, Alexis; Drobna, Zuzana; Keung, Albert J. (October 2020, Stem Cell Reports)

   null (Ed.)
4. Effects of UBE3A on Cell and Liver Metabolism through the Ubiquitination of PDHA1 and ACAT1

   https://doi.org/10.1021/acs.biochem.2c00624  

   Peng, Kangli; Wang, Shirong; Liu, Ruochuan; Zhou, Li; Jeong, Geon H.; Jeong, In Ho; Liu, Xianpeng; Kiyokawa, Hiroaki; Xue, Bingzhong; Zhao, Bo; et al (March 2023, Biochemistry)
5. A bipartite boundary element restricts UBE3A imprinting to mature neurons

   https://doi.org/10.1073/pnas.1815279116  

   Hsiao, Jack S.; Germain, Noelle D.; Wilderman, Andrea; Stoddard, Christopher; Wojenski, Luke A.; Villafano, Geno J.; Core, Leighton; Cotney, Justin; Chamberlain, Stormy J. (February 2019, Proceedings of the National Academy of Sciences)

   Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by the loss of function from the maternal allele of UBE3A , a gene encoding an E3 ubiquitin ligase. UBE3A is only expressed from the maternally inherited allele in mature human neurons due to tissue-specific genomic imprinting. Imprinted expression of UBE3A is restricted to neurons by expression of UBE3A antisense transcript ( UBE3A-ATS ) from the paternally inherited allele, which silences the paternal allele of UBE3A in cis . However, the mechanism restricting UBE3A-ATS expression and UBE3A imprinting to neurons is not understood. We used CRISPR/Cas9-mediated genome editing to functionally define a bipartite boundary element critical for neuron-specific expression of UBE3A-ATS in humans. Removal of this element led to up-regulation of UBE3A-ATS without repressing paternal UBE3A . However, increasing expression of UBE3A-ATS in the absence of the boundary element resulted in full repression of paternal UBE3A , demonstrating that UBE3A imprinting requires both the loss of function from the boundary element as well as the up-regulation of UBE3A-ATS . These results suggest that manipulation of the competition between UBE3A-ATS and UBE3A may provide a potential therapeutic approach for AS. 

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