UBE3A Enzyme Hyperactivity as a Driver of Neurodevelopmental Disease

Abstract

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.