Maternal deficiency of Ube3a affects dendritic and spine morphology. Specifically, Ube3am−/p+ mice have decreased spine density in hippocampal CA1 and cortical layer 3–5 pyramidal neurons (Dindot et al., 2008). In contrast, Ube3am−/p+ mice raised in darkness have similar spine densities in visual cortex, suggesting a deficit specifically in experience-dependent remodeling of synapses (Yashiro et al., 2009). Knockdown of Ube3a isoforms via in utero electroporation of shRNA revealed that Ube3a is also required for apical, but not basal, dendrite outgrowth (Miao et al., 2013). On the other hand, increased Ube3a gene dosage does not affect glutamatergic synapse number in layer 2/3 barrel cortex, as assessed by electron microscopy, immunofluorescence, and golgi staining (Smith et al., 2011).
