Among monogenic neurodevelopmental disorders, Angelman syndrome (AS) is particularly interesting; deletion of only one copy (the maternal allele) of the ubiquitin ligase gene Ube3a confers haploinsufficiency because the paternal allele of Ube3a is imprinted and silenced in neurons of both AS and non-affected subjects (Jiang et al., 2010). The gene discussed is UBE3A; the disease is Angelman syndrome.