By genetically reinstating Ube3a expression from the maternal allele at different developmental ages, rescue experiments in mice show that most of these neurological functions require Ube3a during late embryonic and early postnatal development (Silva-Santos et al., 2015; Rotaru et al., 2018; Gu et al., 2019; Sonzogni et al., 2020), suggesting that the therapeutic window for Angelman syndrome may be limited to very young ages. Here, UBE3A is linked to Angelman syndrome.