In addition to RTT, evidence has shown that MeCP2 regulates the expression of its downstream genes, such as brain-derived neurotrophic factor (BDNF) (Chen et al., 2003) and ubiquitin-protein ligase E3A (UBE3a), the latter being involved in Angelman syndrome (Makedonski et al., 2005). Here, UBE3A is linked to Angelman syndrome.