RTT is commonly caused by a mutation in MeCP2 [59], which is a transcription factor that target genes related to brain and neural development, such as brain-derived neurotrophic factor (Bdnf), [33,111], FK506 binding protein 5 [112], distal-less homeobox 5 (Dlx5) [113], Dlx6 [114], ubiquitin-protein ligase E3A [115], and serum/glucocorticoid regulated kinase 1 [62,63,112]. The gene discussed is BDNF; the disease is Rett syndrome.