BDNF and Rett syndrome: Several studies have identified possible target genes that are controlled by MeCP2, including the gene encoding brain-derived neurotrophic factor (BDNF) [34]–[36], genes encoding inhibitors of differentiation [37], and genes regulated by glucocorticoids [38]; their expression is altered in MECP2 knockout mice, but whether this is responsible for the neuropathology seen in RTT remains questionable.