Phosphorylation of mouse MECP2 at serine 421 (corresponding to S423 in human MECP2 isoform 1) upon neuronal activity has been shown to facilitate the release of a transcription factor from the MECP2 transcriptional repressor complex, coinciding with increased brain-derived neurotrophic factor (BDNF) expression, enhanced synaptic function, and improvement of learning and memory, but the role of these processes in the context of AD is not known [15]. This evidence concerns the gene BDNF and Alzheimer disease.