MECP2 and Rett syndrome: The primary causes of RTT in approximately 95% of patients are de novo mutations at the X-linked MECP2 gene, which encodes for methyl-CpG binding protein 2 (MeCP2), a genome-wide epigenetic modulator responsible for activating/repressing gene transcription, modifying chromatin compaction, and regulating RNA and miRNA processing [7,8].