Researchers have gained new insights into the molecular changes leading to Rett syndrome, a severe neurological disorder caused by mutations in the MeCP2 gene encoding methyl-CpG binding protein 2 (MeCP2). The team reports that loss of MeCP2 in adulthood causes immediate progressive dysregulation of hundreds of genes — some are activated while others are suppressed — and these changes occur well before any measurable deficiencies in neurological function.