MECP2 and nervous system disorder: Similar to human patients, mouse models with MECP2 mutations show progressive neurological dysfunctions recapitulating the symptoms in Rett syndrome3; progressive neurological disorders are also found in mice that express MeCP2 at twice the wild-type levels via transgenic insertion of the human MECP2 gene (MECP2 Tg1 mice) or mice that overexpress the mouse MECP2 gene specifically in neurons9, 10.