MECP2 and atypical Rett syndrome: Interestingly, a study in mouse model of Rett Syndrome showed that MeCP2 repressed miR-199b expression in the mouse brain (Urdinguio et al., 2010) and miR-199b has been shown to suppress sirtuin 1 (SIRT1) (Saunders et al., 2010), which is involved in dendritic development (Codocedo et al., 2012).