Cheng et al. demonstrate that MeCP2 (methyl CpG binding protein 2) is modified by O-GlcNAc (O-linked β-N-acetylglucosamine) at threonine 203 (T203), an etiologic site in Rett syndrome, and highlight the critical role of MeCP2 T203 O-GlcNAcylation in neuronal development and synaptic transmission. In this cover image, Aladdin's lamp is symbolizes MeCP2, and the angel with broken wings is reminiscent of a child with Rett syndrome. The flash as the hand touches the lamp represents the T203 site mutation on MeCP2. See pages 113–134 (Cover designed by Dr. Hai-Tao Wu).