MeCP2 stabilizes the glucocorticoid system in active chromatin regions

Methyl-CpG-binding protein 2 (MeCP2), a key epigenetic factor regulating gene expression via DNA/chromatin interactions, causes Rett syndrome when dysfunctional. However, its regulatory mechanisms at the pan-tissue and multi-omics levels remain poorly understood. Here, we constructed comprehensive pan-tissue transcriptional profiles and chromatin accessibility profiles from wild-type and Mecp2-knockout mice. Integrative analyses revealed that glucocorticoid (GC)-induced genes (GIGs) exhibited global hyperactivation following Mecp2 knockout, highlighting a crucial role for MeCP2 in maintaining GC signaling homeostasis. Through innovative single-cell multi-omics profiling of the nervous system, we found that GIG dysregulation primarily disrupts neural homeostasis via non-neuronal cells. Mechanistically, we uncovered a dual regulatory mode of MeCP2: (1) limiting NR3C1 occupancy at GIG cis-regulatory elements in active chromatin regions, and (2) disrupting NR3C1 interaction with its coactivator NCOA1. Importantly, pharmacologically suppressing aberrant GC system activation ameliorated pathological phenotypes and significantly prolonged survival in Mecp2-knockout mice. Our study demonstrates the critical pathological role of hyperactivated GC signaling in the multisystem disturbances of Mecp2-knockout mice and suggests potential therapeutic targets for Rett syndrome.