Molecular and Functional Dysregulations in Novel, Rett Syndrome Patient-Derived Cerebral Organoids

Abstract Rett syndrome (RTT) is a severe neurodevelopmental disorder (NDD) caused by mutations in MECP2 . Although existing RTT organoid models recapitulate key disease-associated phenotypes, scalable and patient-relevant platforms for mechanistic and therapeutic studies remain limited. Here, we establish clonal cerebral organoids (COs) derived from patient neural stem cells (NSCs) harboring the R270X mutation to model RTT. Established COs exhibit progressive neuronal maturation, diverse neuronal composition, allele-specific MECP2 expression, and transcriptional dysregulation associated with loss of full-length MECP2 protein. Mutant COs also display reduced organoid size, impaired neurite outgrowth, and altered network activity, consistent with functional neuronal deficits in RTT. In addition, the model supports dose-dependent AAV9 transduction, enabling future evaluation of therapeutic delivery approaches. Together, this work introduces an NSC-derived cerebral organoid platform that captures key molecular and functional features of RTT and provides a scalable, patient-relevant model for mechanistic and therapeutic studies.