Multiplex epigenome editing of MECP2 to rescue Rett syndrome neurons

• DOI: 10.1126/scitranslmed.add4666
• Publication Date: 2023-01-18T18:58:15Z
• Authors: Junming Qian; Xiaonan Guan; Bing Xie; Chuanyun Xu; Jacqueline Niu; Xin Tang; Charles H. Li; Henry M. Colecraft; Rudolf Jaenisch; X. Shawn Liu
• Keywords: Neurons; 0301 basic medicine; Epigenome; Heterozygote; 03 medical and health sciences; Methyl-CpG-Binding Protein 2; Proto-Oncogene Proteins; Mutation; Rett Syndrome; Humans; Female; Mixed Function Oxygenases

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by loss-of-function heterozygous mutations of methyl CpG-binding protein 2 ( MECP2 ) on the X chromosome in young females. Reactivation of the silent wild-type MECP2 allele from the inactive X chromosome (Xi) represents a promising therapeutic opportunity for female patients with RTT. Here, we applied a multiplex epigenome editing approach to reactivate MECP2 from Xi in RTT human embryonic stem cells (hESCs) and derived neurons. Demethylation of the MECP2 promoter by dCas9-Tet1 with target single-guide RNA reactivated MECP2 from Xi in RTT hESCs without detectable off-target effects at the transcriptional level. Neurons derived from methylation-edited RTT hESCs maintained MECP2 reactivation and reversed the smaller soma size and electrophysiological abnormalities, two hallmarks of RTT. In RTT neurons, insulation of the methylation-edited MECP2 locus by dCpf1-CTCF (a catalytically dead Cpf1 fused with CCCTC-binding factor) with target CRISPR RNA enhanced MECP2 reactivation and rescued RTT-related neuronal defects, providing a proof-of-concept study for epigenome editing to treat RTT and potentially other dominant X-linked diseases.