Clinically applicable gene therapy for RTT will likely need to move beyond simple MECP2 replacement and instead rely on precise cell- and dose-dependent regulation of its expression, with an emphasis on non-coding RNA-based and epigenetic mechanisms.
Abstract
Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder that is caused in most cases by pathogenic variants in MECP2, the gene encoding methyl-CpG-binding protein 2 (MeCP2). Despite substantial progress in the development of gene therapy, restoring MECP2 expression remains challenging because MeCP2 is highly dosage-sensitive. Both deficiency and excessive expression of this protein are associated with severe neurological abnormalities. This makes simple viral vector-mediated replacement of MECP2 potentially unsafe and underscores the need for multilayered systems that control transgene expression. This review discusses current and emerging strategies for regulating MeCP2 expression in RTT, with an emphasis on non-coding RNA-based and epigenetic mechanisms. Particular attention is given to the limitations of conventional AAV-mediated gene therapy, the use of cell-specific and endogenous promoters, miRNA-regulated elements, autoregulatory systems, and post-transcriptional control of MECP2 expression. Strategies for reactivating the inactive X chromosome are also discussed, including XIST-dependent regulation and epigenome editing. In addition, the review considers CRISPR-mediated regulation, selective epigenetic activation, and combined therapeutic platforms that integrate viral delivery, RNA-dependent post-transcriptional control, and endogenous gene regulation. Overall, clinically applicable gene therapy for RTT will likely need to move beyond simple MECP2 replacement and instead rely on precise cell- and dose-dependent regulation of its expression. Non-coding RNA and epigenetic mechanisms represent important layers of such control and may contribute to the development of safer gene therapy strategies for RTT.
ASXL3 patient truncations in neurodevelopmental condition Bainbridge-Ropers syndrome are shown to mediates gain-of-function (GOF) by escaping nonsense-mediated decay and Cullin 4-dependent degradation, resulting in aberrant protein accumulation, widespread transcriptional dysregulation, and altered chromatin accessibility.
Y. Nakamura, T. Nguyen, N. Mor et al.· medRxiv· 0 citations
Excessive cobalt exposure adversely affects the nervous system, yet the underlying neurotoxic mechanisms remain largely elusive. In the present study, using human neuroblastoma H4 cells exposed to cobalt chloride (CoCl₂) as an in vitro model, we demonstrate for the first time that CoCl₂ induces widespread alterations in m7G modification in genes associated with neurodegenerative disease. MeRIP-sequencing (MeRIP-seq) analysis revealed significant remodeling of m7G modification features, including sequence motifs, genomic distribution, and peak densities following CoCl₂ exposure. Differentially methylated genes were enriched in pathways governing nervous system function, neurotransmitter transport, neuronal projection guidance, axonogenesis, and axonal guidance. Integration of MeRIP-seq and RNA-seq data further demonstrated that CoCl₂ concurrently induced differential m7G methylation and expression of genes implicated in central nervous system function and neurodegenerative disease pathways. Mechanistically, CoCl₂ suppressed m7G modification levels by downregulating the methyltransferase complex components methyltransferase-like 1 (METTL1) and WD repeat domain 4 (WDR4). More importantly, METTL1 overexpression attenuated CoCl₂-induced downregulation of neurodegenerative disease-associated genes runt-related transcription factor 2 (RUNX2), repulsive guidance molecule A (RGMA), and unc-5 netrin receptor C (UNC5C) by modulating mRNA decay. Moreover, MeRIP-qPCR further confirmed that cobalt exposure significantly reduced m7G modification on these transcripts, and this reduction was restored by METTL1 overexpression, thereby supporting a regulatory role of m7G modification in target mRNA expression. These findings establish a pivotal role for m7G modification in environmental neurotoxicant-induced neurodegeneration and reveal cobalt-related RNA regulatory paradigm that expands our understanding of heavy metal-driven epitranscriptomic dysregulation, and hence offering novel therapeutic targets.
Jianping Tang, Yapeng Ren, Jingwen Li et al.· Ecotoxicology and Environmen...· 0 citations
Fragile X syndrome (FXS), the leading genetic cause of intellectual disability, arises from FMR1 gene silencing and the subsequent loss of the RNA-binding protein FMRP. N6-methyladenosine (m6A) is a prevalent mRNA modification essential for post-transcriptional regulation. FMRP binds and regulates the stability of m6A-containing transcripts. However, how FMRP deficiency impacts transcriptome-wide m6A modifications in FXS remains unknown. To address this, we generated cortical neurons from induced pluripotent stem cells (iPSCs) derived from healthy individuals and FXS patients. Electrophysiology recordings revealed synaptic and neuronal network defects in FXS iPSC-derived neurons. Transcriptome-wide analysis revealed striking m6A hypermethylation predominantly affecting synapse-associated transcripts. Mechanistically, we demonstrated that FMRP deficiency drives the aberrant translational upregulation of core m6A writers, a causal relationship definitively validated using CGG-corrected isogenic control lines. Targeted genetic knockdown of the m6A writer METTL3 successfully rescued synaptic phenotypes in FXS neurons, whereas its overexpression in control neurons phenocopied these synaptic defects, confirming the causal role of m6A dysregulation in FXS pathology. Notably, pharmacological intervention with the METTL3 inhibitor STM-2457 normalized methylation on synapse-associated transcripts and restored synaptic transmission in FXS neurons. Together, our findings uncover an FMRP-dependent epitranscriptomic mechanism contributing to FXS pathogenesis and suggest a promising avenue for m6A-targeted therapies.
Lu Lu, Avijite Kumer Sarkar, Lan Dao et al.· Molecular Psychiatry· 0 citations
In vivo proof-of-concept for SNCA-targeted transcriptional repression therapy in a PD-mouse model is provided and its further preclinical development toward investigational new drug enablement is supported.
Bernadette O'Donovan, Joseph E. Rittiner, Suraj Upadhya et al.· Neurotherapeutics· 0 citations
The CRISPR strategy shows compelling evidence as a therapeutic approach targeting PE in cancer and other human diseases as well as the preferential advantages of CRISPR over the antisense technology recently developed targeting the PE of EZH2.
Cell-specific epigenetic editing holds very high therapeutic value for atherosclerosis, cardiomyopathy, and fibrosis, provided that delivery, specificity, and safety challenges are also addressed.
Majed Alsulami, Mahmood Rasool, Ahmed Masoud et al.· The Cardiology· 0 citations