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Nature Oct 2020Methyl CpG binding protein 2 (MeCP2) is a key component of constitutive heterochromatin, which is crucial for chromosome maintenance and transcriptional silencing....
Methyl CpG binding protein 2 (MeCP2) is a key component of constitutive heterochromatin, which is crucial for chromosome maintenance and transcriptional silencing. Mutations in the MECP2 gene cause the progressive neurodevelopmental disorder Rett syndrome, which is associated with severe mental disability and autism-like symptoms that affect girls during early childhood. Although previously thought to be a dense and relatively static structure, heterochromatin is now understood to exhibit properties consistent with a liquid-like condensate. Here we show that MeCP2 is a dynamic component of heterochromatin condensates in cells, and is stimulated by DNA to form liquid-like condensates. MeCP2 contains several domains that contribute to the formation of condensates, and mutations in MECP2 that lead to Rett syndrome disrupt the ability of MeCP2 to form condensates. Condensates formed by MeCP2 selectively incorporate and concentrate heterochromatin cofactors rather than components of euchromatic transcriptionally active condensates. We propose that MeCP2 enhances the separation of heterochromatin and euchromatin through its condensate partitioning properties, and that disruption of condensates may be a common consequence of mutations in MeCP2 that cause Rett syndrome.
Topics: Adaptive Immunity; Animals; Female; Heterochromatin; Immunity, Innate; Intellectual Disability; Methyl-CpG-Binding Protein 2; Mice; Mutation; Neurons; Phenotype; Rett Syndrome
PubMed: 32698189
DOI: 10.1038/s41586-020-2574-4 -
Nature Neuroscience Oct 2021Brain organoids represent a powerful tool for studying human neurological diseases, particularly those that affect brain growth and structure. However, many diseases...
Brain organoids represent a powerful tool for studying human neurological diseases, particularly those that affect brain growth and structure. However, many diseases manifest with clear evidence of physiological and network abnormality in the absence of anatomical changes, raising the question of whether organoids possess sufficient neural network complexity to model these conditions. Here, we explore the network-level functions of brain organoids using calcium sensor imaging and extracellular recording approaches that together reveal the existence of complex network dynamics reminiscent of intact brain preparations. We demonstrate highly abnormal and epileptiform-like activity in organoids derived from induced pluripotent stem cells from individuals with Rett syndrome, accompanied by transcriptomic differences revealed by single-cell analyses. We also rescue key physiological activities with an unconventional neuroregulatory drug, pifithrin-α. Together, these findings provide an essential foundation for the utilization of brain organoids to study intact and disordered human brain network formation and illustrate their utility in therapeutic discovery.
Topics: Adult; Benzothiazoles; Brain; Calcium Signaling; Child, Preschool; Epilepsy; Female; Humans; Induced Pluripotent Stem Cells; Methyl-CpG-Binding Protein 2; Nerve Net; Neurogenesis; Neuroimaging; Neurons; Rett Syndrome; Single-Cell Analysis; Synapses; Toluene; Transcriptome
PubMed: 34426698
DOI: 10.1038/s41593-021-00906-5 -
Nature Neuroscience Sep 2022Astrocytes negatively impact neuronal development in many models of neurodevelopmental disorders (NDs); however, how they do this, and if mechanisms are shared across...
Astrocytes negatively impact neuronal development in many models of neurodevelopmental disorders (NDs); however, how they do this, and if mechanisms are shared across disorders, is not known. In this study, we developed a cell culture system to ask how astrocyte protein secretion and gene expression change in three mouse models of genetic NDs (Rett, Fragile X and Down syndromes). ND astrocytes increase release of Igfbp2, a secreted inhibitor of insulin-like growth factor (IGF). IGF rescues neuronal deficits in many NDs, and we found that blocking Igfbp2 partially rescues inhibitory effects of Rett syndrome astrocytes, suggesting that increased astrocyte Igfbp2 contributes to decreased IGF signaling in NDs. We identified that increased BMP signaling is upstream of protein secretion changes, including Igfbp2, and blocking BMP signaling in Fragile X and Rett syndrome astrocytes reverses inhibitory effects on neurite outgrowth. This work provides a resource of astrocyte-secreted proteins in health and ND models and identifies novel targets for intervention in diverse NDs.
Topics: Animals; Astrocytes; Mice; Neurodevelopmental Disorders; Neurogenesis; Neurons; Rett Syndrome
PubMed: 36042312
DOI: 10.1038/s41593-022-01150-1 -
Science Translational Medicine Jan 2023Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by loss-of-function heterozygous mutations of methyl CpG-binding protein 2 () on the X chromosome...
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by loss-of-function heterozygous mutations of methyl CpG-binding protein 2 () on the X chromosome in young females. Reactivation of the silent wild-type 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 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 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.
Topics: Humans; Female; Rett Syndrome; Epigenome; Methyl-CpG-Binding Protein 2; Neurons; Mutation; Heterozygote; Mixed Function Oxygenases; Proto-Oncogene Proteins
PubMed: 36652535
DOI: 10.1126/scitranslmed.add4666 -
Brain : a Journal of Neurology Nov 2021MECP2 gene transfer has been shown to extend the survival of Mecp2-/y knockout mice modelling Rett syndrome, an X-linked neurodevelopmental disorder. However,...
MECP2 gene transfer has been shown to extend the survival of Mecp2-/y knockout mice modelling Rett syndrome, an X-linked neurodevelopmental disorder. However, controlling deleterious overexpression of MECP2 remains the critical unmet obstacle towards a safe and effective gene therapy approach for Rett syndrome. A recently developed truncated miniMECP2 gene has also been shown to be therapeutic after AAV9-mediated gene transfer in knockout neonates. We show that AAV9/miniMECP2 has a similar dose-dependent toxicity profile to that of a published second-generation AAV9/MECP2 vector after treatment in adolescent mice. To overcome that toxicity, we developed a risk-driven viral genome design strategy rooted in high-throughput profiling and genome mining to rationally develop a compact, synthetic microRNA target panel (miR-responsive auto-regulatory element, 'miRARE') to minimize the possibility of miniMECP2 transgene overexpression in the context of Rett syndrome gene therapy. The goal of miRARE is to have a built-in inhibitory element responsive to MECP2 overexpression. The data provided herein show that insertion of miRARE into the miniMECP2 gene expression cassette greatly improved the safety of miniMECP2 gene transfer without compromising efficacy. Importantly, this built-in regulation system does not require any additional exogenous drug application, and no miRNAs are expressed from the transgene cassette. Although broad applications of miRARE have yet to be determined, the design of miRARE suggests a potential use in gene therapy approaches for other dose-sensitive genes.
Topics: Animals; Genetic Therapy; Humans; Injections, Spinal; Methyl-CpG-Binding Protein 2; Mice; Mice, Knockout; MicroRNAs; Protein Engineering; Regulatory Elements, Transcriptional; Rett Syndrome
PubMed: 33950254
DOI: 10.1093/brain/awab182 -
Molecular Therapy : the Journal of the... Sep 2023The AAV9 gene therapy vector presented in this study is safe in mice and non-human primates and highly efficacious without causing overexpression toxicity, a major...
The AAV9 gene therapy vector presented in this study is safe in mice and non-human primates and highly efficacious without causing overexpression toxicity, a major challenge for clinical translation of Rett syndrome gene therapy vectors to date. Our team designed a new truncated methyl-CpG-binding protein 2 (MECP2) promoter allowing widespread expression of MECP2 in mice and non-human primates after a single injection into the cerebrospinal fluid without causing overexpression symptoms up to 18 months after injection. Additionally, this new vector is highly efficacious at lower doses compared with previous constructs as demonstrated in extensive efficacy studies performed by two independent laboratories in two different Rett syndrome mouse models carrying either a knockout or one of the most frequent human mutations of Mecp2. Overall, data from this multicenter study highlight the efficacy and safety of this gene therapy construct, making it a promising candidate for first-in-human studies to treat Rett syndrome.
Topics: Humans; Mice; Animals; Rett Syndrome; Primates; Genetic Therapy; Mutation
PubMed: 37481701
DOI: 10.1016/j.ymthe.2023.07.013 -
Cells Apr 2020Methyl-CpG binding protein 2 (MeCP2) is a multifunctional epigenetic reader playing a role in transcriptional regulation and chromatin structure, which was linked to... (Review)
Review
Methyl-CpG binding protein 2 (MeCP2) is a multifunctional epigenetic reader playing a role in transcriptional regulation and chromatin structure, which was linked to Rett syndrome in humans. Here, we focus on its isoforms and functional domains, interactions, modifications and mutations found in Rett patients. Finally, we address how these properties regulate and mediate the ability of MeCP2 to orchestrate chromatin compartmentalization and higher order genome architecture.
Topics: Animals; Chromatin; Humans; Methyl-CpG-Binding Protein 2; Models, Biological; Protein Binding; Protein Processing, Post-Translational; Rett Syndrome
PubMed: 32260176
DOI: 10.3390/cells9040878 -
Handbook of Clinical Neurology 2022Rett Syndrome is an X-linked neurological disorder characterized by behavioral and neurological regression, seizures, motor deficits, and dysautonomia. A particularly... (Review)
Review
Rett Syndrome is an X-linked neurological disorder characterized by behavioral and neurological regression, seizures, motor deficits, and dysautonomia. A particularly prominent presentation includes breathing abnormalities characterized by breathing irregularities, hyperventilation, repetitive breathholding during wakefulness, obstructive and central apneas during sleep, and abnormal responses to hypoxia and hypercapnia. The condition and pathology of the respiratory system is further complicated by dysfunctions of breathing-motor coordination, which is reflected in dysphagia. The discovery of the X-linked mutations in the MECP2 gene has transformed our understanding of the cellular and molecular mechanisms that are at the root of various clinical phenotypes. However, the genotype-phenotype relationship is complicated by various factors which include not only X-inactivation but also consequences of the intermittent hypoxia and oxidative stress associated with the breathing abnormalities.
Topics: Humans; Hypoxia; Respiration; Respiration Disorders; Rett Syndrome; Sleep
PubMed: 36031301
DOI: 10.1016/B978-0-323-91532-8.00018-5 -
Genes & Development Oct 2023Mutations in the methyl-DNA binding domain of MECP2 cause Rett syndrome; however, distinct mutations are associated with different severity of the disease. Live-cell... (Review)
Review
Mutations in the methyl-DNA binding domain of MECP2 cause Rett syndrome; however, distinct mutations are associated with different severity of the disease. Live-cell imaging and single-molecule tracking are sensitive methods to quantify the DNA binding affinity and diffusion dynamics of nuclear proteins. In this issue of , Zhou and colleagues (pp. 883-900) used these imaging methods to quantitatively describe the partial loss of DNA binding resulting from a novel pathological mutation with intermediate disease severity. These data demonstrate how single-molecule tracking can advance understanding of the molecular mechanisms connecting mutations with Rett syndrome pathophysiology.
Topics: Humans; Rett Syndrome; Methyl-CpG-Binding Protein 2; DNA; Mutation; Nuclear Proteins; Protein Domains
PubMed: 37914350
DOI: 10.1101/gad.351285.123 -
Nature Reviews. Drug Discovery Sep 2019
Topics: Animals; Gene Expression; Humans; Methyl-CpG-Binding Protein 2; Mice; Neurons; Rett Syndrome; Symporters
PubMed: 31570839
DOI: 10.1038/d41573-019-00143-3