Multiplex epigenome editing of
            <i>MECP2</i>
            to rescue Rett syndrome neurons

Qian, Junming; Guan, Xiaonan; Xie, Bing; Xu, Chuanyun; Niu, Jacqueline; Tang, Xin; Li, Charles Han; Colecraft, Henry M.; Jaenisch, Rudolf; Liu, Shawn

doi:10.1126/scitranslmed.add4666

Cited by 36 publications

(19 citation statements)

References 54 publications

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“…Our work builds upon other studies that have used targeted DNA demethylation editing to restore silenced gene expression in stem cells and neurons, including BDNF , FMR1 , MECP2 , and the imprinted Dlk1-Dio3 locus (Liu et al, 2016, Liu et al, 2018, Qian et al, 2023, Kojima et al, 2022). These studies have demonstrated that targeting a dCas9-TET1 fusion to the methylated promoter of the silenced gene is sufficient to activate its expression.…”

Section: Discussionmentioning

confidence: 97%

Activation of the imprinted Prader-Willi Syndrome locus by CRISPR-based epigenome editing

Rohm,

Black,

McCutcheon

et al. 2024

Preprint

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Epigenome editing with DNA-targeting technologies such as CRISPR-dCas9 can be used to dissect gene regulatory mechanisms and potentially treat associated disorders. For example, Prader-Willi Syndrome (PWS) is caused by loss of paternally expressed imprinted genes on chromosome 15q11.2-q13.3, although the maternal allele is intact but epigenetically silenced. Using CRISPR repression and activation screens in human induced pluripotent stem cells (iPSCs), we identified genomic elements that control expression of the PWS gene SNRPN from the paternal and maternal chromosomes. We showed that either targeted transcriptional activation or DNA demethylation can activate the silenced maternal SNRPN and downstream PWS transcripts. However, these two approaches function at unique regions, preferentially activating different transcript variants and involving distinct epigenetic reprogramming mechanisms. Remarkably, transient expression of the targeted demethylase leads to stable, long-term maternal SNRPN expression in PWS iPSCs. This work uncovers targeted epigenetic manipulations to reprogram a disease-associated imprinted locus and suggests possible therapeutic interventions.

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Section: Discussionmentioning

confidence: 97%

Activation of the imprinted Prader-Willi Syndrome locus by CRISPR-based epigenome editing

Rohm,

Black,

McCutcheon

et al. 2024

Preprint

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“…Transduction of hESC derived neurons with dCas9-Tet1/sgRNA proved that demethylation of the MECP2 promoter reactivated the wild type allele located on the Xi (82% of protein expression). Moreover, direct epigenome editing of neurons, carrying on Xi MeCP2 exon 3 fused with GFP and its methylated promoter and on Xa MeCP2 exon 3 fused with tdTomato, showed a moderate reactivation of MeCP2-GFP (17,7% of protein expression) without affecting the expression of other genes on both X chromosomes ( Qian et al, 2023 ). Although precise DNA methylation editing of MECP2 displayed encouraging results, further validation in in vivo animal models of RTT is essential for the translational value of this approach.…”

Section: Reactivation Of the Inactive X Chromosomementioning

confidence: 99%

Advanced genetic therapies for the treatment of Rett syndrome: state of the art and future perspectives

2023

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Loss and gain of functions mutations in the X-linked MECP2 (methyl-CpG-binding protein 2) gene are responsible for a set of generally severe neurological disorders that can affect both genders. In particular, Mecp2 deficiency is mainly associated with Rett syndrome (RTT) in girls, while duplication of the MECP2 gene leads, mainly in boys, to the MECP2 duplication syndrome (MDS). No cure is currently available for MECP2 related disorders. However, several studies have reported that by re-expressing the wild-type gene is possible to restore defective phenotypes of Mecp2 null animals. This proof of principle endorsed many laboratories to search for novel therapeutic strategies to cure RTT. Besides pharmacological approaches aimed at modulating MeCP2-downstream pathways, genetic targeting of MECP2 or its transcript have been largely proposed. Remarkably, two studies focused on augmentative gene therapy were recently approved for clinical trials. Both use molecular strategies to well-control gene dosage. Notably, the recent development of genome editing technologies has opened an alternative way to specifically target MECP2 without altering its physiological levels. Other attractive approaches exclusively applicable for nonsense mutations are the translational read-through (TR) and t-RNA suppressor therapy. Reactivation of the MECP2 locus on the silent X chromosome represents another valid choice for the disease. In this article, we intend to review the most recent genetic interventions for the treatment of RTT, describing the current state of the art, and the related advantages and concerns. We will also discuss the possible application of other advanced therapies, based on molecular delivery through nanoparticles, already proposed for other neurological disorders but still not tested in RTT.

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“…93 A recent study described that reactivating the MeCP2 gene locus in the silenced but normal X-chromosome by demethylation rescues abnormalities in Rett neurons. 94 Separate studies have described that suppressing MeCP2 expression using antisense oligonucleotides and other genetic methods can reduce behavioral defects in a transgenic mouse model of MeCP2 duplication syndrome. 95,96 However, in these studies, the line of MeCP2 used exhibits very mild symptoms relative to patients with MeCP2 duplication syndrome.…”

Section: The Principalsmentioning

confidence: 99%

Rett and Rett-related disorders: Common mechanisms for shared symptoms?

D’Mello

2023

Exp Biol Med (Maywood)

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Rett syndrome is a neurodevelopmental disorder caused by loss-of-function mutations in the methyl-CpG binding protein-2 (MeCP2) gene that is characterized by epilepsy, intellectual disability, autistic features, speech deficits, and sleep and breathing abnormalities. Neurologically, patients with all three disorders display microcephaly, aberrant dendritic morphology, reduced spine density, and an imbalance of excitatory/inhibitory signaling. Loss-of-function mutations in the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1 genes also cause similar behavioral and neurobiological defects and were referred to as congenital or variant Rett syndrome. The relatively recent realization that CDKL5 deficiency disorder (CDD), FOXG1 syndrome, and Rett syndrome are distinct neurodevelopmental disorders with some distinctive features have resulted in separate focus being placed on each disorder with the assumption that distinct molecular mechanisms underlie their pathogenesis. However, given that many of the core symptoms and neurological features are shared, it is likely that the disorders share some critical molecular underpinnings. This review discusses the possibility that deregulation of common molecules in neurons and astrocytes plays a central role in key behavioral and neurological abnormalities in all three disorders. These include KCC2, a chloride transporter, vGlut1, a vesicular glutamate transporter, GluD1, an orphan-glutamate receptor subunit, and PSD-95, a postsynaptic scaffolding protein. We propose that reduced expression or activity of KCC2, vGlut1, PSD-95, and AKT, along with increased expression of GluD1, is involved in the excitatory/inhibitory that represents a key aspect in all three disorders. In addition, astrocyte-derived brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and inflammatory cytokines likely affect the expression and functioning of these molecules resulting in disease-associated abnormalities.

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Multiplex epigenome editing of MECP2 to rescue Rett syndrome neurons

Cited by 36 publications

References 54 publications

Activation of the imprinted Prader-Willi Syndrome locus by CRISPR-based epigenome editing

Activation of the imprinted Prader-Willi Syndrome locus by CRISPR-based epigenome editing

Advanced genetic therapies for the treatment of Rett syndrome: state of the art and future perspectives

Rett and Rett-related disorders: Common mechanisms for shared symptoms?

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