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MECP2-related pathways are dysregulated in a cortical organoid model of Myotonic dystrophy [eCLIP]

ABSTRACT: Myotonic dystrophy type 1 (DM1) is a multisystem, autosomal-dominant inherited disorder caused by CTG microsatellite repeat expansions (MREs) in the 3’ untranslated region of the dystrophia myotonica-protein kinase (DMPK) gene. Despite its prominence as the most common adult-onset muscular dystrophy, patients with congenital to juvenile-onset forms of DM1 can present with debilitating neurocognitive symptoms along the autism spectrum, characteristic of possible in utero cortical defects. However, the molecular mechanism by which CTG MREs lead to these developmental central nervous system (CNS) manifestations is unknown. Here, we showed that CUG foci discovered early in maturation of three-dimensional cortical organoids from DM1 patient-derived induced pluripotent stem cells, cause hyperphosphorylation of CUGBP Elav-Like Family Member 2 (CELF2 ) protein. Integrative single-cell RNA-seq and enhanced crosslinking and immunoprecipitation (eCLIP ) analysis revealed reduced CELF2 protein-RNA substrate interactions resulting in mis-regulation of genes critical for excitatory synaptic signaling in glutamatergic neurons, including key components of the Methyl-CpG binding protein 2 (MECP2) pathway. Comparisons to MECP2(-/-) cortical organoids revealed convergent molecular and cellular defects such as glutamate toxicity and neuronal loss. Our findings provide evidence suggesting that early-onset DM1 might involve neurodevelopmental disorder-associated pathways and identify N-Methyl-D-aspartic acid (NMDA ) antagonists as potential treatment avenues for neuronal defects in DM1. To evaluate if the post-translational modification of CELF2 impacts its RNA targets, we generated transcriptome-wide eCLIP maps of CELF2 protein-RNA interactions in mature, 6-month-old control and DM1 cortical organoids. All CELF2 eCLIP libraries per organoid line were performed in biologically independent duplicates, with each replicate experiment consisting of a CELF2 (IP) and a paired size-matched input (SMInput) library . We used CLIPper to identify clusters of reads representing regions in the transcriptome significantly associated with CELF2 binding in both neurotypical lines and compared them to DM1 cortical organoids with 600 and 1200 CUG repeats.

ORGANISM(S): Homo sapiens

PROVIDER: GSE201895 | GEO | 2022/06/30

REPOSITORIES: GEO

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Project description:Myotonic dystrophy type 1 (DM1) is a multisystem, autosomal-dominant inherited disorder caused by CTG microsatellite repeat expansions (MREs) in the 3’ untranslated region of the dystrophia myotonica-protein kinase (DMPK) gene. Despite its prominence as the most common adult-onset muscular dystrophy, patients with congenital to juvenile-onset forms of DM1 can present with debilitating neurocognitive symptoms along the autism spectrum, characteristic of possible in utero cortical defects. However, the molecular mechanism by which CTG MREs lead to these developmental central nervous system (CNS) manifestations is unknown. Here, we showed that CUG foci discovered early in maturation of three-dimensional cortical organoids from DM1 patient-derived induced pluripotent stem cells, cause hyperphosphorylation of CUGBP Elav-Like Family Member 2 (CELF2 ) protein. Integrative single-cell RNA-seq and enhanced crosslinking and immunoprecipitation (eCLIP ) analysis revealed reduced CELF2 protein-RNA substrate interactions resulting in mis-regulation of genes critical for excitatory synaptic signaling in glutamatergic neurons, including key components of the Methyl-CpG binding protein 2 (MECP2) pathway. Comparisons to MECP2(-/-) cortical organoids revealed convergent molecular and cellular defects such as glutamate toxicity and neuronal loss. Our findings provide evidence suggesting that early-onset DM1 might involve neurodevelopmental disorder-associated pathways and identify N-Methyl-D-aspartic acid (NMDA ) antagonists as potential treatment avenues for neuronal defects in DM1. To determine if CUG expansions in DMPK alter cellular RNA composition during differentiation, we performed transcriptomic analyses using RNA-seq at four consecutive developmental stages, ranging from iPSCs to 6-month-old cortical organoids from two independent differentiations. mine We then performed gene expression profiling analysis using data obtained from RNA-seq of 4 different time points.

Project description:Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by a non-coding CTG repeat expansion in the DMPK gene. This mutation generates a toxic CUG RNA that interferes with the RNA processing of target genes in multiple tissues. Despite debilitating neurological impairment, the pathophysiological cascade of molecular and cellular events in the central nervous system has been less extensively characterized than the molecular pathogenesis of muscle/cardiac dysfunction. Particularly, the contribution of different cell types to DM1 brain disease is not clearly understood. We first used transcriptomics to compare the impact of expanded CUG RNA on the transcriptome of primary neurons, astrocytes and oligodendrocytes derived from DMSXL mice, a transgenic model of DM1. RNA sequencing revealed more frequent expression and splicing changes in glia than neuronal cells. In particular, primary DMSXL oligodendrocytes showed the highest number of transcripts differentially expressed, while DMSXL astrocytes displayed the most severe splicing dysregulation. Interestingly, the expression and splicing defects of DMSXL glia recreated molecular signatures suggestive of impaired cell differentiation: while DMSXL oligodendrocytes failed to upregulate a subset of genes that are naturally activated during the oligodendroglia differentiation, a significant proportion of missplicing events in DMSXL oligodendrocytes and astrocytes increased the expression of RNA isoforms typical of precursor cell stages. Together these data suggest that expanded CUG RNA in glial cells affects preferentially differentiation-regulated molecular events. This hypothesis was corroborated by gene ontology (GO) analyses, which revealed an enrichment for biological processes and cellular components with critical roles during cell differentiation. Finally, we combined exon ontology with phosphoproteomics and cell imaging to explore the functional impact of CUG-associated spliceopathy on downstream protein metabolism. Changes in phosphorylation, protein isoform expression and intracellular localization in DMSXL astrocytes demonstrate the far-reaching impact of the DM1 repeat expansion on cell metabolism. Our multi-omics approaches provide insight into the mechanisms of CUG RNA toxicity in the CNS with cell type resolution, and support the priority for future research on non-neuronal mechanisms and proteomic changes in DM1 brain disease.

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MECP2-related pathways are dysregulated in a cortical organoid model of Myotonic dystrophy [eCLIP]

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