Site-specific R-loop formation induces CGG repeat contraction and Fragile X gene reactivation
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA765296 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR16005738_1.fastq.gz | Fastqsanger.gz | |||
| SRR16005738_2.fastq.gz | Fastqsanger.gz | |||
| SRR16005739_1.fastq.gz | Fastqsanger.gz | |||
| SRR16005739_2.fastq.gz | Fastqsanger.gz | |||
| SRR16005740_1.fastq.gz | Fastqsanger.gz |
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Project description:Fragile X syndrome (FXS) is a neurodevelopmental disorder and a leading cause of intellectual disability. In FXS, the neuronal regulator, FMR1, is epigenetically silenced by a CGG repeat expansion. Here, we investigate conditions under which repeat expansion and gene silencing could be reversed. Surprisingly, inducing formation of R-loops (3-stranded RNA-DNA structures) within FMR1 is sufficient to initiate CGG contraction, promoter demethylation, and FMR1 reactivation. Recruiting RNaseH degrades the R-loop and abolishes the response. Targeting the nascent mRNA for degradation also eliminates the response. Thus, we have identified an exogenous nuclease-free method of contracting CGG repeats and reversing FMR1 silencing. We propose that DNA demethylation, new transcription, and R-loop formation engage in a feed-forward cycle to contract CGG repeats and reactivate FMR1.
2023-05-19 | GSE184580 | GEO
Project description:Transcribed CGG repeat expansions cause the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). CGG repeat RNAs sequester RNA-binding proteins (RBPs) into nuclear foci and undergo repeat-associated non-AUG (RAN) translation into toxic peptides in the cytoplasm. To identify proteins involved in these processes, we employed a CGG repeat RNA-tagging system to capture repeat associated RBPs by mass spectrometry in mammalian cells. We identified several SR (serine/arginine-rich domain) proteins that interact selectively with CGG repeats basally and under cellular stress. These same proteins modify toxicity in a Drosophila model of FXTAS. Genetic or pharmacological targeting of serine/arginine protein kinases (SRPKs) inhibits RAN translation in cells and toxicity in both FXTAS and C9orf72 ALS/FTD model flies. Furthermore, SRPK inhibitors suppressed CGG repeat toxicity in rodent neurons. These findings demonstrate roles for CGG repeat RNA binding proteins in repeat toxicity and support further evaluation of SRPK inhibitors in modulating RAN translation associated with repeat expansion disorders.
2021-09-28 | PXD027000 | Pride
Project description:Fragile X syndrome (FXS) is the most common form of inherited intellectual disability, resulting from a CGG repeat expansion in the fragile X mental retardation 1 (FMR1) gene. Here we report a strategy for CGG repeat correction using CRISPR/Cas9 for targeted deletion in both embryonic stem cells and induced pluripotent stem cells derived from FXS patients. Following gene correction in FXS induced pluripotent stem cells, FMR1 expression was restored and sustained in neural precursor cells and mature neurons. Strikingly, after removal of the CGG repeats, the upstream CpG island of the FMR1 promoter showed extensive demethylation, an open chromatin state, and transcription initiation. These results suggest a silencing maintenance mechanism for the FMR1 promoter that is dependent on the existence of the CGG repeat expansion. Our strategy for deletion of trinucleotide repeats provides further insights into the molecular mechanisms of FXS and future therapies of trinucleotide repeat disorders.
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Project description:Aberrant alternative splicing of mRNAs results in dysregulated gene expression in multiple neurological disorders. Here we show that hundreds of mRNAs are incorrectly expressed and spliced in white blood cells and brain tissue of individuals with fragile X syndrome (FXS). Surprisingly, the FMR1 (Fragile X Messenger Ribonucleoprotein 1) gene is transcribed in >70% of the FXS tissues. In all FMR1 expressing FXS tissues, FMR1 RNA itself is mis-spliced in a CGG expansion-dependent manner to generate the little-known FMR1-217 RNA isoform, which is comprised of FMR1 exon 1 and a pseudo-exon in intron 1. FMR1-217 is also expressed in FXS premutation carrier-derived skin fibroblasts and brain tissue. We show that in cells aberrantly expressing mis-spliced FMR1, antisense oligonucleotide (ASO) treatment reduces FMR1-217, rescues full-length FMR1 RNA, and restores FMRP (Fragile X Messenger RibonucleoProtein) to normal levels. Notably, FMR1 gene reactivation in transcriptionally silent FXS cells using 5-aza-2′-deoxycytidine (5-AzadC), which prevents DNA methylation, increases FMR1-217 RNA levels but not FMRP. ASO treatment of cells prior to 5-AzadC application rescues full-length FMR1 expression and restores FMRP. These findings indicate that mis-regulated RNA processing events in blood could serve as potent biomarkers for FXS and that in those individuals expressing FMR1-217, ASO treatment may offer a new therapeutic approach to mitigate the disorder.
2023-06-14 | GSE202178 | GEO
Project description:Aberrant alternative splicing of mRNAs results in dysregulated gene expression in multiple neurological disorders. Here we show that hundreds of mRNAs are incorrectly expressed and spliced in white blood cells and brain tissue of individuals with fragile X syndrome (FXS). Surprisingly, the FMR1 (Fragile X Messenger Ribonucleoprotein 1) gene is transcribed in >70% of the FXS tissues. In all FMR1 expressing FXS tissues, FMR1 RNA itself is mis-spliced in a CGG expansion-dependent manner to generate the little-known FMR1-217 RNA isoform, which is comprised of FMR1 exon 1 and a pseudo-exon in intron 1. FMR1-217 is also expressed in FXS premutation carrier-derived skin fibroblasts and brain tissue. We show that in cells aberrantly expressing mis-spliced FMR1, antisense oligonucleotide (ASO) treatment reduces FMR1-217, rescues full-length FMR1 RNA, and restores FMRP (Fragile X Messenger RibonucleoProtein) to normal levels. Notably, FMR1 gene reactivation in transcriptionally silent FXS cells using 5-aza-2′-deoxycytidine (5-AzadC), which prevents DNA methylation, increases FMR1-217 RNA levels but not FMRP. ASO treatment of cells prior to 5-AzadC application rescues full-length FMR1 expression and restores FMRP. These findings indicate that mis-regulated RNA processing events in blood could serve as potent biomarkers for FXS and that in those individuals expressing FMR1-217, ASO treatment may offer a new therapeutic approach to mitigate the disorder.
2023-06-14 | GSE202177 | GEO
Project description:Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find Megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X-chromosome in induced pluripotent stem cell (iPSC)-derived neural progenitors, B-cells, and fibroblasts with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication stress-induced double strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the full-mutation CGG to premutation-length reverses H3K9me3 domains on the X-chromosome and multiple autosomes, refolds TADs, and restores expression. H3K9me3 domains also arise in a subset of normal-length iPSCs with increased STR instability burden. Our results reveal Mb-scale heterochromatinization and trans interactions among chromosomes susceptible to repeat genetic instability.
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Project description:Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find Megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X-chromosome in induced pluripotent stem cell (iPSC)-derived neural progenitors, B-cells, and fibroblasts with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication stress-induced double strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the full-mutation CGG to premutation-length reverses H3K9me3 domains on the X-chromosome and multiple autosomes, refolds TADs, and restores expression. H3K9me3 domains also arise in a subset of normal-length iPSCs with increased STR instability burden. Our results reveal Mb-scale heterochromatinization and trans interactions among chromosomes susceptible to repeat genetic instability.
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Project description:Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find Megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X-chromosome in induced pluripotent stem cell (iPSC)-derived neural progenitors, B-cells, and fibroblasts with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication stress-induced double strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the full-mutation CGG to premutation-length reverses H3K9me3 domains on the X-chromosome and multiple autosomes, refolds TADs, and restores expression. H3K9me3 domains also arise in a subset of normal-length iPSCs with increased STR instability burden. Our results reveal Mb-scale heterochromatinization and trans interactions among chromosomes susceptible to repeat genetic instability.
2023-12-21 | GSE218677 | GEO
Project description:Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find Megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X-chromosome in induced pluripotent stem cell (iPSC)-derived neural progenitors, B-cells, and fibroblasts with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication stress-induced double strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the full-mutation CGG to premutation-length reverses H3K9me3 domains on the X-chromosome and multiple autosomes, refolds TADs, and restores expression. H3K9me3 domains also arise in a subset of normal-length iPSCs with increased STR instability burden. Our results reveal Mb-scale heterochromatinization and trans interactions among chromosomes susceptible to repeat genetic instability.
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Project description:Short tandem repeat (STR) instability causes transcriptional silencing in several repeat expansion disorders. In fragile X syndrome (FXS), mutation-length expansion of a CGG STR represses FMR1 via local DNA methylation. Here, we find Megabase-scale H3K9me3 domains on autosomes and encompassing FMR1 on the X-chromosome in induced pluripotent stem cell (iPSC)-derived neural progenitors, B-cells, and fibroblasts with mutation-length CGG expansion. H3K9me3 domains connect via inter-chromosomal interactions and demarcate severe misfolding of TADs and loops. They harbor long synaptic genes replicating at the end of S phase, replication stress-induced double strand breaks, and STRs prone to stepwise somatic instability. CRISPR engineering of the full-mutation CGG to premutation-length reverses H3K9me3 domains on the X-chromosome and multiple autosomes, refolds TADs, and restores expression. H3K9me3 domains also arise in a subset of normal-length iPSCs with increased STR instability burden. Our results reveal Mb-scale heterochromatinization and trans interactions among chromosomes susceptible to repeat genetic instability.
2023-12-21 | GSE218675 | GEO