Fragile X syndrome (FXS), the most common genetic form of intellectual disability in male, is caused by silencing of the FMR1 gene by hypermethylation of the CGG expansion mutation in the 5'UTR region of FMR1 in FXS patients. Here, we applied recently developed DNA methylation editing tools to reverse this hypermethylation event. Targeted demethylation of the CGG expansion by dCas9-Tet1/sgRNA switched the heterochromatin status of the upstream FMR1 promoter to an active chromatin state restoring a persistent expression of FMR1 in FXS iPSCs. Neurons derived from methylation edited FXS iPSCs rescued the electrophysiological abnormalities and restored a wild-type phenotype upon the mutant neurons. FMR1 expression in edited neurons was maintained in vivo after engrafting into the mouse brain. Finally, demethylation of the CGG repeats in post-mitotic FXS neurons also reactivated FMR1. Our data establish demethylation of the CGG expansion is sufficient for FMR1 reactivation, suggesting potential therapeutic strategies for FXS. Overall design: RNA-seq of FXS iPSC and neurons derived from FXS iPSC infected with lentiviruses expressing dCas9-Tet1-P2A-tBFP (dC-T) and a mCherry-expressing sgRNA targeting CGG repeats.
Rescue of Fragile X Syndrome Neurons by DNA Methylation Editing of the FMR1 Gene.
Specimen part, Subject
View SamplesThe control of cell identity is orchestrated by transcriptional and chromatin regulators in the context of specific chromosome structures. With the recent isolation of human naive embryonic stem cells (ESCs) representative of the ground state of pluripotency, it is possible to deduce this regulatory landscape in one of the earliest stages of human development. Here we generate cohesin ChIA-PET chromatin interaction data in naive and primed human ESCs and use it to reconstruct and compare the 3D regulatory landscapes of these two stages of early human development. The results reveal shared and stage-specific regulatory landscapes of topological domains and their subdomains, which consist of CTCF-CTCF/cohesin loops and enhancer-promoter/cohesin loops. The enhancer-promoter loop data reveal that genes with key roles in pluripotency are nearly always regulated by one or more super-enhancers, and show that these genes tend to occur in insulated neighborhoods. Our results reveal the key features of the 3D regulatory landscape of early human cells that form the foundation for embryonic development. Overall design: Polyadenylated RNA-seq from naive and primed human embroynic stem cells.
3D Chromosome Regulatory Landscape of Human Pluripotent Cells.
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View SamplesThere is considerable evidence that chromosome structure plays important roles in gene control, but we have limited understanding of the proteins that contribute to structural interactions between gene promoters and their enhancer elements. Large DNA loops that encompass genes and their regulatory elements depend on CTCF-CTCF interactions, but most enhancer-promoter interactions do not depend on this structural protein. Here we show that the transcription factor Yin Yang 1 (YY1) contributes to enhancer-promoter structural interactions in a manner analogous to DNA interactions mediated by CTCF. YY1 binds to active enhancers and promoter-proximal elements in all cells examined. YY1 forms dimers that can facilitate DNA interactions. Deletion of YY1 binding sites or depletion of YY1 can disrupt enhancer-promoter looping and normal gene expression. We propose that YY1-mediated enhancer-promoter interactions are a general feature of mammalian gene control. Overall design: Single-end 40 bp Poly-A RNA-seq in mouse embryonic stem cells before and after YY1 depletion
YY1 Is a Structural Regulator of Enhancer-Promoter Loops.
Specimen part, Treatment, Subject, Time
View SamplesThere is considerable evidence that chromosome structure plays important roles in gene control, but we have limited understanding of the proteins that contribute to structural interactions between gene promoters and their enhancer elements. Large DNA loops that encompass genes and their regulatory elements depend on CTCF-CTCF interactions, but most enhancer-promoter interactions do not depend on this structural protein. Here we show that the transcription factor Yin Yang 1 (YY1) contributes to enhancer-promoter structural interactions in a manner analogous to DNA interactions mediated by CTCF. YY1 binds to active enhancers and promoter-proximal elements in all cells examined. YY1 forms dimers that can facilitate DNA interactions. Deletion of YY1 binding sites or depletion of YY1 can disrupt enhancer-promoter looping and normal gene expression. We propose that YY1-mediated enhancer-promoter interactions are a general feature of mammalian gene control. Overall design: Single-cell RNA-seq in mouse embryonic stem cells with and without YY1 protein
YY1 Is a Structural Regulator of Enhancer-Promoter Loops.
Specimen part, Subject
View SamplesSuper-enhancers (SEs) are clusters of enhancers that cooperatively assemble a high density of transcriptional apparatus to drive robust expression of genes with prominent roles in cell identity. We recently proposed that a phase-separated multi-molecular assembly underlies the formation and function of SEs. Here, we demonstrate that the SE-enriched factors BRD4 and MED1 form nuclear puncta that occur at SEs and exhibit properties of liquid-like condensates. Disruption of BRD4 and MED1 puncta by 1,6-hexanediol is accompanied by a loss of BRD4 and MED1 at SEs and a loss of RNAPII from SE-driven genes. We find that the intrinsically disordered regions (IDRs) of BRD4 and MED1 are sufficient to form phase-separated droplets in vitro and the MED1 IDR promotes phase separation in living cells. The MED1 IDR droplets are capable of compartmentalizing BRD4 and other transcriptional machinery in nuclear extracts. These results support the idea that SEs form phase-separated condensates that compartmentalize the transcription apparatus at key genes, provide insights into the role of cofactor IDRs in this process, and offer new insights into mechanisms involved in control of key cell identity genes. Overall design: polyA RNA-Seq in mouse embryonic stem cells
Coactivator condensation at super-enhancers links phase separation and gene control.
Specimen part, Subject
View SamplesWe analyzed a role of histone deacetylases in alternative splicing regulation. Using human exon arrays we identified a list of 683 genes whose splicing changes after HDAC inhibition with sodium butyrate.
Histone deacetylase activity modulates alternative splicing.
Cell line
View SamplesWe analyzed a role of Brd2 protein in transcription and alternative splicing. 289 genes change alternative splicing after Brd2 knockdown and 1459 genes alter gene expression compared to cells treated with negative control siRNA.
The C-terminal domain of Brd2 is important for chromatin interaction and regulation of transcription and alternative splicing.
Cell line
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