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No upregulation of homologous sequence expression in zebrafish larvae homozygous for the hu2787 nonsense mutant allele of fmr1.

ABSTRACT: The zebrafish has proven to be a versatile and valuable model for investigating the molecular and cellular basis of Fragile X syndrome (FXS). Reduction of expression of the zebrafish FMR1-ortholgous gene, fmr1, causes developmental and behavioural phenotypes related to the human syndrome. The hu2787 nonsense mutation allele of fmr1 is now the most widely used zebrafish model of FXS, although the FXS-relevant phenotypes seen from morpholino antisense oligonucleotide (morpholino) suppression of fmr1 transcript translation were not observed when this allele was first described. The subsequent discovery of genetic compensation, whereby morpholino-directed knockdown can give a more “pure” loss-of-function phenotype while mutations causing nonsense mediated decay of transcripts cause compensatory upregulation of homologous transcripts, suggested an explanation for the differences observed. To test for molecular evidence of genetic compensation in fmr1hu2787 homozygous mutants, we compared the transcriptomes of homozygous mutant and wild type larvae at 2 days post fertilisation. We observed statistically significant changes in the expression of a number of gene transcripts, but none with sequence homology to fmr1. Curiously, the majority of differentially expressed genes are located, like fmr1, on chromosome 14. Quantitative PCR tests on genomic DNA did not support that the apparent expression differences were artefacts due to changes in relative chromosome abundance. The coordinate dysregulation of chromosome 14 genes due to mutation of fmr1 supports this gene’s involvement in a chromosome-wide gene regulation complex.

ORGANISM(S): Danio rerio

PROVIDER: GSE151443 | GEO | 2020/05/30

REPOSITORIES: GEO

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Role of FMRP in neurogenesis

Project description:Fragile X syndrome (FXS) is a rare disease but is the most common form of inherited intellectual disability and a leading cause of autism. FXS is due to the absence of the Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein mainly involved in translational control. Even if this molecular defect is known, no specific therapy is available for FXS. The first alteration observed in the brain of FXS patients and of Fmr1 KO mice, model for FXS, is represented by an abnormal dendritic morphology that is associated with an altered synaptic plasticity. These findings led to numerous studies focused on mature neurons. However, recently, an increasing body of evidence is pointing out the importance of FMRP in the early steps of brain development. Thus, with the purpose to decipher the earliest molecular events leading to FXS we developed a stem-cell-based disease model by knocking-down the expression of Fmr1 in mouse embryonic stem (ES) cells. To gain insights in the pathways that are affected when FMRP is repressed, we performed a gene expression profile analysis comparing total RNA from shFmr1 and shControl ES cells using whole genome mouse microarrays. Transcripts were clustered according to their Gene Ontology classification using the DAVID software. Surprisingly, the most altered functional category was Nervous system development and function, highlighting the role of FMRP also during the earliest steps of neural development. To study the precise role of FMRP in Embryonic stem (ES) cells, we used an RNAi-based loss-of-function strategy by transducing mouse ES cells with a lentivirus expressing GFP and a shRNA targeting the constitutive exon 1 of Fmr1 (shFmr1). A random shRNA (shCT) was used as a control sequence. Transduced cells were sorted by flow cytometry and established as non-clonal cell populations. RNA samples were harvested and profiling experiments were performed in â??dye-balanceâ?? as indicated for each replicate.

2016-07-04 | E-GEOD-71184 | biostudies-arrayexpress

Rescue of Fragile X syndrome by DNA methylation editing of the FMR1 [ChIP-seq II]

Project description:Fragile X syndrome (FXS), the most common genetic form of intellectual disability in male, is caused by the silence of FMR1. Hypermethylation of the CGG expansion mutation in the 5’UTR region of FMR1 in FXS patients was thought to epigenetically silence FMR1. Here, we applied our previously developed DNA methylation editing tool to reverse this hypermethylation event. Targeted demethylation of the CGG expansion by dCas9-Tet1/gRNA switched the heterochromatin status of the FMR1 promoter to an active chromatin status and subsequently restored FMR1 expression in FXS iPSCs. Neurons derived from methylation edited FXS iPSCs showed a similar electrophysiological property as wild-type neurons, and maintained FMR1 expression for months after engrafting into the mouse brain. Reactivation of FMR1 can be achieved in FXS neurons with demethylation of the CGG expansion. Lastly, we showed that targeted demethylation of the FMR1 promoter can reactivate FMR1 as well suggesting potential therapeutic approaches for FXS.

2018-02-16 | GSE102684 | GEO

Rescue of Fragile X syndrome by DNA methylation editing of the FMR1 [ChIP-seq]

2018-02-16 | GSE102655 | GEO

Genome-wide analysis identifies aberrant methylation in Fragile X syndrome is specific to the FMR1 locus

Project description:Fragile X syndrome (FXS) is a common form of inherited intellectual disability and is caused by an expansion of CGG repeats located in the 5Õ untranslated region (UTR) of the FMR1 gene, leading to hypermethylation and silencing of this locus. While the dramatic increase in DNA methylation (DNAm) of the FMR1 full mutation allele is well documented, the extent that these changes affect DNAm throughout the entire gene and the rest of the genome remains unexplored. Here, we examine the genome-wide methylation in peripheral blood (N = 9) as well as induced pluripotent stem cells (iPSCs; N = 10) from FXS individuals and controls (N = 53 and 9, respectively) and find the expected significant DNAm differences in the FMR1 promoter and 5Õ UTR, but also that these changes inversely persist throughout the FMR1 gene body. Importantly, we find there are no additional differential methylated loci (DML) throughout the remainder of the genome, indicating that the aberrant methylation of the FMR1 in FXS is locus-specific and does not change DNAm genome-wide. This study provides a comprehensive methylation profile of FXS and refines mechanistic considerations of FMR1 silencing. A total of 62 blood (53 controls + 9 Fragile X) samples analyzed using a linear regression model.

2013-04-15 | E-GEOD-41273 | biostudies-arrayexpress

Proteomic profiling of brain and testis reveals the diverse changes in ribosome proteins in fmr1 knockout mice

Project description:Fragile X syndrome (FXS), the leading cause of inherited form of mental retardation and autism, is caused by the transcriptional silencing of fmr1 encoding the protein of FMRP. FMRP, acting as an RNA binding protein, FMRP is a wide expressed protein, but primarily in the brain and testis and can regulate approximately 4% of transcripts. Macroorchidism is one of the common symptoms observed both in the FXS people and mice. Thus, we analyzed the protein profiles of cerebral cortex, hippocampus and testis from both the fmr1-KO and WT mouse using a quantitative proteomics. Proteins (FMRP, RS8, RL23A and MPZ) identified by MS/MS were also verified by Western blot. Among the identified proteins, most of the significant changed proteins were downregulated in the FMRP absence. The Gene Ontology and pathway analysis revealed that the changed proteins were clustered in polyribosome and RNA binding proteins in both cerebral cortex and hippocampus, but not the same in testis. Our results provide detailed insights to the ribosome protein profiles of cerebral cortex, hippocampus and testis in the absence of FMRP. Our studies also give a better understanding of protein profile changes and underling dysregulated pathways arising from the fmr1 silencing in the FXS.

2022-02-28 | PXD005089 | Pride

Rescue of Fragile X syndrome neurons by DNA methylation editing of the FMR1 gene [RNA-seq]

Project description: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.

2018-02-16 | GSE108498 | GEO

Rescue of Fragile X syndrome neurons by DNA methylation editing of the FMR1 gene [methylation]

2018-02-16 | GSE108171 | GEO

Antisense Oligonucleotide Rescue of CGG Expansion-Dependent FMR1 Mis-Splicing in Fragile X Syndrome Restores FMRP

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

Antisense Oligonucleotide Rescue of CGG Expansion-Dependent FMR1 Mis-Splicing in Fragile X Syndrome Restores FMRP

2023-06-14 | GSE202177 | GEO

RNA metabolic rates profiling in Fragile X neurons

Project description:Fragile X syndrome (FXS) is caused by inactivation of FMR1 gene and loss of its encoded product the RNA binding protein FMRP, which generally represses translation of its target transcripts in the brain. In mouse models of FXS (i.e., Fmr1 knockout animals; Fmr1 KO), deletion of Cpeb1, which encodes a translational activator, mitigates nearly all pathophysiologies associated with the disorder. We have observed that the wide-spread dys-regulation of RNA abundance in Fmr1 KO brain cortex and its rescue to normal levels in Fmr1/Cpeb1 double KO mice were the driver of the observed dys-regulation and rescue of translation as measured by whole transcriptome ribosome occupany in the brain. We hypothesize that in Fragile X brain there is wide spread dys-regulation at RNA stability level. Here we test this hypothesis by profiling RNA synthesis, processing and degradation rates in Fragile X and wild type neurons, by taking advantage of short 5-EU labeling and computational modeling. We show that, while RNA synthesis and processing rates were barely changed, there is wide-spread evelated RNA degradation rates in the Fragile X neurons, particularly for genes using optimal codons.

2020-06-01 | GSE140642 | GEO

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