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.
Project description:Fragile X syndrome (FXS) is caused by the absence of the fragile X mental retardation protein (FMRP). We have previously generated FXS-induced pluripotent stem cells (iPSCs) from patients' fibroblasts. In this study, we aimed at unraveling the molecular phenotype of the disease. Our data revealed aberrant regulation of neural differentiation and axon guidance genes in FXS-derived neurons, which are regulated by the RE-1 silencing transcription factor (REST). Moreover, we found REST to be elevated in FXS-derived neurons. As FMRP is involved in the microRNA (miRNA) pathway we employed microRNA-array analyses and uncovered several miRNAs dysregulated in FXS-derived neurons. We found hsa-mir-382 to be down-regulated in FXS-derived neurons, and introduction of mimic-mir-382 into these neurons was sufficient to repress REST and up-regulate its axon guidance target genes. Our data link, FMRP and REST, through the miRNA pathway, and show a new aspect in the development of FXS. Affimetrix miRNA array of two WT and two fragile X syndrome derived 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. Here we reveal unexpected wide-spread dys-regulation of RNA abundance in Fmr1 KO brain cortex and its rescue to normal levels in Fmr1/Cpeb1 double KO mice. Alteration and restoration of RNA levels are the dominant molecular events that drive the observed dys-regulation and rescue of translation as measured by whole transcriptome ribosome occupany in the brain. The RNAs down-regulated and rescued in these animal models are highly enriched for FMRP binding targets and have an optimal codon bias that would predict their stability in wild type and possible instability in FMRP knock-out brain. These results leads to a further study to profile RNA metabolism rates in Fragile X neurons.
Project description:Fragile X syndrome (FXS) is caused by the absence of the fragile X mental retardation protein (FMRP). We have previously generated FXS-induced pluripotent stem cells (iPSCs) from patients' fibroblasts. In this study, we aimed at unraveling the molecular phenotype of the disease. Our data revealed aberrant regulation of neural differentiation and axon guidance genes in FXS-derived neurons, which are regulated by the RE-1 silencing transcription factor (REST). Moreover, we found REST to be elevated in FXS-derived neurons. As FMRP is involved in the microRNA (miRNA) pathway we employed microRNA-array analyses and uncovered several miRNAs dysregulated in FXS-derived neurons. We found hsa-mir-382 to be down-regulated in FXS-derived neurons, and introduction of mimic-mir-382 into these neurons was sufficient to repress REST and up-regulate its axon guidance target genes. Our data link, FMRP and REST, through the miRNA pathway, and show a new aspect in the development of FXS.
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.
Project description:ene pleiotropy defines the capacity of a gene to impact multiple phenotypic characters. The Fragile X Mental Retardation 1 (FMR1) gene is a candidate for pleiotropy, as it controls protein synthesis through its product, the translational regulator FMRP. As FMR1 loss-of-function leads to neurodevelopmental defects and Fragile X Syndrome (FXS), intellectual disability and autism, FMR1 functions have been mostly studied in the brain. FMR1-deficiency could also have yet unexplored consequences in periphery and impact metabolism through translational repression in peripheral organs. We combined 1H NMR-based metabolic phenotyping and proteomics to reveal the pleiotropic metabolic effects associated with FMR1-deficiency in mouse and human. We demonstrate that Fmr1-deficiency in the mouse increases hepatic translation, improves glucose tolerance and insulin sensitivity and reduces adiposity, while enhancing -adrenergic driven lipolysis and utilization of lipid energetic substrates. Last, we provide converging evidences in FXS patients that the levels of glucose, insulin and free fatty acids are modified, suggesting that FMR1-deficiency also drives metabolic readjustments in human. As part of a larger study investigating the involvement of fmr in metabolic alteration in fmr1-KO mice, fmr1-KO mouse livers were analysed by MS.
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.
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.