Project description:Intellectual disability (ID) is a clinically important disease and a most prevalent neurodevelopmental disorder. The etiology and pathogenesis of ID are poorly recognized. Exome sequencing revealed a homozygous missense mutation in the POLR3B gene in a consanguineous family with three Intellectual disability with craniofacal anomalies patients. POLR3B gene encoding the second largest subunit of RNA polymerase III. To explore how genetic variants alter cell expression in ID patients, RNA sequencing on blood samples was performed and to obtain insights into the biological pathways influenced by POLR3B mutation, we applied our RNA-Seq data to several gene ontology programs such as ToppGene, Enrichr, KEGG. We detected a significant decrease expression of several spliceosomal RNAs, ribosomal proteins and transcription factors in our ID patients. We hypothesize that POLR3B mutation dysregulates the expression of some important transcription factors, ribosomal and spliceosomal genes and impairments in protein synthesis and splicing mediated in part by transcription factors such as FOXC2, GATA1, .. contribute to impaired neuronal function and concurrence of intellectual disability and craniofacial anomalies in our patients. Our study highlights the emerging role of spliceosome and ribosomal proteins in intellectual disability.
Project description:An increasing number of genes involved in chromatin structure and epigenetic regulation has been implicated in a variety of developmental disorders, often including intellectual disability. By trio exome sequencing and subsequent mutational screening we now identified two de novo frameshift mutations and one de novo missense mutation in the CTCF gene in individuals with intellectual disability, microcephaly and growth retardation. Furthermore, a patient with a larger deletion including CTCF was identified. CTCF (CCCTC-binding factor) is one of the most important chromatin organizers in vertebrates and is involved in various chromatin regulation processes such as higher order of chromatin organization, enhancer function, and maintenance of three-dimensional chromatin structure. Transcriptome analyses in all three patients with point mutations revealed deregulation of genes involved in signal transduction and emphasized the role of CTCF in enhancer-driven expression of genes. Our findings indicate that haploinsufficiency of CTCF affects genomic interaction of enhancers and their regulated gene promoters that drive developmental processes and cognition. ChIP-seq analysis of CTCF genomic binding sites in lymphocytes of a control individual (no replicates).
Project description:An increasing number of genes involved in chromatin structure and epigenetic regulation has been implicated in a variety of developmental disorders, often including intellectual disability. By trio exome sequencing and subsequent mutational screening we now identified two de novo frameshift mutations and one de novo missense mutation in the CTCF gene in individuals with intellectual disability, microcephaly and growth retardation. Furthermore, a patient with a larger deletion including CTCF was identified. CTCF (CCCTC-binding factor) is one of the most important chromatin organizers in vertebrates and is involved in various chromatin regulation processes such as higher order of chromatin organization, enhancer function, and maintenance of three-dimensional chromatin structure. Transcriptome analyses in all three patients with point mutations revealed deregulation of genes involved in signal transduction and emphasized the role of CTCF in enhancer-driven expression of genes. Our findings indicate that haploinsufficiency of CTCF affects genomic interaction of enhancers and their regulated gene promoters that drive developmental processes and cognition. Comparison of lymphocyte gene expression between 3 de novo CTCF mutation patients and 8 controls (4 technical replicates each, no biological replicates).
Project description:Intellectual disability is a neurodevelopmental disorder that affects 2-3% of the general population. Syndromic forms of intellectual disability frequently have a genetic basis and are often accompanied by additional developmental anomalies. Pathogenic variants in components of TATA-binding protein associated factors (TAFs) have recently been identified in a subset of patients with intellectual disability, craniofacial hypoplasia, and congenital heart disease. This syndrome has been termed as a TAFopathy and includes mutations in TATA binding protein (TBP), TAF1, TAF2, and TAF6. The underlying mechanism by which TAFopathies give rise to neurodevelopmental, craniofacial, and cardiac abnormalities remains to be defined. Through a forward genetic screen in zebrafish, we have recovered a recessive mutant phenotype characterized by craniofacial hypoplasia, ventricular hypoplasia, heart failure at 96 hours post-fertilization and lethality, and show it is caused by a nonsense mutation in taf5. CRISPR/CAS9 mediated gene editing revealed that these defects where phenocopied by mutations in taf1 and taf5. Mechanistically, taf5-/- zebrafish displayed misregulation in metabolic gene expression and metabolism as evidenced by RNA sequencing, respiration assays, and metabolite studies. Collectively, these findings suggest that the TAF complex may contribute to neurologic, craniofacial, and cardiac development through regulation of metabolism.
Project description:Loss of function of FMR2 due to either hypermethylation of the CpG island as a consequence of the expansion of the CCG repeat near its transcription start site, or internal deletion of FMR2 is considered to be the major cause of FRAXE fragile site associated intellectual disability. FMR2 was shown to be a potent transcription activator as well as an RNA binding protein capable of regulating alternative splicing. Using whole transcriptome approach, we aimed to identify genes regulated by FMR2 and to study their contribution to the underlying causes of intellectual disability in the patients. We subjected total RNA extracted from fibroblasts of FRAXE patients (n=8), and unrelated controls (n=4) to Affymetrix Human Exon 1.0 ST array
Project description:We generated human induced pluripotent cells from intellectual disability patients carrying the c.2T>C mutation in KDM5C (Called “Mutant”). We generated a paired, isogenic human iPS cell line (called “Corrected”) using CRISPR/Cas9 and PiggyBac gene-editing technologies and conducted neuronal differentiation based on “Yichen Shi et al. Nat. Protoc. 7, 1836–1846 (2012)” to define differences in gene expression between the Mutant and Corrected during neurodevelopment.
Project description:Homozygous mutations in the gene encoding the scavenger mRNA-decapping enzyme, DcpS, have been shown to underlie developmental delay and intellectual disability. Intellectual disability is associated with both abnormal neocortical development and mRNA metabolism. However, the role of DcpS and its scavenger decapping activity in proper neuronal development is unknown. Here, we show that differentiation of human induced pluripotent stem cell derived neurons, from patients with a DcpS mutation, are impaired and have compromised neurite outgrowth. Moreover, misexpression of DcpS in developing mouse neocortex revealed that DcpS is required for the multipolar morphology acquisition, neurite outgrowth and identity of developing neocortical glutamatergic neurons in the mouse brain. Collectively, these findings demonstrate the scavenger mRNA decapping activity contributes to multiple pivotal roles in neurodevelopment, and further corroborate that mRNA metabolism and neocortical pathologies are associated with intellectual disability.
Project description:Identifying causes of sporadic intellectual disability remains a considerable medical challenge. Here, we demonstrate that null mutations in the NONO gene, a member of the Drosophila Behavior Human Splicing (DBHS) protein family, are a novel cause of X-linked syndromic intellectual disability. Comparing humans to Nono-deficient mice revealed related behavioral and craniofacial anomalies, as well as global transcriptional dysregulation. Nono-deficient mice also showed deregulation of a large number of synaptic transcripts, causing a disorganization of inhibitory synapses, with impaired postsynaptic scaffolding of gephyrin. Alteration of gephyrin clustering could be rescued by over-expression of Gabra2 in NONO-compromised neurons. These findings link NONO to intellectual disability and first highlight the key role of DBHS proteins in functional organization of GABAergic synapses.
Project description:Identifying causes of sporadic intellectual disability remains a considerable medical challenge. Here, we demonstrate that null mutations in the NONO gene, a member of the Drosophila Behavior Human Splicing (DBHS) protein family, are a novel cause of X-linked syndromic intellectual disability. Comparing humans to Nono-deficient mice revealed related behavioral and craniofacial anomalies, as well as global transcriptional dysregulation. Nono-deficient mice also showed deregulation of a large number of synaptic transcripts, causing a disorganization of inhibitory synapses, with impaired postsynaptic scaffolding of gephyrin. Alteration of gephyrin clustering could be rescued by over-expression of Gabra2 in NONO-compromised neurons. These findings link NONO to intellectual disability and first highlight the key role of DBHS proteins in functional organization of GABAergic synapses.