Project description:Heterozygous loss-of-function mutations in the synaptic scaffolding gene SHANK2 are strongly associated with autism spectrum disorder (ASD). To investigate their effect on synaptic connectivity, we generated cortical neurons from induced pluripotent stem cells (iPSC) derived from neurotypic and ASD-affected donors. We developed Sparse coculture for Connectivity (SparCon) assays where SHANK2 and control neurons were differentially labeled and sparsely seeded together on a lawn of unlabeled control neurons. We observed striking increases in total synapse number and dendrite complexity. Dendrite length increases were exacerbated by IGF1 or BDNF treatment. Increased excitatory synapse function in haploinsufficient SHANK2 neurons was phenocopied in gene-edited knockout SHANK2 neurons. Gene correction of an ASD SHANK2 mutation rescued excitatory synapse function supporting a role for SHANK2 as a negative regulator of connectivity in developing human neurons. The transcriptome in these isogenic SHANK2 neurons was deeply perturbed in synaptic and plasticity gene sets and ASD gene modules, and activity dependent dendrite extension was defective. Our unexpected findings provide evidence for hyperconnectivity and profoundly altered transcriptome in SHANK2 neurons derived from ASD subjects.
Project description:Heterozygous loss-of-function mutations in SHANK2 are associated with autism spectrum disorder (ASD). We generated cortical neurons from induced pluripotent stem cells derived from neurotypic and ASD-affected donors. We developed sparse coculture for connectivity assays where SHANK2 and control neurons were differentially labeled and sparsely seeded together on a lawn of unlabeled control neurons. We observed increases in dendrite length, dendrite complexity, synapse number, and frequency of spontaneous excitatory postsynaptic currents. These findings were phenocopied in gene-edited homozygous SHANK2 knockout cells and rescued by gene correction of an ASD SHANK2 mutation. Dendrite length increases were exacerbated by IGF1, TG003, or BDNF, and suppressed by DHPG treatment. The transcriptome in isogenic SHANK2 neurons was perturbed in synapse, plasticity, and neuronal morphogenesis gene sets and ASD gene modules, and activity-dependent dendrite extension was impaired. Our findings provide evidence for hyperconnectivity and altered transcriptome in SHANK2 neurons derived from ASD subjects.
Project description:Heterozygous loss-of-function mutations in the synaptic scaffolding gene SHANK2 are strongly associated with autism spectrum disorder (ASD). To investigate their effect on synaptic connectivity, we generated cortical neurons from induced pluripotent stem cells (iPSC) derived from neurotypic and ASD-affected donors. We developed Sparse coculture for Connectivity (SparCon) assays where SHANK2 and control neurons were differentially labeled and sparsely seeded together on a lawn of unlabeled control neurons. We observed striking increases in dendrite length, dendrite complexity, total synapse number, and frequency of spontaneous excitatory postsynaptic currents. These findings were phenocopied in gene-edited homozygous SHANK2 knockout cells and rescued by gene correction of an ASD SHANK2 muation, supporting a role for SHANK2 as a regulator of connectivity in developing human neurons. Dendrite length increases were exacerbated by IGF1, TG003, or BDNF, and suppressed by DHPG treatment. The transcriptome in these isogenic SHANK2 neurons was deeply perturbed in synapse, plasticity, and neuronal morphogenesis gene sets and ASD gene modules, and activity-dependent dendrite extension was impaired. Our unexpected findings provide evidence for hyperconnectivity and profoundly altered transcriptome in SHANK2 neurons derived from ASD subjects.
Project description:To investigate the molecular basis for the B cell developmental arrest in Pax5R31Q/– mice, we performed RNA-sequencing (RNA-seq) with ex vivo sorted Pax5+/+ and Pax5R31Q/– pro-B cells. We identified Pax5-activated and Pax5-repressed genes that were no longer properly regulated by the Pax5-R31Q protein in Pax5R31Q/– pro-B cells. Notably, these genes were only a subset of the activated and repressed genes identified by comparing Pax5+/+ and Pax5–/– pro-B cells, which raised the question whether binding of the Pax5-R31Q protein may be selectively lost at the subset of deregulated genes in Pax5R31Q/– pro-B cells. By using a Pax5 paired domain antibody for chromatin immunoprecipitation coupled with deep sequencing (ChIP-seq) of short-term cultured Pax5+/+ and Pax5R31Q/– pro-B cells, we identified all associated Pax5 binding sites. Common Pax5 peaks had a similar Pax5-binding density in contrast to the strong binding difference observed at the unique peaks present in Pax5+/+ pro-B cells. To investigate a correlation between the loss of Pax5 binding and gene expression, we focused our analysis on Pax5 peaks in the TSS region of activated genes. We systematically investigated the correlation between loss of Pax5 binding at the TSS and down-regulation of gene expression in Pax5R31Q/– pro-B cells. The ratio of Pax5 binding between Pax5R31Q/– and Pax5+/+ pro-B cells at the TSS of these activated genes was significantly reduced compared to that of expressed non-regulated genes. We next explored whether the Pax5-binding difference at the TSS also correlated with the magnitude of gene expression difference. The loss of Pax5 binding at the TSS also correlated with the degree of expression change in Pax5R31Q/– pro-B cells compared to Pax5+/+ pro-B cells. We conclude therefore that the selective DNA-binding of Pax5-R31Q is responsible for the observed gene expression differences in Pax5R31Q/– pro-B cells.
Project description:Approximately one-third of children with autism spectrum disorder (ASD) reportedly lose skills within the first 3 years, yet a causal mechanism remains elusive. Considering evidence of strong genetic effects for ASD and findings that distinct phenotypes in ASD associate with specific genetic events, we examined rates of parent-reported regression in the Simons Simplex Collection with likely gene disrupting mutations from five distinct classes: FMRP target genes, genes encoding chromatin modifiers, genes expressed preferentially in embryos, genes encoding postsynaptic density proteins, and essential genes. Children with ASD and mutations in postsynaptic density genes were more likely to experience regression, while a trend suggested that children with ASD and mutations in embryonic genes were less likely to have skill losses.
Project description:RELN encodes a large, secreted glycoprotein integral to proper neuronal positioning during development and regulation of synaptic function postnatally. Rare, homozygous, null mutations lead to lissencephaly with cerebellar hypoplasia (LCH), accompanied by developmental delay and epilepsy. Until recently, little was known about the frequency or consequences of heterozygous mutations. Several lines of evidence from multiple studies now implicate heterozygous mutations in RELN in autism spectrum disorders (ASD). RELN maps to the AUTS1 locus on 7q22, and at this time over 40 distinct mutations have been identified that would alter the protein sequence, four of which are de novo. The RELN mutations that are most clearly consequential are those that are predicted to inactivate the signaling function of the encoded protein and those that fall in a highly conserved RXR motif found at the core of the 16 Reelin subrepeats. Despite the growing evidence of RELN dysfunction in ASD, it appears that these mutations in isolation are insufficient and that secondary genetic or environmental factors are likely required for a diagnosis.
Project description:BACKGROUND:Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders. Genetically based subtype identification may prove more beneficial not only in illuminating the course and prognosis, but also for individualized treatment targets of an ASD sub-group. Increasing evidence has shown that de novo loss-of-function mutations in the chromodomain helicase DNA-binding protein 8 (CHD8) gene are associated with an ASD sub-group. CASE PRESENTATION:Here we describe two ASD cases in children with mild intellectual disability, early motor deficits, and speech delay, without distinct structural or EEG brain anomalies. Exome sequencing revealed a novel heterozygous nonsense/missense mutations(c.2647C?>?A/p.E883X and c.1677C?>?A/p.M559I respectively) in CHD8 gene. CONCLUSIONS:There were few cases in the literature reporting de novo mutation of CHD8 in ASD. As demonstrated in our patients, along with other previously reported studies support that disruption of the CHD8 gene represents a specific genetic sub-type of ASD.
Project description:Mutations in SHANK3, which encodes a synaptic scaffolding protein, have been described in subjects with an autism spectrum disorder (ASD). To assess the quantitative contribution of SHANK3 to the pathogenesis of autism, we determined the frequency of DNA sequence and copy-number variants in this gene in 400 ASD-affected subjects ascertained in Canada. One de novo mutation and two gene deletions were discovered, indicating a contribution of 0.75% in this cohort. One additional SHANK3 deletion was characterized in two ASD-affected siblings from another collection, which brings the total number of published mutations in unrelated ASD-affected families to seven. The combined data provide support that haploinsufficiency of SHANK3 can cause a monogenic form of autism in sufficient frequency to warrant consideration in clinical diagnostic testing.