Disruption of Autism Spectrum Disorder-Susceptibility Genes Predominantly Reduces Functional Connectivity of Isogenic Human Neurons
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ABSTRACT: Autism Spectrum Disorder (ASD) is phenotypically and genetically heterogeneous, but genomic analyses have identified candidate susceptibility genes. We present a CRISPR gene editing strategy to insert a protein tag and premature termination sites creating an induced pluripotent stem cell (iPSC) knockout resource for functional studies of 10 ASD-relevant genes (AFF2/FMR2, ANOS1, ASTN2, ATRX, CACNA1C, CHD8, DLGAP2, KCNQ2, SCN2A, TENM1). Neurogenin 2 (NEUROG2)-directed differentiation of iPSCs allowed production of cortical excitatory neurons, and mutant proteins were not detectable. Using both patch-clamp and multi-electrode array approaches, the electrophysiological deficits measured were distinct for different mutations. However, they culminated in a consistent reduction in synaptic activity, including reduced spontaneous excitatory post-synaptic current frequencies in AFF2/FMR2-, ASTN2-, ATRX-, KCNQ2- and SCN2A-null neurons. RNAseq revealed convergence of several neuronal networks. Despite ASD susceptibility genes belonging to different gene ontologies, isogenic stem cell resources can reveal common functional phenotypes, such as reduced functional connectivity.
Project description:Autism spectrum disorder (ASD) is characterized by a complex etiology, with genetic determinants significantly influencing its manifestation. Among these, the Scn2a gene emerges as a pivotal player, crucially involved in oligodendrocyte (OL) function. The present study elucidates the underexplored roles of Scn2a in OL functionality, subsequently affecting myelination and auditory neural processes. The results reveal a nuanced interplay between OLs and axons, where Scn2a deletion causes alterations in OL differentiation and myelination. This disruption, in turn, instigates changes in axonal properties and neuronal activities at the single cell level. Furthermore, OL-specific Scn2a deletion compromises the integrity of neural circuitry within auditory pathways, leading to auditory hypersensitivity—a common sensory abnormality observed in ASD. Through transcriptional profiling, we identified alterations in the expression of myelin-associated genes, highlighting the cellular consequences engendered by Scn2a deletion. In summary, the findings of this study provide unprecedented insights into the pathway from Scn2a deletion in OL to sensory abnormalities in ASD, underscoring the integral role of Scn2a-mediated OL myelination in auditory responses. This research thereby provides novel insights into the intricate tapestry of genetic and cellular interactions inherent in ASD.
Project description:The Xp22.11 locus that encompasses PTCHD1, DDX53, and the long noncoding RNA (lncRNA) PTCHD1-AS is frequently disrupted in males with autism spectrum disorder (ASD), but the functional consequences of these genetic risk factors for ASD are unknown. : iPSC-derived neurons from the ASD subjects exhibited reduced miniature excitatory post-synaptic current (mEPSC) frequency and NMDA receptor hypofunction. We found that 35 ASD-associated deletions mapping to the PTCHD1 locus disrupt exons of PTCHD1-AS. We also report a novel ASD-associated deletion of PTCHD1-AS exon 3, and we show exon 3 loss alters PTCHD1-AS splicing without affecting expression of the neighboring PTCHD1 coding gene. Finally, targeted disruption of PTCHD1-AS exon 3 recapitulated diminished mEPSC frequency, supporting a role for the lncRNA in the etiology of ASD. Our genetic findings provide strong evidence that PTCHD1-AS deletions are risk factors for ASD, and human iPSC-derived neurons implicate these deletions in the neurophysiology of excitatory synapses and in ASD-associated synaptic impairment.
Project description:MDGA2 is an excitatory synaptic suppressor and its mutations have been associated with autism spectrum disorder (ASD). However, the detailed physiological function of MDGA2 and the mechanism underlying MDGA2 deficiency-caused ASD has yet to be elucidated. Herein, we not only confirm that Mdga2+/- mice exhibit increased excitatory synapse transmission and ASD-like behaviors, but also identify aberrant BDNF/TrkB signaling activation in these mice. We demonstrate that MDGA2 interacts with TrkB through its MAM domain, thereby competing the binding of BDNF to TrkB. Both loss of MDGA2 and the ASD-associated MDGA2 V930I mutation promote the BDNF/TrkB signaling activity. Importantly, we demonstrate that inhibiting the BDNF/TrkB signaling by both small molecular compound and MDGA2-derived peptide can attenuate the increase of AMPA receptor-mediated excitatory synaptic activity and social deficits in MDGA2 deficient mice. These results highlight a novel MDGA2-BDNF/TrkB-dependent mechanism underlying the synaptic function regulation, which may become a therapeutic target for ASD.
Project description:Synaptic dysfunction represents a key pathophysiology in neurodevelopmental disorders such as autism spectrum disorder (ASD). Rare mutation R451C in human Neuroligin 3 (NLGN3, encoded by X-linked gene NLGN3), a cell adhesion molecule essential for synapse formation, has been linked to ASD. Despite success in recapitulating the social interaction behavioral deficits and the underlying synaptic abnormalities in mouse model, the impact of NLGN3 R451C on the human neuronal system remains elusive. Here, we generated isogenic knock-in human pluripotent stem cell lines harboring NLGN3 R451C allele and examined its impact on synaptic transmission. Analysis of co-cultured excitatory and inhibitory induced neurons (iNs) with mutation revealed an augmentation in excitatory synaptic strength comparing to isogenic control, but not in inhibitory synaptic transmission. Consistently, the augmentation in excitatory transmission was confirmed in iNs transplanted into mouse forebrain. Using single-cell RNA seq on co-cultured excitatory and inhibitory iNs, we identified differential expression genes (DEGs) and found NLGN3 R451C alters gene networks associated with synaptic transmission. Gene ontology and enrichment analysis revealed convergent gene networks associated with ASD and other mental disorders. Our finding suggests that the NLGN3 R451C mutation could preferentially impact excitatory neurons, which causes overall network properties changes and excitation-inhibition imbalance related to mental disorders.
Project description:Autism spectrum disorders (ASD) represent neurodevelopmental disorders characterized by social deficits, repetitive behaviors, and various comorbidities, including epilepsy. ANK2, which encodes a neuronal scaffolding protein, is frequently mutated in ASD, but its in vivo functions and disease-related mechanisms are largely unknown. Here, we report that mice with Ank2 knockout restricted to cortical and hippocampal excitatory neurons (Ank2-cKO mice) show ASD-related behavioral abnormalities and juvenile seizure-related death. Ank2-cKO cortical neurons show abnormally increased excitability and firing rate. These changes accompanied decreases in the total level and function of the Kv7.2/KCNQ2 and Kv7.3/KCNQ3 potassium channels and the density of these channels in the enlengthened axon initial segment. Importantly, the Kv7 agonist, retigabine, rescued neuronal excitability, juvenile seizure-related death, and hyperactivity in Ank2-cKO mice. These results suggest that Ank2 regulates neuronal excitability by regulating the length of and Kv7 density in the AIS and that Kv7 channelopathy is involved in Ank2-related brain dysfunctions.
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:Ablation of the ATRX chromatin remodeler specifically in forebrain excitatory neurons of mice causes male-specific deficits in long-term spatial memory associated with miR-137 overexpression, transcriptional changes and structural alterations corresponding to pre- and post-synaptic abnormalities.
Project description:Dyrk1A deficiency is linked to various neurodevelopmental disorders, including developmental delays, intellectual disability (ID) and autism spectrum disorders (ASD). Haploinsufficiency of Dyrk1a in mice reportedly leads to ASD-related phenotypes. However, the key pathological mechanisms remain unclear and human DYRK1A mutations remain uncharacterized in mice. Here, we generated and studied Dyrk1a-knockin mice carrying a human ASD patient mutation (Ile48LysfsX2; Dyrk1a-I48K mice). These mice display severe microcephaly, social and cognitive deficits, dendritic shrinkage, excitatory synaptic deficits, and altered phospho-proteomic patterns enriched for multiple signaling pathways and synaptic proteins.
Project description:Shank2 is an abundant excitatory postsynaptic scaffolding protein implicated in neurodevelopmental disorders, including autism spectrum disorders (ASD), intellectual disability, developmental delay, and schizophrenia. Shank2-mutant mice with a homozygous deletion of exons 6 and 7 (Shank2-HM mice) show ASD-like behavioral deficits and altered synaptic functions, although little is known about how different brain regions contribute to Shank2-mutant phenotypes. Here we attempted transcriptomic analyses of the prefrontal cortex, hippocampus, and striatum in adult Shank2-heterozygous/HT and Shank2-homozygous/HM mice. The mutant cortex, hippocampus, and striatum displayed distinct sets of differentially expressed genes associated with neuronal and synaptic functions in a gene dosage-differential manner. Gene set enrichment analyses of cortical Shank2-HT transcripts revealed increased synaptic gene expression and transcriptomic changes that are opposite to those observed in ASD (reverse-ASD), whereas cortical Shank2-HM transcripts displayed decreased synaptic gene expression and ASD-like transcriptomic patterns. The hippocampal Shank2-HT transcripts displayed minimally altered synaptic gene expression and mixed ASD-like and reverse-ASD patterns, whereas the Shank2-HM-hippocampus showed increased synaptic gene expression and reverse-ASD patterns. The striatal Shank2-HT/HM transcriptomes were largely similar to the hippocampal transcriptomes, although the main changes were observed in cell-type-specific genes, unlike the hippocampal changes mainly involving ASD-related/risk genes. These results indicate that heterozygous and homozygous Shank2 deletions in mice lead to brain region- and gene dosage-differential transcriptomic changes.
Project description:Shank2 is an abundant postsynaptic scaffolding protein known to regulate excitatory synaptic assembly and function and is implicated in autism spectrum disorders (ASD). Whereas patient Shank2 mutations in autistic individuals are heterozygous, Shank2 functions studied in mice have mainly relied on the results from homozygous mutant mice, largely because of relatively strong synaptic and behavioral phenotypes. Moreover, although synaptic changes at juvenile and adult Shank2-mutant mice seem to be largely similar, it remains unclear whether there are any age-dependent changes across these stages at the molecular level. To address these questions, we attempted RNA-Seq analyses of the transcriptomes in the prefrontal cortex of both heterozygous and homozygous Shank2-mutant mice lacking exons 6 and 7 at juvenile and adult stages. The results indicate that heterozygous, but not homozygous, juvenile Shank2-mutant mice show strong transcriptomic changes that promote excitatory synaptic transmission and suppress ASD-related gene expressions. In contrast, adult Shank2-mutant mice show largely similar and dosage-dependent transcriptomic changes.