Project description:Autism spectrum disorder (ASD) is a common, highly heritable neuro-developmental condition characterized by marked genetic heterogeneity. Thus, a fundamental question is whether autism represents an etiologically heterogeneous disorder in which the myriad genetic or environmental risk factors perturb common underlying molecular pathways in the brain. Here, we demonstrate consistent differences in transcriptome organization between autistic and normal brain by gene co-expression network analysis. Remarkably, regional patterns of gene expression that typically distinguish frontal and temporal cortex are significantly attenuated in the ASD brain, suggesting abnormalities in cortical patterning. We further identify discrete modules of co-expressed genes associated with autism: a neuronal module enriched for known autism susceptibility genes, including the neuronal specific splicing factor A2BP1/FOX1, and a module enriched for immune genes and glial markers. Using high-throughput RNA-sequencing we demonstrate dysregulated splicing of A2BP1-dependent alternative exons in ASD brain. Moreover, using a published autism GWAS dataset, we show that the neuronal module is enriched for genetically associated variants, providing independent support for the causal involvement of these genes in autism. In contrast, the immune-glial module showed no enrichment for autism GWAS signals, indicating a non-genetic etiology for this process. Collectively, our results provide strong evidence for convergent molecular abnormalities in ASD, and implicate transcriptional and splicing dysregulation as underlying mechanisms of neuronal dysfunction in this disorder. Total RNA was extracted from approximately 100mg of postmortem brain tissue representing Cerebellum (C), Frontal cortex (F), and Temporal cortex (T), from autistic and control individuals.
Project description:Reciprocal deletion and duplication of 16p11.2 is the most common copy number variation (CNV) associated with Autism Spectrum Disorder (ASD) and other developmental disorders, and has significant effect on brain size. We used cortical organoids derived from ASD cases to investigate neurodevelopmental pathways dysregulated by dosage changes of 16p11.2 CNV. We show that organoids recapitulate patients’ macrocephaly and microcephaly phenotypes. Deletions and duplications have “mirror” effects on cell proliferation, maturation and synapse number, consistent with “mirror” effects on brain development in humans. Neuronal migration was decreased in both, deletion and duplication organoids. Transcriptomic and proteomic profiling revealed synaptic defects and neuronal migration as key drivers of 16p11.2 functional effect. We implicate upregulation of small GTPase RhoA involved in regulation of cytoskeletal dynamics, neuron migration and neurite outgrowth as one of the pathways impacted by the 16p11.2 CNV in ASD. Treatment with the RhoA inhibitor Rhosin rescued neuron migration, but not synaptic defects. This study identifies pathways dysregulated by the 16p11.2 CNV during early neocortical development using cortical organoid models. Grant ID: Simons Foundation, #345469 Grant Title: Translational dysregulation of the RhoA pathway in autism Affiliation: University of California San Diego Name: Lilia M. Iakoucheva; Alysson R. Muotri
Project description:Autism spectrum disorder (ASD) is a common, highly heritable neuro-developmental condition characterized by marked genetic heterogeneity. Thus, a fundamental question is whether autism represents an etiologically heterogeneous disorder in which the myriad genetic or environmental risk factors perturb common underlying molecular pathways in the brain. Here, we demonstrate consistent differences in transcriptome organization between autistic and normal brain by gene co-expression network analysis. Remarkably, regional patterns of gene expression that typically distinguish frontal and temporal cortex are significantly attenuated in the ASD brain, suggesting abnormalities in cortical patterning. We further identify discrete modules of co-expressed genes associated with autism: a neuronal module enriched for known autism susceptibility genes, including the neuronal specific splicing factor A2BP1/FOX1, and a module enriched for immune genes and glial markers. Using high-throughput RNA-sequencing we demonstrate dysregulated splicing of A2BP1-dependent alternative exons in ASD brain. Moreover, using a published autism GWAS dataset, we show that the neuronal module is enriched for genetically associated variants, providing independent support for the causal involvement of these genes in autism. In contrast, the immune-glial module showed no enrichment for autism GWAS signals, indicating a non-genetic etiology for this process. Collectively, our results provide strong evidence for convergent molecular abnormalities in ASD, and implicate transcriptional and splicing dysregulation as underlying mechanisms of neuronal dysfunction in this disorder.
Project description:We used the Illumina 450KMethylation BeadChip to measure DNA methylation at 485,512 loci across the genome for 40 postmortem brain samples. The purpose of our study was to identify differentially methylated regions (DMRs) associated with autism. Samples included 16 temporal cortex brain tissue samples (6 cases and 10 controls), 11 prefrontal cortex brain tissue samples (6 cases and 5 controls), and 13 cerebellum brain tissue samples (7 cases and 6 controls). We bisulfute converted DNA from the 40 brain tissue samples, processed, and hybridized them to the Illumina Infinium 450K HumanMethylation450 BeadChip as specificed by the manufacturer.
Project description:Environmental factors, including pesticides, have been linked to autism and neurodegeneration risk using retrospective epidemiological studies. Here, we sought to prospectively identify chemicals that share transcriptomic signatures with neurological disorders by exposing mouse cortical neuron-enriched cultures to hundreds of chemicals commonly found in the environment and on food. We find that rotenone, a pesticide associated with Parkinsonâs disease risk, and certain fungicides, including pyraclostrobin, trifloxystrobin, famoxadone, and fenamidone, produce transcriptional changes in vitro that are similar to those seen in brain samples from humans with autism, advanced age and neurodegeneration (Alzheimerâs disease, Huntingtonâs disease). These chemicals stimulate free radical production and disrupt microtubules in neurons, effects that can be reduced by pretreating with a microtubule stabilizer, an antioxidant, or with sulforaphane. Our study provides an approach to prospectively identify environmental chemicals that transcriptionally mimic autism and other brain disorders. 405 total samples, consisting of 297 unique chemicals and vehicle controls.
Project description:E3-ubiquitin ligase Cullin3 (Cul3) is a high confidence risk gene for Neurodevelopmental Disorders such as Autism Spectrum Disorder (ASD) and Developmental Delay (DD). This study identifies the impact of the ASD-associated de novo Cul3-mutation on brain anatomy, behavior, molecular, cellular, and circuit-level mechanisms during early neocortical development. We report that Cul3 mutant mice have microcephaly and severe brain structure defects. This mouse model exhibits social and cognitive deficits and hyperactivity behavior. Spatiotemporal transcriptomic and proteomic profiling of Cul3 mouse brain implicates neurogenesis and cytoskeletal defects as key drivers of Cul3 functional effect. We show that Cul3 is critical for neuron growth and development. Cultured cortical neurons from the mutant mice have reduced dendritic length, actin cytosketon defects, reduced network activity, and increased cell death. At the molecular level, we implicate upregulation of small GTPase RhoA, involved in regulation of cytoskeletal dynamics, and neurite outgrowth as one of the pathways impacted by the de novo Cul3 mutations in ASD. Treatment with small molecule RhoA inhibitor Rhosin rescues dendrite length phenotype and implicates RhoA pathway in ASD.