Project description:Autism spectrum disorder (ASD) is a common, highly heritable neurodevelopmental condition characterized by marked genetic heterogeneity. Thus, a fundamental question is whether autism represents an aetiologically 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 (also known as 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 the ASD brain. Moreover, using a published autism genome-wide association study (GWAS) data set, 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 aetiology 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. To identify potential A2BP1-dependent differential splicing events in ASD brain, we performed high-throughput RNA sequencing (RNA-Seq) on three autism samples with significant downregulation of A2BP1 (average fold change by quantitative RT-PCR = 5.9) and three control samples with average A2BP1 levels. The list of potential A2BP1-depending differential splicing events in ASD is given in the Supplementary file linked at the foot of this record.
Project description:Background: Autism spectrum disorder (ASD) is a severe early onset neurodevelopmental disorder with high heritability but significant heterogeneity. Traditional genome-wide approaches to test for association of common variants with autism susceptibility risk has met with limited success. However, novel methods to identify moderate risk alleles in attainable sample sizes are now gaining momentum. Methods:M-BM- In this study, we utilized publically available GWAS data from the Autism Genome Project (AGP) and annotated the results (p < 0.001) for eQTLs present in the parietal lobe, cerebellum, and lymphoblastoid cell lines. We then performed a test of enrichment by comparing these results to simulated data conditioned on minor allele frequency in order to generate an empirical p-value indicating statistically significant enrichment of eQTLs in top results from the autism GWAS. Results:M-BM- Our findings show a global enrichment of brain eQTLs, but not LCL eQTLs, among top SNPs from an autism GWAS. Additionally, the data implicates individual genesM-BM- SLC25A12,M-BM- PANX1M-BM- andM-BM- PANX2, as well as pathways previously implicated in autism. Conclusions:M-BM- These findings provide supportive rationale for the use of annotation-based approaches to GWAS. We use microarray technology to understand the etiology and pathology of psychiatric diseases at the transcriptomic level. Postmortem human brain samples came from the Stanley Medical Research InstituteM-bM-^@M-^Ys Neuropathology Consortium and Array collections, including schizophrenia, bipolar disorder and control samples.
Project description:Background: Autism spectrum disorder (ASD) is a severe early onset neurodevelopmental disorder with high heritability but significant heterogeneity. Traditional genome-wide approaches to test for association of common variants with autism susceptibility risk has met with limited success. However, novel methods to identify moderate risk alleles in attainable sample sizes are now gaining momentum. Methods:M-BM- In this study, we utilized publically available GWAS data from the Autism Genome Project (AGP) and annotated the results (p < 0.001) for eQTLs present in the parietal lobe, cerebellum, and lymphoblastoid cell lines. We then performed a test of enrichment by comparing these results to simulated data conditioned on minor allele frequency in order to generate an empirical p-value indicating statistically significant enrichment of eQTLs in top results from the autism GWAS. Results:M-BM- Our findings show a global enrichment of brain eQTLs, but not LCL eQTLs, among top SNPs from an autism GWAS. Additionally, the data implicates individual genesM-BM- SLC25A12,M-BM- PANX1M-BM- andM-BM- PANX2, as well as pathways previously implicated in autism. Conclusions:M-BM- These findings provide supportive rationale for the use of annotation-based approaches to GWAS. We use microarray technology to understand the etiology and pathology of psychiatric diseases at the transcriptomic level. Postmortem human brain samples came from the Stanley Medical Research InstituteM-bM-^@M-^Ys Neuropathology Consortium and Array collections, including schizophrenia, bipolar disorder and control samples.
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.