Cumulative Impact of Polychlorinated Biphenyl and Large Chromosomal Duplications on DNA Methylation, Chromatin, and Expression of Autism Candidate Genes.
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE81541 | GEO | 2016/12/13
SECONDARY ACCESSION(S): PRJNA321909
REPOSITORIES: GEO
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Project description:The dysregulation of genes in neurodevelopmental disorders that lead to social and cognitive phenotypes is a complex, multilayered process involving both genetics and epigenetics. Parent-of-origin effects of deletion and duplication of the 15q11-q13 locus leading to Angelman, Prader-Willi, and Dup15q syndromes are due to imprinted genes, including UBE3A, which is maternally expressed exclusively in neurons. UBE3A encodes a ubiquitin E3 ligase protein with multiple downstream targets, including RING1B, which in turn monoubiquitinates histone variant H2A.Z. To understand the impact of neuronal UBE3A levels on epigenome-wide marks of DNA methylation, histone variant H2A.Z positioning, active H3K4me3 promoter marks, and gene expression, we took a multi-layered genomics approach. We performed an siRNA knockdown of UBE3A in two human neuroblastoma cell lines, including parental SH-SY5Y and the SH(15M) model of Dup15q. Genes differentially methylated across cells with differing UBE3A levels were enriched for functions in gene regulation, DNA binding, and brain morphology. Importantly, we found that altering UBE3A levels had a profound epigenetic effect on the methylation levels of up to half of known imprinted genes. Genes with differential H2A.Z peaks in SH(15M) compared to SH-SY5Y were enriched for ubiquitin and protease functions and associated with autism, hypoactivity, and energy expenditure. Together, these results support a genome-wide epigenetic consequence of altered UBE3A levels in neurons and suggest that UBE3A regulates an imprinted gene network involving DNA methylation patterning and H2A.Z deposition.
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Project description:DNA methylation is essential for embryonic and neuronal differentiation, but the function of most genomic DNA methylation marks are poorly understood. Generally the human genome is highly methylated (>70%) except for CpG islands and gene promoters. However, it was recently shown that the IMR90 human fetal lung fibroblast cells have large regions of the genome with partially methylated domains (PMDs, <70% average methylation), in contrast to the rest of the genome which is in highly methylated domains (HMDs, >70% average methylation). Using bisulfite conversion followed by high-throughput sequencing (MethylC-seq), we discovered that human SH-SY5Y neuronal cells also contain PMDs. We developed a novel hidden Markov model (HMM) to computationally map the genomic locations of PMDs in both cell types and found that autosomal PMDs can be over 9 Mb in length and cover 41% of the IMR90 genome and 19% of the SH-SY5Y genome. Genomic regions marked by cell line specific PMDs contain genes that are expressed in a tissue-specific manner, with PMDs being a mark of repressed transcription. Genes contained within N-HMDs (neuronal HMDs, defined as a PMD in IMR90 but HMD in SH-SY5Y) were significantly enriched for calcium signaling, synaptic transmission and neuron differentiation functions. Autism candidate genes were enriched within PMDs and the largest PMD observed in SH-SY5Y cells marked a 10 Mb cluster of cadherin genes with strong genetic association to autism. Our results suggest that these large-scale methylation domain maps could be relevant to interpreting and directing future investigations into the elusive etiology of autism. Examined DNA methylation in a human neuronal cell line and cerebral cortex
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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.
2011-07-12 | E-GEOD-30573 | biostudies-arrayexpress
Project description:The human 16p11.2 gene locus is a hot spot for copy number variations, which predispose carriers to a range of neuropsychiatric phenotypes. Microduplications of 16p11.2 are associated with autism spectrum disorder (ASD), intellectual disability (ID), and schizophrenia (SZ). Despite the debilitating nature of 16p11.2 duplications, the underlying molecular mechanisms remain poorly understood. Here we performed a comprehensive behavioral characterization of 16p11.2 duplication mice (16p11.2dp/+) and identified social and cognitive deficits reminiscent of ASD and ID phenotypes. 16p11.2dp/+ mice did not exhibit the SZ-related sensorimotor gating deficits, psychostimulant-induced hypersensitivity, or motor impairment. Electrophysiological recordings of 16p11.2dp/+ mice found deficient GABAergic synaptic transmission and elevated neuronal excitability in the prefrontal cortex (PFC), a brain region critical for social and cognitive functions. RNA-sequencing identified genome-wide transcriptional aberrance in the PFC of 16p11.2dp/+ mice, including downregulation of the GABA synapse regulator Npas4. Restoring Npas4 expression in PFC of 16p11.2dp/+ mice ameliorated the social and cognitive deficits and reversed GABAergic synaptic impairment and neuronal hyperexcitability. These findings suggest that prefrontal cortical GABAergic synaptic circuitry and Npas4 are strongly implicated in 16p11.2 duplication pathology, and may represent potential targets for therapeutic intervention in ASD.
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2014-10-09 | E-GEOD-32563 | biostudies-arrayexpress
Project description:Genetic variants associated with autism spectrum disorders (ASDs) are enriched for genes encoding synaptic proteins and chromatin regulators. Although the role of synaptic proteins in ASDs is well studied, the mechanism by which disruptions of chromatin regulators promote the development of ASDs remains unclear. Here we identify 184 neuronal long genes containing super-enhancer-like chromatin modifications across their gene bodies, which we term SE long genes. We show that SE long genes exhibit reduced transcriptional RNA Polymerase II pausing, higher transcription initiation frequency, and higher expression levels. The gene body regions of SE long genes display active epigenomic status and are organized into a highly connected chromatin unit. Notably, SE long genes are enriched in known ASD-associated genes related to the synapse and signaling pathways. These characteristics present a molecular link between chromatin regulators and synaptic function, and suggest a mechanism by which disruptions in these chromatin regulators compromise the synapse. Indeed, we show that the expression of SE long genes is more sensitive to the disruptions of autism-risk chromatin regulators, including Kmt2c, Kdm5c, Kdm6b, and Mecp2, than non-SE long genes. We propose that the transcriptional impairment of SE long genes by dysfunctional chromatin regulators is a general molecular mechanism for ASD pathogenesis.
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Project description:Asthma is one of the most common chronic diseases among pregnant women, and symptoms often worsen during pregnancy. Dysregulation in immune responses during pregnancy, such as those that develop with chronic allergic asthma, increase the risk of a having a child with an Autism Spectrum Disorder (ASD). We recently developed a mouse model of maternal allergic asthma (MAA) that induces alterations in behavioral outcomes of the offspring including changes in sociability, repetitive and perseverative behaviors. Pregnancy is also a time when epigenetic changes help a static genome adapt to the maternal environment, and consequently activation of the maternal immune system may alter the regulation of gene expression in the developing fetal brain. Perinatal exposure to maternal asthma alters DNA methylation of immune-related genes in human infants, suggesting that maternal asthma has long-lasting effects on the offspring’s’ immune function. Here we used the genome-wide approaches of whole genome bisulfite sequencing to examine DNA methylation combined with RNA sequencing to examine gene expression in acutely isolated microglia from juvenile MAA offspring. Differential analysis revealed significant alterations in the epigenome of microglia from MAA compared to PBS treated control offspring and identified genes involved in controlling microglial sensitivity to the environment and shaping both synaptic and long-range neuronal connections in the developing brain. Genes with altered methylation and expression in MAA juvenile microglia significantly overlapped with those identified in adult cortex from offspring of a different maternal immune activation (polyIC) autism model and with a curated list of autism risk genes in human, supporting a role for microglia in the pathogenesis of ASD.
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