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Deficiency of autism risk factor ASH1L in prefrontal cortex induces epigenetic aberrations and seizures

ABSTRACT: ASH1L, a histone methyltransferase, is identified as a top-ranking risk factor for autism spectrum disorder (ASD), however, little is known about the biological mechanisms underlying the link of ASH1L haploinsufficiency to ASD. Here we show that ASH1L expression and H3K4me3 level are significantly decreased in the prefrontal cortex (PFC) of postmortem tissues from ASD patients. Knockdown of Ash1L in PFC of juvenile mice induces the downregulation of risk genes associated with ASD, intellectual disability (ID) and epilepsy. These downregulated genes are enriched in excitatory and inhibitory synaptic function and have decreased H3K4me3 occupancy at their promoters. Furthermore, Ash1L deficiency in PFC causes the diminished GABAergic inhibition, enhanced glutamatergic transmission, and elevated PFC pyramidal neuronal excitability, which is associated with severe seizures and early mortality. Chemogenetic inhibition of PFC pyramidal neuronal activity, combined with the administration of GABA enhancer diazepam, rescues PFC synaptic imbalance and seizures, but not autistic social deficits or anxiety-like behaviors. These results have revealed the critical role of ASH1L in regulating synaptic gene expression and seizures, which provides insights into treatment strategies for ASH1L-associated brain diseases. ASH1L haploinsufficiency is strongly linked to autism, despite the unknown mechanism. Here, the authors show that ASH1L deficiency in prefrontal cortex causes the downregulation of synaptic genes, leading to seizures, which is rescued by chemogenetic and pharmacological restoration of excitation/inhibition balance.

SUBMITTER: Qin L

PROVIDER: S-EPMC8593046 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveProinflammatory cytokines have recently received considerable attention for their role in suicidal behavior; however, how the expression of cytokine genes is regulated is not clearly known. The authors examined underlying mechanisms of critical cytokine gene tumor necrosis factor-alpha (TNF-α) dysregulation in the brains of individuals who died by suicide.MethodTNF-α expression was examined in the dorsolateral prefrontal cortex of the postmortem brains of persons with and without major depressive disorder who died by suicide and of persons with major depressive disorder who died of causes other than suicide. The role of putative microRNAs targeting TNF-α and RNA-binding protein Hu antigen R (HuR) was tested with in vitro and in vivo approaches and by examining expression of transactivation response RNA binding protein (TRBP). Genetic influence on TNF-α expression was determined by expression quantitative trait loci analysis and by genotyping three single-nucleotide polymorphisms in the promoter region of the TNF-α gene. Promoter methylation of TNF-α was determined by using methylated DNA immunoprecipitation assay. Expression of miR-19a-3p and TNF-α was also determined in the peripheral blood mononuclear cells of 12 healthy control subjects and 12 currently depressed patients with severe suicidal ideation.ResultsTNF-α expression was significantly higher in the dorsolateral prefrontal cortex of individuals who died by suicide, regardless of psychiatric diagnosis. Its expression level was also increased in individuals with major depressive disorder who died by causes other than suicide. On the other hand, expression of miR-19a-3p was upregulated specifically in individuals who died by suicide. In a preliminary observation, similar upregulation of TNF-α and miR-19a-3p was observed in the peripheral blood mononuclear cells of depressed patients with suicidal ideation. Despite its ability to directly target TNF-α in vitro, miR-19a-3p showed no interaction with TNF-α in the dorsolateral prefrontal cortex. HuR potentially stabilized TNF-α transcript, presumably by sequestering its 3' untranslated region from miR-19a-3p-mediated inhibition. Furthermore, decreased TRBP expression supported abnormality in the interaction between miR-19a-3p and TNF-α. Additionally, TNF-α transcriptional upregulation was associated with promoter hypomethylation, whereas no genetic influence on altered TNF-α or miR-19a-3p expression was observed in individuals who died by suicide.ConclusionsThe data in this study provide mechanistic insights into the dysregulation of the TNF-α gene in the brains of individuals who died by suicide, which could potentially be involved in suicidal behavior.

Project description:Autism comprises a spectrum of behavioral and cognitive disturbances of childhood development and is known to be highly heritable. Although numerous approaches have been used to identify genes implicated in the development of autism, less than 10% of autism cases have been attributed to single gene disorders.We describe the use of high-resolution genome-wide tilepath microarrays and comparative genomic hybridization to identify copy number variants within 119 probands from multiplex autism families. We next carried out DNA methylation analysis by bisulfite sequencing in a proband and his family, expanding this analysis to methylation analysis of peripheral blood and temporal cortex DNA of autism cases and matched controls from independent datasets. We also assessed oxytocin receptor (OXTR) gene expression within the temporal cortex tissue by quantitative real-time polymerase chain reaction (PCR).Our analysis revealed a genomic deletion containing the oxytocin receptor gene, OXTR (MIM accession no.: 167055), previously implicated in autism, was present in an autism proband and his mother who exhibits symptoms of obsessive-compulsive disorder. The proband's affected sibling did not harbor this deletion but instead may exhibit epigenetic misregulation of this gene through aberrant gene silencing by DNA methylation. Further DNA methylation analysis of the CpG island known to regulate OXTR expression identified several CpG dinucleotides that show independent statistically significant increases in the DNA methylation status in the peripheral blood cells and temporal cortex in independent datasets of individuals with autism as compared to control samples. Associated with the increase in methylation of these CpG dinucleotides is our finding that OXTR mRNA showed decreased expression in the temporal cortex tissue of autism cases matched for age and sex compared to controls.Together, these data provide further evidence for the role of OXTR and the oxytocin signaling pathway in the etiology of autism and, for the first time, implicate the epigenetic regulation of OXTR in the development of the disorder.See the related commentary by Gurrieri and Neri: http://www.biomedcentral.com/1741-7015/7/63.

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Deficiency of autism risk factor ASH1L in prefrontal cortex induces epigenetic aberrations and seizures

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