Project description:Autism is currently considered a multigene disorder with epigenetic influences. To investigate the contribution of DNA methylation to autism spectrum disorders, we have recently completed large-scale methylation profiling by CpG island microarray analysis of lymphoblastoid cell lines (LCL) derived from monozygotic twins discordant for diagnosis of autism and their nonautistic siblings. Methylation profiling revealed many candidate genes differentially methylated between discordant MZ twins as well as between both twins and nonautistic siblings. Bioinformatics analysis of the differentially methylated genes demonstrated enrichment for high level functions including gene transcription, nervous system development, cell death/survival, and other biological processes implicated in autism. The methylation status of two of these candidate genes, BCL-2 and retinoic acid receptor (RAR)-related orphan receptor alpha (RORA), was further confirmed by bisulfite sequencing and methylation-specific PCR, respectively. Immunohistochemical analyses of tissue arrays containing slices of the cerebellum and frontal cortex of autistic and age- and sex-matched control subjects revealed decreased expression of RORA and BCL-2 proteins in the autistic brain. Our data thus confirm the role of epigenetic regulation of gene expression via differential DNA methylation in idiopathic autism, and furthermore link molecular changes in a peripheral cell model with brain pathobiology in autism. Global methylation profiling was performed on lymphoblastoid cell lines (LCLs) derived from three pairs of male monozygotic twins discordant for diagnosis of autism as determined by the Autism Diagnostic Interview-Revised (ADI-R). As controls, cell lines derived from non-autistic siblings of two pairs of twins were also included in the analyses, in addition to cell lines derived from a set of monozygotic twins unaffected by autism. For all paired analyses, a direct comparison was performed in which the methylation-enriched fractions from two individuals were pooled and hybridized onto the same microarray. In addition, indirect comparisons were performed by co-hybridizing the methylation-enriched (MIRA) fraction with the respective unenriched DNA fraction obtained from the same individual. For each paired analysis (between autistic MZ twins and/or between autistic co-twin and unaffected sibling), a total number of 4 replicates were performed, including direct and indirect comparisons.

Project description:Background: We have recently identified the nuclear hormone receptor RORA (retinoic acid-related orphan receptor-alpha) as a novel candidate gene for autism spectrum disorder (ASD). Our independent cohort studies have consistently demonstrated the reduction of RORA transcript and/or protein levels in blood-derived lymphoblasts as well as the postmortem prefrontal cortex and cerebellum of individuals with ASD. Moreover, we have also shown that RORA has the potential to be under negative and positive regulation by androgen and estrogen, respectively, suggesting the possibility that RORA may contribute to the male bias of ASD. However, little is known about transcriptional targets of this nuclear receptor, particularly in humans. Methods: Here we comprehensively identify transcriptional targets of RORA in human neuronal cells using chromatin immunoprecipitation (ChIP), followed by whole-genome promoter array (chip) analysis. Selected potential targets of RORA were then further validated by an independent chromatin immunoprecipitation, followed by qPCR analysis. To further demonstrate that reduced RORA expression results in aberrant transcription of RORA targets, we determined the expression levels of selected transcriptional targets in RORA-deficient human neuronal cells, as well as in postmortem brain tissues from individuals with ASD who exhibit reduced RORA expression. Results: The ChIP-on-chip analysis reveals that RORA1, a major isoform of RORA protein in human brain, can be recruited to as many as 1,338 genomic locations corresponding to promoter regions of 1,274 genes across the human genome. Among the genes potentially directly regulated by RORA1 are genes known to have biological functions negatively impacted in individuals with ASD, including neuronal adhesion and survival, synaptogenesis, and development of the cortex and the cerebellum. Independent ChIP-qPCR analyses confirm binding of RORA1 to promoter regions of several ASD-associated genes, including A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, whose expression levels are also decreased in RORA1-repressed human neuronal cells and in prefrontal cortex tissues from individuals with ASD. Conclusion: Findings from this study indicate that RORA transcriptionally regulates A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, and strongly suggest that reduction of this sex hormone-sensitive nuclear receptor in the brain causes dysregulated expression of these genes which, in turn, may contribute to the underlying pathobiology of ASD. Nuclear lysates from the human neuroblastoma cell line SH-SY5Y were chromatin-immunoprecipitated with goat anti-RORA1 antibody vs. normal goat IgG antibody

Project description:Background: We have recently identified the nuclear hormone receptor RORA (retinoic acid-related orphan receptor-alpha) as a novel candidate gene for autism spectrum disorder (ASD). Our independent cohort studies have consistently demonstrated the reduction of RORA transcript and/or protein levels in blood-derived lymphoblasts as well as the postmortem prefrontal cortex and cerebellum of individuals with ASD. Moreover, we have also shown that RORA has the potential to be under negative and positive regulation by androgen and estrogen, respectively, suggesting the possibility that RORA may contribute to the male bias of ASD. However, little is known about transcriptional targets of this nuclear receptor, particularly in humans. Methods: Here we comprehensively identify transcriptional targets of RORA in human neuronal cells using chromatin immunoprecipitation (ChIP), followed by whole-genome promoter array (chip) analysis. Selected potential targets of RORA were then further validated by an independent chromatin immunoprecipitation, followed by qPCR analysis. To further demonstrate that reduced RORA expression results in aberrant transcription of RORA targets, we determined the expression levels of selected transcriptional targets in RORA-deficient human neuronal cells, as well as in postmortem brain tissues from individuals with ASD who exhibit reduced RORA expression. Results: The ChIP-on-chip analysis reveals that RORA1, a major isoform of RORA protein in human brain, can be recruited to as many as 1,338 genomic locations corresponding to promoter regions of 1,274 genes across the human genome. Among the genes potentially directly regulated by RORA1 are genes known to have biological functions negatively impacted in individuals with ASD, including neuronal adhesion and survival, synaptogenesis, and development of the cortex and the cerebellum. Independent ChIP-qPCR analyses confirm binding of RORA1 to promoter regions of several ASD-associated genes, including A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, whose expression levels are also decreased in RORA1-repressed human neuronal cells and in prefrontal cortex tissues from individuals with ASD. Conclusion: Findings from this study indicate that RORA transcriptionally regulates A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, and strongly suggest that reduction of this sex hormone-sensitive nuclear receptor in the brain causes dysregulated expression of these genes which, in turn, may contribute to the underlying pathobiology of ASD.

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