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A Chromatin Accessibility Atlas of the Developing Human Telencephalon

ABSTRACT: Gene expression differs between cell types and regions within complex tissues such as the developing brain. To discover regulatory elements underlying this specificity, we generated genome-wide maps of chromatin accessibility in nine anatomically-defined regions of the developing human telencephalon. Additionally, we defined the histone modification landscape of the prefrontal cortex and generated chromatin accessibility maps of its upper and deep layers. We predicted a subset of open chromatin regions (18%) that are most likely to be active enhancers, many of which are dynamic with 26% differing between early and late mid-gestation and 28% present in only one brain region. These predicted regulatory elements (pREs) are enriched proximal to genes with expression differences across developmental stages, regions, and cortical laminae; they harbor distinct sequence motifs that suggest potential upstream regulators. We leveraged this atlas to predict and validate novel regulatory elements of genes that control cortex laminar identity and genes associated with autism spectrum disorder (ASD). These include enhancers proximal to FEZF2 and BCL11A that were validated in mouse, and an enhancer of ASD gene SLC6A1 containing two functional de novo mutations in individuals with ASD whose enhancer function we validated via CRISPRa. These applications demonstrate the utility of this atlas for decoding neurodevelopmental gene regulation in health and disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE149268 | GEO | 2020/04/25

REPOSITORIES: GEO

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Project description:Eukaryotic gene regulatory information is contained within the DNA sequences of cis-regulatory elements and the epigenetic features of the chromatin surrounding these elements. Recent investigations in yeast, fly, and mammalian systems have made significant contributions toward our understanding of the relationship between gene activation and chromatin architecture at transcriptional promoters, but much work remains to improve our knowledge of this relationship at human promoters and other transcriptional regulatory elements, such as enhancers. Here, we report that human promoters and enhancers are associated with distinct chromatin signatures that can be employed to predict these classes of regulatory elements in the human genome. Using a combination of chromatin immunoprecipitation (ChIP) and microarray (ChIP-chip) experiments, we generated high-resolution maps of the chromatin architecture along 30 Mbp of the human genome, located promoters and enhancers in these regions, and characterized the histone modification features of these regulatory elements. We found that active promoters are marked by tri-methylation of histone H3 lysine 4 (H3K4me3) at the transcriptional start site (TSS) and mono-methylation of this residue (H3K4me1) downstream and upstream of the TSS. In contrast, enhancers are marked by H3K4me1 but not H3K4me3. Both types of regulatory elements are also associated with nucleosome depletion and varying degrees of histone acetylation and H3K4me2. We developed computational prediction algorithms that employ the distinct chromatin signatures to identify new promoters and enhancers, predicting over 200 promoters and 400 enhancers within the 30 Mbp regions. This approach correctly predicted over 84% of the regulatory elements identified in an independent, unbiased study of transcription factor binding in the same regions. Our results suggest a histone code for distinct classes of transcriptional regulatory elements, offering insights into the functional relationships between chromatin modifications and regulatory activity in human cells and providing a new resource for the functional annotation of the human genome. Keywords: ChIP-chip

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

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A Chromatin Accessibility Atlas of the Developing Human Telencephalon

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