Project description:Common genetic risk for neuropsychiatric disorders is enriched in regulatory elements active during cortical neurogenesis. However, it remains poorly understood as to how these variants influence gene regulation. To model the functional impact of common genetic variation on the noncoding genome during human cortical development, we performed the assay for transposase accessible chromatin using sequencing (ATAC-seq) and analyzed chromatin accessibility quantitative trait loci (QTL) in cultured human neural progenitor cells and their differentiated neuronal progeny from 87 donors. We identified significant genetic effects on 988/1,839 neuron/progenitor regulatory elements, with highly cell-type and temporally specific effects. A subset (roughly 30%) of chromatin accessibility-QTL were also associated with changes in gene expression. Motif-disrupting alleles of transcriptional activators generally led to decreases in chromatin accessibility, whereas motif-disrupting alleles of repressors led to increases in chromatin accessibility. By integrating cell-type-specific chromatin accessibility-QTL and brain-relevant genome-wide association data, we were able to fine-map and identify regulatory mechanisms underlying noncoding neuropsychiatric disorder risk loci.
Project description:To identify chromatin mechanisms of neuronal differentiation, we characterized the relationship between chromatin accessibility and gene expression in cerebellar granule neurons (CGNs) of the developing mouse. We used DNase-seq to globally map accessibility of cis-regulatory elements and RNA-seq to profile transcript abundance at key points in postnatal neuronal differentiation in vivo and in culture. We observed thousands of chromatin accessibility changes as CGNs differentiated and determined that many of these regions function as stage-specific neuronal enhancers. Motif discovery within differentially accessible chromatin regions suggested a novel role for the Zic family of transcription factors in CGN maturation, and we confirmed the association of Zic with these elements by ChIP-seq. Knockdown of Zic1 and Zic2 indicated Zic transcription factors are required to coordinate mature neuronal gene expression patterns. These data reveal chromatin dynamics at thousands of gene regulatory elements that facilitate gene expression patterns necessary for neuronal differentiation and function. Biological triplicate DNase-seq and RNA-seq samples from 3 in vivo cerebellum developmental stages (P7, P14, P60) and 3 cultured CGN stages (isolated granule neuron precursors, +3DIV, and +7DIV) obtained. Zic1 and Zic2 were separately knocked down by lentiviral shRNA in cultured CGNs followed by RNA-seq (2 biological replicates per KD and 2 controls). Zic1/2 ChIP-seq was performed with in vivo cerebellum at two developmental stages (P7 and P60) in duplicate with matching input and IgG controls.
Project description:Chromatin accessibility is an important functional genomics phenotype that influences transcription factor binding and gene expression. Genome-scale technologies allow chromatin accessibility to be mapped with high-resolution, facilitating detailed analyses into the genetic architecture and evolution of chromatin structure within and between species. We performed Formaldehyde-Assisted Isolation of Regulatory Elements sequencing (FAIRE-Seq) to map chromatin accessibility in two parental haploid yeast species, Saccharomyces cerevisiae and Saccharomyces paradoxus and their diploid hybrid. We show that although broad-scale characteristics of the chromatin landscape are well conserved between these species, accessibility is significantly different for 947 regions upstream of genes that are enriched for GO terms such as intracellular transport and protein localization exhibit. We also develop new statistical methods to investigate the genetic architecture of variation in chromatin accessibility between species, and find that cis effects are more common and of greater magnitude than trans effects. Interestingly, we find that cis and trans effects at individual genes are often negatively correlated, suggesting widespread compensatory evolution to stabilize levels of chromatin accessibility. Finally, we demonstrate that the relationship between chromatin accessibility and gene expression levels is complex, and a significant proportion of differences in chromatin accessibility might be functionally benign. There are 20 samples in total. These consist of 10 FAIRE-seq samples, specifically 6 haploid samples, S. cerevisiae strain UWOPS05_217_3 replicates 1 and 2, S. cerevisiae strain DBVPG1373 replicates 1 and 2, and S. paradoxus strain CBS432 replicates 1 and 2. There are also 4 diploid hybrid samples, hybrid between S. cerevisiae strain UWOPS05_217_3 and S. paradoxus strain CBS432 replicates 1 and 2, and the hybrid between S. cerevisiae strain DBVPG1373 and S. paradoxus strain CBS432 replicates 1 and 2. There are also RNA-seq samples for each of these 10 samples.
Project description:Assembly of transcriptomes encoding unique neuronal identities requires selective accessibility of transcription factors to cis-regulatory sequences in nucleosome-embedded postmitotic chromatin. Yet, the mechanisms controlling postmitotic neuronal chromatin accessibility are poorly understood. Here, we show that unique distal enhancers define the Pet1 neuron lineage that generates serotonin (5-HT) neurons. Heterogeneous single cell chromatin landscapes are established early in postmitotic Pet1 neurons and reveal the putative regulatory programs driving Pet1 neuron subtype identities. Distal enhancer accessibility is highly dynamic as Pet1 neurons mature, suggesting the existence of regulatory factors that reorganize postmitotic neuronal chromatin. We find that Pet1 and Lmx1b control chromatin accessibility to select Pet1-lineage specific enhancers for 5-HT neurotransmission. Additionally, these factors are required to maintain chromatin accessibility during early maturation suggesting that postmitotic neuronal open chromatin is unstable and requires continuous regulatory input. Together our findings reveal postmitotic transcription factors that reorganize accessible chromatin for neuron specialization.
Project description:Chromatin organization is a highly orchestrated process that influences gene expression, in part by modulating access of regulatory factors to DNA and nucleosomes. We found that the chromatin accessibility regulator HMGN1, a target of recurrent DNA copy gains in leukemia, controls myeloid differentiation. HMGN1 amplification was associated with increased accessibility, expression, and histone H3K27 acetylation of loci important for hematopoietic stem cell (HSC) function and AML, such as HoxA cluster genes. In vivo, HMGN1 overexpression was linked to decreased quiescence and increased HSC activity in bone marrow transplantation. HMGN1 overexpression also cooperated with the AML-ETO9a fusion oncoprotein to impair myeloid differentiation and enhance leukemia stem cell (LSC) activity. Inhibition of histone acetyltransferases CBP/p300 relieved the HMGN1-associated differentiation block. These data nominate factors that modulate chromatin accessibility as regulators of HSCs and LSCs and suggest that targeting HMGN1 or its downstream effects on histone acetylation could be therapeutically active in AML.