ATAC-Seq
This method utilizes a hyperactive Tn5 transposase to selectively tag and amplify accessible DNA regions, providing insights into cellular regulatory mechanisms and chromatin architecture.
ATAC-Seq has become an essential tool for researchers studying gene expression, transcriptional regulation, and chromatin dynamics acoss a variety of biological systems and disease states.
With its high sensitivity, low input requirements, and streamlined workflow, ATAC-Seq has emerged as a preffered approach for interrogating the epigenomic landscape.
Most cited protocols related to «ATAC-Seq»
For clarity, we overview the analytical workflows for each data type below:
Single-cell gene expression: We analyze scRNA-seq data using standard pipelines in Seurat which include normalization, feature selection, and dimensional reduction with PCA. We then construct a KNN graph after dimensional reduction.
Single-cell cell surface protein level expression: We analyze single-cell protein data (representing the quantification of antibody-derived tags (ADTs) in CITE-seq or ASAP-seq data) using a similar workflow to scRNA-seq. We normalize protein expression levels within a cell using the centered-log ratio (CLR) transform, followed by dimensional reduction with PCA, and subsequently construct a KNN graph. Unless otherwise specified, we do not perform feature selection on protein data, and use all measured proteins during dimensional reduction.
Single-cell chromatin accessibility: We analyze single-cell ATAC-seq data using our previously described workflow (Stuart et al., 2019 (link)), as implemented in the Signac package. We reduced the dimensionality of the scATAC-seq data by performing latent semantic indexing (LSI) on the scATAC-seq peak matrix, as suggested by Cusanovich et al. (2018) (link). We first computed the term frequency-inverse document frequency (TF-IDF) of the peak matrix by dividing the accessibility of each peak in each cell by the total accessibility in the cell (the “term frequency”), and multiplied this by the inverse accessibility of the peak in the cell population. This step ‘upweights’ the contribution of highly variable peaks and down-weights peaks that are accessible in all cells. We then multiplied these values by 10,000 and log-transformed this TF-IDF matrix, adding a pseudocount of 1 to avoid computing the log of 0. We decomposed the TF-IDF matrix via SVD to return LSI components, and scaled LSI loadings for each LSI component to mean 0 and standard deviation 1.
Most recents protocols related to «ATAC-Seq»
RNA-seq reads were mapped to the human genome GRCh38 (hg38) using STAR v2.3.0 (Dobin et al., 2013 (link)). The expression threshold for eRNAs was determined using an adapted method from Zhang et al., 2019 (link). Briefly, total RNA-seq reads were integrated into genomic regions from the intergenic patient ATAC-seq peakset. Putative eRNA and mRNA read counts were determined using featureCounts (Liao et al., 2014 (link)) and FPM values determined using DESeq2 (Love et al., 2014 (link)). Putative eRNA regions with average counts and FPM values of ≥3 and 1.5, respectively, were taken forward for further analysis. Differentially expressed eRNAs and mRNAs were determined using DESeq2 (Love et al., 2014 (link)). For eRNAs, a log2-fold change of ±0.5 and p-valueadj <0.05 defined differential expression. For BO and OAC mRNAs, a log2-fold change of ±0.9 and ±1.5, respectively, and p-valueadj <0.05 defined differential expression. ERBB2-positive OAC samples (ERBB2AMP) were determined based on these samples having expression of ERBB2 greater than the median ERBB2 expression +2 SD. Morpheus (
HOMER v4.9 was used for de novo transcription factor motif enrichment analysis. To analyse footprinting signatures at putative eRNA regions, TOBIAS v0.5.1 was used (Bentsen et al., 2020 (link)). eRNAs were annotated to genes by the nearest gene model and assessed for CpG content using HOMER v4.9. Super enhancers were identified using HOMER v4.9 findPeaks.pl -style super. Net enhancer activity was calculated as in Bi et al., 2020 (link). Briefly, neighbouring genes of eRNA regions in both BO and OAC were identified and stratified into nine groups based on the net eRNA change within 200 kb of the TSS of each gene: + (or −1) stands for 1 net gained (or lost) eRNA from BO to OAC. Bidirectionality score was calculated using HOMER v4.9 analyzeRepeats.pl with the −strand option applied for each strand and score defined as log10((+strand expression score + 1)/(−strand expression score + 1)) + 1.
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More about "ATAC-Seq"
This method utilizes a hyperactive Tn5 transposase to selectively tag and amplify accessible DNA regions, providing insights into cellular regulatory mechanisms and chromatin architecture.
ATAC-Seq has become an essential tool for researchers studying gene expression, transcriptional regulation, and chromatin dynamics across a variety of biological systems and disease states.
With its high sensitivity, low input requirements, and streamlined workflow, ATAC-Seq has emerged as a preferred approach for interrogating the epigenomic landscape.
The technique involves the use of the MinElute PCR Purification Kit, NextSeq 500, HiSeq 2500, MinElute kit, AMPure XP beads, and the Nextera DNA Library Prep Kit to prepare and sequence the ATAC-Seq libraries.
The Tn5 transposase is a key component, responsible for selectively tagging and amplifying the accessible DNA regions.
ATAC-Seq can be performed on a variety of sequencing platforms, including the HiSeq 4000, NovaSeq 6000, and HiSeq 2000, allowing researchers to generate high-quality, genome-wide data on chromatin accessibility.
By leveraging the insights from ATAC-Seq, researchers can uncover the underlying regulatory mechanisms governing gene expression, cellular differentiation, and disease pathogenesis, ultimately advancing our understanding of the epigenomic landscape.