Unknown,Transcriptomics,Genomics,Proteomics

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Cell-free DNA comprises an in vivo, genome-wide nucleosome footprint that informs its tissue(s)-of-origin

ABSTRACT: Nucleosomes are the basic unit of packaging of eukaryotic chromatin, and nucleosome positioning can differ substantially between cell types. Here, we sequence 14.5 billion plasma-borne cell-free DNA (cfDNA) fragments (700-fold coverage) to generate genome-wide maps of in vivo nucleosome occupancy. We identify 13 million local maxima of nucleosome protection, spanning 2.53 gigabases (Gb) of the human genome, whose positions and spacings correlate with nuclear architecture, gene structure and gene expression. We further show that short cfDNA fragments - poorly recovered by standard protocols - directly footprint the in vivo occupancy of DNA-bound transcription factors such as CTCF. The sequence composition of cfDNA has previously been used to noninvasively monitor cancer, pregnancy and organ transplantation, but a key limitation of this paradigm is its dependence on genotypic differences to distinguish between contributing tissues. We show that nucleosome spacing in gene bodies and cis-regulatory elements, inferred from cfDNA in healthy individuals, correlates most strongly with transcriptional and epigenetic features of lymphoid and myeloid cells, consistent with hematopoietic cell death as the normal source of cfDNA. We build on this observation to show how in vivo nucleosome footprints can be used to infer the cell types that contribute to circulating cfDNA in pathological states such as cancer. Because it does not rely on genotypic differences, this strategy may enable the noninvasive cfDNA-based monitoring of a much broader set of clinical conditions than is currently possible. Sequencing of cfDNA libraries from healthy individuals, pooled healthy individuals and individuals with disease for the identification of nucleosomes and protection from other DNA binding proteins.

ORGANISM(S): Homo sapiens

SUBMITTER: Jay Shendure

PROVIDER: E-GEOD-71378 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:We determined the strand-specific transcriptome of the fission yeast S. pombe under multiple growth conditions using a novel RNA/DNA hybridization mapping (HybMap) technique. HybMap uses an antibody against an RNA/DNA hybrid to detect RNA molecules hybridized to a high density DNA oligonucleotide tiling microarray. HybMap exhibited exceptional dynamic range and reproducibility, and clearly revealed coding, non-coding and structural RNAs, as well as new RNAs conserved in distant yeast species. Virtually the entire euchromatic genome (including intergenics) is transcribed, with heterochromatin dampening intergenic transcription. Transcriptomes of alternative growth conditions reveal changes in both coding and non-coding RNAs. Interestingly, our analysis reveals large numbers of non-coding RNAs, extensive antisense transcription, new properties of antisense transcripts, and induced divergent transcription. Furthermore, HybMap informed the efficiency and locations of RNA splicing genome-wide. Finally, a remarkable feature is observed at heterochromatin boundaries inside centromeres; strand-specific transcription islands around tRNAs. These new features are discussed in terms of organism fitness and transcriptome evolution. Keywords: yeast, gene expression, bioinformatics The dynamic transcriptome of S.pombe was determined using a whole genome tiling array hybridized to total RNA. Transcripts were detected using an antibody specific to RNA/DNA hybrids. This technique, called HybMap, was used across three different growth conditions (Heat shock, MMS treatment, and minimal media) in addtion to standard conditions. To further understand the transcriptome, we isolated PolyA RNA from S.pombe grown in standard conditions and used the HybMap method. Finally, the transcriptome was compared to Pol II, histone, and H3K36me3 ChIP occupancy. NOTE: Processed microarray data values listed in this repository represent only those probes that align to unique genomic positions. Probes that align to multiple genomic locations (reported in the Platform description) may not have values. Please refer to the web link above for a complete genomic data set.

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Cell-free DNA comprises an in vivo, genome-wide nucleosome footprint that informs its tissue(s)-of-origin

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