Project description:Whole-genome bisulfite sequencing (BS-Seq) measures cytosine methylation changes at single-base resolution and can be used to profile cell-free DNA (cfDNA). In plasma, ultrashort single-stranded cfDNA (uscfDNA, ~50 nt) has been identified together with 167 bp double-stranded mononucleosomal cell-free DNA (mncfDNA). However, the methylation profile of uscfDNA has not been described. Conventional BS-Seq workflows may not be helpful because bisulfite conversion degrades larger DNA into smaller fragments, leading to erroneous categorization as uscfDNA. We describe the “5mCAdpBS-Seq” workflow in which pre-methylated 5mC (5-methylcytosine) single-stranded adapters are ligated to heat-denatured cfDNA before bisulfite conversion. This method retains only DNA fragments that are unaltered by bisulfite treatment, resulting in less biased uscfDNA methylation analysis. Using 5mCAdpBS-Seq, uscfDNA had lower levels of DNA methylation (~15%) and was enriched in promoters and CpG islands. Hypomethylated uscfDNA fragments were enriched in upstream transcription start sites (TSSs), and the intensity of enrichment positively affected gene expression of hemopoietic cells. Using tissue-of-origin deconvolution, we inferred that uscfDNA is derived primarily from eosinophils, neutrophils, and monocytes. As proof-of-principle, we show that characteristics of the methylation profile of uscfDNA can distinguish non-small cell lung carcinoma from non-cancer samples. The 5mCAdpBS-Seq workflow is recommended for any cfDNA methylation-based investigations.
2024-03-28 | GSE252088 | GEO
Project description:cell-free DNA sequencing of plasma
Project description:We used bs-ATLAS-seq to comprehensively map the genomic location and assess the DNA methylation status of human full-length LINE-1 elements (L1) in the genome of 2102Ep cells (E-MTAB-10895). We also achieved targeted nanopore sequencing to assay DNA methylation over a subset of loci (E-MTAB-12247). To further study the link between L1 DNA methylation and expression, we performed, in the same cell line, RNA-seq (E-MTAB-12246), as well as YY1 and H3K4me3 ChIP-seq (this dataset).
Project description:Interventions: Gold Standard:;Index test:
Primary outcome(s): concentration of cell-free DNA in plasma;integrity of cell-free DNA in plasma
Study Design: Diagnostic test: case-control
Project description:We performed poly(A)+ stranded RNA-seq of a panel of the human colorectal adenocarcinoma cell line HCT-116 treated with 5-aza-2’-deoxycytidine. In parallel, we determined the genomic location and DNA methylation levels of human full-length LINE-1 elements (L1) from the same samples using bs-ATLAS-seq (E-MTAB-12240). To link DNA methylation and L1 expression, we used cell pellets from the same cell culture to perform both RNA-seq and bs-ATLAS-seq.