Epigenomics and Cancer Risk Factors

Tagmentation-based whole genome bisulfite sequencing (TB-WGBS)

TB-WGBS enables to determine the quantitative methylation states of all CpGs in a genome with tiny amounts of input DNA, as low as 2 ng.

Conventional (A) vs. transposase Tn5-based NGS library prep (B)

modified from Adey & Shendure, Genome Research 2012
© CSH Press

(A) The conventional protocol for the attachment of PCR adapters requires several steps prone to substantial loss of DNA. (B) Tagmentation appends PCR adapters in a single step and, hence, DNA loss is minimized.Common to both methods in (A) and (B) is the generation of sequencing libraries by PCR.

Schematic overview of TB-WGBS

modified from Adey & Shendure, Genome Research 2012
© CSH Press

The transposase-adapter complex fragments genomic DNA and simultaneously appends the partially methylated DNA adapter to the fragments. Remaining gaps on both strands are filled up (in case, the oligonucleotides adjacent to the gaps are unmethylated, they are replaced by methylated oligonucleotides). The tagmented DNA is bisulfite treated and finally subjected to PCR for limited amplification and attachment of sequencing primers.

Reference:

Wang Q, Gu L, Adey A, Radlwimmer B, Wang W, Hovestadt V, Bähr M, Wolf S, Shendure J, Eils R, Plass C, Weichenhan D. Tagmentation-based whole-genome bisulfite sequencing. Nat Protoc. 2013; 8: 2022-32. Abstract

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