Zeggar, H. R. | Search bioRxiv

bioRxiv2025

Genome-wide extraction of differentially methylated DNA regions using adapter-anchored proximity primers

The epigenetic deregulation of CpG islands (CGIs) plays a crucial role in cancer initiation and progression. CGIs comprise 1-2% of the human genome and are rich in differentially methylated regions (DMRs) that can serve as cancer biomarkers in clinical samples and liquid biopsies. Focusing epigenetic sequencing on CpG-rich sequences, including CGIs and avoiding non-informative regions, offers an efficient and sensitive approach for cancer identification and tracking, especially within samples containing excess of unaltered, normal DNA. To this end, we have developed Adaptor-anchored Methylation amplification via Proximity Primers (aMAPP), a versatile PCR-based enrichment method. aMAPP employs specially designed primers to selectively enrich either methylated or unmethylated CpGs, depending on the upstream methylation conversion method employed. aMAPP achieves high coverage of genome-wide CGIs and detects hundreds of DMRs in tumor samples compared to adjacent normal tissue using ultra-low depth sequencing ([~]300,000 reads). It enables tracing of aberrant methylation down to allelic frequency 0.01% in dilutions of tumor DNA and in cell-free DNA samples, can be applied using picogram amounts of DNA, and can be adapted to enrich either small panels of cancer-specific DMRs, or the majority (>90%) of genomic CGIs and CpGs. aMAPP offers a simple, cost-effective, and highly sensitive approach for capturing the epigenetic footprint of genome-wide CpGs and identifying aberrantly methylated or un-methylated genomic regions. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/660377v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@b8b303org.highwire.dtl.DTLVardef@1f0a70corg.highwire.dtl.DTLVardef@67391dorg.highwire.dtl.DTLVardef@d6ac75_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Methyl-CODEC enables simultaneous methylation and duplex sequencing

DNA mutations and methylation often contribute to disease development in a synergistic manner. While duplex sequencing is the most accurate method for detecting DNA mutations, it typically lacks the ability to simultaneously assess methylation or requires many reads. Here, we developed Methyl-CODEC to enable simultaneous methylation sequencing and duplex sequencing using single read pairs. To achieve this, Methyl-CODEC links an enzymatically deaminated sense strand to the reverse complement of the antisense strand, which is protected from conversion by using conversion-resistant dCTPs in the strand linking step of CODEC. Methyl-CODEC shows high concordance with standard enzymatic or bisulfite based whole genome methylation sequencing, while also uniquely preserving the original DNA sequence. This improves genetic sequencing accuracy, enables better alignment for next-generation sequencing (NGS), and distinguishes C>T mutations from unmethylated Cs. It also identifies rare mutations including those producing methylated Cs, which are enriched in CpG contexts. Methyl-CODEC opens new horizons for enhanced detection of biomarkers in cancer and molecular medicine.

genomics↗