What is the minimum DNA input for Target-BS?

We require ≥ 50 ng of high-quality genomic DNA, but multi-gene amplification can be performed with as little as 20 ng for well-preserved samples.

What is the typical sequencing depth per amplicon?

We target ≥ 300× average depth per amplicon, with typical results ranging from 300× to 1000×. This enables reliable detection of methylation differences as low as 1%.

How does Target-BS compare to WGBS for biomarker validation?

Target-BS provides dramatically higher sequencing depth (>300× vs 10–30×) at a fraction of the per-sample cost, making it ideal for validating WGBS-discovered biomarkers in large cohorts.

Target Bisulfite Sequencing (Target-BS) Service: High-Resolution Targeted Methylation Analysis

Target Bisulfite Sequencing (Target-BS) is a high-throughput method for targeted DNA methylation analysis at single-base resolution. Combining bisulfite conversion with multiplex target enrichment (amplicon-based or hybridization capture-based), Target-BS delivers ultra-deep sequencing coverage (>300×) across selected genomic regions of interest — promoters, CpG islands, or custom gene panels. Unlike genome-wide approaches, Target-BS concentrates sequencing power on the regions that matter most to your study, making it the cost-effective choice for methylation biomarker validation, cohort screening, and clinical sample analysis.

Key Highlights of Our Target-BS Service:

Ultra-High Sequencing Depth (>300×) — Multiplex targeted enrichment achieves deep coverage that detects methylation changes as low as <1%, surpassing the sensitivity of conventional bisulfite cloning.
Minimal DNA Input — Multi-gene amplification from as little as 20 ng genomic DNA, enabling analysis of precious or limited samples including FFPE and cfDNA.
Custom Panel Flexibility — Design your own target gene panel with our proprietary multiplex primer design software, supporting up to hundreds of loci in a single reaction.
Rapid, Cost-Effective Turnaround — Significantly lower per-sample cost than whole-genome approaches, with streamlined workflows delivering results in weeks rather than months.

Available Target-BS Study Options:

CD Genomics supports amplicon-based Target-BS for focused gene panels and hybridization capture-based Target-BS for broader targeted regions. Custom panel design, primer synthesis, and validation are included in every project.

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3D illustration of bisulfite conversion of unmethylated cytosines to uracil while methylated cytosines remain protected, followed by targeted PCR amplification

Advantages

Core Technical Advantages of Target-BS

Target-BS bridges the gap between discovery-phase methylation studies and validation-phase biomarker development, delivering single-base resolution with ultra-high depth at a fraction of whole-genome costs.

Target-BS workflow: bisulfite-converted DNA, multiplex targeted PCR, library preparation, ultra-deep sequencing, methylation analysis

Single-Base Resolution with Ultra-High Depth — Unlike methylation arrays that interrogate fixed sets of CpG probes, Target-BS provides single-base resolution across every CpG within your targeted regions. Typical coverage depths of >300× enable reliable detection of methylation heterogeneity and rare methylated alleles (<1% detection sensitivity), critical for applications such as circulating tumor DNA (ctDNA) methylation monitoring.
Custom Panel Design for Any Genomic Region — Our proprietary multiplex primer design software optimizes amplicon placement across your regions of interest, avoiding SNPs, repetitive elements, and bisulfite conversion biases. Panels can be designed for promoter regions, CpG islands, enhancer regions, or custom-defined loci across any species — including non-model organisms.
Versatile Sample Compatibility — Target-BS is compatible with genomic DNA, FFPE-derived DNA, and cell-free DNA (cfDNA). Bisulfite conversion chemistry has been optimized for each sample type to maximize conversion efficiency (>99%) while minimizing DNA degradation.
Streamlined Bioinformatics with Methylation-Specific Tools — Bisulfite-aware alignment (Bismark, bwa-meth), per-CpG methylation quantification, and differential methylation analysis are performed with dedicated pipelines. Results include methylation levels for every CpG site, sample-to-sample comparisons, and publication-ready visual outputs.

Applications

Applications in Epigenetics Research

Target-BS is the method of choice when your research has progressed from genome-wide discovery to focused validation and translation.

Methylation Biomarker Validation

Validate candidate methylation biomarkers identified from WGBS, RRBS, or array-based discovery studies. Target-BS provides quantitative, single-base methylation data across focused gene panels in large validation cohorts.

Large-Scale Cohort Screening

Screen hundreds to thousands of samples across a defined panel of methylation biomarkers. The cost efficiency and high throughput of Target-BS make it ideal for population-level methylation studies and epidemiology cohorts.

Precision Oncology & Liquid Biopsy

Analyze methylation patterns in cfDNA from plasma or other biofluids for non-invasive cancer detection and monitoring. Target-BS achieves the sensitivity needed to detect tumor-derived methylation signals in circulating DNA.

Non-Model Organisms & Agriculture

Design custom Target-BS panels for crop plants, livestock, or any non-model organism where commercial arrays are unavailable. Our panel design accommodates any reference genome.

Workflow

Optimized Target-BS Workflow and Stringent QC Metrics

CD Genomics maintains a rigorous end-to-end workflow to ensure data integrity and biological relevance.

Panel Design & Primer Synthesis: Target regions defined based on your research goals. Proprietary multiplex primer design software generates optimized amplicons. Primers synthesized and validated in our laboratory.
DNA QC & Bisulfite Conversion: DNA quantified via Qubit, integrity assessed. Bisulfite conversion performed with >99% conversion efficiency, monitored by spike-in controls.
Targeted Library Preparation: Multiplex PCR amplification of target regions from bisulfite-converted DNA. Amplicons purified, end-repaired, and ligated to sequencing adapters with unique dual-indices.
Ultra-Deep Sequencing: High-throughput paired-end sequencing (PE150) on Illumina platforms. Recommended depth: ≥300× per amplicon (typical 300–1000×). Minimum 1 Gb raw data per sample.
Bioinformatics Analysis: Bisulfite-aware alignment, per-CpG methylation calling, differential methylation analysis, and publication-ready report compilation.

Sample Requirements

Sample Type	Recommended Input	Container & Shipping	QC Requirements	Notes
Genomic DNA	≥ 50 ng	1.5 mL tube, dry ice	OD260/280 = 1.8–2.0, no degradation	≥ 10 ng/μL concentration recommended
FFPE DNA	≥ 100 ng	1.5 mL tube, dry ice	DV200 assessment recommended	Degraded samples accepted; panel design may be adjusted
cfDNA (plasma/serum)	≥ 10 ng	cfDNA BCT tube, 4°C	Fragment size ~167 bp	Specialized extraction and bisulfite conversion protocols
Tissue	≥ 20 mg	Cryovial, dry ice	Flash-frozen preferred	Avoid repeated freeze-thaw cycles

Demo Results

Publication-Ready Demo Results

Per-CpG Methylation Heatmap: Hierarchically clustered heatmap showing methylation levels (0–100%) for every CpG site across all samples, enabling rapid identification of differentially methylated loci.
Locus-Specific Methylation Bar Plot: Bar charts displaying average methylation levels at individual CpG sites, comparing experimental groups with error bars.
Differential Methylation Volcano Plot: Highlights statistically significant differentially methylated CpG positions between groups.
Methylation Correlation Matrix: Pairwise sample correlation matrix showing reproducibility across replicates.
Bisulfite Conversion Efficiency QC: Conversion rate plot confirming >99% conversion efficiency.
Coverage Depth Distribution: Bar chart showing sequencing depth per amplicon.

Bioinformatics

Comprehensive Target-BS Bioinformatics Pipeline

Standard Methylation Analysis:

Raw Data QC & Filtering: Adapter trimming, quality filtering (FastQC, Cutadapt), removal of low-quality reads.
Bisulfite-Aware Alignment: Reads mapped to reference genome using Bismark or bwa-meth, accounting for C-to-T conversion.
Per-CpG Methylation Calling: Bismark methylation extractor or MethylDackel for quantitative methylation values at each CpG site.
Coverage Analysis: Depth-of-coverage calculation per amplicon, ensuring uniform representation across target regions.

Advanced Analysis:

Differential Methylation: Statistical comparison using methylKit or DSS (FDR < 0.05).
Multi-Region Visualization: Integrated visualization across multiple loci.
Custom Panel Reporting: Comprehensive report with per-CpG tables and publication-ready figures.
Multi-Omics Integration: Correlation with RNA-seq or other epigenomic data available upon request.

Comparison

Target-BS vs. WGBS vs. RRBS vs. Methylation Array

Feature	Target-BS	WGBS	RRBS	Methylation Array
Genomic Coverage	User-defined target regions	Whole genome	CpG-rich regions (~10-20% genome)	Fixed probe set (450K/850K CpGs)
Resolution	Single-base	Single-base	Single-base	Probe-level
Sequencing Depth	>300× (ultra-deep)	10–30×	10–30×	N/A
Detection Sensitivity	<1% methylation	~5–10%	~5–10%	Probe-dependent
DNA Input	≥ 20 ng	≥ 100 ng – 1 μg	≥ 100 ng	≥ 250 ng
Cost per Sample	Low (targeted)	High	Moderate	Low
Best For	Biomarker validation, cohort screening, cfDNA	Whole-methylome discovery	Promoter/CGI-focused discovery	Large GWAS-scale cohorts

Selection Strategy: Choose Target-BS when you have defined candidate regions from prior discovery work and need cost-effective, high-depth methylation data across large sample cohorts. For genome-wide discovery without prior candidates, WGBS or RRBS are more appropriate. Methylation arrays offer pre-designed probe sets ideal for standardized population studies but lack single-base resolution.

Case Study

Case Study: Ultrasensitive Cancer Detection from Cell-Free DNA via Targeted Bisulfite Sequencing

LABS: Linear Amplification-Based Bisulfite Sequencing for Ultrasensitive Cancer Detection from Cell-Free DNA

Background: Cell-free DNA (cfDNA) methylation analysis holds great promise for non-invasive cancer detection, but the limited quantity and high fragmentation of cfDNA in plasma pose significant technical challenges. Standard bisulfite sequencing methods suffer from amplification bias and require large amounts of input DNA, limiting their clinical applicability.

Methods: Researchers developed LABS (Linear Amplification-Based Bisulfite Sequencing), a method that uses T7 RNA polymerase-mediated in vitro transcription to achieve linear, unbiased amplification of bisulfite-treated DNA. The method was validated on cfDNA from 50 colorectal cancer (CRC) patients, 16 pancreatic ductal adenocarcinoma (PDAC) patients, and 34 healthy controls, enabling detection of as little as 10 pg of input DNA.

Results: LABS achieved only 9.72% duplication rate at 100 pg input (vs. >96% for conventional methods) and maintained uniform coverage even in extreme GC regions. The assay detected 1,362–10,716 differentially methylated regions (DMRs) in cancer cfDNA, including the known CRC biomarker SEPT9 promoter. By integrating methylation, copy number, and immune cell composition features, a random forest classifier achieved an AUC of 0.93 for cancer detection.

Figure: LABS enables linear, unbiased amplification of bisulfite-treated cfDNA, achieving AUC 0.93 for cancer detection by integrating methylation, copy number, and immune cell features. (Adapted from Cui et al., Genome Biology, 2024.)

Conclusion: The LABS method demonstrates that advanced targeted bisulfite sequencing approaches can achieve highly sensitive cancer detection from minimal cfDNA input. The integration of multi-dimensional epigenomic features significantly improves diagnostic accuracy compared to methylation analysis alone, highlighting the power of targeted bisulfite sequencing for liquid biopsy applications.

Source: Cui, X.-L., Nie, J., Zhu, H., et al. "LABS: linear amplification-based bisulfite sequencing for ultrasensitive cancer detection from cell-free DNA." Genome Biology, vol. 25, 2024, 157.

FAQ

Frequently Asked Questions (FAQ)

References

Cui, X.-L., Nie, J., Zhu, H., et al. "LABS: linear amplification-based bisulfite sequencing for ultrasensitive cancer detection from cell-free DNA." Genome Biology, vol. 25, 2024, 157.
Bernstein, D. L., et al. "The BisPCR2 method for targeted bisulfite sequencing." Epigenetics & Chromatin, vol. 8, 2015, 27.
Pu, W., et al. "Targeted bisulfite sequencing identified a panel of DNA methylation-based biomarkers for esophageal squamous cell carcinoma." Clinical Epigenetics, vol. 9, 2017, 129.

Disclaimer: Research Use Only (RUO). All services, protocols, and data analysis provided by CD Genomics are intended strictly for basic research and discovery purposes. They are not intended, nor validated, for use in diagnostic, therapeutic, or clinical applications.