Investigating Single-Molecule Molecular Inversion Probes for Medium-Scale Targeted DNA Methylation Analysis

Area of Science:

• Epigenetics
• Molecular Biology
• Biotechnology

Background:

• CpG methylation is a key epigenetic biomarker in clinical and forensic applications.
• A cost-effective, sensitive method for medium-scale CpG analysis with low DNA input (<10 ng) is needed.
• Single-molecule molecular inversion probes (smMIPs) are explored for simultaneous analysis of hundreds of CpGs.

Purpose of the Study:

• To investigate the utility of smMIPs for analyzing hundreds of user-defined CpGs.
• To develop a novel smMIP design tool (Locksmith) for bisulfite-converted DNA.
• To optimize smMIP capture conditions for sensitive methylation analysis.

Main Methods:

• Developed a novel smMIP design tool (Locksmith) tailored for bisulfite-converted DNA.
• Optimized smMIP capture through single-probe testing and full panel evaluation.
• Varied hybridization/elongation temperatures, smMIP/DNA amounts, dNTP concentration, and elongation time.

Main Results:

• Capture efficiency varied significantly based on probe sequence, leading to heterogeneous CpG coverage.
• Robust methylation detection was achieved for CpGs with ≥20X coverage, comparable to EPIC microarray analysis (r=0.96).
• Low specificity and uniformity were observed across the tested smMIP panel.

Conclusions:

• Current smMIP designs exhibit low specificity and uniformity with bisulfite-converted DNA.
• smMIPs, in their present form, are not suitable for analyzing the reduced complexity of bisulfite-converted DNA.
• Further optimization of smMIP design and protocols is required for effective epigenetic analysis.