Forensic DNA methylation profiling from minimal traces: How low can we go?

Area of Science:

• Forensic Science
• Epigenetics
• Molecular Biology

Background:

• Human DNA methylation (DNAm) analysis offers forensic insights like tissue type, age, and twin differentiation.
• Unlike genetic profiles, DNAm varies between cells; at the single-cell level, it's binary (methylated/non-methylated).
• In forensic samples, DNAm levels represent an average across molecules, with low DNA amounts being common.

Purpose of the Study:

• To analyze DNA methylation profiling and its dependency on input DNA quantity.
• To investigate the impact of DNA input variations on forensic DNAm analysis.
• To assess the consequences for DNAm-based forensic applications like body fluid identification and age determination.

Main Methods:

• Conceptual analysis of DNA methylation profiling.
• Examination of DNA methylation analysis variations based on input DNA amount.
• Comparison of confidence intervals for DNA methylation measurements across different DNA input levels.

Main Results:

• Stochastic variations significantly affect DNA methylation analysis, especially with low DNA input (1pg - 1ng).
• The 95% confidence interval for measured DNAm narrows as DNA input amount increases.
• DNA amount is a critical factor influencing the reliability of DNA methylation-based forensic applications.

Conclusions:

• Low DNA input levels in forensic samples can lead to substantial fluctuations in DNA methylation analysis due to stochasticity.
• Increasing DNA input amount improves the precision of DNA methylation measurements.
• Forensic DNA methylation applications must carefully consider the amount of input DNA for accurate results.