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A collaborative exercise on DNA methylation-based age prediction and body fluid typing.
Ji Eun Lee1, Jeong Min Lee1, Jana Naue2
1Department of Forensic Medicine, Seoul National University College of Medicine, Seoul, South Korea.
Forensic Science International. Genetics
|January 1, 2022
Summary
Forensic DNA methylation analysis using SNaPshot multiplex assays showed accurate age prediction and body fluid identification. Key factors influencing results included genetic analyzer type and PCR conditions, highlighting the need for assay validation.
Area of Science:
- Forensic Science
- Molecular Biology
- Genetics
Background:
- DNA methylation is a key biomarker for age prediction and body fluid identification in forensics.
- SNaPshot assays offer multiplexing and compatibility with existing forensic instrumentation (STR analysis).
- Technical validation is essential for integrating new forensic assays into routine workflows.
Purpose of the Study:
- To technically validate SNaPshot multiplex assays for DNA methylation-based age prediction and body fluid identification.
- To identify factors influencing the accuracy and consistency of SNaPshot methylation analysis across different laboratories.
- To assess the performance of age prediction and body fluid identification assays under realistic forensic conditions.
Main Methods:
- A collaborative exercise involving twelve laboratories testing two SNaPshot age prediction assays and one body fluid identification assay.
- Experimental design mimicked the complete SNaPshot methylation analysis workflow, including bisulfite conversion and PCR.
- Four tasks of increasing complexity were used to evaluate factors affecting methylation measurements.
Main Results:
- Body fluid identification results informed subsequent age prediction analyses.
- Genetic analyzer type was the primary source of DNA methylation variation between laboratories.
- PCR conditions, including primer binding and DNA input volume, significantly impacted methylation measurements.
- Analyst proficiency and experimental conditions were crucial for consistent results.
- Mean absolute age prediction errors were low: 2.7 years (semen), 5.0 years (blood), and 3.8 years (saliva).
Conclusions:
- SNaPshot multiplex assays are viable for forensic age prediction and body fluid identification.
- Standardization of genetic analyzers and optimization of PCR conditions are critical for inter-laboratory consistency.
- The study successfully identified key variables affecting SNaPshot methylation analysis, paving the way for improved forensic applications.
