Journal of Forensic Research

DNA Methylation-based Age Prediction from Blood Samples of French Child and Adult Individuals

Abstract

Camille Ropert, Simon Buré, Adèle Sourisce, Caroline Gallois, Myriam Siffointe, Laurent Bartholin, Fabrice Besacier, Romain Appourchaux*, and Mathieu Gabut*

Objective: Identifying the origin of human biological traces detected at crime scenes by comparing DNA profiles to national or international forensic databases is often key to provide new orientations to police investigations. However, when unknown profiles are established, investigators can benefit from forensic genetics to propose new leads, for example by predicting the physical appearance of individuals. Since blood traces are of primary interest for forensic investigators and often lead to the extraction of usable genetic material, in this study, we developed a methodology to predict the biological age from blood samples based on the analysis of DNA methylation of human genomic regions.

Methods: We first established a cohort of blood samples obtained from 170 French donors aged from 0 to 101 years old. We analyzed the methylation status of 5 age-associated CpG sites using the SNaPshot method, a primer-extension based assay routinely used in the French forensic police laboratories. Using a training set of 136 samples, we generated an age-prediction model based on multiple regression analyses of DNA methylation data and we tested its predictive performances on a validation set.

Results: The SNaPshot assay was adapted to limiting quantities of genomic DNA relevant for forensic investigations. The DNA methylation levels were established for 5 age-related CpG sites in 170 blood samples collected from French male and female donors. We established a statistical model optimized for 5 CpG sites that can explain 97% of age variation with a Mean Absolute Error (MAE) of 3.45 years between the estimated biological and chronological age of individuals. Conclusion: We developed an approach to predict the biological age of individuals strictly based on the methylation levels of 5 CpG sites from circulating blood samples and that is compatible with routine genetic analyses in French forensic police laboratories.

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