DNA Methylation as a Biomarker for Body Fluid Identification

Abstract

Currently, available identification techniques for forensic samples are either enzyme or protein based, which can be subjected to degradation, thus limiting its storage potentials. Epigenetic changes arising due to DNA methylation and histone acetylation can be used for body fluid identification. Markers DACT1, USP49, ZC3H12D, FGF7, cg23521140, cg17610929, chromosome 4 (25287119–25287254), chromosome 11 (72085678–72085798, 57171095–57171236, 1493401–1493538), and chromosome 19 (47395505–47395651) are currently being used for semen identification. Markers cg26107890, cg20691722, cg01774894 and cg14991487 are used to differentiate saliva and vaginal secretions from other body fluids. However, such markers show overlapping methylation pattern. This review article aimed to highlight the feasibility of using DNA methylation of certain genetic markers in body fluid identification and its implications for forensic investigations. The reviewed articles have employed molecular genetics techniques such as Bisulfite sequencing PCR (BSP), methylation specific PCR (MSP), Pyrosequencing, Combined Bisulfite Restriction Analysis (COBRA), Methylation-sensitive Single Nucleotide Primer Extension (SNuPE), and Multiplex SNaPshot Microarray. Bioinformatics software such as MATLAB and BiQ Analyzer has been used. Biological fluids have different methylation patterns and thus, this difference can be used to identify the nature of the biological fluid found at the crime scene. Using DNA methylation to identify the body fluids gives accurate results without consumption of the trace evidence and requires a minute amount of DNA for analysis. Recent studies have incorporated next-generation sequencing aiming to find out more reliable markers that can differentiate between different body fluids. Nonetheless, new DNA methylation markers are yet to be discovered to accurately differentiate between saliva and vaginal secretions with high confidence. Epigenetic changes are dynamic and it is important to find stable DNA sequences that can be used as biomarkers.

Keywords: Forensic Science; DNA analysis; Methylation; body fluid; identification;  Pyrosequencing; DACT1; USP49; ZC3H12D; FGF7.