![handle is hein.journals/injlegame134 and id is 1 raw text is: International Journal of Legal Medicine (2020) 134:1-20
https://doi.org/10.1007/s00414-019-02181-3
REVIEW
Characterization of DNA methylation-based markers for human body '
fluid identification in forensics: a critical review
Farzeen Kader' Meenu Ghai' - Ademola O. Olaniran2
Received: 13 March 2019 /Accepted: 15 October 2019 /Published online: 12 November 2019
C Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Body fluid identification in crime scene investigations aids in reconstruction of crime scenes. Several studies have identified and
reported differentially methylated sites (DMSs) and regions (DMRs) which differ between forensically relevant tissues (tDMRs)
and body fluids. Diverse factors affect methylation patterns such as the environment, diets, lifestyle, disease, ethnicity, genetic
variation, amongst others. Thus, it is important to analyse the stability of markers employed for forensic identification.
Furthermore, even though epigenetic modifications are described as stable and heritable, epigenetic inheritance of potential
markers for body fluid identification needs to be assessed in the long term. Here, we discuss the current status of reported
DNA methylation-based markers and their verification studies. Such thorough investigation is crucial to develop a stable panel of
DNA methylation-based markers for accurate body fluid identification.
Keywords DNA methylation . Forensic science . Body fluid identification . Mutations Genetic variation . Heritability
Introduction
DNA methylation
Epigenetics is the study of reversible, heritable changes that
influence gene regulation without altering the underlying
DNA sequence [1]. Perhaps, the most well characterised is
DNA methylation, an epigenetic modification whereby a
methyl group is covalently added to cytosine in DNA [2].
Most DNA methylation occurs in CpG dinucleotides [3];
however, methylation elsewhere (CpT, CpA and CpC) has
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00414-019-02181-3) contains supplementary
material, which is available to authorized users.
Meenu Ghai
ghai@ukzn.ac.za
Discipline of Genetics, School of Life Sciences, College of
Agriculture, Engineering and Science, University of KwaZulu-Natal
(Westville Campus), Private Bag X54001, Durban, Republic of
South Africa
2 Discipline of Microbiology, School of Life Sciences, College of
Agriculture, Engineering and Science, University of KwaZulu-Natal
(Westville Campus), Private Bag X54001, Durban, Republic of
South Africa
been documented [4, 5]. The human genome harbours mil-
lions of CpGs which may exist in a methylated, semi-
methylated or unmethylated state depending on the chromo-
somal location, alleles, cell type or developmental phase
[6-8]. Introns, 3' untranslated regions (UTRs) and intergenic
sequences are severely depleted in CpGs, whereas exons have
a somewhat higher density of CpGs [9]. It is estimated that
between 60 and 90% of CpGs are methylated. Unmethylated
CpGs were originally thought to be grouped in regions known
as CpG islands (CGIs); however, CGIs have also been report-
ed to exist in methylated states. CGIs are often located in
promoter regions and control gene expression via DNA-
differentiated methylation levels [10]. CGIs are 300-
3000 bp long, with a CpG content of above 50%. DNA meth-
ylation is essential in mammalian development, partaking in
numerous processes including genome stability, X-
chromosome inactivation, genomic imprinting, aging and car-
cinogenesis [2, 3]. Aberrant DNA methylation patterns are
said to be implicated in numerous diseases such as cancers
[11], autoimmune diseases [12], diabetes [13], neurodegener-
ative [14] and psychological disorders [15].
DNA methylation patterns are the collective result of meth-
ylation establishment and maintenance [extensively described
in 6, 16-18]. Such established methylation patterns may be
stored as well as stably inherited and may affect an organism
phenotype [19]. Even though DNA methylation is heritable
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