Authors
Somya Jinghania, Arti Varshney
Abstract
In recent years, forensic research has focused on age estimation using DNA methylation pattern analysis. It is still unclear if other specimen types are appropriate for forensic epigenetic age assessment and whether further decomposition may impact the patterns of methylation of CpG sites. Buccal swabs from living individuals are a convenient way to gather DNA for estimating epigenetic age. The age at death-calculation of the unidentified deceased may be another forensic use for epigenetic age estimation. Numerous studies have documented age-related DNA methylation alterations in different tissues and bodily fluids, as well as age-predictive models. Despite the fact that age-related DNA methylation alterations can be tissue-specific, there is a multi-tissue age estimator that has substantial applicability to a variety of tissues and body fluids. Keywords: DNA Methylation, age estimation, buccal swabs, forensic anthropology
Introduction
In a similar way to how the term "genome" refers to a cell's genetic makeup, the phrase "epigenome" describes its entire epigenetic state. The collection of chemical alterations to DNA known as the epigenome affects gene expression. Epigenetic modifications influence how and when genes are switched on or off, which controls how much protein is produced in particular cells. chromatic structuring, histone modification, and DNA methylation are examples of epigenetic variation types. One frequent kind of epigenetic change is DNA methylation. Only the essential genes are expressed when the chromatin proteins connected to DNA are activated or silenced, such as when producing specific proteins (Bird, 2007; Vidaki et al., 2013). In a manner similar to how the DNA sequence is passed down from each generation to the next, the epigenetic sequence is maintained during cell division. However, during the course of a person's lifetime, they can evolve.
A methyl group (-CH3) is added to the 5′ carbon (C5) of cytosines and guanines in the DNA double helix in mammalian cells. This chemical alteration of DNA methylation occurs in a 5′-3′ orientation. The majority of the human genome's "CpG" dinucleotides are methylated (Ehrlich et al., 1982) which are 5′-3′ CG methylation regions in DNA. Unmethylated CpGs, also known as "CpG islands," is most frequently seen in 300–3000 bp–long clusters that have a large CG density (>55% CG material), and are typically found at the promoter of keeping genes (Antequera and Bird, 1993; Espada and Esteller, 2010). Recent research has demonstrated that as a person ages, specific CpG sites frequently become either hypermethylated or hypomethylated (Zhang et al., 2011).
The development of a biological profile is crucial for searching missing person reports in forensic investigations involving skeletal remains in order to identify probable matches and aid in victim identification (Cunha et al., 2009) Height, ancestry, sex, and age are frequently found in biological profiles. Thus, one of the crucial elements used for the recognition of human remains is age estimation.
A potential answer to this issue would be the use of biological methods that are based on the aging process. It used to be thought that the most reliable method for determining an adult's age was to racemize the aspartic acid in dentin. However, it has been demonstrated that a study of transmissible alterations in gene expression known as epigenetics (Egger et al., 2004) can be a useful and more precise technique for age prediction. It has been demonstrated that the process of epigenetic DNA methylation, which entails the inclusion of a methyl group to a cytosine nucleotide in CpG islands, is particularly beneficial (Declerck and Berghe, 2018).
This approach has its origins in earlier research that involved building "epigenetic clocks" based on the association between patterns of methylation and age. This assumption, together with the requirement to broaden the use of DNA methylation in the field of forensic anthropology, serves as the foundation for the review's objective, which is to examine the patterns of methylation in buccal swabs tissue from humans and link these patterns with age in order to improve existing age-at-death estimates (Horvath, 2013).
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