Forensic MicroRNA (miRNA) Analysis of Skin Specific Markers

Conventional body fluid identification methods are typically presumptive tests. These tests have a large number of false positives and because of this they are not confirmatory.
Messenger RNA (mRNA) profiling was developed as a body fluid identification method as it was determined that mRNAs are expressed in a tissue-specific manner. Unfortunately,
given mRNA’s size (~200-300 nucleotides), using this technique may not be ideal for compromised or degraded samples often encountered in forensic casework1.
MicroRNAs (miRNA) are small, non-protein coding RNA molecules approximately 22 nucleotides in length. The first miRNA was discovered by Rosalind Lee et al. in 1993, whilst
studying the lin-14 gene in C. elegans development2.
miRNAs are believed to control gene expression involved in metastasis, proliferation, apoptosis and differentiation3. A large number of cellular pathways are affected by the
regulatory function of miRNAs; the most notable of these pathways control oncogenic and developmental processes. It has also been found that miRNA processing defects can
enhance tumorigenesis4.
Many people argue that there is no need to test for the presence of a specific body fluid as the analysis of any DNA present can confirm a body fluid is present. This is true, DNA
won’t be present if a biological material isn’t present, but the confirmation of the body fluid could prove crucial in the investigation of a case. There is a need to identify skin
alongside other body fluids within forensic investigations, especially sexual offences. For example, it is not currently possible to distinguish between vaginal material and skin cells
from, for example, fingernail scrapings. Thus, in order to develop a technique that is capable of doing so, it is necessary to be able to identify skin cells.
The aim of this project was to determine whether skin, saliva and vaginal material (VM) could be correctly differentiated from one another using microRNA analysis.