New RNA methods for the identification of body fluids and cell types

Abstract

Messenger RNA profiling to identify forensically relevant body fluids is gaining popularity in forensic science. The question surrounding the specificity of body fluid markers can depend on the method used to detect the mRNA transcripts. Next generation sequencing (NGS) offers a new opportunity in forensic science. While optimised for use with high quality and high concentrations of template, we have shown that degraded RNA can be sequenced using NGS and have found that body fluid mRNA transcripts thought to be specific for one body fluid can be detected in other body fluids. However, while the mRNA transcript may be detected, mRNA gene expression does not always correlate to the level of protein present in the cell. While mRNA for human oestrogen receptor-1 (ESR-1) is not specific to vaginal samples, using a fluorescently labelled monoclonal antibody specific for ESR-1, we have been able to distinguish between vaginal and buccal epithelial cells. The vaginal cells were fluorescently labelled whereas the buccal cells showed little, if any, fluorescence. This promising result has potential to be used in forensic casework where the source of the epithelial cell and the resulting DNA profile is crucial to the case.