The identification of forensically relevant human body fluids through messenger RNA (mRNA) profiling
is of interest to the forensic community. Previous studies have proposed several tissue-specific mRNA
markers to achieve this goal. Seven markers for the following genes were selected for evaluation in this
study: histatin 3 (HTN3) and statherin (STATH) for saliva, mucin 4 (MUC4) for vaginal secretions, matrix
metalloproteinase 7 (MMP7) for menstrual blood, delta-aminolevulinate synthase 2 (ALAS2) for
peripheral blood, and protamine 2 (PRM2) and transglutaminase 4 (TGM4) for semen. The expression of
these markers was examined in each body fluid. All mRNA markers were present in their target body
fluids. Peripheral blood and saliva showed little cross-reactivity with the selected markers. However, a
high level of cross-reactivity was observed between the vaginal secretion marker MUC4 and saliva stains.
Semen showed a high level of cross-reactivity with the selected markers. Co-expression of the predicted
body fluid markers was detected in menstrual blood and vaginal secretion stains. The expression pattern
of these mRNA markers varied through the menstrual cycle time points tested. Differences in gene
expression levels and marker cross-reactivity were observed in the donors tested. Despite the presence
of cross-reactivity and co-expression, each of the body fluids examined have distinct gene expression
profiles, allowing for body fluid identification based on mRNA profiling.