Expression of statherin mRNA and protein in nasal and vaginal secretions

Nasal secretion has been regarded as one of the most difficult body fluids to identify and is especially difficult to discriminate from vaginal secretions and saliva. At present, few specific markers are known for nasal secretions. The aim of this study is to find a new approach for the identification of nasal secretions. We examined expression levels of statherin and histatin, peptides which are commonly found in saliva, in nasal and vaginal secretions by real-time RT-PCR and ELISA assays. Statherin mRNA was highly expressed in all nasal samples (dCt value=-1.49±1.10, n=8) and was detected even in 1-day-old 0.1-μL stains. However, the stability of mRNA in nasal stains was significantly (P<0.01) lower than in saliva. Low levels of statherin mRNA were detected in 4 of the 17 vaginal samples (dCt value=11.65-14.72). Histatin mRNA was not detected in any nasal or vaginal samples, although it was highly expressed in all saliva samples. ELISA assays with anti-statherin goat polyclonal antibody showed that statherin peptide was detected in all nasal and saliva samples even after dilution of more than 1000-fold. The statherin peptide was not detected in any vaginal samples, including samples that expressed low levels of statherin mRNA. The amount of statherin peptide in vaginal samples might be less than the limit of detection of this assay. In the present study, statherin was highly expressed in nasal secretions, but histatin was not. These markers may be useful for discriminating nasal secretions from vaginal secretions and saliva. However, the usefulness of these markers in practical forensic case samples has not yet been examined. Therefore, further research is required to establish the utility of these assays for identification of nasal secretions.