Characterization of cellular and extracellular DNA in saliva

Although the presence of extracellular DNA in various body fluids was discovered long ago, only recently has it begun to attract attention for examining the genetic profiles of individuals in forensics studies. However, information on extracellular DNA is scarce. Among human body fluids, saliva is known to be rich in extracellular DNA. In this study, to analyze the possibility of identifying individuals and body fluids by using only extracellular DNA of saliva, we investigated the amount, size distribution, short tandem repeat (STR) profile, and methylation pattern of extracellular DNA from saliva and compared these with those of cellular DNA. The amount and size distribution of extracellular DNA was different from that of cellular DNA. However, their respective STR profiles were the same. The methylation patterns of the BCAS4 gene were different among donors, but no significant difference was observed between cellular and extracellular DNA. The results of our study suggest that identification of individuals and body fluids from saliva may be possible without the need for cells.