Specific micro-RNA signatures for the detection of saliva and blood in forensic body-fluid identification

Micro-RNAs (miRNAs) are a class of small noncoding RNA (ncRNA) molecules with a length of 18-24 nucleotides which play an essential regulative role for many cellular processes. Evidence suggests that the miRNome is a more precise and meaningful representation of a cell type and condition than the mRNA transcriptome. To identify miRNAs that are suitable for forensic body-fluid identification, a global screening by microarray analysis of c. 800 miRNAs of forensic blood and saliva samples was performed, and by bioinformatic processing, three differentially expressed candidate miRNAs for saliva and blood each were selected. The six candidates were then validated and confirmed via quantitative PCR. Herein, we present miRNA assays consisting of three differentially expressed miRNAs for the identification of blood (miR-126, miR-150, miR-451) and saliva (miR-200c, miR-203, miR-205), respectively. We conclude that miRNA extraction from forensic samples is possible and support a "proof of concept" that body-fluid identification by miRNA analysis may become a potent forensic technique.