Simultaneous analysis of micro-RNA and DNA for determining the body fluid origin of DNA profiles

Micro-RNAs (miRNAs) can be specifically expressed in forensically relevant body fluids such as blood or saliva. The aim of the study was to develop a simultaneous extraction and analysis protocol that allows for the acquisition of a DNA profile and the identity of the body fluid using a single process. DNA and micro-RNA were extracted from blood and saliva before undergoing a cDNA synthesis step by using stem-loop reverse transcription PCR. The resulting extracts containing DNA and cDNA synthesized from body fluid-specific miRNA markers then underwent standard STR analysis using a modified ABI AmpFℓSTR(®) NGM SElect™ kit. In all samples, a full DNA profile was obtained along with additional peaks corresponding to the miRNA marker targeted. In all cases, blood samples profiled exhibited a peak indicating the presence of the blood-specific miRNA marker and the saliva sample profiled exhibited a peak indicating the presence of the saliva-specific miRNA marker.