The screening and validation of lnc-SLC25A39 and lnc-LINC00279-202 for distinguishing tissue origins of peripheral blood and semen samples by RT-qPCR

RNA markers have attracted widespread attention in the field of body fluid identification due to their tissue specificity and relative stability. Long RNAs including message RNA (mRNAs) and long non-coding RNAs (lncRNAs) have a higher probability of containing more polymorphic sites and can be used to identify specific body fluid samples of the donors, however, people suspect that these long RNAs may not be conducive to the identification of degraded samples. The mRNA markers have been reported in multiple studies to be used to identify the tissue origins of forensic body fluids. However, few studies have shown the forensic application of the lncRNA in identifying tissue origins of body fluid samples. In this study, two lncRNAs (lnc-SLC25A39 and lnc-LINC00279-202) were screened out and combined with two previously popular mRNA markers (HBB and PRM1) to distinguish the peripheral blood (PB) from other kinds of body fluids, or semen (SE) from other kinds of body fluids. RT-qPCR validation experiments revealed that lnc-SLC25A39 was the PB-specific marker; and lnc-LINC00279-202 was the SE-specific marker in both single- and mixed-origin samples, and this is consistent with the results of ten machine-learning models. Furthermore, the stability of these selected RNAs was demonstrated when the PB and SE samples have exposed to room temperature for a period of one year. The results of this study indicate that the application of lncRNA may offer a novel approach for the tissue origin identifications of different kinds of body fluids.