A method of identifying the blood contributor in mixture stains through detecting blood‐specific mRNA polymorphism

Abstract

In the past decades, messenger RNA (mRNA) biomarkers have been employed to identify the origin of body fluids in forensic medicine. We hypothesized that the polymorphism of mRNA could be applied to identifying individuals in mixture samples composed of two body fluids. In this study, we selected 5 blood‐specific mRNA biomarkers of venous blood (SPTB, CD3G, AMICA1, ANK1, GYPA) that encompass 16 SNPs to identify the mixture contributor(s). Five specific gene markers for menstrual blood, semen, skin, saliva and vaginal secretions were amplified and typed as body‐fluid positive controls. We established the system of multiplex PCR and single base extension reaction (SBE) followed by capillary electrophoresis. The amplicon size was between 90bp‐294bp. The peripheral blood specificity was examined against other human body fluids, including saliva, semen, skin, menstrual blood, and vaginal secretion. The 16 SNPs were peripheral blood specific and could be successfully typed in home‐made mixtures which are composed of different body fluids with 1ng peripheral blood mRNA added. This system showed a super sensitivity (1:100) in detecting the trace amount of peripheral blood mixed in other body fluids and a combined discrimination power (CDP) of 0.99929 in Chinese population. It was the first time to establish a method of identifying the blood donors and deconvoluting mixtures through detecting mRNA polymorphism with SNaPshot assay. This peripheral blood‐specific SNP typing system showed high sensitivity to the typing of blood‐source specific markers regardless of other body fluids in the mixture. This article is protected by copyright. All rights reserved