Messenger RNA based skin identification using skin specific markers from fingerprint impressions

The study of forensic science may be complex especially in the areas of nucleic acids and trace evidence. Oftentimes, forensic scientists recover minute quantities of biological material from scenes therefore the need to generate the genetic profiles and identify the source of the material. The aim of this study is to determine the expression levels of skin-specific gene markers - Loricrin (LOR), Corneodesmosin (CDSN) and Keratine 9 (KRT9), on fingerprint impressions of individuals of specific age group and genders. Thumbprints were collected using labelled frosted microscope glass slides and cello tapes. Messenger RNA was extracted from the samples, converted to cDNA and amplified by qPCR with its specific primer sequences. In males, RNA yield was higher in the slide (26.96±8.68) compared to cello tape (18.32±4.52) while the reverse was the case in the females. Across gender, RNA purity and yield were higher in males than females. In males, KRT9, LOR and CDSN genes were more expressed using frosted slide (37.03±0.77, 40.46±2.66, 35.62±2.82) compared to cello tapes (35.33±0.3, 32.11±0.5, 35.28±0.86) respectively. In females, LOR, CDSN and ACTB genes were more expressed using frosted slides (36.26±0.8, 37.37±0.58, 26.63±0.12) compared to cello tapes (35.52±1.01, 35.57±3.22, 26.57±1.18) respectively. Across gender, LOR, KRT9 and ACTB genes were more expressed in males than females while CDSN was more expressed in females than males. The expression levels of CDSN and ACTB genes were significantly (p≤0.01) correlated. This study shows that mRNA markers LOR, CDSN and KRT9, analysed via the RT-qPCR assays, are highly suitable for identifying skin cells even in small traces.