Exploration of RNA degradation in dried body fluid stains as a means of estimating the age of the samples

The investigation of a crime generally involves answering the question of who, what, where, and when. Of these questions, forensic genetic technologies are presently unable to answer the question of when within the context of the age of a biological crime scene sample. In previous studies from this laboratory, the transcriptomes of body fluid stains aged for periods of up to a year were analyzed to explore a possible correlation between age and degree of RNA degradation. Transcripts were identified that exhibit degradation kinetics that suggest a correlation with sample age. RNA sequencing results also suggested that the 5' end of a transcript degrades faster than the 3' end. This observation spawned the development of a modified qPCR assay that quantifies the 5' and 3' ends of a panel of transcripts enabling a standard curve of delta Ct (5' Ct minus 3' Ct) versus sample age to be created. This assay has demonstrated accuracy and reliability in estimating the age of dried bloodstains and holds potential to be easily transferred to the forensic DNA laboratory for this purpose. To date, body fluid stains have been stored under rather ideal conditions in the laboratory. The project proposed here is to investigate the effects of the environment on RNA degradation. Temperature, humidity, sunlight exposure, and the substrate a stain is deposited on will be systematically evaluated for their effects on the degradation kinetics of RNA transcripts compared with kinetics for stains stored in the lab. If environmental effects are observed, it is proposed that the effect of those conditions will be reflected in changes to the rate constants for degradation of the different markers, and that those changes can be incorporated into an algorithm that estimates age. One anticipated outcome of the project will be the development of a reliable technology with which to age biological evidence; perhaps with the development of a qPCR kit for that purpose. The proposed project will also explore more deeply the RNA degradation process in tissues in hopes of exploring the application of the technology with the determination of the postmortem interval and the age of skeletal remains.

This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14).

CA/NCF