RNA Analysis in Forensic Molecular Biology

Abstract

Background: Different types of RNA take on multiple crucial functions in living cells and tissues. Messenger RNA (mRNA) is a temporary molecular carrier of genetic information. Analysis of the composition of all mRNA contained in a cell at a given moment, the so-called transcriptome, enables the determination of the type of cell and its condition, e.g., in pathologically altered states.

Methods: This review is based on pertinent publications retrieved by a selective literature search.

Results: The analysis of differential gene expression has already been used in forensic molecular biology to determine the type of tissue contained in biological specimens. It is also being used in criminal investigations to determine the composition of mixed traces of various bodily fluids and/or organ tissues. The method is limited by degradation of the mRNA molecules through environmental influences. The use of newly developed molecular biological methods such as massive parallel sequencing can expand the information obtainable by this investigative method. Current research also addresses the forensic potential of deriving relevant information about the crime-e.g., its timing, or the condition of the involved persons-from the totality of mRNA species present in the specimens.

Conclusion: Forensic RNA analysis can yield a great deal of relevant information. It is likely to be applicable in a much wider variety of forensic situations in the near future.

Figure 1

Flowchart of the co-analysis of DNA and RNA in forensic casework Co-extraction allows the simultaneous extraction of DNA and RNA from biological trace material. Specific regions of DNA (known as STR loci) are amplified in forensic DNA analysis. The combination of these amplified STR sequences produces a profile which, when compared with the profile of reference persons, enables an assessment of the origin of the trace. The extracted RNA is first converted to cDNA by reverse transcription. Transcripts specifically expressed in body fluid or organ tissues are amplified in multiplex PCR. Examination of these transcripts allows identification of the body fluids or organ tissue present in the trace sample. cDNA, complementary DNA; CE, capillary electrophoresis; PCR, polymerase chain reaction; STR, short tandem repeats

Figure 2

Schematic representation of the RNA sequence-based assignment of donors to the components of a mixed trace Donor A has the same expression in SNP 1 of his/her genomic DNA as cSNP 1 in the saliva-specific marker; however, the expression of SNP 2 in his/her genomic DNA does not match the cSNP 2 in the blood-specific marker; Donor B has the same expression in SNP 2 of his/her genomic DNA as cSNP 2 in the blood-specific marker; however, the expression of SNP 1 in his/her genomic DNA does not match cSNP 1 in the blood-specific marker. cSNP, complementary single nucleotide polymorphism, sequence with single nucleotide polymorphism resulting from reverse transcription of the mRNA (genetic variant); DNA-A, DNA of donor A; DNA-B, DNA of donor B

Figure 3

Versatility of forensic RNA analysis Summary of various application options for forensic RNA analysis. The current level of knowledge can be divided into three different categories which are presented in the Figure using colors and symbols. PMI, postmortem interval; SIDS, sudden infant death syndrome