The cellular origin of the biological sample

Over the past decade, DNA typing has grown to be a powerful method able to discriminate individuals from a variety of biological samples. Despite the enormous potential to determine a donor of a stain, DNA cannot be used to determine the origin of a biological sample. Current methods of detection of body fluids focus on tissue specific proteins, like for instance amylase present in saliva and hemoglobin present in blood. These tests are often not human specific (e.g. hemoglobin is also present in animal blood) or can give false positive/negative results due to chemical contamination. Especially in cases in which mixed DNA profiles have been obtained, information about the biological origin of the sample can provide valuable information.

RNA is becoming increasingly popular in the field of forensic genetics. Gene expression is often specific to certain tissue types enabling the use of tissue specific messenger RNA markers for body fluid identification. In project C of the FGCN project we will develop new multiplex reverse transcription – polymerase chain reaction assays for the absolute detection of human body fluids based on mRNA markers. The multiplexes will be developed for blood, menstrual blood, saliva, vaginal epithelia, semen and skin epithelia and will include preferably 2 genes per body fluid along with two housekeeping genes. Since isolation of both DNA and RNA from the same sample is desired, the biological samples will be subjected to a DNA/RNA co-isolation. The tissue specific markers used for this study are provided by partners of FGCN and are the result of extensive whole-genome gene expression analyses. An important feature of these markers is the proven strong stability over time enabling RNA profiling of old samples. Also known markers from literature are included.

The use of mRNA markers will enable the absolute determination of body fluids which is suitable for use in court of law without having the problems encountered using presumptive tests.