The TV franchise CSI: Crime Scene Investigation makes it seem like analyzing biological samples in a criminal investigation is as simple as pushing a button on a fancy gizmo and having the results printed out within seconds. (Of course, they also solve complex mysteries in under an hour every week, so I guess you can’t believe everything you see on TV.) It’s not quite so easy…yet, but researchers are creating clever new techniques to help; like this one that uses miRNAs to tell investigators what body fluid a sample came from.
Previous work, from groups like Jack Ballantyne’s at University of South Florida, who presented his findings (Analytical Biochemistry, April 2009) at the recent 2010 CHI Molecular Medicine Tri-Conference, have shown that miRNAs make for great markers of body fluids due mostly to their small-size, resistance to degradation, and tissue specificity.
Research published this week by scientists at Erasmus University Medical Center Rotterdam examined the miRNA profile of five different types of bodily fluid. These fluids were easily distinguishable by their miRNA microarray profiles, but that method isn’t so practical for the needs of a forensics laboratory. So to confirm their screening results, and develop a more sensitive assay for labs to use, they put the same samples through some TaqMan-based multiplex RT-PCR assays, and were able to come up with a workable set of miRNA markers.
The Dutch group also found that:
- They could clearly identify venous blood and semen
- Markers for menstrual blood, saliva, and vaginal secretion – found by microarray – weren’t as clear cut by RT-PCR, perhaps due to non-specific binding of the array probes and/or natural bacterial and fungal contamination in those samples
- Samples could be stored in the lab for up to a year without loss of results
- Markers were detectable by RT-PCR using as little as 2pg (0.1 pg/reaction) of total RNA. That’s down to the amount in a single cell
To conduct your own investigation of the miRNAs markers they identified, and what still needs to be worked out, check out the International Journal of Legal Medicine, February 2010