Use of fluorescence in situ hybridisation and laser microdissection to isolate male non-sperm cells in cases of sexual assault

Evaluation of three DNA extraction protocols for forensic STR typing after laser capture microdissection

In forensic sciences, short tandem repeat (STR) analysis is a valuable tool in identifying the donor(s) of biological stains. Laser capture microdissection (LCM) can be used as a cell separating technique to isolate specific cell types in mixed samples. An important challenge lies in the development of a DNA isolation method appropriate for laser microdissected cells, as these samples usually contain minute amounts of cells. In this study three different DNA isolation methods for LCM collected cells were compared. The PicoPure DNA extraction method outperformed both other methods (IQ™ system and short alkaline method). Consequently, the minimal number of LCM collected cells necessary for STR typing was determined. Using the PicoPure DNA extraction method, full DNA profiles could be obtained from as little as 10 cells. Nevertheless, despite the occurrence of allelic drop out in some of the samples, lower amounts of cells gave rise to useful DNA profiles.

Laser capture microdissection in forensic research: a review

In forensic sciences, short tandem repeat (STR) analysis has become the prime tool for DNA-based identification of the donor(s) of biological stains and/or traces. Many traces, however, contain cells and, hence, DNA, from more than a single individual, giving rise to mixed genotypes and the subsequent difficulties in interpreting the results. An even more challenging situation occurs when cells of a victim are much more abundant than the cells of the perpetrator. Therefore, the forensic community seeks to improve cell-separation methods in order to generate single-donor cell populations from a mixed trace in order to facilitate DNA typing and identification. Laser capture microdissection (LCM) offers a valuable tool for precise separation of specific cells. This review summarises all possible forensic applications of LCM, gives an overview of the staining and detection options, including automated detection and retrieval of cells of interest, and reviews the DNA extraction protocols compatible with LCM of cells from forensic samples.

Isolating cells from non-sperm cellular mixtures using the PALM® microlaser micro dissection system

Use of the Positioning Ablation Laser MicroBeam (PALM) microlaser system to isolate specific cellular components from somatic cellular mixtures (blood and saliva) prior to DNA extraction and typing is compared with routine DNA extraction and typing of the same mixture samples. Mixtures of blood and saliva at differing ratios generated complex DNA profiles that included allele peaks originating from each of the donors, or just those of the major contributor. Isolation of cells with the PALM microlaser prior to DNA extraction allowed informative, single-source, DNA profiles to be generated from a known cell type/origin.