Results of a collaborative study on DNA identification of aged bone samples

Costal cartilage ensures low degradation of DNA needed for genetic identification of human remains retrieved at different decomposition stages and different postmortem intervals

Introduction

The study aimed to evaluate if costal cartilage is a good source of DNA for genetic individual identification tests performed in forensic autopsies.

Materials and Methods

The study included samples of costal cartilage collected from 80 cadavers retrieved from different environments: indoors (flat/hospital), outdoors (primarily in the forest), a coal mine, a fire site, uninhabited buildings, a basement, bodies of fresh water, exhumation sites, and unknown locations. After isolation of DNA chondrocytes, T. Large autosomal chromosome (214 bp), T. Small autosomal chromosome (80 bp), and the Y chromosome (75 bp; for male cadavers), sequences were amplified using real-time PCR. Additionally, 23 autosomal short tandem repeat (STR) loci and 16 Y chromosome STR loci were amplified using multiplex PCR. Forensic DNA typing was done using capillary electrophoresis and all results were analyzed.

Results

There was no statistically significant difference in DNA concentration after T. Large, T. Small autosomal chromosome and the Y chromosome amplification between samples collected from cadavers retrieved from different environments. The DNA degradation index was the same regardless of the postmortem interval. The results show that it is possible to generate a full genetic profile from costal cartilage samples collected from cadavers retrieved from different environments and at different times elapsed after death.

Conclusions

The results suggest that costal cartilage can be routinely collected during forensic autopsies, especially from cadavers at the advanced decomposition stage.

Progress in forensic bone DNA analysis: Lessons learned from ancient DNA

Research on ancient and forensic DNA is related in many ways, and the two fields must deal with similar obstacles. Therefore, communication between these two communities has the potential to improve results in both research fields. Here, we present the insights gained in the ancient DNA community with regard to analyzing DNA from aged skeletal material and the potential use of the developed protocols in forensic work. We discuss the various steps, from choosing samples for DNA extraction to deciding between classical PCR amplification and massively parallel sequencing approaches. Based on the progress made in ancient DNA analyses combined with the requirements of forensic work, we suggest that there is substantial potential for incorporating ancient DNA approaches into forensic protocols, a process that has already begun to a considerable extent. However, taking full advantage of the experiences gained from ancient DNA work will require comparative studies by the forensic DNA community to tailor the methods developed for ancient samples to the specific needs of forensic studies and case work. If successful, in our view, the benefits for both communities would be considerable.

Large fragment demineralization: an alternative pretreatment for forensic DNA typing of bones

In forensic genetics, the analysis of postmortem bones is one of the most challenging due to the low quantity of degraded endogenous DNA. The most widely used approach for sample preparation, in those cases, is pulverizing the bone. However, processing pulverized bone is extremely delicate, requiring strict laboratory conditions and operating procedures. In fact, several recent publications have focused on non-powder approaches. The objectives of this study were, thus, to validate a non-powder protocol for DNA extraction from forensic bones and an alternative pretreatment, large fragment demineralization (LFD). Thirty human femurs and tibiae received by the Legal Medicine Institute of Brescia, Italy, were included in the study. Bone powder and one transversal section of the diaphysis were sampled from each bone. DNA extraction from the powder was carried out using PrepFiler BTA (BTA), while the transversal section was submitted to the alternative demineralizing pretreatment (LFD) followed by DNA extraction using the QIAamp DNA Investigator. DNA extracts were assessed for human DNA quantity and degradation by means of a validated in-house qPCR assay and amplified with commercial kits. Inhibition assessment was carried out through Quality Sensor analysis using 24plex QS Kit. The differences in quantity, quality of human DNA, and number of alleles detected between both methods were comparable and not statistically significant. We propose the use of the LFD protocol as a complementary approach capable of confirming the genotypes or detect alleles not observed using BTA, without the need for pulverization.

Histomorphological aspects of cadaveric skin and its possible use in forensic genetics

The skin is rarely considered as good biological material for successful DNA typing when a corpse is found in a leathery, mummified or partially skeletonised state, as bones and teeth are the gold standard in these cases. This study evaluates the histomorphological aspects of nuclear chromatin (Lillie's staining) in leathery and mummified skin samples as an indicator for possible successful DNA typing. Chromatin was found in samples that underwent mummification or partial skeletonisation but not in samples in a wet type of post-mortem transformation, such as saponification or leathery transformation. As a preliminary result, a positive detection of DNA profiles was only observed in 1-year-old mummified or partially skeletonised samples. These findings suggest that specific areas of skin, even from severely deteriorated cadavers, can show nuclear chromatin and DNA. These preliminary results raise the potential use of skin samples as an alternative source of DNA in highly degraded corpses.

Identification of human remains using Rapid DNA analysis

Rapid identification of human remains following mass casualty events is essential to bring closure to family members and friends of the victims. Unfortunately, disaster victim identification, missing persons identification, and forensic casework analysis are often complicated by sample degradation due to exposure to harsh environmental conditions. Following a mass disaster, forensic laboratories may be overwhelmed by the number of dissociated portions that require identification and reassociation or compromised by the event itself. The interval between the disaster and receipt of victim samples at a laboratory is critical in that sample quality deteriorates as the postmortem interval increases. When bodies decompose due to delay in collection, transport, and sample processing, DNA becomes progressively fragmented, adversely impacting identification. We have previously developed a fully automated, field-forward Rapid DNA identification system that produces STR profiles (also referred to as DNA IDs or DNA fingerprints) from buccal and crime scene samples. The system performs all sample processing and data interpretation in less than 2 h. Here, we present results on Rapid DNA identification performed on several tissue types (including buccal, muscle, liver, brain, tooth, and bone) from exposed human bodies placed above ground or stored in a morgue/cooler, two scenarios commonly encountered following mass disasters. We demonstrate that for exposed remains, buccal swabs are the sample of choice for up to 11 days exposure and bone and tooth samples generated excellent DNA IDs for the 1-year duration of the study. For refrigerated remains, all sample types generated excellent DNA IDs for the 3-month testing period.