Preservation of and DNA Extraction from Muscle Tissue

As well as protecting DNA for subsequent analysis, tissue preservation methods ideally should be safe, readily available, and easy to transport at relatively low cost. Formalin (formaldehyde solution), used extensively to preserve medical and museum specimens, irreparably damages DNA. We have found four tissue preservatives (solid salt, salt-saturated dimethyl sulfoxide (DMSO)-EDTA solution, ethanol solution, and ethanol-EDTA solution) that preserved muscle tissue at 35 °C for up to 1 month: full short tandem repeat (STR) profiles were obtained after preservation. In addition, salt-saturated DMSO-EDTA solution yielded full STR profiles from aliquots of the liquid preservative surrounding muscle tissue.

DNA analysis in Disaster Victim Identification

DNA profiling and matching is one of the primary methods to identify missing persons in a disaster, as defined by the Interpol Disaster Victim Identification Guide. The process to identify a victim by DNA includes: the collection of the best possible ante-mortem (AM) samples, the choice of post-mortem (PM) samples, DNA-analysis, matching and statistical weighting of the genetic relationship or match. Each disaster has its own scenario, and each scenario defines its own methods for identification of the deceased.

Long-term room temperature preservation of corpse soft tissue: an approach for tissue sample storage

Background

Disaster victim identification (DVI) represents one of the most difficult challenges in forensic sciences, and subsequent DNA typing is essential. Collected samples for DNA-based human identification are usually stored at low temperature to halt the degradation processes of human remains. We have developed a simple and reliable procedure for soft tissue storage and preservation for DNA extraction. It ensures high quality DNA suitable for PCR-based DNA typing after at least 1 year of room temperature storage.

Methods

Fragments of human psoas muscle were exposed to three different environmental conditions for diverse time periods at room temperature. Storage conditions included: (a) a preserving medium consisting of solid sodium chloride (salt), (b) no additional substances and (c) garden soil. DNA was extracted with proteinase K/SDS followed by organic solvent treatment and concentration by centrifugal filter devices. Quantification was carried out by real-time PCR using commercial kits. Short tandem repeat (STR) typing profiles were analysed with 'expert software'.

Results

DNA quantities recovered from samples stored in salt were similar up to the complete storage time and underscored the effectiveness of the preservation method. It was possible to reliably and accurately type different genetic systems including autosomal STRs and mitochondrial and Y-chromosome haplogroups. Autosomal STR typing quality was evaluated by expert software, denoting high quality profiles from DNA samples obtained from corpse tissue stored in salt for up to 365 days.

Conclusions

The procedure proposed herein is a cost efficient alternative for storage of human remains in challenging environmental areas, such as mass disaster locations, mass graves and exhumations. This technique should be considered as an additional method for sample storage when preservation of DNA integrity is required for PCR-based DNA typing.

Simplified field preservation of tissues for subsequent DNA analyses

Successful DNA-based identification of mass disaster victims depends on acquiring tissues that are not highly degraded. In this study, multiple protocols for field preservation of tissues for later DNA analysis were tested. Skin and muscle samples were collected from decaying pig carcasses. Tissues were preserved using cold storage, desiccation, or room temperature storage in preservative solutions for up to 6 months. DNA quality was assessed through amplification of successively larger segments of nuclear DNA. Solution-based storage, including a DMSO/NaCl/EDTA mixture, alcohols, and RNAlater preserved DNA of the highest quality, refrigeration was intermediate, and desiccation was least effective. Tissue type and extent of decomposition significantly affected stored DNA quality. Overall, the results indicate that any tissue preservation attempt is far superior to delaying or forgoing preservation efforts, and that simple, inexpensive methods can be highly effective in preserving DNA, thus should be initiated as quickly as possible.

Comparison of short-term and long-term protocols for stabilization and preservation of RNA and DNA of Leishmania, Trypanosoma, and Plasmodium

Molecular tools continue to be important in the prevention and control of parasitic diseases. However, using these techniques directly in the field remains a major challenge. Therefore, the preservation of clinical samples collected from endemic field areas for later analysis remains an important preanalytical process. This study aimed at identifying a suitable protocol for stabilization and preservation of RNA and DNA in bioclinical specimens for Trypanosoma, Leishmania, and Plasmodium research. Both spiked and unspiked blood samples were preserved in 7 protocols (different media; storage temperatures). Samples were evaluated for possible degradation of DNA and RNA along the storage duration up to the 10th week. Nucleic acid targets were assessed as follows: (i) Trypanosoma and Plasmodium RNA analysis was done using real-time nucleic acid sequence-based amplification (RT-NASBA) for 18S rRNA and for stage-specific Pfs25 mRNA, respectively; (ii) Trypanosoma DNA assessment analysis was conducted by using a conventional PCR for 18S rDNA; (iii) Leishmania RNA analysis was performed with a quantitative NASBA for 18S rRNA and Leishmania DNA assessment with an RT-PCR for 18S rDNA. Findings suggested that a newly developed L3™ buffer proved to be reliable and suitable for both short- and long-term preservation of parasite nucleic acid material. This buffer is envisaged to be suitable for utilization in field situations where resources are limited.

The use of commercial alcohol products to sterilize bones prior to DNA sampling

In disaster situations it is not always possible to maintain an adequate supply of standard equipment and sterilizing solutions. We have compared bone samples from cadavers cleaned in commercial white alcohol to samples from the same individuals cleaned with 95% surgical spirit. We have found that it is possible to use a commercial, white spirit to clean specimens taken from human cadavers femoral diaphysis collected for DNA analysis.

DNA Commission of the International Society for Forensic Genetics (ISFG): recommendations regarding the role of forensic genetics for disaster victim identification (DVI)

The ISFG membership consists of scientists and medical professionals specialized in using genetic testing for kinship analysis and the individualization of biological material. This expertise makes the forensic geneticist a resource of advice to international and national organizations dealing with human identifications and causes many DNA laboratories to get involved in DVI tasks. The present recommendations are meant to educate more forensic geneticists about their potential involvement in mass fatality preparedness and possible DVI efforts, as well as to provide practical guidance for each of the laboratories' individual tasks. The idea to work on DNA-specific recommendations was born after a round table discussion dealing with the 2004 Tsunami disaster in south east Asia during the 21st congress of the International Society for Forensic Genetics on the Azores, Portugal, in September 2005. The ensuing discussion between scientists and pathologists that had been involved in the International Center in Khao Lak, Thailand, revealed the need for the scientific community to be better prepared to answer the local authorities' questions by formulating generally acceptable scientific standards for the most efficient use of DNA-based victim identification methods. These recommendations, as well as the many cited references, are intended to provide guidance on establishing preparedness for the forensic genetics laboratory, on collecting and storing ante-mortem and post-mortem samples suitable for DNA analysis, on DNA extraction and genetic typing strategies, on data management, and on issues related to the biostatistical interpretation and reporting of results.

Evaluation of a novel tagging and tissue preservation system for potential use in forensic sample collection

The authors describe a new, easy-to-use barcode-based tissue collection, preservation and body tracking system, which might prove instrumental in the containment of mass fatalities such as aircraft accidents, war related accidents, environmental disasters (e.g. earthquakes, hurricanes, and floods) terrorist bombings or mass murders.