The use of FTA cards to acquire DNA profiles from postmortem cases.

Filter papers have been used for many years in different applications of molecular biology and have been proven to be a stable way to store DNA waiting to be analyzed. Sampling of DNA on FTA (Flinders Technology Associates) cards is convenient and cost effective compared to alternative approaches involving DNA extractions and storage of DNA extracts. FTA cards are analyzed at many forensic laboratories, and the way to perform direct genetic profiling on buccal swab cards has developed into an almost industrial process. The possibility to include postmortem (PM) samples into an FTA-based workflow would facilitate and speed up the genetic identification process compared to conventional methods, both on a regular basis and in a mass casualty event. In this study, we investigated if FTA cards may be used to carry tissue DNA from deceased and present a high-quality DNA profile from the individual in order to be useful for the identification process. The study also aimed to investigate if a specific body tissue would be preferable, and if decomposed tissue is suitable at all to put on an FTA card in order to obtain a DNA profile. We have compared the quality of the DNA profiles acquired from postmortem tissue on FTA cards, with the results acquired with conventional methods from reference bone/muscle samples from the same individual. Several types of tissues have been tested from different identification cases and scenarios. We concluded that tissue cells from inner organs are suitable to put on FTA cards, and that the obtained DNA profiles have the potential to serve as PM data for identification purposes. In cases including compromised samples, however, it is recommended to keep the tissue sample as a backup if further DNA has to be extracted.

DNA identification of compromised samples with massive parallel sequencing.

Genetic profiling is a standard procedure for human identification, i.e. in criminal cases and mass disasters, and has been proven to be an important part in the process in the repatriation of victims to their relatives. In the event of a catastrophe whether it be a natural disaster, terror attack or accident, fatalities of many nationalities may be a consequence and international collaboration becomes necessary. Current DNA techniques used on a routine basis at forensic laboratories world-wide are very useful, and results reported from different labs are compared, making it possible to be matched in order to declare the identification of a victim. Statistical calculations of possibilities of a random match are achievable since population data from many parts of the world are available. However, decomposition and degradation of the remains are not uncommon in the aftermath of a catastrophe and hence it may be difficult to retrieve detailed DNA profiles from such samples. Massive parallel sequencing (MPS) is a technique capable of producing a vast amount of DNA sequence data in a high-through put manner, and panels of single nucleotide polymorphism (SNP) markers allow the amplification of small DNA fragments, often seen in compromised samples. Here, we report the results from a set of 10 samples from missing person identification cases, analyzed with an MPS based method comprising 131 SNP markers and compared with direct reference material or buccal swab samples collected from relatives of the deceased. We assess the weight of evidence of a match by statistical calculation. Furthermore, we compare results reported on different platforms using different SNP panels, and conclude that more work has to be done if results from missing person identification cases analyzed on MPS with SNP panels at different laboratories are to be fully reliable and thus comparable.

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.

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.

Genetic variation of 15 autosomal STR loci in a Somali population.

Allele frequencies for 15 autosomal STR loci included in the AmpFlSTR Identifiler kit (CSF1PO, D13S317, D16S539, D18S51, D19S433, D21S11, D2S1338, D3S1358, D5S818, D7S820, D8S1179, FGA, TH01, TPOX, VWA) were obtained from the analysis of 404 individuals with Somali origin. The overall match probability for the 15 studied loci was 1 in 1.18 x 10(17) and the combined power of exclusion was 0.999997676. Deviation from Hardy-Weinberg equilibrium was observed for locus D2S1338 after correction for multiple testing. When comparing allele frequencies with five other African populations (Karamoja (Uganda), Mozambique, Tanzania and two other Somali population sample sets), only the Somali populations did not show significant differences for any of the tested loci.

STR data for the AmpFlSTR Identifiler loci from Swedish population in comparison to European, as well as with non-European population.

The modern Swedish population is a mixture of people that originate from different parts of the world. This is also the truth for the clients participating in the paternity cases investigated at the department. Calculations based on a Swedish frequency database only, could give us overestimated figures of probability and power of exclusion in cases including clients with a genetic background other than Swedish. Here, we describe allele frequencies regarding the markers in the Identifiler-kit. We have compared three sets of population samples; Swedish, European and non-European to investigate how these three groups of population samples differ. Also, all three population sets were compared to data reported from other European and non-European populations. Swedish allele frequencies for the 15 autosomal STRs included in the Identifiler kit were obtained from unrelated blood donors with Swedish names. The European and non-European frequencies were based on DNA-profiles of alleged fathers from our paternity cases in 2005 and 2006.

Analysis of linkage and linkage disequilibrium for eight X-STR markers.

X-chromosomal short tandem repeats (X-STR) have proven to be informative and useful in complex relationship testing. The main feature of X-STR markers, compared to autosomal forensic markers, is that all loci are located on the same chromosome. Thus, linkage and linkage disequilibrium may occur. The aim of this work was to study population genetic parameters of eight X-STR markers, located in four linkage groups. We present haplotype frequencies, based on 718 Swedish males, for the four linkage groups included in the Argus X-8 kit. Forensic efficiency parameters have been calculated as well as the allelic association between the tested markers for detection of linkage disequilibrium. To study the occurrences of recombination between the loci, both Swedish and Somali families were typed. A mathematical model for the estimation of recombination frequencies is presented and applied on the family samples. Our study showed that the tested markers all have highly informative forensic values and that there is a significant degree of linkage disequilibrium between the STR markers within the four linkage groups. Furthermore, based on the tested families, we also demonstrated that two of the linkage groups are partially linked. A consequence of these findings is that both linkage and linkage disequilibrium should be accounted for when producing likelihood ratios in relationship testing with X-STR markers.