Comprehensive body fluid identification and contributor assignment by combining targeted sequencing of mRNA and coding region SNPs.

Forensic genetic analyses aim to retrieve as much information as possible from biological trace material recovered from crime scenes. While standard short tandem repeat (STR) profiling is essential to individualize biological traces, its significance is diminished in crime scenarios where the presence of a suspect's DNA is acknowledged by all parties. In such cases, forensic (m)RNA analysis can provide crucial contextualizing information on the source level about a trace's composition, i.e., body fluids/tissues, and has therefore emerged as a powerful tool for modern forensic investigations. However, the question which of several suspects contributed a specific component (body fluid) to a mixed trace cannot be answered by RNA analysis using conventional methods. This individualizing information is stored within the sequence of the mRNA transcripts. Massively parallel sequencing (MPS) represents a promising alternative, offering not only higher multiplex capacity, but also the typing of individual coding region SNPs (cSNPs) to enable the assignment of contributors to mixture components, thereby reducing the risk of association fallacies. Herein, we describe the development of an extensive mRNA/cSNP panel for targeted sequencing on the IonTorrent S5 platform. Our panel comprises 30 markers for the detection of six body fluids/tissues (blood, saliva, semen, skin, vaginal and menstrual secretion), along with 70 linkage-controlled cSNPs for contributor assignment. It exhibited high reliable detection sensitivity with RNA inputs down to 0.75 ng and a conservatively calculated probability of identity of 0.03 - 6 % for individual body fluid-specific cSNP profiles. Limitations and areas for future work include RNA-related allele imbalances, inclusion of markers to correctly identify rectal mucosa and the optimization of specific markers. In summary, our new panel is intended to be a major step forward to interpret biological evidence at sub-source and source level based on cSNP attribution of a body fluid component to a suspect and victim, respectively.

Spitting in the wind?-The challenges of RNA sequencing for biomarker discovery from saliva.

Forensic trace contextualization, i.e., assessing information beyond who deposited a biological stain, has become an issue of great and steadily growing importance in forensic genetic casework and research. The human transcriptome encodes a wide variety of information and thus has received increasing interest for the identification of biomarkers for different aspects of forensic trace contextualization over the past years. Massively parallel sequencing of reverse-transcribed RNA ("RNA sequencing") has emerged as the gold standard technology to characterize the transcriptome in its entirety and identify RNA markers showing significant expression differences not only between different forensically relevant body fluids but also within a single body fluid between forensically relevant conditions of interest. Here, we analyze the quality and composition of four RNA sequencing datasets (whole transcriptome as well as miRNA sequencing) from two different research projects (the RNAgE project and the TrACES project), aiming at identifying contextualizing forensic biomarker from the forensically relevant body fluid saliva. We describe and characterize challenges of RNA sequencing of saliva samples arising from the presence of oral bacteria, the heterogeneity of sample composition, and the confounding factor of degradation. Based on these observations, we formulate recommendations that might help to improve RNA biomarker discovery from the challenging but forensically relevant body fluid saliva.

TrACES of time: Transcriptomic analyses for the contextualization of evidential stains - Identification of RNA markers for estimating time-of-day of bloodstain deposition.

Obtaining forensically relevant information beyond who deposited a biological stain on how and under which circumstances it was deposited is a question of increasing importance in forensic molecular biology. In the past few years, several studies have been produced on the potential of gene expression analysis to deliver relevant contextualizing information, e.g. on nature and condition of a stain as well as aspects of stain deposition timing. However, previous attempts to predict the time-of-day of sample deposition were all based on and thus limited by previously described diurnal oscillators. Herein, we newly approached this goal by applying current sequencing technologies and statistical methods to identify novel candidate markers for forensic time-of-day predictions from whole transcriptome analyses. To this purpose, we collected whole blood samples from ten individuals at eight different time points throughout the day, performed whole transcriptome sequencing and applied biostatistical algorithms to identify 81 mRNA markers with significantly differential expression as candidates to predict the time of day. In addition, we performed qPCR analysis to assess the characteristics of a subset of 13 candidate predictors in dried and aged blood stains. While we demonstrated the general possibility of using the selected candidate markers to predict time-of-day of sample deposition, we also observed notable variation between different donors and storage conditions, highlighting the relevance of employing accurate quantification methods in combination with robust normalization procedures.This study's results are foundational and may be built upon when developing a targeted assay for time-of-day predictions from forensic blood samples in the future.

Old meets new: Comparative examination of conventional and innovative RNA-based methods for body fluid identification of laundered seminal fluid stains after modular extraction of DNA and RNA.

The knowledge about the type of the body fluid/tissue that contributed to a trace can provide contextual insight into crime scene reconstruction and connect a suspect or a victim to a crime scene. Especially in sexual assault cases, it is important to verify the presence of spermatozoa. Victims often tend to clean their underwear/bedding after a sexual assault. If they later decide to report the crime to the police, in our experience, investigators usually do not send laundered items for DNA examination, since they believe that analysis after washing is no longer promising. As not only the individualization of traces on laundered items could be important in court, but also the type of biological material, we compared the potential of modular DNA and RNA extraction from the same specimen for simultaneous body fluid identification (BFI) and STR profiling of laundered items. BFI included the comparison of a broad range of conventional approaches, as wells as new molecular mRNA- and miRNA-based methods. The examination comprises the assessment of different fabrics and washing temperatures and multiple washing steps. Our results indicate that although conventional enzymatic and immunochromatographical approaches show limitations for BFI of laundered stains, the RSID test was sensitive enough to detect seminal fluid in 80% of all tested samples. Furthermore, the HY-Liter fluorescence analysis successfully detected spermatozoa, even in cloths that were washed twice. For the first time, it could be shown that a marker set of mRNAs can be applied for the identification of seminal fluid stained cotton and synthetic fiber fabrics that have been washed at 40 °C. Our experiments demonstrate that analysis of DNA and RNA of laundered items is feasible, giving the possibility to identify the perpetrator as well as the biological properties of the same laundered (seminal) stain under certain conditions.

Comprehensive examination of conventional and innovative body fluid identification approaches and DNA profiling of laundered blood- and saliva-stained pieces of cloths.

Body fluids like blood and saliva are commonly encountered during investigations of high volume crimes like homicides. The identification of the cellular origin and the composition of the trace can link suspects or victims to a certain crime scene and provide a probative value for criminal investigations. To erase all traces from the crime scene, perpetrators often wash away their traces. Characteristically, items that show exposed stains like blood are commonly cleaned or laundered to free them from potential visible leftovers. Mostly, investigators do not delegate the DNA analysis of laundered items. However, some studies have already revealed that items can still be used for DNA analysis even after they have been laundered. Nonetheless, a systematical evaluation of laundered blood and saliva traces that provides a comparison of different established and newly developed methods for body fluid identification (BFI) is still missing. Herein, we present the results of a comprehensive study of laundered blood- and saliva-stained pieces of cloths that were applied to a broad range of methods for BFI including conventional approaches as well as molecular mRNA profiling. The study included the evaluation of cellular origin as well as DNA profiling of blood- and saliva-stained (synthetic fiber and cotton) pieces of cloths, which have been washed at various washing temperatures for one or multiple times. Our experiments demonstrate that, while STR profiling seems to be sufficiently sensitive for the individualization of laundered items, there is a lack of approaches for BFI with the same sensitivity and specificity allowing to characterize the cellular origin of challenging, particularly laundered, blood and saliva samples.

Automation of DNA and miRNA co-extraction for miRNA-based identification of human body fluids and tissues.

In the last years, microRNA (miRNA) analysis came into focus in the field of forensic genetics. Yet, no standardized and recommendable protocols for co-isolation of miRNA and DNA from forensic relevant samples have been developed so far. Hence, this study evaluated the performance of an automated Maxwell® 16 System-based strategy (Promega) for co-extraction of DNA and miRNA from forensically relevant (blood and saliva) samples compared to (semi-)manual extraction methods. Three procedures were compared on the basis of recovered quantity of DNA and miRNA (as determined by real-time PCR and Bioanalyzer), miRNA profiling (shown by Cq values and extraction efficiency), STR profiles, duration, contamination risk and handling. All in all, the results highlight that the automated co-extraction procedure yielded the highest miRNA and DNA amounts from saliva and blood samples compared to both (semi-)manual protocols. Also, for aged and genuine samples of forensically relevant traces the miRNA and DNA yields were sufficient for subsequent downstream analysis. Furthermore, the strategy allows miRNA extraction only in cases where it is relevant to obtain additional information about the sample type. Besides, this system enables flexible sample throughput and labor-saving sample processing with reduced risk of cross-contamination.

Comparative evaluation of different extraction and quantification methods for forensic RNA analysis.

Since about 2005, there is increasing interest in forensic RNA analysis whose versatility may very favorably complement traditional DNA profiling in forensic casework. There is, however, no method available specifically dedicated for extraction of RNA from forensically relevant sample material. In this study we compared five commercially available and commonly used RNA extraction kits and methods (mirVana™ miRNA Isolation Kit Ambion; Trizol® Reagent, Invitrogen; NucleoSpin® miRNA Kit Macherey-Nagel; AllPrep DNA/RNA Mini Kit and RNeasy® Mini Kit both Qiagen) to assess their relative effectiveness of yielding RNA of good quality and their compatibility with co-extraction of DNA amenable to STR profiling. We set up samples of small amounts of dried blood, liquid saliva, semen and buccal mucosa that were aged for different time intervals for co-extraction of RNA and DNA. RNA quality was assessed by determination of 'RNA integrity number' (RIN) and quantitative PCR based expression analysis. DNA quality was assessed via monitoring STR typing success rates. By comparison, the different methods exhibited considerable differences between RNA and DNA yields, RNA quality values and expression levels, and STR profiling success, with the AllPrep DNA/RNA Mini Kit and the NucleoSpin® miRNA Kit excelling at DNA co-extraction and RNA results, respectively. Overall, there was no 'best' method to satisfy all demands of comprehensible co-analysis of RNA and DNA and it appears that each method has specific merits and flaws. We recommend to cautiously choose from available methods and align its characteristics with the needs of the experimental setting at hand.