RNA/DNA co-analysis from blood stains--results of a second collaborative EDNAP exercise.

A second collaborative exercise on RNA/DNA co-analysis for body fluid identification and STR profiling was organized by the European DNA Profiling Group (EDNAP). Six human blood stains, two blood dilution series (5-0.001 µl blood) and, optionally, bona fide or mock casework samples of human or non-human origin were analyzed by the participating laboratories using a RNA/DNA co-extraction or solely RNA extraction method. Two novel mRNA multiplexes were used for the identification of blood: a highly sensitive duplex (HBA, HBB) and a moderately sensitive pentaplex (ALAS2, CD3G, ANK1, SPTB and PBGD). The laboratories used different chemistries and instrumentation. All of the 18 participating laboratories were able to successfully isolate and detect mRNA in dried blood stains. Thirteen laboratories simultaneously extracted RNA and DNA from individual stains and were able to utilize mRNA profiling to confirm the presence of blood and to obtain autosomal STR profiles from the blood stain donors. The positive identification of blood and good quality DNA profiles were also obtained from old and compromised casework samples. The method proved to be reproducible and sensitive using different analysis strategies. The results of this collaborative exercise involving a RNA/DNA co-extraction strategy support the potential use of an mRNA based system for the identification of blood in forensic casework that is compatible with current DNA analysis methodology.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry-based single nucleotide polymorphism genotyping assay using iPLEX gold technology for identification of Mycobacterium tuberculosis complex species and lineages.

The major goal of the present study was to investigate the potential use of a novel single nucleotide polymorphism (SNP) genotyping technology, called iPLEX Gold (Sequenom), for the simultaneous analysis of 16 SNPs that have been previously validated as useful for identification of Mycobacterium tuberculosis complex (MTBC) species and classification of MTBC isolates into distinct genetic lineages, known as principal genetic groups (PGGs) and SNP cluster groups (SCGs). In this context, we developed a 16-plex iPLEX assay based on an allele-specific-primer single-base-extension reaction using the iPLEX Gold kit (Sequenom), followed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis on the commercially available Sequenom MassARRAY platform. This assay was tested on a panel of 55 well-characterized MTBC strains that were also genotyped for the same loci using the previously reported SNaPshot assay, as well as 10 non-MTBC mycobacteria and 4 bacteria not belonging to the genus Mycobacterium. All MTBC samples were successfully analyzed with the iPLEX assay, which yielded clear allelic data for 99.9% of the SNPs (879 out of 880). No false-positive results were obtained with the negative controls. Compared to the SNaPshot assay, the newly developed 16-plex iPLEX assay produced fully concordant results that allowed reliable differentiation of MTBC species and recognition of lineages, thus demonstrating its potential value in diagnostic, epidemiological, and evolutionary applications. Compared to the SNaPshot approach, the implementation of the iPLEX technology could offer a higher throughput and could be a more flexible and cost-effective option for microbiology laboratories.

mRNA profiling for the identification of blood--results of a collaborative EDNAP exercise.

A collaborative exercise on mRNA profiling for the identification of blood was organized by the European DNA Profiling Group (EDNAP). Seven blood samples and one blood dilution series were analyzed by the participating laboratories for the reportedly blood-specific markers HBB, SPTB and PBGD, using different kits, chemistries and instrumentation. The results demonstrate that HBB is expressed abundantly in blood, SPTB moderately and PBGD significantly less. All but one of the 16 participating laboratories were able to successfully isolate and detect RNA from the dried bloodstains even though a majority of the laboratories had no prior experience with RNA. Despite some expected variation in sensitivity between laboratories, the method proved to be reproducible and sensitive using different analysis strategies. The results of this collaborative exercise support the potential use of mRNA profiling as an alternative to conventional serological tests.

Identification and genotyping of Mycobacterium tuberculosis complex species by use of a SNaPshot Minisequencing-based assay.

The aim of the present study was to investigate the use of the SNaPshot minisequencing method for the identification of Mycobacterium tuberculosis complex (MTBC) isolates to the species level and for further genotyping of M. tuberculosis isolates. We developed an innovative strategy based on two multiplex allele-specific minisequencing assays that allowed detection of eight species-specific and eight lineage-specific single nucleotide polymorphisms (SNPs). Each assay consisted of an eightplex PCR amplification, followed by an eightplex minisequencing reaction with the SNaPshot multiplex kit (Applied Biosystems) and, finally, analysis of the extension products by capillary electrophoresis. The whole strategy was developed with a panel of 56 MTBC strains and 15 negative controls. All MTBC strains tested except one M. africanum clinical isolate were accurately identified to the species level, and all M. tuberculosis isolates were successfully further genotyped. This two-step strategy based on SNaPshot minisequencing allows the simultaneous differentiation of closely related members of the MTBC, the distinction between principal genetic groups, and the characterization of M. tuberculosis isolates into one of the seven prominent SNP cluster groups (SCGs) and could be a useful tool for diagnostic and epidemiological purposes.

First successful assay of Y-SNP typing by SNaPshot minisequencing on ancient DNA.

In the present study, a set of 13 Y-chromosomal single nucleotide polymorphisms (Y-SNPs) selected for the identification of the most frequent Asian Y-haplogroups was included in an allele-specific primer extension assay. Single nucleotide polymorphism (SNP) genotyping was accomplished by co-amplification of these 13 DNA fragments within 2 multiplex PCRs followed by detection with 1 minisequencing reaction using the SNaPshottrade mark Multiplex kit and analysis of extension products by capillary electrophoresis. First developed on modern samples, the assay was optimized for the analysis of 11 ancient DNA (aDNA) samples from the Krasnoyarsk region (southern Siberia) that were dated from 5,500-1,800 years before present (YBP). SNP typing was successful for most of them, which were all assigned to Y-haplogroup R1a1 except one. These results show that SNPs are well-suited for the analysis of aged and degraded DNA samples. Moreover, we found that the SNaPshot minisequencing methodology is a convenient, robust, and efficient method for SNP typing. To our knowledge, this study reports the first successful investigation of Y-SNPs on aDNA samples. The potential use of Y-SNPs in both evolutionary and forensic fields is also discussed.