Evaluation of post-PCR purification methods and subsequent optimisation of the MinElute® PCR Purification Kit for low input DNA samples amplified with PowerPlex® 21.

Weak and partial DNA profiles are commonly encountered within forensic casework due to amplification of low DNA input samples. One option for increasing allelic detection in such samples is the purification of amplified PCR product using commercially available column-based methods. In this study, four commercially available post-PCR purification methods, QIAGEN MinElute®, Independent Forensics Amplicon™ Rx, Millipore Microcon® and Thermo Fisher Scientific ExoSAP-IT™ were evaluated, comparing the quality of PowerPlex® 21 DNA profiles produced to the standard DNA profile generated prior to purification. An increased detection of alleles above the analytical threshold was observed following purification with the MinElute®, Amplicon™ Rx and Microcon® methods, allowing informative DNA profiles to be recovered using as little as 8 pg DNA. However, post-PCR purification using the ExoSAP-IT™ kit was unsuccessful, with no alleles detected above analytical threshold in samples with ≤16 pg DNA. The MinElute® kit was selected for optimisation on the basis of DNA profile quality, including increased detection of alleles and minimal artefacts. The MinElute® method was optimised by evaluating the number of washes and final elution buffer volume, resulting in a further increase in detection of alleles by reducing the elution buffer volume. Overall, this study showed that PowerPlex® 21 DNA profiles from low input DNA can be successfully enhanced by employing the MinElute® post-PCR purification method.

Interpretation and reporting considerations of low-level DNA profiles following MinElute® purification of PowerPlex® 21 amplified products.

The generation of high-quality DNA profiles from trace amounts of DNA continues to be an issue in forensic casework. Several methods have been proposed over the years to increase recovery rates for low input DNA, including purification of PCR products, an increase in PCR cycle numbers and increasing injection time or voltage during electrophoresis. In this study, the characteristics of DNA profiles generated using QIAGEN MinElute® purification of Promega PowerPlex® 21 amplified products for low DNA input samples, ranging from 80 pg down to 4 pg, were evaluated. MinElute® purification was found to be a simple, effective and time efficient method, which can greatly improve the resolution of amplified PCR products, recovering 100% of donor concordant alleles from as little 16 pg of input template DNA and generating sufficient allelic information for interpretation from as low as 4 pg inputs. However, as is commonly observed with low template DNA samples, the results exhibited extensive disparity in the effects of stochastic variation in amplification, including increased heterozygote peak height imbalance, stutter ratios and instances of allelic drop-in and drop-out, both within and between replicates. As such, it is important that the extent and variability of these stochastic effects are appropriately incorporated in the development of robust profile interpretation guidelines for DNA profiles generated from purified PCR products.

Developmental validation of an efficient differential separation method incorporating the i-sep® DL spin column with high sperm DNA recovery for the processing of sexual assault samples.

The differential separation method is key to recovering a DNA profile of the sperm donor from sexual assault samples. However, low numbers of spermatozoa from the perpetrator are often swamped by the victim's epithelial cells or lost during the separation process, with the separation process labor-intensive, time-consuming, and operator-dependent. The self-sealing filter of the i-sep® DL spin column allows direct lysis of the substrate throughout the differential separation process while preventing intact sperm cells from passing through, maximizing DNA recovery, and separation of non-sperm and sperm cells present. This study investigated the efficacy of a modified differential separation method, which incorporated the i-sep® DL spin column in comparison with the conventional pellet-based differential separation method. Using semen dilution series and mock post-coital samples, the sensitivity, reproducibility, repeatability, and efficiency of sperm DNA recovery of the pellet-based differential to the i-sep® method were evaluated side by side. The i-sep® differential method was more sensitive in capturing sperm fraction DNA, with informative semen donor alleles detected from high dilutions of semen inputs where the pellet method has been unsuccessful. The i-sep® differential method reduces manual handling, generating repeatable, and reproducible results between operators. Re-extraction of samples previously processed by the pellet or i-sep® differential method showed that the pellet method failed to recover 15-88% of sperm fraction DNA, while the i-sep® differential method was able to recover >99% in the initial extraction. The i-sep® method is robust for processing sexual assault samples, overcoming the challenges of sperm DNA losses encountered by pellet-based methods.

Fusobacterium nucleatum and Bacteroides fragilis detection in colorectal tumours: Optimal target site and correlation with total bacterial load.

BACKGROUND: Mucosal infiltration by certain bacterial species may contribute to the development and progression of colorectal cancer (CRC). There is considerable variation in reported detection rates in human CRC samples and the extent to which bacterial infiltration varies across regions of the primary tumour is unknown. This study aimed to determine if there is an optimal site for bacterial detection within CRC tumours. METHODS: Presence of target bacterial species was assessed by quantitative real-time PCR (qPCR) in 42 human CRC tumours. Abundance in primary tumour regions, normal epithelium and at metastatic sites was investigated in an expanded cohort of 51 patients. Species presence/absence was confirmed by diversity profiling in five patients. Correlation with total bacterial load and clinicopathological features was assessed. RESULTS: Fusobacterium nucleatum and Bacteroides fragilis were detected in tumours from 43% and 24% of patients, respectively (17% positive for both species). The optimal detection site was the tumour luminal surface (TLS). Patients testing positive at the TLS frequently tested negative at other sites, including central tumour and invasive margin. F. nucleatum was detected at a higher frequency in tumour versus normal epithelium (p < 0.01) and was associated with more advanced disease (p = 0.01). Detection of both species correlated with total bacterial load. However, corroboration of qPCR results via diversity profiling suggests detection of these species may indicate a specific microbial signature. CONCLUSIONS: This study supports a role for F. nucleatum in CRC development. Presence of F. nucleatum and B. fragilis varies across primary tumour regions, with the TLS representing the optimal site for bacterial detection.

Evaluation of DNA Extraction Methods for Processing Fingerprint Powder-Coated Forensic Evidence.

In unison, fingerprinting and DNA analysis have played a pivotal role in forensic investigations. Fingerprint powders that are available on the market can come in a range of colors and with specific properties. This study evaluated the efficiency of DNA extraction from samples coated with 3 brands of fingerprint powders: Lightning, Sirchie, and SupraNano, covering a range of colors and properties. A total of 23 fingerprint powders were tested using the Chelex, Promega DNA IQ™, and Applied Biosystems™ PrepFiler™ DNA extraction protocols. The DNA IQ™ and PrepFiler™ methods extracted higher yields of DNA in comparison to Chelex, which also accounted for better quality of PowerPlex x00AE; 21 DNA profiles recovered. There were no signs of degradation or inhibition in the quantification data, indicating that samples returning low DNA yield was due to interference during DNA extraction and not PCR inhibition. DNA profiles were recovered from the majority of fingerprint powders with only a single powder, Sirchie Magnetic Silver, failing to produce a profile using any of the methods tested. A link was observed between the DNA extraction chemistry, fingerprint powder property, that is, nonmagnetic, magnetic and aqueous, and the brand of fingerprint powder. Overall, the DNA IQ™ method was favorable for nonmagnetic fingerprint powders, while magnetic fingerprint powders produced more DNA profiles when extracted with the PrepFiler™ chemistry. This study highlights the importance of screening DNA extraction chemistries for the type of fingerprint powder used, as there is not a single DNA extraction method that suits all fingerprint powder brands and properties.

Genetic and functional evidence for a locus controlling otitis media at chromosome 10q26.3.

BACKGROUND: Otitis media (OM) is a common childhood disease characterised by middle ear effusion and inflammation. Susceptibility to recurrent acute OM and chronic OM with effusion is 40-70% heritable. Linkage studies provide evidence for multiple putative OM susceptibility loci. This study attempts to replicate these linkages in a Western Australian (WA) population, and to identify the etiological gene(s) in a replicated region. METHODS: Microsatellites were genotyped in 468 individuals from 101 multicase families (208 OM cases) from the WA Family Study of OM (WAFSOM) and non-parametric linkage analysis carried out in ALLEGRO. Association mapping utilized dense single nucleotide polymorphism (SNP) data extracted from Illumina 660 W-Quad analysis of 256 OM cases and 575 controls from the WA Pregnancy Cohort (Raine) Study. Logistic regression analysis was undertaken in ProbABEL. RT-PCR was used to compare gene expression in paired adenoid and tonsil samples, and in epithelial and macrophage cell lines. Comparative genomics methods were used to identify putative regulatory elements and transcription factor binding sites potentially affected by associated SNPs. RESULTS: Evidence for linkage was observed at 10q26.3 (Zlr = 2.69; P = 0.0036; D10S1770) with borderline evidence for linkage at 10q22.3 (Zlr = 1.64; P = 0.05; D10S206). No evidence for linkage was seen at 3p25.3, 17q12, or 19q13.43. Peak association at 10q26.3 was in the intergenic region between TCERG1L and PPP2R2D (rs7922424; P = 9.47 × 10-6), immediately under the peak of linkage. Independent associations were observed at DOCK1 (rs9418832; P = 7.48 × 10-5) and ADAM12 (rs7902734; P = 8.04 × 10-4). RT-PCR analysis confirmed expression of all 4 genes in adenoid samples. ADAM12, DOCK1 and PPP2R2D, but not TCERG1L, were expressed in respiratory epithelial and macrophage cell lines. A significantly associated polymorphism (rs7087384) in strong LD with the top SNP (rs7922424; r2 = 0.97) alters a transcription factor binding site (CREB/CREBP) in the intergenic region between TCERG1L and PPP2R2D. CONCLUSIONS: OM linkage was replicated at 10q26.3. Whilst multiple genes could contribute to this linkage, the weight of evidence supports PPP2R2D, a TGF-ß/Activin/Nodal pathway modulator, as the more likely functional candidate lying immediately under the linkage peak for OM susceptibility at chromosome 10q26.3.

Genetic and functional evidence for a role for SLC11A1 in susceptibility to otitis media in early childhood in a Western Australian population.

Otitis media (OM) is a common disease in early childhood characterised by inflammation of the middle ear. Susceptibility to recurrent acute OM (rAOM; ≥3 episodes AOM in 6 months) and chronic OM with effusion (COME; middle ear effusion ≥3 months) is 40-70% heritable. Three bacterial pathogens commonly associated with OM, Streptococcus pneumoniae (Sp), non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mc), have been observed within adenoids and as facultative intracellular pathogens that invade and survive in mononuclear cells. Case/pseudo-control conditional logistic regression analysis of variants in the SLC11A1 gene, initially identified for its role in resistance to intra-macrophage pathogens in mice, revealed association with OM at four polymorphisms (Pbest=0.025) in 531 families (660 affected children) from the Western Australian Family Study of Otitis Media. This included association at the functional promoter GTn polymorphism (rs34448891) with alleles that regulate high (allele 3; odds ratio=1.2, 95% CI 1.00-1.44, P=0.04) versus low (allele 2; odds ratio=0.83, 95% CI 0.69-0.99, P=0.04) SLC11A1 expression. Haplotype and stepwise conditional logistic regression analyses support a single genetic effect in the proximal region of SLC11A1, with the haplotype 3_C_C_G across rs34448891_rs2276631_rs3731865_rs2695343 significantly (P=0.008) over-transmitted to affected offspring. Stratified analysis showed no association with OM in children who had undergone adenoidectomy (296 children), whereas children with adenoids intact (364 children) showed improved significance at the GTn polymorphism (allele 3: odds ratio=1.38, 95% CI=1.10-1.75, P=0.006). Quantitative RT/PCR demonstrated high expression of SLC11A1 in mononuclear cells isolated from adenoid tissue, with a trend for decreased expression with increasing copies of GTn allele 2. Expression of SLC11A1 was enhanced at 12 (P=1.2×10(-3)) and 24h (P<1.0×10(-4)) after infection of Mono-Mac-6 cells with NTHi. This study identifies SLC11A1 as a novel candidate for OM susceptibility, particularly in children with adenoids intact. Further analysis in other cohorts is required to validate these observations.

Genome-wide association study to identify the genetic determinants of otitis media susceptibility in childhood.

BACKGROUND: Otitis media (OM) is a common childhood disease characterised by middle ear inflammation and effusion. Susceptibility to recurrent acute OM (rAOM; ≥ 3 episodes of AOM in 6 months) and chronic OM with effusion (COME; MEE ≥ 3 months) is 40-70% heritable. Few underlying genes have been identified to date, and no genome-wide association study (GWAS) of OM has been reported. METHODS AND FINDINGS: Data for 2,524,817 single nucleotide polymorphisms (SNPs; 535,544 quality-controlled SNPs genotyped by Illumina 660W-Quad; 1,989,273 by imputation) were analysed for association with OM in 416 cases and 1,075 controls from the Western Australian Pregnancy Cohort (Raine) Study. Logistic regression analyses under an additive model undertaken in GenABEL/ProbABEL adjusting for population substructure using principal components identified SNPs at CAPN14 (rs6755194: OR = 1.90; 95%CI 1.47-2.45; P(adj-PCA) = 8.3 × 10(-7)) on chromosome 2p23.1 as the top hit, with independent effects (rs1862981: OR = 1.60; 95%CI 1.29-1.99; P(adj-PCA) = 2.2 × 10(-5)) observed at the adjacent GALNT14 gene. In a gene-based analysis in VEGAS, BPIFA3 (P(Gene) = 2 × 10(-5)) and BPIFA1 (P(Gene) = 1.07 × 10(-4)) in the BPIFA gene cluster on chromosome 20q11.21 were the top hits. In all, 32 genomic regions show evidence of association (P(adj-PCA)<10(-5)) in this GWAS, with pathway analysis showing a connection between top candidates and the TGFß pathway. However, top and tag-SNP analysis for seven selected candidate genes in this pathway did not replicate in 645 families (793 affected individuals) from the Western Australian Family Study of Otitis Media (WAFSOM). Lack of replication may be explained by sample size, difference in OM disease severity between primary and replication cohorts or due to type I error in the primary GWAS. CONCLUSIONS: This first discovery GWAS for an OM phenotype has identified CAPN14 and GALNT14 on chromosome 2p23.1 and the BPIFA gene cluster on chromosome 20q11.21 as novel candidate genes which warrant further analysis in cohorts matched more precisely for clinical phenotypes.

Genetic susceptibility to otitis media in childhood.

Otitis media (OM) is a common disease in early childhood characterized by inflammation of the middle ear cavity. Heritability studies suggest that there is a substantial genetic component (40%-70%) to the risk of recurrent acute OM, defined as three or more episodes in 6 months or four or more episodes in a year, or chronic OM with effusion (COME), defined as middle ear fluid for ≥ 3 months. To date, only a handful of the regions/genes underlying this genetic susceptibility have been identified. These include several regions of linkage on chromosome 3p25, 10q22, 10q26, 17q12, and 19q13 identified by two genome-wide linkage scans, which appear to harbor susceptibility loci. Fine mapping of these regions has yet to identify the causative genes. Several candidate genes studies have also been reported, with candidates selected on the basis of a plausible biological role in OM or through OM mouse models. Reviewed in this article, these studies have identified positive association at 21 genes, including FBXO11, TLR4, and TNF, with association at five of these replicated in independent populations. However, these studies have been based on small sample sizes, and it is only recently that well-powered OM cohorts suitable for genome-wide association studies (GWAS) have become available. Results from such GWAS will identify novel genes involved in this complex disease. Identification of the genes that contribute to OM susceptibility in childhood will provide important insights into the biological complexity of this disease that could ultimately contribute to improved preventative and therapeutic strategies to reduce the incidence of this disease.

Unraveling the genetics of otitis media: from mouse to human and back again.

Otitis media (OM) is among the most common illnesses of early childhood, characterised by the presence of inflammation in the middle ear cavity. Acute OM and chronic OM with effusion (COME) affect the majority of children by school age and have heritability estimates of 40-70%. However, the majority of genes underlying this susceptibility are, as yet, unidentified. One method of identifying genes and pathways that may contribute to OM susceptibility is to look at mouse mutants displaying a comparable phenotype. Single-gene mouse mutants with OM have identified a number of genes, namely, Eya4, Tlr4, p73, MyD88, Fas, E2f4, Plg, Fbxo11, and Evi1, as potential and biologically relevant candidates for human disease. Recent studies suggest that this "mouse-to-human" approach is likely to yield relevant data, with significant associations reported between polymorphisms at the FBXO11, TLR4, and PAI1 genes and disease in humans. An association between TP73 and chronic rhinosinusitis has also been reported. In addition, the biobanks of available mouse mutants provide a powerful resource for functional studies of loci identified by future genome-wide association studies of OM in humans. Mouse models of OM therefore are an important component of current approaches attempting to understand the complex genetic susceptibility to OM in humans, and which aim to facilitate the development of preventative and therapeutic interventions for this important and common disease.