Project description:ObjectiveTo assess in a US general adult population the effect of the functional single-nucleotide polymorphism rs198389 in the promoter region of the gene of brain-type natriuretic peptide (BNP) on 3 commonly used BNP assays, clinical phenotype, disease prevalence, overall survival, and diagnostic test characteristics of BNP as a biomarker.Patients and methodsWe genotyped for rs198389 in a random sample of the general population (aged ≥ 45 years; n = 1970; enrolled between June 1, 1997, and September 30, 2000) from Olmsted County, Minnesota. Patients were characterized biochemically, clinically, echocardiographically, and regarding BNP molecular forms (2 assays for BNP and 1 assay for amino-terminal proBNP). Median follow-up was 9 years.ResultsGenotype frequencies were in Hardy-Weinberg equilibrium (P = .98): TT genotype, n = 645 (32.7%); TC genotype, n = 983 (49.9%); and CC genotype, n = 342 (17.4%). The C allele independently predicted higher BNP forms (P<.001 for all assays). Genotypes did not differ with regard to clinical and echocardiographic phenotype or overall survival. When previously reported genotype-unadjusted cut points for the detection of left ventricular ejection fraction less than or equal to 40% (n = 37 [1.9%]) and less than or equal to 50% (n = 116 [6.0%]) were used, sensitivity generally increased with the number of C alleles, whereas specificity decreased, both on average by more than 10% for the TT vs CC genotype.ConclusionThe C allele of rs198389 is common in the general US population and is associated with higher concentrations of BNP molecular forms but not with cardiovascular phenotype or survival. The C allele confounds the test characteristics of commonly used assays.
Project description:BackgroundEfficient screening of bacterial artificial chromosome (BAC) libraries with polymerase chain reaction (PCR)-based markers is feasible provided that a multidimensional pooling strategy is implemented. Single nucleotide polymorphisms (SNPs) can be screened in multiplexed format, therefore this marker type lends itself particularly well for medium- to high-throughput applications. Combining the power of multiplex-PCR assays with a multidimensional pooling system may prove to be especially challenging in a polyploid genome. In polyploid genomes two classes of SNPs need to be distinguished, polymorphisms between accessions (intragenomic SNPs) and those differentiating between homoeologous genomes (intergenomic SNPs). We have assessed whether the highly parallel Illumina GoldenGate Genotyping Assay is suitable for the screening of a BAC library of the polyploid Brassica napus genome.ResultsA multidimensional screening platform was developed for a Brassica napus BAC library which is composed of almost 83,000 clones. Intragenomic and intergenomic SNPs were included in Illumina's GoldenGate Genotyping Assay and both SNP classes were used successfully for screening of the multidimensional BAC pools of the Brassica napus library. An optimized scoring method is proposed which is especially valuable for SNP calling of intergenomic SNPs. Validation of the genotyping results by independent methods revealed a success of approximately 80% for the multiplex PCR-based screening regardless of whether intra- or intergenomic SNPs were evaluated.ConclusionsIllumina's GoldenGate Genotyping Assay can be efficiently used for screening of multidimensional Brassica napus BAC pools. SNP calling was specifically tailored for the evaluation of BAC pool screening data. The developed scoring method can be implemented independently of plant reference samples. It is demonstrated that intergenomic SNPs represent a powerful tool for BAC library screening of a polyploid genome.
Project description:BackgroundWe evaluated the performance of single-nucleotide polymorphism (SNP) genotyping arrays OncoScan (Thermo Fisher Scientific, San Diego, CA) and Infinium CytoSNP-850K (CytoSNP; Illumina, Waltham, MA) for assessing homologous recombination deficiency (HRD) genomic instability.MethodsDNA (pretreatment samples) across 20 tumor types was evaluated with OncoScan, CytoSNP, and the clinically validated HRD test. Copy number variation (CNV) and loss of heterozygosity (LOH) analyses were performed with ASCATv2.5.1. Aggregate HRD genomic metrics included LOH, telomeric-allelic imbalance number (TAI), and large-scale state transition (LST). Associations between BRCA mutation (BRCAm) status and the clinically validated HRD test metric (dichotomized at a clinical cut-off) were evaluated using area under the receiver operating characteristic (AUROC); Spearman ρ was calculated for continuous metrics. CNV segmentation and HRD genomic metrics were calculated (n = 120, n = 106, and n = 126 for OncoScan, CytoSNP and clinically validated HRD test, respectively).ResultsWhen assessed by SNP arrays, the genomic metric demonstrated good association with BRCAm (AUROC of HRD: OncoScan, 0.87; CytoSNP, 0.75) and the clinically validated test (cut-off, 42; AUROC of HRD: OncoScan, 0.92; CytoSNP, 0.91). The genomic metrics demonstrated good correlation with the clinically validated aggregate HRD test metric (ρ: OncoScan, 0.82; CytoSNP, 0.81) and for each component (ρ: OncoScan, 0.68 [LOH], 0.76 [TAI], and 0.78 [LST]; CytoSNP, 0.59 [LOH], 0.77 [TAI], and 0.82 [LST]). HRD assessed by SNP genotyping arrays and the clinically validated test showed good correlation.ConclusionOncoScan and CytoSNP may potentially identify most HRD-positive tumors with appropriate clinically relevant cut-offs.
Project description:Tuna are economically important as food resources in food markets. However, because tuna is often processed into steaks or fillets, the meat can be difficult to identify through morphological features. For effective fishery management and to protect the rights of consumers, it is necessary to develop a molecular method to accurately identify the species used in tuna products. Herein, we discovered five single-nucleotide polymorphism (SNP) sites via 2b-RAD sequencing and developed five SNP-based real-time polymerase chain reaction assays for the rapid identification of five highly priced tuna species. Three species-specific TaqMan systems were designed to identify albacore tuna (Thunnus alalunga), bigeye tuna (T. obesus), and southern bluefin tuna (T. maccoyii) and two cycling systems were designed to identify yellowfin tuna (T. albacares) and Atlantic bluefin tuna (T. thynnus). The systems showed good specificity and sensitivity (sensitivity of 0.0002 ng μL-1 for albacore tuna, bigeye tuna, and southern bluefin tuna and 0.002 ng μL-1 for yellowfin tuna and Atlantic bluefin tuna). Both systems were able to distinguish the target species from other species in a specific, sensitive, and accurate manner. Thus, these methods can be employed for the identification of species used in tuna products, protecting consumers and producers from economic fraud.
Project description:Highly precise diagnostics and forensic assays can be developed through a combination of evolutionary analysis and the exhaustive examination of genomic sequences. In Bacillus anthracis, whole-genome sequencing efforts revealed ca. 3,500 single-nucleotide polymorphisms (SNPs) among eight different strains and evolutionary analysis provides the identification of canonical SNPs. We have previously shown that SNPs are highly evolutionarily stable, and the clonal nature of B. anthracis makes them ideal signatures for subtyping this pathogen. Here we identified SNPs that define the lineage of B. anthracis that contains the Ames strain, the strain used in the 2001 bioterrorist attacks in the United States. Sequencing and real-time PCR were used to validate these SNPs across B. anthracis strains, including (i) 88 globally and genetically diverse isolates; (ii) isolates that were shown to be genetic relatives of the Ames strain by multiple-locus variable number tandem repeat analysis (MLVA); and (iii) several different lab stocks of the Ames strain, including a clinical isolate from the 2001 letter attack. Six SNPs were found to be highly specific for the Ames strain; four on the chromosome, one on the pX01 plasmid, and one on the pX02 plasmid. All six SNPs differentiated the B. anthracis Ames strain from the 88 unique B. anthracis strains, while five of the six separated Ames from its close genetic relatives. The use of these SNPs coupled with real-time PCR allows specific and sensitive (<100 fg of template DNA) identification of the Ames strain. This evolutionary and genomics-based approach provides an effective means for the discovery of strain-specific SNPs in B. anthracis.
Project description:Listeria monocytogenes is responsible for serious invasive illness associated with consumption of contaminated food and places a significant burden on public health and the agricultural economy. We recently developed a multilocus genotyping (MLGT) assay for high-throughput subtype determination of L. monocytogenes lineage I isolates based on interrogation of single nucleotide polymorphisms (SNPs) via multiplexed primer extension reactions. Here we report the development and validation of two additional MLGT assays that address the need for comprehensive DNA sequence-based subtyping of L. monocytogenes. The first of these novel MLGT assays targeted variation segregating within lineage II, while the second assay combined probes for lineage III strains with probes for strains representing a recently characterized fourth evolutionary lineage (IV) of L. monocytogenes. These assays were based on nucleotide variation identified in >3.8 Mb of comparative DNA sequence and consisted of 115 total probes that differentiated 93% of the 100 haplotypes defined by the multilocus sequence data. MLGT reproducibly typed the 173 isolates used in SNP discovery, and the 10,448 genotypes derived from MLGT analysis of these isolates were consistent with DNA sequence data. Application of the MLGT assays to assess subtype prevalence among isolates from ready-to-eat foods and food-processing facilities indicated a low frequency (6.3%) of epidemic clone subtypes and a substantial population of isolates (>30%) harboring mutations in inlA associated with attenuated virulence in cell culture and animal models. These mutations were restricted to serogroup 1/2 isolates, which may explain the overrepresentation of serotype 4b isolates in human listeriosis cases.
Project description:Elevated expression of the prostaglandin synthase cyclooxygenase-2 (COX-2) is commonly observed in many chronic inflammatory diseases and cancer. However, the mechanisms allowing for pathogenic COX-2 overexpression are largely unknown. The gene for COX-2 (PTGS2) carries a common single-nucleotide polymorphism (SNP) at position 8473 (T8473C), in exon 10 that is associated with diseases in which COX-2 overexpression is a contributing factor. We demonstrate that the T8473C SNP resides within a region that targets COX-2 mRNA for degradation through microRNA-mediated regulation. miR-542-3p was identified to bind transcripts derived from the 8473T allele and promote mRNA decay. By contrast, the presence of the variant 8473C allele interfered with miR-542-3p binding, allowing for mRNA stabilization, and this effect was rescued using a mutated miR-542-3p at the respective 8473 site. Colon cancer cells and tissue displayed COX-2 mRNA levels that were dependent on T8473C allele dosage, and allele-specific expression of COX-2 was observed to be a contributing factor promoting COX-2 overexpression. These findings provide a novel molecular explanation underlying disease susceptibility associated with COX-2 T8473C SNP, and identify it as a potential marker for identifying cancer patients best served through selective COX-2 inhibition.
Project description:Acute inflammation is heterogeneous in critical illness and predictive of outcome. We hypothesized that genetic variability in novel, yet common, gene variants contributes to this heterogeneity and could stratify patient outcomes. We searched algorithmically for significant differences in systemic inflammatory mediators associated with any of 551,839 SNPs in one derivation (n = 380 patients with blunt trauma) and two validation (n = 75 trauma and n = 537 non-trauma patients) cohorts. This analysis identified rs10404939 in the LYPD4 gene. Trauma patients homozygous for the A allele (rs10404939AA; 27%) had different trajectories of systemic inflammation along with persistently elevated multiple organ dysfunction (MOD) indices vs. patients homozygous for the G allele (rs10404939GG; 26%). rs10404939AA homozygotes in the trauma validation cohort had elevated MOD indices, and non-trauma patients displayed more complex inflammatory networks and worse 90-day survival compared to rs10404939GG homozygotes. Thus, rs10404939 emerged as a common, broadly prognostic SNP in critical illness.