Shoufang Qu

A reference human genome dataset of the BGISEQ-500 sequencer

Abstract Background: BGISEQ-500 is a new desktop sequencer developed by BGI. Using DNA nanoball and combinational probe anchor synthesis developed from Complete Genomics™ sequencing technologies, it generates short reads at a large scale. Findings: Here, we present the first human whole-genome sequencing dataset of BGISEQ-500. The dataset was generated by sequencing the widely used cell line HG001 (NA12878) in two sequencing runs of paired-end 50 bp (PE50) and two sequencing runs of paired-end 100 bp (PE100). We also include examples of the raw images from the sequencer for reference. Finally, we identified variations using this dataset, estimated the accuracy of the variations, and compared to that of the variations identified from similar amounts of publicly available HiSeq2500 data. Conclusions: We found similar single nucleotide polymorphism (SNP) detection accuracy for the BGISEQ-500 PE100 data (false positive rate [FPR] = 0.00020%, sensitivity = 96.20%) compared to the PE150 HiSeq2500 data (FPR = 0.00017%, sensitivity = 96.60%) better SNP detection accuracy than the PE50 data (FPR = 0.0006%, sensitivity = 94.15%). But for insertions and deletions (indels), we found lower accuracy for BGISEQ-500 data (FPR = 0.00069% and 0.00067% for PE100 and PE50 respectively, sensitivity = 88.52% and 70.93%) than the HiSeq2500 data (FPR = 0.00032%, sensitivity = 96.28%). Our dataset can serve as the reference dataset, providing basic information not just for future development, but also for all research and applications based on the new sequencing platform.

Sensitive detection of trace amounts of KRAS codon 12 mutations by a fast and novel one-step technique.

OBJECTIVES The objective of this study is to develop a novel and sensitive method for KRAS codon 12 mutation testing. DESIGN AND METHODS We developed a sensitive one-step real-time digestion-and-block TaqMan probe PCR (RTDB-PCR) technique that uses a thermostable endonuclease and a minor groove binder (MGB) blocker to detect KRAS codon 12 mutations. Dilution mimic DNA panels were used to assess the sensitivity of this technique. The RTDB-PCR method was performed and compared with three other methods: PCR sequencing, mutant-enriched PCR sequencing and mutant-enriched PCR-MassArray. A total of 100 formalin-fixed paraffin-embedded (FFPE) metastatic colorectal cancer (mCRC) specimens were also tested by all four methods. RESULTS The RTDB-PCR was sensitive to as little as 0.01% mutant DNA, significantly higher than other methods. Among the 100 FFPE mCRC specimens examined, 45 tested positive for KRAS codon 12 mutations according to RTDB-PCR, 44 tested positive according to mutant-enriched PCR sequencing and mutant-enriched PCR-MassArray, and only 26 samples tested positive according to PCR sequencing. CONCLUSIONS Compared with mutant-enriched PCR sequencing and mutant-enriched PCR-MassArray, RTDB-PCR is more cost effective, saves time, and is easier to use, making it suitable for the detection of low-level KRAS mutations in the clinic.

A Comparison of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and Surface Plasmon Resonance for Genotyping of High-Risk Human Papillomaviruses

Background: Human papillomavirus (HPV) testing coupled with appropriate clinical management is associated with a significant decline in the rate of advanced cervical cancer and associated death. Methods: In this present study, we evaluated the performance of 2 new HPV genotyping methods, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and surface plasmon resonance (SPR) in 30 kinds of HPV control materials and in 129 cases of cervical smears including 79 HPV-positive samples screened from 1,600 abnormal clinical samples and 50 cervical cytology samples. Results: The HPV genotyping accuracy of both MALDI-TOFMS and SPR was 100% for the HPV genotyping of control materials. In the analysis of the 79 HPV-positive samples by MALDI-TOFMS, HPV positivity was 88.6% (70/79). Nine samples were non-high-risk HPV (non-HR-HPV), which were not targets of MALDI-TOFMS. In the analysis of the 50 cervical samples, the agreement of both tests was 84% with a ĸ value of 0.660. By using consensus results that mean agreement between 2 of 3 methods, the HR-HPV genotyping accuracy was 100% (77/77) by MALDI-TOFMS and 94.8% (73/77) by SPR in the 129 cervical samples. The sensitivity (88.2%; 82/93) and specificity (88.9%; 32/36) of MALDI-TOFMS were similar to those of SPR. Conclusion: These results support that MALDI-TOFMS is a sensitive, specific and feasible method for HR-HPV detection in clinical application, compared with the SPR method.

Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing

Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.

Detection of low-level DNA mutation by ARMS-blocker-Tm PCR.

BACKGROUND Low-level DNA mutations play important roles in cancer prognosis and treatment. However, most existing methods for the detection of low-level DNA mutations are insufficient for clinical applications because of the high background of wild-type DNA. DESIGN AND METHOD In this study, a novel assay based on Tm-dependent inhibition of wild type template amplification was developed. The defining characteristic of this assay is an additional annealing step was introduced into the ARMS-blocker PCR. The temperature of this additional annealing step is equal to the Tm of the blocker. Due to this additional annealing step, the blocker can preferentially and specifically bind the wild-type DNA. Thus, the inhibition of wild type template is realized and the mutant DNA is enriched. RESULTS The sensitivity of this assay was between 10(-4) and 10(-5), which is approximately 5 to 10 times greater than the sensitivity of the assay without the additional annealing step. To evaluate the performance of this assay in detecting K-ras mutation, we analyzed 100 formalin-fixed paraffin-embedded (FFPE) specimens from colorectal cancer patients using this new assay and Sanger sequencing. Of the clinical samples, 27 samples were positive for K-ras mutation by both methods. CONCLUSIONS Our results indicated that this new assay is a highly selective, convenient, and economical method for detecting rare mutations in the presence of higher concentrations of wild-type DNA.

Restriction endonuclease-mediated real-time digestion-PCR for somatic mutation detection.

PCR is a powerful platform for clinical and diagnostic applications, but challenges remain in detecting somatic mutations, as mutant cells are often mixed with more numerous wild‐type cells at the tissue‐sample sites. Here, we describe a novel method that couples PCR with restriction endonuclease digestion (designated real‐time digestion‐PCR, or RTD‐PCR) in a one‐step reaction tube for detecting somatic mutations from a minority of cells. The PCR mixture contains a thermostable restriction enzyme that digests wild‐type alleles during the PCR program, allowing selective amplification of the mutant alleles. To validate this method, we used real‐time digestion‐PCR for the specific detection of the EGFR (epidermal growth factor receptor) treatment resistance‐inducing mutation, T790M, combining with three different platforms: Sanger sequencing, TaqMan probe PCR and Sequenom MassArray. From 78 clinical samples, seven T790M mutations were consistently detected on all three platforms, indicating that RTD‐PCR may be a useful clinical tool for analyzing the T790M point mutation.

MGB-based one-step multiplex real-time PCR method for rapid detection of HPV

AIM For full-scale analysis of Human Papillomavirus (HPV) status in humans, two minor groove binder (MGB)-based one-step multiplex real-time PCR systems were developed: one to screen 16 high-risk HPV (HR-HPV) types, and one to screen a broader spectrum of HPV types (common HPV or C-HPV). METHODS Sensitivity and specificity were evaluated using diluted reference plasmids and 20 control human DNA samples. For clinical evaluation, 510 cervical scrape samples were evaluated. RESULTS The sensitivity assays revealed that the C-HPV detection system could detect 10 ~ 100 plasmid copies/reaction, while the HR-HPV detection system detected 10 ~ 500 copies. The specificity test revealed that the systems did not yield positive signals from the 20 human genomic DNA samples. Performance was tested on 510 usable clinical samples. The HR-HPV results were compared to those from the Hybrid Capture 2 (HC2) test, which assesses 13 HR-HPV types; the concordance level between the two methods was 90.8% with a kappa value of 0.813. CONCLUSIONS These results showed that our novel MGB-based one-step multiplex real-time PCR method may be used for the diagnosis and mass screening of HPV in clinical and large-scale epidemiological studies.

A novel RFLP‑ARMS TaqMan PCR‑based method for detecting the BRAF V600E mutation in melanoma

To enable the rapid and sensitive screening of the BRAF V600E mutation in clinical samples, a novel method combining restriction fragment length polymorphism (RFLP) analysis with the popular amplification refractory mutation system (ARMS) TaqMan quantitative (qPCR) genotyping method in a single reaction tube was developed. A total of 2 primer pairs were designed to enrich for and genotype the BRAF mutational hotspot (RFLP primers and ARMS primers) and a restriction enzyme was used to remove the wild-type alleles. The analysis revealed that this method detected mutant alleles in mixed samples containing >0.1% mutant sequences. In a survey of 53 melanoma samples, this method detected 21 mutation-positive samples. This novel RFLP-ARMS TaqMan qPCR protocol may prove useful for detecting mutations in clinical samples containing only a small proportion of mutant alleles.