Explore the vast range of titles available.

Background Massively-parallel-sequencing, coupled with sample multiplexing, has made genetic tests broadly affordable. However, intractable index mis-assignments (commonly exceeds 1%) were repeatedly reported on some widely used sequencing platforms. Results Here, we investigated this quality issue on BGI sequencers using three library preparation methods: whole genome sequencing (WGS) with PCR, PCR-free WGS, and two-step targeted PCR. BGI’s sequencers utilize a unique DNA nanoball (DNB) technology which uses rolling circle replication for DNA-nanoball preparation; this linear amplification is PCR free and can avoid error accumulation. We demonstrated that single index mis-assignment from free indexed oligos occurs at a rate of one in 36 million reads, suggesting virtually no index hopping during DNB creation and arraying. Furthermore, the DNB-based NGS libraries have achieved an unprecedentedly low sample-to-sample mis-assignment rate of 0.0001 to 0.0004% under recommended procedures. Conclusions Single indexing with DNB technology provides a simple but effective method for sensitive genetic assays with large sample numbers.

Mutants remain a powerful means for dissecting gene function in model organisms such as Caenorhabditis elegans. Massively parallel sequencing has simplified the detection of variants after mutagenesis but determining precisely which change is responsible for phenotypic perturbation remains a key step. Genetic mapping paradigms in C. elegans rely on bulk segregant populations produced by crosses with the problematic Hawaiian wild isolate and an excess of redundant information from whole-genome sequencing (WGS). To increase the repertoire of available mutants and to simplify identification of the causal change, we performed WGS on 173 temperature-sensitive (TS) lethal mutants and devised a novel mapping method. The mapping method uses molecular inversion probes (MIP-MAP) in a targeted sequencing approach to genetic mapping, and replaces the Hawaiian strain with a Million Mutation Project strain with high genomic and phenotypic similarity to the laboratory wild-type strain N2. We validated MIP-MAP on a subset of the TS mutants using a competitive selection approach to produce TS candidate mapping intervals with a mean size < 3 Mb. MIP-MAP successfully uses a non-Hawaiian mapping strain and multiplexed libraries are sequenced at a fraction of the cost of WGS mapping approaches. Our mapping results suggest that the collection of TS mutants contains a diverse library of TS alleles for genes essential to development and reproduction. MIP-MAP is a robust method to genetically map mutations in both viable and essential genes and should be adaptable to other organisms. It may also simplify tracking of individual genotypes within population mixtures.

Abstract Background Antimicrobial resistance (AMR) of Neisseria gonorrhoeae has spread worldwide. Rapid and comprehensive methods are needed to describe N. gonorrhoeae AMR profiles accurately. A method based on multiplex amplicon sequencing was developed to simultaneously sequence 13 genes related to AMR in N. gonorrhoeae directly from clinical samples. Methods Nine N. gonorrhoeae strains were used for the establishment and validation of the method. Eleven urethral swabs and their corresponding cultured isolates were matched as pairs to determine the accuracy of the method. Mock samples with different dilutions were prepared to determine the sensitivity of the method. Five nongonococcal Neisseria strains and 24 N. gonorrhoeae negative clinical samples were used to evaluate the cross-reactivity. Finally, the method was applied to 64 clinical samples to assess its performance. Results Using Sanger sequencing as a reference method, sequences recovered from amplicon sequencing had a base accuracy of over 99.5% and the AMR sites were correctly identified. The limit of detection (LOD) was lower than 31 copies/reaction. No significant cross-reactivity was observed. Furthermore, target genes were successfully recovered from 64 clinical samples including 9 urines, demonstrating this method could be used in different types of samples. For clinical samples, the results can be obtained within a time frame of 7 h 40 min to 10 h 40 min, while for isolates, the turnaround time was approximately 2 h shorter. Conclusions This method can serve as a versatile and convenient culture-free diagnostic method with the advantages of high sensitivity and accuracy.

Background With the widespread use of multiple amplicon-sequencing (MAS) in genetic variation detection, an efficient tool is required to remove primer sequences from short reads to ensure the reliability of downstream analysis. Although some tools are currently available, their efficiency and accuracy require improvement in trimming large scale of primers in high throughput target genome sequencing. This issue is becoming more urgent considering the potential clinical implementation of MAS for processing patient samples. We here developed pTrimmer that could handle thousands of primers simultaneously with greatly improved accuracy and performance. Result pTrimmer combines the two algorithms of k-mers and Needleman-Wunsch algorithm, which ensures its accuracy even with the presence of sequencing errors. pTrimmer has an improvement of 28.59% sensitivity and 11.87% accuracy compared to the similar tools. The simulation showed pTrimmer has an ultra-high sensitivity rate of 99.96% and accuracy of 97.38% compared to cutPrimers (70.85% sensitivity rate and 58.73% accuracy). And the performance of pTrimmer is notably higher. It is about 370 times faster than cutPrimers and even 17,000 times faster than cutadapt per threads. Trimming 2158 pairs of primers from 11 million reads (Illumina PE 150 bp) takes only 37 s and no more than 100 MB of memory consumption. Conclusions pTrimmer is designed to trim primer sequence from multiplex amplicon sequencing and target sequencing. It is highly sensitive and specific compared to other three similar tools, which could help users to get more reliable mutational information for downstream analysis.

Background Malaria still poses one of the major threats to human health. Development of effective antimalarial drugs has decreased this threat; however, the emergence of drug-resistant Plasmodium falciparum , a cause of Malaria, is disconcerting. The antimalarial drug chloroquine has been effectively used, but resistant parasites have spread worldwide. Interestingly, the withdrawal of the drug reportedly leads to an increased population of susceptible parasites in some cases. We examined the prevalence of genomic polymorphisms in a malaria parasite P. falciparum , associated with resistance to an antimalarial drug chloroquine, after the withdrawal of the drug from Indonesia. Results Blood samples were collected from 95 malaria patients in North Sulawesi, Indonesia, in 2010. Parasite DNA was extracted and analyzed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) for pfcrt and pfmdr1 . In parallel, multiplex amplicon sequencing for the same genes was carried out with Illumina MiSeq. Of the 59 cases diagnosed as P. falciparum infection by microscopy, PCR–RFLP analysis clearly identified the genotype 76T in pfcrt in 44 cases. Sequencing analysis validated the identified genotypes in the 44 cases and demonstrated that the haplotype in the surrounding genomic region was exclusively SVMNT. Results of pfmdr1 were successfully obtained for 51 samples, where the genotyping results obtained by the two methods were completely consistent. In pfmdr1 , the 86Y mutant genotype was observed in 45 cases (88.2%). Conclusions Our results suggest that the prevalence of the mutated genotypes remained dominant even 6 years after the withdrawal of chloroquine from this region. Diversified haplotype of the resistance-related locus, potentially involved in fitness costs, unauthorized usage of chloroquine, and/or a short post-withdrawal period may account for the observed high persistence of prevalence.

Objective To explore the clinical application of NeoSeq in newborn screening. Methods Based on the results obtained from traditional newborn screening (NBS) with tandem mass spectrometry (TMS), three cohorts were recruited into the present study: 36 true positive cases (TPC), 60 false-positive cases (FPC), and 100 negative cases. The dried blood spots of the infants were analyzed with NeoSeq, which is based on multiplex PCR amplicon sequencing. Results Overall, the sensitivity of NeoSeq was 55.6% (20/36) in the detection of TPC. NeoSeq detected disease-related genes in 20 of 36 TPC infants, while it could not identify these genes in eight children. Five cases (3.1%) with disease risk were additionally found in the FPC and NC cohorts. There was a significant difference in the diagnostic time between the two methods—10 days for NeoSeq vs. 43 days for traditional NBS. Conclusions NeoSeq is an economic genomic screening test for newborn screening. It can detect most inborn errors of metabolism, reduce the rate of false positive results, shorten the porting cycles, and reduce the screening cost. However, it is still necessary to further optimize the panel design and add more clinically relevant genomic variants to increase its sensitivity.

Northern temperate forest soils and Sphagnum-dominated peatlands are a major source and sink of methane. In these ecosystems, methane is mainly oxidized by aerobic methanotrophic bacteria, which are typically found in aerated forest soils, surface peat, and Sphagnum moss. We contrasted methanotrophic bacterial diversity and abundances from the (i) organic horizon of forest soil; (ii) surface peat; and (iii) submerged Sphagnum moss from Cranesville Swamp Preserve, West Virginia, using multiplex sequencing of bacterial 16S rRNA (V3 region) gene amplicons. From ~1 million reads, >50,000 unique OTUs (Operational Taxonomic Units), 29 and 34 unique sequences were detected in the Methylococcaceae and Methylocystaceae, respectively, and 24 potential methanotrophs in the Beijerinckiaceae were also identified. Methylacidiphilum-like methanotrophs were not detected. Proteobacterial methanotrophic bacteria constitute <2% of microbiota in these environments, with the Methylocystaceae one to two orders of magnitude more abundant than the Methylococcaceae in all environments sampled. The Methylococcaceae are also less diverse in forest soil compared to the other two habitats. Nonmetric multidimensional scaling analyses indicated that the majority of methanotrophs from the Methylococcaceae and Methylocystaceae tend to occur in one habitat only (peat or Sphagnum moss) or co-occurred in both Sphagnum moss and peat. This study provides insights into the structure of methanotrophic communities in relationship to habitat type, and suggests that peat and Sphagnum moss can influence methanotroph community structure and biogeography.

Copy number variation (CNV) contributes in phenotypically relevant ways to the genetic variability of many organisms. Cost-effective genomewide methods for identifying copy number variation are necessary to elucidate the contribution that these structural variants make to the genomes of model organisms. We have developed a novel approach for the identification of copy number variation by next generation sequencing. As a proof of concept our method has been applied to map the deletions of three Drosophila deficiency strains. We demonstrate that low sequence coverage is sufficient for identifying and mapping large deletions at kilobase resolution, suggesting that data generated from high-throughput sequencing experiments are sufficient for simultaneously analyzing many strains. Genomic DNA from two Drosophila deficiency stocks was barcoded and sequenced in multiplex, and the breakpoints associated with each deletion were successfully identified. The approach we describe is immediately applicable to the systematic exploration of copy number variation in model organisms and humans.

Background Constitutive activation of the PI3K-AKT-mTOR pathway (mTOR pathway) underlies megalencephaly in many patients. Yet, prevalence of the involvement of the PI3K-AKT-mTOR pathway in patients with megalencephaly remains to be elucidated, and molecular diagnosis is challenging. Here, we have successfully established a combination of genetic and biochemical methods for diagnosis of mTOR pathway-associated megalencephaly, and have attempted to delineate the clinical characteristics of the disorder. Methods Thirteen patients with an increased head circumference and neurological symptoms participated in the study. To evaluate the activation of the mTOR pathway, we performed western blot analysis to determine the expression levels of phosphorylated S6 ribosomal protein (phospho-S6 protein) in lymphoblastoid cell lines from 12 patients. Multiplex targeted sequencing analysis for 15 genes involved in the mTOR pathway was performed on 12 patients, and whole-exome sequencing was performed on one additional patient. Clinical features and MRI findings were also investigated. Results We identified pathogenic mutations in six ( AKT3 , 1 patient; PIK3R2 , 2 patients; PTEN , 3 patients) of the 13 patients. Increased expression of phospho-S6 protein was demonstrated in all five mutation-positive patients in whom western blotting was performed, as well as in three mutation-negative patients. Developmental delay, dysmorphic facial features were observed in almost all patients. Syndactyly/polydactyly and capillary malformations were not observed, even in patients with AKT3 or PIK3R2 mutations. There were no common phenotypes or MRI findings among these patients. Conclusions A combination of genetic and biochemical methods successfully identified mTOR pathway involvement in nine of 13 (approximately 70%) patients with megalencephaly, indicating a major contribution of the pathway to the pathogenesis of megalencephaly. Our combined approach could be useful to identify patients who are suitable for future clinical trials using an mTOR inhibitor.

Background & objectives: The global incidence of dengue has grown dramatically in recent decades and Assam, India has witnessed several outbreaks of dengue since 2015. Although during post-monsoon months (September to December), most cases of dengue in Assam are recorded but incidence of dengue in Assam has been slowly changing from being endemic to being hyper endemic. Therefore, this study was carried out to determine the serotypes and genotypes of dengue virus prevalent in Assam during the period of 2016-2017. Methods: This is a prospective study conducted for a period of two years from 2016 to 2017. Department of Microbiology, Gauhati Medical College and Hospital (GMCH) had received a total of ~12000 and ~9000 sera sample during 2016 and 2017 respectively for confirmation of clinically suspected dengue cases. For confirmation, dengue NS1 antigen and IgM antibody ELISA tests were performed. Multiplex RT-PCR was performed for serotyping of dengue viruses and representative samples found positive in PCR were sequenced to determine the genotypes of circulating dengue virus serotypes. Results: In the year 2016, 6157 sera samples and in 2017, 3386 sera samples were found positive in ELISA test. A total of 157 dengue positive sera samples representing 17 districts of Assam were further tested by multiplex RT-PCR for serotyping of the virus. In PCR, out of 157, 107 samples (68.15%) were found positive for the presence of dengue virus genome. Out of 107, 74 samples (69.15%) were positive for dengue virus serotype-1 (DENV-1), 32 samples (29.90%) for dengue virus serotype-2 (DENV-2) and one sample (0.93%) positive for dengue virus serotype-3 (DENV-3). Out of 107 PCR positive samples, 25 samples were sequenced to identify their genotypes. Phylogenetic analysis of sequenced dengue viruses revealed that all the seven DENV-1 strains were genotype V, 17 DENV-2 strains were genotype IV (Cosmopolitan genotype) and one DENV-3 strain was genotype III. Interpretation & conclusion: These findings improve our knowledge of circulating dengue virus serotypes in Assam. Co-circulation of three serotypes of dengue virus highlights the need for establishment of active dengue surveillance. The genotypic data of our findings will be helpful for future dengue molecular epidemiology studies and to control the disease in the region.