Unknown,Transcriptomics,Genomics,Proteomics

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LoRTIS: A long read method for analysis of large transposon mutant libraries

ABSTRACT: Transposon insertion site sequencing (TIS) is a powerful method for associating genotype to phenotype. However, all TIS methods described to date use short nucleotide sequence reads which cannot uniquely determine the locations of transposon insertions within repeating genomic sequences where the repeat units are longer than the sequence read length. To overcome this limitation, we have developed a TIS method using Oxford Nanopore sequencing technology that generates and uses long nucleotide sequence reads; we have called this method LoRTIS (Long Read Transposon Insertion-site Sequencing). This experiment data contains sequence files generated using Nanopore and Illumina platforms. Biotin1308.fastq.gz and Biotin2508.fastq.gz are fastq files generated from nanopore technology. Rep1-Tn.fastq.gz and Rep1-Tn.fastq.gz are fastq files generated using Illumina platform. In this study, we have compared the efficiency of two methods in identification of transposon insertion sites.

INSTRUMENT(S): MinION, NextSeq 500

ORGANISM(S): Escherichia coli BW25113

SUBMITTER: Muhammad Yasir

PROVIDER: E-MTAB-11351 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Somatic transposon mutagenesis in mice is an efficient strategy to investigate the genetic mechanisms of tumorigenesis. The identification of tumor driving transposon insertions traditionally requires the generation of large tumor cohorts to obtain information about common insertion sites. Tumor driving insertions are also characterized by their clonal expansion in tumor tissue, a phenomenon that is facilitated by the slow and evolving transformation process of transposon mutagenesis. We describe here an improved approach for the detection of tumor driving insertions that assesses the clonal expansion of insertions by quantifying the relative proportion of sequence reads obtained in individual tumors. To this end, we have developed a protocol for insertion site sequencing that utilizes acoustic shearing of tumor DNA and Illumina sequencing. We analyzed various solid tumors generated by PiggyBac mutagenesis and for each tumor >10^6 reads corresponding to >10^4 insertion sites were obtained. In each tumor, 9 to 25 insertions stood out by their enriched sequence read frequencies when compared to frequencies obtained from tail DNA controls. These enriched insertions are potential clonally expanded tumor driving insertions, and thus identify candidate cancer genes. The candidate cancer genes of our study comprised many established cancer genes, but also novel candidate genes such as Mastermind-like1 (Mamld1) and Diacylglycerolkinase delta (Dgkd). We show that clonal expansion analysis by high-throughput sequencing is a robust approach for the identification of candidate cancer genes in insertional mutagenesis screens on the level of individual tumors. Solid tumors in mice were generated by somatic transposon mutagenesis with a PiggyBac transposon system. Insertion sites of transposons in 11 tumors and 6 non-cancerous tail controls were determined by Illumina high-throughput sequencing. Insertions were determined both on 5' and 3' sides of the transposon (PB5 and PB3, respectively). Quantitative analysis of read numbers revealed enrichment of certain insertions in tumors, but not in controls, and these enriched insertions identify candidate cancer genes.

Project description:A whole genome screen was used to assay every gene of Escherichia coli strain BW25113 to identify genes involved in susceptibility to the monobactam (beta-lactam) antibiotic aztreonam. The methodology has been called TraDIS-Xpress, and is a version of TraDIS or Tn-seq. A transposon mutant library consisting of several hundred thousand mutants was constructed using a Tn5-derived transposon incorporating an inducible outward transcribing promoter. All the mutants were grown in LB broth cultures supplemented with aztreonam at 2 x, 1 x, 0.5 x and 0.25 x MIC with induction of the transposon promoter using 0.2 mM IPTG or 1 mM IPTG or without induction. Following growth, mutants with increased susceptibility show reduced numbers and those with reduced susceptibility show increased numbers. Each condition was performed in duplicate. The methodology enable genes to be assayed by insertional inactivation or by changes in expression. Expression changes result from altered transcription from upstream transposon insertions transcribing into the gene, or downstream insertions transcribing into the gene in the reverse direction leading to RNA interference through the generation of reverse and complementary RNA. Thus, essential genes into which transposon insertions are not tolerated may be assayed also by changes in numbers of upstream or downstream insertion mutants. Changes to high throughput sequencing protocols permit the generation of nucleotide sequence reads from the known transposon sequences into the surrounding insertion site for all the mutants in the mixture simultaneously. Matching the sequence of the reads to the genome nucleotide sequence of E. coli BW25113 then allows the precise locations of all the transposon insertion sites of all the mutants to be mapped simultaneously. The relative changes in mutants between control (without) and selective condition (with aztreonam) then indicates which genes are involved in susceptibility. The numbers of sequence reads that match is reflected by the number of mutants, and so the degree of susceptibility can also be estimated.

Project description:The transposon site hybridization (TraSH) technique (Sassetti, CM et al. 2001. PNAS 98:12712-7) was utilized to identify genes important for the survival of Y. pestis within murine macrophages. A transposon library was created with ~31,500 Y. pestis KIM6+ insertion mutants. A portion of the Y. pestis transposon insertion mutant library was used to infect BMMs and the surviving bacteria (output pool) were recovered. TraSH was used to compare the output pool to a portion of the library that was not subjected to selection (input pool) in order to identify Y. pestis genes important for survival in macrophages. Each end of the transposon used for mutagenesis contains an outward-reading T7 RNA polymerase promoter. RNAs transcribed from the T7 promoters are complementary to the chromosomal DNA flanking each transposon in the library, so the RNAs can be used as “targets” to identify the approximate position of each transposon insertion in the mutant pool. Differentially labeled targets generated from the output and input pools are competitively hybridized to the 70-mer oligonucleotide microarrays obtained from Pathogen Functional Genomics Resource Center/J. Craig Venter Institute. Genes important for survival of Y. pestis in macrophages are identified by determining the ratio of the signal intensities for the output and input targets hybridizing to a given probe. A transposon library was created with ~31,500 Y. pestis KIM6+ insertion mutants. A portion of the Y. pestis transposon insertion mutant library was used to infect BMMs and the surviving bacteria (output pool) were recovered. TraSH was used to compare the output pool to a portion of the library that was not subjected to selection (input pool). Each end of the transposon used for mutagenesis contains an outward-reading T7 RNA polymerase promoter. RNAs transcribed from the T7 promoters are complementary to the chromosomal DNA flanking each transposon in the library, so the RNAs was used as “targets” to identify the approximate position of each transposon insertion in the mutant pool. Differentially labeled targets generated from the output and input pools are competitively hybridized to the 70-mer oligonucleotide microarrays obtained from Pathogen Functional Genomics Resource Center/J. Craig Venter Institute. Genes important for survival of Y. pestis in macrophages are identified by determining the ratio of the signal intensities for the output and input targets hybridizing to a given probe.

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LoRTIS: A long read method for analysis of large transposon mutant libraries

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