Understanding the genetic basis of infectious diseases is critical to enacting effective treatments, and several large-scale sequencing initiatives are underway to collect this information. Sequencing bacterial samples is typically performed by mapping sequence reads against genomes of known reference strains. While such resequencing informs on the spectrum of single-nucleotide differences relative to the chosen reference, it can miss numerous other forms of variation known to influence pathogenicity: structural variations (duplications, inversions), acquisition of mobile elements (phages, plasmids), homonucleotide length variation causing phase variation, and epigenetic marks (methylation, phosphorothioation) that influence gene expression to switch bacteria from non- pathogenic to pathogenic…
Background: To better understand the relationships among HIV-1 viruses in linked transmission pairs, we sequenced several samples representing HIV transmission pairs from the Zambia Emory HIV Research Project (Lusaka, Zambia) using Single Molecule, Real-Time (SMRT) Sequencing. Methods: Single molecules were sequenced as full-length (9.6 kb) amplicons directly from PCR products without shearing. This resulted in multiple, fully-phased, complete HIV-1 genomes for each patient. We examined Single Genome Amplification (SGA) prepped samples, as well as samples containing complex mixtures of genomes. We detail mathematical techniques used in viral variant subspecies identification, including clustering distance metrics and mutual information, which were used…
PacBio 2013 User Group Meeting Presentation Slides: Lisbeth Guethlein from Stanford University School of Medicine looked at highly repetitive and variable immune regions of the orangutan genome. Guethlein reported that “PacBio managed to accomplish in a week what I have been working on for a couple years” (with Sanger sequencing), and the results were concordant. “Long story short, I was a happy customer.”
Understanding the genetic basis of infectious diseases is critical to enacting effective treatments, and several large-scale sequencing initiatives are underway to collect this information. Sequencing bacterial samples is typically performed by mapping sequence reads against genomes of known reference strains. While such resequencing informs on the spectrum of single nucleotide differences relative to the chosen reference, it can miss numerous other forms of variation known to influence pathogenicity: structural variations (duplications, inversions), acquisition of mobile elements (phages, plasmids), homonucleotide length variation causing phase variation, and epigenetic marks (methylation, phosphorothioation) that influence gene expression to switch bacteria from non-pathogenic to pathogenic…
PacBio 2013 User Group Meeting Presentation Slides: Lance Hepler from UC San Diego’s Center for AIDS Research used the PacBio RS to study intra-host diversity in HIV-1. He compared PacBio’s performance to that of 454® sequencer, the platform he and his team previously used. Hepler noted that in general, there was strong agreement between the platforms; where results differed, he said that PacBio data had significantly better reproducibility and accuracy. “PacBio does not suffer from local coverage loss post-processing, whereas 454 has homopolymer problems,” he noted. Hepler said they are moving away from using 454 in favor of the PacBio…
The three classes of genes that comprise the MHC gene family are actively involved in determining donor-recipient compatibility for organ transplant, as well as susceptibility to autoimmune diseases via cross-reacting immunization. Specifically, Class I genes HLA-A, -B, -C, and class II genes HLA-DR, -DQ and -DP are considered medically important for genetic analysis to determine histocompatibility. They are highly polymorphic and have thousands of alleles implicated in disease resistance and susceptibility. The importance of full-length HLA gene sequencing for genotyping, detection of null alleles, and phasing is now widely acknowledged. While DNA-sequencing-based HLA genotyping has become routine, only 7% of…
PacBio RS II sequencing chemistries provide read lengths beyond 20 kb with high consensus accuracy. The long read lengths of P4-C2 chemistry and demonstrated consensus accuracy of 99.999% are ideal for applications such as de novo assembly, targeted sequencing and isoform sequencing. The recently launched P5-C3 chemistry generates even longer reads with N50 often >10,000 bp, making it the best choice for scaffolding and spanning structural rearrangements. With these chemistry advances, PacBio’s read length performance is now primarily determined by the SMRTbell library itself. Size selection of a high-quality, sheared 20 kb library using the BluePippin™ System has been demonstrated…
Alternative splicing of RNA is an important mechanism that increases protein diversity and is pervasive in the most complex biological functions. While advances in RNA sequencing methods have accelerated our understanding of the transcriptome, isoform discovery remains computationally challenging due to short read lengths. Here, we describe the Isoform Sequencing (Iso-Seq) method using long reads generated by the PacBio RS II. We sequenced rat heart and lung RNA using the Clontech® SMARTer® cDNA preparation kit followed by size selection using agarose gel. Additionally, we tested the BluePippin™ device from Sage Science for efficiently extracting longer transcripts = 3 kb. Post-sequencing,…
PacBio SMRT Sequencing has the unique ability to directly detect base modifications in addition to the nucleotide sequence of DNA. Because eukaryotes use base modifications to regulate gene expression, the absence or presence of epigenetic events relative to the location of genes is critical to elucidate the function of the modification. Therefore an integrated approach that combines multiple omic-scale assays is necessary to study complex organisms. Here, we present an integrated analysis of three sequencing experiments: 1) DNA sequencing, 2) base-modification detection, and 3) Iso-seq analysis, in Neurospora crassa, a filamentous fungus that has been used to make many landmark…
Pulmonary non-tuberculous mycobacterial (PNTM) infections occur in patients with chronic lung disease, but also in a distinct group of elderly women without lung defects who share a common body morphology: tall and lean with scoliosis, pectus excavatum, and mitral valve prolapse. In order to characterize the human host susceptibility to PNTM, we performed whole exome sequencing (WES) of 44 individuals in extended families of patients with active PNTM as well as 55 additional unrelated individuals with PNTM. This unique collection of familial cohorts in PNTM represents an important opportunity for a high yield search for genes that regulate mucosal immunity.…
The newer hierarchical genome assembly process (HGAP) performs de novo assembly using data from a single PacBio long insert library. To assess the benefits of this method, DNA from several Salmonella enterica serovars was isolated from a pure culture. Genome sequencing was performed using Pacific Biosciences RS sequencing technology. The HGAP process enabled us to close sixteen Salmonella subsp. enterica genomes and their associated mobile elements: The ten serotypes include: Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) S. Bareilly, S. Heidelberg, S. Cubana, S. Javiana and S. Typhimurium, S. Newport, S. Montevideo, S. Agona, and S. Tennessee. In addition,…
Background: Genotypic testing of chronic viral infections is an important part of patient therapy and requires assays capable of detecting the entire spectrum of viral mutations. Single Molecule, Real-Time (SMRT) sequencing offers several advantages to other sequencing technologies, including superior resolution of mixed populations and long read lengths capable of spanning entire viral protein coding regions. We examined detection sensitivity of SMRT sequencing using a mixture of HIV-1 RT gene coding regions containing single NNRTI mutations. Methodology: SMRTbell templates were prepared from PCR products generated from a prospective reference material being developed by BC Center of Excellence for HIV/AIDS, and…
Background: HIV-1 proviruses in peripheral blood mononuclear cells (PBMCs) are felt to be an important reservoir of HIV-1 infection. Given that this pool represents an archival library, it can be used to study virus evolution and CD4+ T cell survival. Accurate study of this pool is burdened by difficulties encountered in sequencing a full-length proviral genome, typically accomplished by assembling overlapping pieces and imputing the full genome. Methodology: Cryopreserved PBMCs collected from a total of 8 HIV+ patients from 1997-2001 were used for genomic DNA extraction. Patients had been receiving cART for 2-8 years at the time samples were obtained.…
Background: The use of next generation sequencing (NGS) to examine circulating HIV env variants has been limited due to env’s length (2.6 kb), extensive indel polymorphism, GC deficiency, and long homopolymeric regions. We developed and standardized protocols for isolation, RT-PCR amplification, single molecule real-time (SMRT) sequencing, and haplotype analysis of circulating HIV-1 env variants to evaluate viral diversity in primary infection. Methodology: HIV RNA was extracted from 7 blood plasma samples (1 mL) collected from 5 subjects (one individual sampled and sequenced at 3 time points) in the San Diego Primary Infection Cohort between 3-33 months from their estimated date…
Single Molecule, Real-Time (SMRT) Sequencing holds promise for addressing new frontiers in large genome complexities, such as long, highly repetitive, low-complexity regions and duplication events, and differentiating between transcript isoforms that are difficult to resolve with short-read technologies. We present solutions available for both reference genome improvement (>100 MB) and transcriptome research to best leverage long reads that have exceeded 20 Kb in length. Benefits for these applications are further realized with consistent use of size-selection of input sample using the BluePippin™ device from Sage Science. Highlights from our genome assembly projects using the latest P5-C3 chemistry on model organisms…