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.”
Determination of unique individual haplotypes is an essential first step toward understanding how identical genotypes having different phases lead to different biological interpretations of function, phenotype, and disease. Genome-wide methods for identifying individual genetic variation have been limited in their ability to acquire phased, extended, and complete genomic sequences that are long enough to assemble haplotypes with high confidence. We explore a recombineering approach for isolation and sequencing of a tiling of targeted fosmids to capture interesting regions from human genome. Each individual fosmid contains large genomic fragments (~35?kb) that are sequenced with long-read SMRT technology to generate contiguous long…
As a cost-effective alternative to whole genome human sequencing, targeted sequencing of specific regions, such as exomes or panels of relevant genes, has become increasingly common. These methods typically include direct PCR amplification of the genomic DNA of interest, or the capture of these targets via probe-based hybridization. Commonly, these approaches are designed to amplify or capture exonic regions and thereby result in amplicons or fragments that are a few hundred base pairs in length, a length that is well-addressed with short-read sequencing technologies. These approaches typically provide very good coverage and can identify SNPs in the targeted region, but…
A longstanding goal of genomic analysis is the identification of causal genetic factors contributing to disease. While the common disease/common variant hypothesis has been tested in many genome-wide association studies, few advancements in identifying causal variation have been realized, and instead recent findings point away from common variants towards aggregate rare variants as causal. A challenge is obtaining complete phased genomic sequences over extended genomic regions from sufficient numbers of cases and controls to identify all potential variation causal of a disease. To address this, we modified methods for targeted DNA isolation using fosmid technology and single-molecule, long-sequence-read generaton that…
We show that linearizing and directly sequencing full-length fosmids simplifies the assembly problem such that it is possible to unambiguously assemble individual haplotypes for the highly repetitive 100-200 kb killer Ig-like receptor (KIR) gene loci of chromosome 19. A tiling of targeted fosmids can be used to clone extended lengths of genomic DNA, 100s of kb in length, but repeat complexity in regions of particular interest, such as the KIR locus, means that sequence assembly of pooled samples into complete haplotypes is difficult and in many cases impossible. The current maximum read length generated by SMRT Sequencing exceeds the length…
The long reads, random error, and unbiased sampling of SMRT Sequencing enables high quality, de novo assembly of the human genome. PacBio long reads are capable of resolving genomic variations at all size scales, including SNPs, insertions, deletions, inversions, translocations, and repeat expansions, all of which are important in understanding the genetic basis for human disease and difficult to access via other technologies. In demonstration of this, we report a new high-quality, diploid aware de novo assembly of Craig Venter’s well-studied genome.
The complex immune regions of the genome, including MHC and KIR, contain large copy number variants (CNVs), a high density of genes, hyper-polymorphic gene alleles, and conserved extended haplotypes (CEH) with enormous linkage disequilibrium (LDs). This level of complexity and inherent biases of short-read sequencing make it challenging for extracting immune region haplotype information from reference-reliant, shotgun sequencing and GWAS methods. As NGS based genome and exome sequencing and SNP arrays have become a routine for population studies, numerous efforts are being made for developing software to extract and or impute the immune gene information from these datasets. Despite these…
The killer immunoglobulin-like receptors (KIR) genes belong to the immunoglobulin superfamily and are widely studied due to the critical role they play in coordinating the innate immune response to infection and disease. Highly accurate, contiguous, long reads, like those generated by SMRT Sequencing, when combined with target-enrichment protocols, provide a straightforward strategy for generating complete de novo assembled KIR haplotypes. We have explored two different methods to capture the KIR region; one applying the use of fosmid clones and one using Nimblegen capture.
The human immunoglobulin heavy chain locus (IGH) remains among the most understudied regions of the human genome. Recent efforts have shown that haplotype diversity within IGH is elevated and exhibits population specific patterns; for example, our re-sequencing of the locus from only a single chromosome uncovered >100 Kb of novel sequence, including descriptions of six novel alleles, and four previously unmapped genes. Historically, this complex locus architecture has hindered the characterization of IGH germline single nucleotide, copy number, and structural variants (SNVs; CNVs; SVs), and as a result, there remains little known about the role of IGH polymorphisms in inter-individual…
Learn how Single Molecule, Real-Time (SMRT) Sequencing and the Sequel IIe System and will accelerate your research by delivering highly accurate long reads to provide the most comprehensive view of genomes, transcriptomes and epigenomes.
Dan Geraghty explains that while there have been decades’ worth of studies associating the genetics of the major histocompatibility complex (MHC), and the highly polymorphic HLA class 1 and 2 genes, we still haven’t found the key mutations for a variety of different autoimmune diseases such as type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and others. Enormous amounts of linkage disequilibrium in these regions are one factor, as is getting information in phase, so larger stretches of sequence are needed. Recently Geraghty has begun using SMRT Technology with hopes of drilling down to the causal genetics.
In this webinar, the presenters describe a targeted sequencing workflow that combines Roche NimbleGen’s SeqCap EZ enrichment technology with PacBio’ SMRT Sequencing to provide a more comprehensive view of variants and haplotype information over multi-kilobase, contiguous regions. They demonstrate that 6 kb fragments can also be utilized to enrich for long fragments that extend beyond the targeted capture site and well into (and often across) the adjacent intronic regions. When combined with SMRT Sequencing, multi-kilobase genomic regions can be phased and variants, including complex structural variants, can be detected in exons, introns and intergenic regions.
This tutorial provides an overview of the Long Amplicon Analysis (LAA) application. The LAA algorithm generates highly accurate, phased and full-length consensus sequences from long amplicons. Applications of LAA include HLA typing, alternative haplotyping, and localized de novo assemblies of targeted genes. This tutorial covers features of SMRT Link v5.0.0.
In a talk at AGBT 2017, Histogenetics CEO Nezih Cereb reported on how SMRT Sequencing is allowing his team to produce full-length, phased sequences for HLA alleles, which are important for matching organ transplants to recipients. The company is typing thousands of samples per day on their PacBio RS II systems and their new Sequel System. Cereb noted that SMRT Sequencing is unique in its ability to reliably phase mutations in the HLA alleles without imputation. Cereb concluded with his plans to use this approach for other complex regions, such as KIR, and announced their continued increasing HLA typing capacity…