Structural variation accounts for much of the variation among human genomes. Structural variants of all types are known to cause Mendelian disease and contribute to complex disease. Learn how long-read sequencing is enabling detection of the full spectrum of structural variants to advance the study of human disease, evolution and genetic diversity.
Interested to learn about pangenomes? Explore this guide to learn how they provide a more complete picture of the core genes of a given species and how that can provide better biological understanding.
The study of genomics has revolutionized our understanding of science, but the field of transcriptomics grew with the need to explore the functional impacts of genetic variation. While different tissues in an organism may share the same genomic DNA, they can differ greatly in what regions are transcribed into RNA and in their patterns of RNA processing. By reviewing the history of transcriptomics, we can see the advantages of RNA sequencing using a full-length transcript approach become clearer.
Explore how long-read sequencing enables solving of rare and mendelian diseases.
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.…
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…
Second-generation sequencing has brought about tremendous insights into the genetic underpinnings of biology. However, there are many functionally important and medically relevant regions of genomes that are currently difficult or impossible to sequence, resulting in incomplete and fragmented views of genomes. Two main causes are (i) limitations to read DNA of extreme sequence content (GC-rich or AT-rich regions, low complexity sequence contexts) and (ii) insufficient read lengths which leave various forms of structural variation unresolved and result in mapping ambiguities.
As the costs for genome sequencing have decreased the number of “genome” sequences have increased at a rapid pace. Unfortunately, the quality and completeness of these so–called “genome” sequences have suffered enormously. We prefer to call such genome assemblies as “gene assembly space” (GAS). We believe it is important to distinguish GAS assemblies from reference genome assemblies (RGAs) as all subsequent research that depends on accurate genome assemblies can be highly compromised if the only assembly available is a GAS assembly.
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…
Most of the base pairs that differ between two human genomes are in intermediate-sized structural variants (50 bp to 5 kb), which are too small to detect with array comparative genomic hybridization or optical mapping but too large to reliably discover with short-read DNA sequencing. Long-read sequencing with PacBio Single Molecule, Real-Time (SMRT) Sequencing platforms fills this technology gap. PacBio SMRT Sequencing detects tens of thousands of structural variants in a human genome with approximately five times the sensitivity of short-read DNA sequencing. Effective application of PacBio SMRT Sequencing to detect structural variants requires quality bioinformatics tools that account for…
Structural variants (SVs) – genomic differences =50 base pairs – are few by count compared to single nucleotide variants (SNVs) and indels but include most of the base pairs that differ between two humans.
Introduction: Long-read sequencing has revealed more than 20,000 structural variants spanning over 12 Mb in a healthy human genome. Short-read sequencing fails to detect most structural variants but has remained the more effective approach for small variants, due to 10-15% error rates in long reads, and copy-number variants (CNVs), due to lack of effective long-read variant callers. The development of PacBio highly accurate long reads (HiFi reads) with read lengths of 10-25 kb and quality >99% presents the opportunity to capture all classes of variation with one approach.Methods: We sequence the Genome in a Bottle benchmark sample HG002 and an…
In this BioConference Live webinar, PacBio CSO Jonas Korlach highlights how multi-kilobase reads from SMRT Sequencing can resolve many of the previously considered ‘difficult-to-sequence’ genomic regions. The long reads also allow phasing of the sequence information along the maternal and paternal alleles, demonstrated by full-length, fully phased HLA class I & II gene sequencing. In addition, characterizing the complex landscape of alternative gene products is currently very difficult with short-read sequencing technologies, and he describes how long-read, full-length mRNA sequencing can be used to describe the diversity of transcript isoforms, with no assembly required. Lastly, in the exciting area of…
This animation depicts a process by which single molecule SMRTbell templates are loaded in the Zero Mode Waveguides (ZMWs) of the PacBio RS II sequencing system using the automated MagBead Station.
PacBio’s SMRT technology harnesses the natural process of DNA replication, which is a highly efficient and accurate process. Our SMRT technology enables the observation of DNA synthesis as it occurs in real time.