Introduction: Around 5% (1,168) of protein-coding genes in the human genome contain an exon that is difficult to map with typical next-generation sequencing (NGS) read lengths due to homologous pseudogenes or segmental duplications. Among the difficult-to-map genes are 193 with known medical relevance, including CYP2D6, GBA, SMN1/2, and VWF. Long-read DNA sequencing provides increased mappability, accessing many of the difficult-to-map regions by connecting the homologous exon to neighboring unique sequence. Until recently, the read-level accuracy of long-read sequencing had made it challenging to accurately call small variants. The recently developed HiFi reads from the PacBio Sequel II System provide both…
This seminar features great hands-on information and best practices for analyzing SMRT Sequencing data for eukaryotic genome assembly. Michael Schatz provides an overview of the assembly tools, provides recommendations for when to use each one, and discusses the challenges of short-read assemblies. James Gurtowski gives an in-depth overview of hybrid assemblies methods, where short read data are used used to correct errors in longer reads. Finally, Sergey Koren presents on chromosome-scale assembly, including the MinHash Alignment Process (MHAP) he developed to dramatically reduce the computational processing power required for genome assemblies.
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…
Dr. Nezih Cereb, CEO & co-founder of HistoGenetics shares his reasons for adopting the PacBio DNA Sequencing platform for their operations and elaborates how the system’s unique ability to sequence full-length HLA amplicons irrespective of insert size and to provide fully phased HLA alleles will be used for HLA typing.
Yunfei Guo, from the University of Southern California, presents his ASHG 2015 poster on a de novo assembly of a diploid Asian genome. The uniform coverage of long-read sequencing helped access regions previously unresolvable due to high GC bias or long repeats. The assembly allowed scientists to fill some 400 gaps in the latest human reference genome, including some as long as 50 kb.
Michael Schatz of Cold Spring Harbor Laboratory and Johns Hopkins University discusses the challenges in detecting structural variations (SVs) in high throughput sequencing data, especially more complex SVs such as a duplication nested within an inversion. To overcome these challenges, Dr. Schatz and his team have been applying long-read sequencing to analyze SVs in a range of samples from small microbial genomes, through mid-sized plant and animal genomes, to large mammalian genomes. The increased read lengths, which currently average over 10kbp and some approach 100kbp, make it possible to span more complex SVs and accurately assess SVs in repetitive regions,…
David Kudrna, Rod Wing, and the Arizona Genomics Institute (AGI) plan to fully sequence and annotate the genomes and transcriptomes of 3-4 accessions from each of the estimated 9-15 subpopulation of rice. These subpopulation-specific references will be used to map resequencing data of 3,000 individuals for variation discovery, GWAS, and genomic selection studies to address important traits such as biotic and abiotic stress tolerances, yield, and grain quality. Here Dr. Kudrna presents the first high-quality genome sequence of the rice variety Nagina22. AGI produced and assembled 65-fold coverage of SMRT Sequencing data, resulting in an assembly of 373 Mb with…
Hélène Berges, managing director of the Plant Genomic Center at the Institut National de la Recherche Agronomique (INRA) in Toulouse, France, discusses how obtaining accurate and reliable sequence data is still challenging when targeting specific genomic regions. These issues are even more noticeable for complex plant genomes. To overcome these issues, Dr. Berges and her team have developed a strategy to reduce the genome complexity by using the large insert BAC libraries combined with next-generation sequencing technologies. She compares different technologies to sequence pools of BAC clones from several species (maize, wheat, strawberry, barley, sugarcane, and sunflower) known to be…
Sergey Koren of the National Biodefense Analysis and Countermeasures Center (NBACC) discusses integrating the MinHash Alignment Process (MHAP) with Celera Assembler to enable reference-grade assemblies of model organisms, revealing novel heterochromatic sequences and filling low-complexity gap sequences in the GRCh38 human reference genome. Dr. Koren and his team have applied this method to assemble the San Clemente goat genome. Combining SMRT Sequencing and next-generation optical mapping from BioNano Genomics generates an assembly that is over 150-fold more contiguous than the latest Capra hircusgoat reference. In combination with Hi-C sequencing, the assembly surpasses reference assemblies de novo, with minimal manual intervention.…
Winston Timp from Johns Hopkins University studies the metabolism of hummingbirds, which sustain the highest metabolic rates among all vertebrates. Notably, hummingbirds can switch rapidly between a fuel of lipids to newly ingested sugars. This remarkable metabolism is supported by enzymes which operate at the extreme limit of catalytic efficiency. Understanding the molecular basis of enzymatic action will provide a foundation enabling rational engineering of metabolic circuits in other systems. To do this, Dr. Timp and his team generated a de novo transcriptome of the hummingbird liver using the Iso-Seq method. Characterization of the resulting protein coding sequences provides clues…
Chetana Pandya, a bioinformatician at the Icahn School of Medicine at Mount Sinai discusses how the institute is using their PacBio Systems in a variety of cancer research project including detecting somatic fusions events in patient-derived cancer samples and validating somatic variants.
Jonas Korlach spoke about recent SMRT Sequencing updates, such as latest Sequel System chemistry release (1.2.1) and updates to the Integrative Genomics Viewer that’s now update optimized for PacBio data. He presented the recent data release of structural variation detected in the NA12878 genome, including many more insertions and deletions than short-read-based technologies were able to find.
This presentation describes a new genome browser for read alignments around complex variation: genomeribbon.com. Ribbon was built for viewing genomic read alignments around structural variants. It is very useful for looking at long-read alignments where we can see a complicated set of variants captured within individual reads. Ribbon can also be used to view assembly alignments such as from MUMmer.
Bioinformatics scientist Chetanya Pandya from the Icahn School of Medicine at Mount Sinai presents a poster comparing short-read and long-read sequencing to detect somatic fusion events in cancer samples. SMRT Sequencing identified significantly more fusions, while many of the short-read calls may have been artifacts from challenging regions of the genome.
In this AGBT 2017 poster, Ulf Gyllensten from Uppsala University presents two local reference genomes generated with PacBio and Bionano Genomics data. These assemblies include structural variation and repetitive regions that have been missed with previous short-read efforts, including some new genes not annotated in the human reference genome.