SMRT Resources

In this presentation, Naomichi Matsumoto from Yokohama City University speaks about the use of SMRT Sequencing to solve Mendelian diseases, including the story of how his lab discovered a 12.4 kb structural variant that’s responsible for progressive myoclonic epilepsy in two siblings. He also reports progress in understanding repeat expansion disorders by pairing SMRT Sequencing with new analysis tools designed to highlight repetitive areas.

In this presentation, Shawn Levy from the HudsonAlpha Institute for Biotechnology and HudsonAlpha Discovery offers a look at his team’s early access experience with the Sequel II System. Recent work includes a project designed to improve sequencing results from FFPE samples with long-read data. The protocol is still being optimized, but preliminary results indicate that SMRT Sequencing improves the quality of data that can be produced from these highly degraded samples. Looking ahead, Levy’s team will be using SMRT Sequencing to generate about 7,000 long-read genome assemblies for the All of Us program.

In this presentation, Emily Hatas of PacBio offers a look a how SMRT Sequencing has changed over the years as well as the most common applications in human genome analysis: high-throughput structural variant detection; comprehensive variant detection; and de novo assembly of reference genomes.

Epigenetics expert Michael Jennings from Griffith University first posited the phasevarion, or the phase variable regulon mechanism in host-adapted pathogens. This mechanism switches expression of multiple genes in a coordinated fashion and has significant implications on pathogen virulence. In his talk, Jennings describes the phasevarion and his use of whole methylome data to rapidly identify methylation targets.

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.

At the PacBio ASHG workshop, Hagen Tilgner describes how he used long-read sequencing with Iso-Seq method to generate the first personal transcriptomes for three individuals. From these three family members, he and his collaborators were able to unambigously assign allele-specific RNA haplotypes, including HLA haplotypes, and demonstrated Mendelian inheritance of RNA molecules.

KIR haplotypes can be determined by physical and computational and statistical methods. Martin Maiers from National Bone Marrow Donor Program (NMDP) presents a summary of their work to determine KIR genomic content for use in clinical transplantation, outcomes of HLA sequencing of KIR region across a variety of methods and shares their data from recent experiments using PacBio single-molecule sequencing of fosmid libraries.

Tim Smith of the USDA presents his work to establish a high-quality reference genome of the San Clemente goat. After generating 70-fold PacBio sequence data, the PacBio assembly proved to be far more complete than the existing draft reference genome, with contigs extending 100 times longer on average.

Robert VanBuren of the Danforth Plant Science Center and winner of the 2014 SMRT Grant Program presents a de novo assembly of the Oro grass genome (Oropetium thomaeum). The reference genome will aid scientist studying drought tolerance in common crop species, especially cereals, though comparative genomics to understand potential key genetic underpinnings for this “resurrection” trait. Initial comparative results to Brachypodium and maize are presented, as well as secondary analysis to identify key metabolic traits.

Research into a bacterial sample from World War I has revealed secrets of the dysentery-causing strain’s success and uncovered the story of the soldier behind the sample.

Lizzie Wilbanks formerly from UC Davis, discusses how longs read from SMRT Sequencing allow accurate assembly of members from the complex pink berry salt marsh community.

Jeong-Sun Seo of Macrogen and Seoul National University College of Medicine reports on sequencing many Asian genomes to better understand genetic variation in that population. He shows that identifying certain structural variants may explain diseases that disproportionately affect Asian people.

Ulf Gyllensten from Uppsala University describes his AGBT poster showing the use of SMRT Sequencing for HLA allele typing. He says long reads are essential for sequencing the HLA genes because they link exons in a single read and do not introduce bias, as short-read sequencers can. Looking at fusion transcripts from CML patients generated information that couldn’t be achieved with any other technology, he adds.

Dan Geraghty from the Fred Hutchinson Cancer Research Center presents his AGBT poster on a new PacBio-based solution to sequence extended genomic regions — in this case, KIR and MHC, two of the most variable regions of the human genome. He reports data revealing for the first time regions that may be associated with autoimmune diseases such as diabetes, rheumatoid arthritis, and multiple sclerosis, and also shows that sequences were phased, complete, and highly accurate.

During this presentation from ASHG 2015, Maria Nattestad of Cold Spring Harbor Laboratory described the study of a Her2-amplified breast cancer cell line using long-read sequencing from PacBio. With reads as long as 71 kb, she was able to characterize extensive and complex rearrangements and found more than 11,000 structural variants. She also used the Iso-Seq method to find gene fusions, including some novel ones.

Richard Gibbs, Director of Baylor College of Medicine’s Human Genome Sequencing Center, talked about the transition to genomic medicine. This hasn’t been as simple as people would like due to such issues as the incomplete reference genome, the difficulty in characterizing some variation, and the lack of knowledge about the function of some genes. At Baylor, most of the human genome sequencing is done for children with Mendelian disorders. He said that among 7,000 samples processed using short-read exome sequencing, only about 25% of these cases are solved. The relatively low diagnosis rate is likely due to structural variation and other regions not captured by short reads. He discussed some ways to get to structural variation including PacBio sequencing and PBJelly and Parliament analysis routines, using as little as 10-fold PacBio coverage. Using these methods they are closing gaps in the genomes of various species, for example – he noted that in the sheep genome they have closed 70% of gaps with PacBio reads. He also mentioned the use of PBHoney to identify inconsistencies between reads and the reference, and that long-range capture strategies using a combination of Nimblegen and PacBio are ‘going beautifully so far.’

Rick Wilson, Director of the McDonnell Genome Institute at Washington University in St. Louis titled his talk “Of reference genomes and precious metals” and walked the audience through definitions and standards for the various quality levels for de novo assembled human genomes, e.g., platinum, gold, and silver. He noted that this was a good topic for this session because of the important role PacBio has played in the community’s work to create reference-grade genomes. For example, PacBio technology has enabled them to sequence additional genomes (CHM1, CHM13) to a very high quality level. Although these sequences were essential for further refining the GRCh38 reference build, the current reference genome is still not optimal for some highly polymorphic and complex regions of the genome, and does not adequately represent diverse ancestries sufficiently. Wilson outlined their definition of a ‘gold’ genome as a high-quality, highly contiguous representation of the genome with haplotype resolution of critical regions – created with PacBio reads to perform de novo assembly, a scaffold created using BioNano and/or Dovetail aligned to reference, and BACs to fill targeted regions and shore up gaps. The list of gold genomes in progress includes the Yuroban, Puerto Rican Han Chinese, CEU, and Luhya. A ‘platinum’ genome is a contiguous, haplotype-resolved representation of the entire genome, two of which currently exist for the CHM1 and CHM13 hydatidiform moles. While ‘silver’ definition standards are to be determined, this category is generally non-trio genomes produced with PacBio and BioNano mapping, and no BAC library.

One of the popular questions on the Mendelspod program is how those doing sequencing decide between the quality of PacBio’s long reads and the cheaper short read technology, such as that of Illumina or Thermo Fisher. Steve Marsh, the Director of Bioinformatics at the Anthony Nolan Research Institute in London, provides the most clear and dramatic answer yet: use the PacBio system exclusively. Established in 1974 by the mother of a boy with a rare blood disease, the Anthony Nolan Institute is a world leader in blood crossmatching and donor/patient registries. Steve and his team at the Institute have dramatically improved the resolution of HLA typing, one of the methods for matching a donor’s blood tissue with that of the transplant recipient. Thirty years ago when Steve entered the field, HLA typing was performed with serology and there were just 119 HLA antigens that were known. “We thought 119 was a lot of diversity,” says Steve. With the advent of genomic tools in the 90’s, HLA typing moved to the level of the genetic allele, done first with PCR and then with sequencing. “We knew that the HLA molecules were polymorphic, but now we know they are hyper-polymorphic. . . For example, ‘A2’ is a specificity, and serologically we recognized the specificity ‘A2,’ and that was it. We now recognize that there are over 500 different variants of A2,” Steve explains. Knowing more about the incredible diversity of blood types can make achieving a donor/patient match seem all the more prohibitive. More variables mean fewer candidates. But research at the Anthony Nolan is now paying off and is robust enough to make a difference in the clinic. Ideally blood registries will provide precise matches and do so immediately. All this explains why Steve is so keen on the PacBio system. In a field where the quality of the sequencing makes the difference between the right match and not, the increased price of the longer reads is worth it.

Neema Mayor from Anthony Nolan Research Institute offers an introduction to the challenges of characterizing the HLA region, noting that improvements in resolution have allowed scientists to dramatically expand the number of classifications used to match donors to recipients. As sequencing resolution improves, Mayor says, scientists expect to find even more polymorphisms than what has been already catalogued.