Swati Ranade from PacBio presents recent efforts to look at challenging regions of the human genome using SMRT Sequencing. She highlights a study just published that fully sequences a particular mucin gene for the first time, as well as work on KIR haplotypes in humans and other primates.
Jason Chin, senior director of bioinformatics at PacBio, talks about using long-read sequence data and string graph assembly for assembling diploid genomes. A major challenge for diploid genome assembly is in distinguishing homologous regions from repeats, so he discusses how long reads are essential for resolving repeat regions. In the presentation, Chin displays data from two inbred Arabidopsis strains used to create a synthetic diploid assembly.
Ali Bashir from the Icahn Institute for Genomics and Multiscale Biology at Mount Sinai describes a tool to detect tandem repeats (PACMonSTR), which he believes are dramatically underrepresented in the human genome reference but that can be discovered with PacBio sequencing. In a collaboration with Cold Spring Harbor Laboratory and Cornell, Bashir and his team generated shotgun, whole-genome sequence data from human genomic DNA using PacBio sequencing. Their goal was to find structural variation features that are not present in the existing reference. He shows numerous examples wherein the long PacBio reads were able to resolve inversions in the sample,…
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.
Evan Eichler, Howard Hughes Medical Investigator from the University of Washington discusses his use of the PacBio system to study difficult-to-sequence regions of the human and chimp genomes. Eichler has identified a number of rapidly evolving hot spots in the human genome that are associated with disease. These regions are quite long and have extremely repetitive DNA sequence, making them difficult to elucidate with short-read sequencing and very expensive to interrogate with Sanger sequencing. Eichler’s goal is to fill in the missing regions of the human genome reference, many of which contain segmental duplications.
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…
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.
Jonas Korlach, Chief Scientific Officer at PacBio, discussed the technology waves that have followed the initial human genome sequencing project, where we are today, and where we are going. Today, we are in what Korlach calls the 4th wave, where more comprehensive whole-genome re-sequencing is occurring, and we are nearing the 5th, when we will actually be able to free ourselves from reference genomes and sequence everything de novo.
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.
Alex Dainis, a graduate student in Euan Ashley’s lab at Stanford University, presents her ASHG 2015 poster on haplotyping for genes linked to hypertrophic cardiomyopathy. Using the Iso-Seq method with SMRT Sequencing, she sequenced full transcripts of two genes of interest, generating data on 150 different isoforms. Rare variants, which could not be found with other technologies, were associated with haplotypes.
Yunfei Guo, a grad student at the University of Southern California, discusses the benefits of SMRT Sequencing: very long reads that make it possible to resolve long repetitive regions and discover structural variants, and a random error mode that allows for extremely high accuracy.
Alex Dainis from Stanford University says the Sequel System from PacBio will offer more power to multiplex samples more efficiently.