The correct phasing of genetic variations is a key challenge for many applications of DNA sequencing. Allele-level resolution is strongly preferred for histocompatibility sequencing where recombined genes can exhibit different compatibilities than their parents. In other contexts, gene complementation can provide protection if deleterious mutations are found on only one allele of a gene. These problems are especially pronounced in immunological domains given the high levels of genetic diversity and recombination seen in regions like the Major Histocompatibility Complex. A new tool for analyzing Single Molecule, Real-Time (SMRT) Sequencing data – Long Amplicon Analysis (LAA) – can generate highly accurate,…
Recent advances in next-generation sequencing have led to an increased use of formalin-fixed and paraffin-embedded (FFPE) tissues for medical samples in disease and scientific research. Single Molecule, Real-Time (SMRT) Sequencing offers a unique advantage for direct analysis of FFPE samples without amplification. However, obtaining ample long-read information from FFPE samples has been a challenge due to the quality and quantity of the extracted DNA. FFPE samples often contain damaged sites, including breaks in the backbone and missing or altered nucleotide bases, which directly impact sequencing and target enrichment. Additionally, the quality and quantity of the recovered DNA vary depending on…
We previously reported on the use of the Ion PGM next generation sequencing (NGS) platform to genotype HLA class I and class II genes by a super-high resolution, single-molecule, sequence-based typing (SS-SBT) method (Shiina et al. 2012). However, HLA alleles could not be assigned at the field 4 level at some HLA loci such as DQA1, DPA1 and DPB1 because the SNP and indel densities were too low to identify and separate both of the phases. In this regard, we have now added the single molecule, real-time (SMRT) DNA sequencer PacBio RS II method to our analysis in order to…
Melissa Laird Smith discussed how the Icahn School of Medicine at Mount Sinai uses long-read sequencing for translational research. She gave several examples of targeted sequencing projects run on the Sequel System including CYP2D6, phased mutations of GLA in Fabry’s disease, structural variation breakpoint validation in glioblastoma, and full-length immune profiling of TCR sequences.
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…
In this AGBT 2017 talk, PacBio CSO Jonas Korlach provided a technology roadmap for the Sequel System, including plans the continue performance and throughput increases through early 2019. Per SMRT Cell throughput of the Sequel System is expected to double this year and again next year. Together with a new higher-capacity SMRT Cell expected to be released by the end of 2018, these improvements result in a ~30-fold increase or ~150 Gb / SMRT Cell allowing a real $1000 real de novo human genome assembly. Also discussed: Additional application protocol improvements, new chemistry and software updates, and a look at…
Human MHC class I genes HLA-A, -B, -C, and class II genes HLA -DR, -DQ, and -DP play a critical role in the immune system as primary factors responsible for organ transplant rejection. Additionally, the HLA genes are important targets for clinical and drug sensitivity research because of their direct or linkage-based association with several diseases, including cancer, and autoimmune diseases. HLA genes are highly polymorphic, and their diversity originates from exonic combinations as well as recombination events. With full-length gene sequencing, a significant increase of new alleles in the HLA database is expected, stressing the need for high-resolution sequencing.…
Studying microbial genomics and infectious disease? Learn how the PacBio Sequel II System can help advance your research, with first-hand perspectives from scientists who are investigating SARS-CoV-2 and COVID-19. In this webinar, Melissa Laird-Smith (Mt. Sinai School of Medicine) discusses her work evaluating the impact of host immune restriction in health and disease with high resolution HLA typing. She is joined by Corey Watson (University of Louisville School of Medicine) who talks about overcoming complexity to elucidate the role of IGH haplotype diversity in antibody-mediated immunity. Hosted by Meredith Ashby, Director of Microbial Genomics at PacBio. Access additional PacBio resources…
Next generation DNA sequencing is used to determine the HLA-A, -B, -C, -DRB1, -DRB3/4/5, and -DQB1 assignments of 1009 unrelated volunteers for the unrelated donor registry in The Netherlands. The analysis characterizes all HLA exons and introns for class I alleles; at least exons 2 to 3 for HLA-DRB1; and exons 2 to 6 for HLA-DQB1. Of the distinct alleles present, there are 229 class I and 71 class II; 36 of these alleles are novel. The majority (approximately 98%) of the cumulative allele frequency at each locus is contributed by alleles that appear three or more times. Alleles encoding…
Our understanding of sequence variation in the HLA-DPB1 gene is largely restricted to the hypervariable antigen recognition domain (ARD) encoded by exon 2. Here, we employed a redundant sequencing strategy combining long-read and short-read data to accurately phase and characterise in full length the majority of common and well-documented (CWD) DPB1 alleles as well as alleles with an observed frequency of at least 0.0006% in our predominantly European sample set. We generated 664 DPB1 sequences, comprising 279 distinct allelic variants. This allows us to present the, to date, most comprehensive analysis of the nature and extent of DPB1 sequence variation.…
HLA matching at an allelic-level resolution for volunteer unrelated donor (VUD) hematopoietic cell transplanta- tion (HCT) results in improved survival and fewer post-transplant complications. Limitations in typing technolo- gies used for the hyperpolymorphic HLA genes have meant that variations outside of the antigen recognition domain (ARD) have not been previously characterized in HCT. Our aim was to explore the extent of diversity out- side of the ARD and determine the impact of this diversity on transplant outcome. Eight hundred ninety-one VUD-HCT donors and their recipients transplanted for a hematologic malignancy in the United Kingdom were ret- rospectively HLA typed at…
Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30-40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are…