AGBT 2013 Presentation Slides: Cold Spring Harbor Laboratory’s Michael Schatz presented strategies for de novo assembly of crop genomes with PacBio technolgy.
The goat (Capra hircus) remains an important livestock species due to the species’ ability to forage and provide milk, meat and wool in arid environments. The current goat reference assembly and annotation borrows heavily from other loosely related livestock species, such as cattle, and may not reflect the unique structural and functional characteristics of the species. We present preliminary data from a new de novo reference assembly for goat that primarily utilizes 38 million PacBio P5-C3 reads generated from an inbred San Clemente goat. This assembly consists of only 5,902 contigs with a contig N50 size of 2.56 megabases which…
Goat is an important source of milk, meat, and fiber, especially in developing countries. An advantage of goats as livestock is the low maintenance requirements and high adaptability compared to other milk producers. The global population of domestic goats exceeds 800 million. In Africa, goat production is characterized by low productivity levels, and attempts to introduce more productive breeds have met with poor success due in part to nutritional constraints. It has been suggested that incorporation of selective breeding within the herds adapted for survival could represent one approach to improving food security across Africa. A recently produced genome assembly…
Whole genome sequencing can provide comprehensive information important for determining the biochemical and genetic nature of all elements inside a genome. The high-quality genome references produced from past genome projects and advances in short-read sequencing technologies have enabled quick and cheap analysis for simple variants. However even with the focus on genome-wide resequencing for SNPs, the heritability of more than 50% of human diseases remains elusive. For non-human organisms, high-contiguity references are deficient, limiting the analysis of genomic features. The long and unbiased reads from single molecule, real-time (SMRT) Sequencing and new de novo assembly approaches have demonstrated the ability…
2015 SMRT Informatics Developers Conference Presentation Slides: Sergey Koren of National Biodefense Analysis and Countermeasures Center (NBACC) provided an overview of the MHAP algorithm, a method for assembling large genomes with Sing-Molecule Sequencing and locality sensitive hashing. Using MHAP, Koren produced a human assembly (CHM1) with a contig N50 of >23 Mb.
Purpose: Clinical laboratories, research laboratories and technology developers all need DNA samples with reliably known genotypes in order to help validate and improve their methods. The Genome in a Bottle Consortium (genomeinabottle.org) has been developing Reference Materials with high-accuracy whole genome sequences to support these efforts.Methodology: Our pilot reference material is based on Coriell sample NA12878 and was released in May 2015 as NIST RM 8398 (tinyurl.com/giabpilot). To minimize bias and improve accuracy, 11 whole-genome and 3 exome data sets produced using 5 different technologies were integrated using a systematic arbitration method [1]. The Genome in a Bottle Analysis Group…
Reference genome assemblies provide important context in genetics by standardizing the order of genes and providing a universal set of coordinates for individual nucleotides. Often due to the high complexity of genic regions and higher copy number of genes involved in immune function, immunity-related genes are often misassembled in current reference assemblies. This problem is particularly ubiquitous in the reference genomes of non-model organisms as they often do not receive the years of curation necessary to resolve annotation and assembly errors. In this study, we reassemble a reference genome of the goat (Capra hircus) using modern PacBio technology in tandem…
Single-molecule sequencing is now routinely used to assemble complete, high-quality microbial genomes, but these assembly methods have not scaled well to large genomes. To address this problem, we previously introduced the MinHash Alignment Process (MHAP) for overlapping single-molecule reads using probabilistic, locality-sensitive hashing. Integrating MHAP with Celera Assembler (CA) has enabled reference-grade assemblies of model organisms, revealing novel heterochromatic sequences and filling low-complexity gap sequences in the GRCh38 human reference genome. We have applied our methods to assemble the San Clemente goat genome. Combining single-molecule sequencing from Pacific Biosciences and BioNano Genomics generates and assembly that is over 150-fold more…
Reference quality de novo genome assemblies were once solely the domain of large, well-funded genome projects. While next-generation short read technology removed some of the cost barriers, accurate chromosome-scale assembly remains a real challenge. Here we present efforts to de novo assemble the goat (Capra hircus) genome. Through the combination of single-molecule technologies from Pacific Biosciences (sequencing) and BioNano Genomics (optical mapping) coupled with high-throughput chromosome conformation capture sequencing (Hi-C), an inbred San Clemente goat genome has been sequenced and assembled to a high degree of completeness at a relatively modest cost. Starting with 38 million PacBio reads, we integrated…
Given a massive collection of sequences, it is infeasible to perform pairwise alignment for basic tasks like sequence clustering and search. To address this problem, we demonstrate that the MinHash technique, first applied to clustering web pages, can be applied to biological sequences with similar effect, and extend this idea to include biologically relevant distance and significance measures. Our new tool, Mash, uses MinHash locality-sensitive hashing to reduce large sequences to a representative sketch and rapidly estimate pairwise distances between genomes or metagenomes. Using Mash, we explored several use cases, including a 5,000-fold size reduction and clustering of all 55,000…
Aedes aegypti is a tropical and subtropical mosquito vector for Zika, yellow fever, dengue fever, chikungunya, and other diseases. The outbreak of Zika in the Americas, which can cause microcephaly in the fetus of infected women, adds urgency to the need for a high-quality reference genome in order to better understand the organism’s biology and its role in transmitting human disease. We describe the first diploid assembly of an insect genome, using SMRT sequencing and the open-source assembler FALCON-Unzip. This assembly has high contiguity (contig N50 1.3 Mb), is more complete than previous assemblies (Length 1.45 Gb with 87% BUSCO…
Aedes aegypti is a tropical and subtropical mosquito vector for Zika, yellow fever, dengue fever, and chikungunya. We describe the first diploid assembly of an insect genome, using SMRT Sequencing and the open-source assembler FALCON-Unzip. This assembly has high contiguity (contig N50 1.3 Mb), is more complete than previous assemblies (Length 1.45 Gb with 87% BUSCO genes complete), and is high quality (mean base >QV30 after polishing). Long-range haplotype structure, in some cases encompassing more than 4 Mb of extremely divergent homologous sequence with dramatic differences in coding sequence content, is resolved using a combination of the FALCON-Unzip assembler, genome…
Haplotype-resolved genomes are important for understanding how combinations of variants impact phenotypes. The study of disease, quantitative traits, forensics, and organ donor matching are aided by phased genomes. Phase is commonly resolved using familial data, population-based imputation, or by isolating and sequencing single haplotypes using fosmids, BACs, or haploid tissues. Because these methods can be prohibitively expensive, or samples may not be available, alternative approaches are required. de novo genome assembly with PacBio Single Molecule, Real-Time (SMRT) data produces highly contiguous, accurate assemblies. For non-inbred samples, including humans, the separate resolution of haplotypes results in higher base accuracy and more…
Recent improvements in sequencing chemistry and instrument performance combine to create a new PacBio data type, Single Molecule High-Fidelity reads (HiFi reads). Increased read length and improvement in library construction enables average read lengths of 10-20 kb with average sequence identity greater than 99% from raw single molecule reads. The resulting reads have the accuracy comparable to short read NGS but with 50-100 times longer read length. Here we benchmark the performance of this data type by sequencing and genotyping the Genome in a Bottle (GIAB) HG0002 human reference sample from the National Institute of Standards and Technology (NIST). We…
At AGBT 2017, the Broad Institute’s Daniel Neafsey reported a large collaborative effort to sequence the mosquito that carries Zika virus. The team is using long-read PacBio sequencing to produce a high-quality genome assembly, which Neafsey expects will replace the 10-year-old Sanger assembly for Aedes aegypti. The new assembly reduces the number of contigs by at least 10-fold, boosts the contig N50 to nearly 2 Mb, and features more complete gene content.