Browsing by Author "Koren, Sergey"

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    Assemblathon 2: evaluating de novo methods of genome assembly in three vertebrate species.
    (Gigascience, 2013-07-22) Bradnam, Keith R; Fass, Joseph N; Alexandrov, Anton; Baranay, Paul; Bechner, Michael; Birol, Inanç; Boisvert, Sébastien; Chapman, Jarrod A; Chapuis, Guillaume; Chikhi, Rayan; Chitsaz, Hamidreza; Chou, Wen-Chi; Corbeil, Jacques; Del Fabbro, Cristian; Docking, T Roderick; Durbin, Richard; Earl, Dent; Emrich, Scott; Fedotov, Pavel; Fonseca, Nuno A; Ganapathy, Ganeshkumar; Gibbs, Richard A; Gnerre, Sante; Godzaridis, Elénie; Goldstein, Steve; Haimel, Matthias; Hall, Giles; Haussler, David; Hiatt, Joseph B; Ho, Isaac Y; Howard, Jason; Hunt, Martin; Jackman, Shaun D; Jaffe, David B; Jarvis, Erich D; Jiang, Huaiyang; Kazakov, Sergey; Kersey, Paul J; Kitzman, Jacob O; Knight, James R; Koren, Sergey; Lam, Tak-Wah; Lavenier, Dominique; Laviolette, François; Li, Yingrui; Li, Zhenyu; Liu, Binghang; Liu, Yue; Luo, Ruibang; Maccallum, Iain; Macmanes, Matthew D; Maillet, Nicolas; Melnikov, Sergey; Naquin, Delphine; Ning, Zemin; Otto, Thomas D; Paten, Benedict; Paulo, Octávio S; Phillippy, Adam M; Pina-Martins, Francisco; Place, Michael; Przybylski, Dariusz; Qin, Xiang; Qu, Carson; Ribeiro, Filipe J; Richards, Stephen; Rokhsar, Daniel S; Ruby, J Graham; Scalabrin, Simone; Schatz, Michael C; Schwartz, David C; Sergushichev, Alexey; Sharpe, Ted; Shaw, Timothy I; Shendure, Jay; Shi, Yujian; Simpson, Jared T; Song, Henry; Tsarev, Fedor; Vezzi, Francesco; Vicedomini, Riccardo; Vieira, Bruno M; Wang, Jun; Wang, Jun; Worley, Kim C; Yin, Shuangye; Yiu, Siu-Ming; Yuan, Jianying; Zhang, Guojie; Zhang, Hao; Zhou, Shiguo; Korf, Ian F
    BACKGROUND: The process of generating raw genome sequence data continues to become cheaper, faster, and more accurate. However, assembly of such data into high-quality, finished genome sequences remains challenging. Many genome assembly tools are available, but they differ greatly in terms of their performance (speed, scalability, hardware requirements, acceptance of newer read technologies) and in their final output (composition of assembled sequence). More importantly, it remains largely unclear how to best assess the quality of assembled genome sequences. The Assemblathon competitions are intended to assess current state-of-the-art methods in genome assembly. RESULTS: In Assemblathon 2, we provided a variety of sequence data to be assembled for three vertebrate species (a bird, a fish, and snake). This resulted in a total of 43 submitted assemblies from 21 participating teams. We evaluated these assemblies using a combination of optical map data, Fosmid sequences, and several statistical methods. From over 100 different metrics, we chose ten key measures by which to assess the overall quality of the assemblies. CONCLUSIONS: Many current genome assemblers produced useful assemblies, containing a significant representation of their genes and overall genome structure. However, the high degree of variability between the entries suggests that there is still much room for improvement in the field of genome assembly and that approaches which work well in assembling the genome of one species may not necessarily work well for another.
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    High-coverage sequencing and annotated assemblies of the budgerigar genome.
    (Gigascience, 2014) Ganapathy, Ganeshkumar; Howard, Jason T; Ward, James M; Li, Jianwen; Li, Bo; Li, Yingrui; Xiong, Yingqi; Zhang, Yong; Zhou, Shiguo; Schwartz, David C; Schatz, Michael; Aboukhalil, Robert; Fedrigo, Olivier; Bukovnik, Lisa; Wang, Ty; Wray, Greg; Rasolonjatovo, Isabelle; Winer, Roger; Knight, James R; Koren, Sergey; Warren, Wesley C; Zhang, Guojie; Phillippy, Adam M; Jarvis, Erich D
    BACKGROUND: Parrots belong to a group of behaviorally advanced vertebrates and have an advanced ability of vocal learning relative to other vocal-learning birds. They can imitate human speech, synchronize their body movements to a rhythmic beat, and understand complex concepts of referential meaning to sounds. However, little is known about the genetics of these traits. Elucidating the genetic bases would require whole genome sequencing and a robust assembly of a parrot genome. FINDINGS: We present a genomic resource for the budgerigar, an Australian Parakeet (Melopsittacus undulatus) -- the most widely studied parrot species in neuroscience and behavior. We present genomic sequence data that includes over 300× raw read coverage from multiple sequencing technologies and chromosome optical maps from a single male animal. The reads and optical maps were used to create three hybrid assemblies representing some of the largest genomic scaffolds to date for a bird; two of which were annotated based on similarities to reference sets of non-redundant human, zebra finch and chicken proteins, and budgerigar transcriptome sequence assemblies. The sequence reads for this project were in part generated and used for both the Assemblathon 2 competition and the first de novo assembly of a giga-scale vertebrate genome utilizing PacBio single-molecule sequencing. CONCLUSIONS: Across several quality metrics, these budgerigar assemblies are comparable to or better than the chicken and zebra finch genome assemblies built from traditional Sanger sequencing reads, and are sufficient to analyze regions that are difficult to sequence and assemble, including those not yet assembled in prior bird genomes, and promoter regions of genes differentially regulated in vocal learning brain regions. This work provides valuable data and material for genome technology development and for investigating the genomics of complex behavioral traits.
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    Hybrid error correction and de novo assembly of single-molecule sequencing reads.
    (Nat Biotechnol, 2012-07-01) Koren, Sergey; Schatz, Michael C; Walenz, Brian P; Martin, Jeffrey; Howard, Jason T; Ganapathy, Ganeshkumar; Wang, Zhong; Rasko, David A; McCombie, W Richard; Jarvis, Erich D; Adam M Phillippy
    Single-molecule sequencing instruments can generate multikilobase sequences with the potential to greatly improve genome and transcriptome assembly. However, the error rates of single-molecule reads are high, which has limited their use thus far to resequencing bacteria. To address this limitation, we introduce a correction algorithm and assembly strategy that uses short, high-fidelity sequences to correct the error in single-molecule sequences. We demonstrate the utility of this approach on reads generated by a PacBio RS instrument from phage, prokaryotic and eukaryotic whole genomes, including the previously unsequenced genome of the parrot Melopsittacus undulatus, as well as for RNA-Seq reads of the corn (Zea mays) transcriptome. Our long-read correction achieves >99.9% base-call accuracy, leading to substantially better assemblies than current sequencing strategies: in the best example, the median contig size was quintupled relative to high-coverage, second-generation assemblies. Greater gains are predicted if read lengths continue to increase, including the prospect of single-contig bacterial chromosome assembly.
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    Telomere-to-telomere assembly of a complete human X chromosome.
    (Nature, 2020-09) Miga, Karen H; Koren, Sergey; Rhie, Arang; Vollger, Mitchell R; Gershman, Ariel; Bzikadze, Andrey; Brooks, Shelise; Howe, Edmund; Porubsky, David; Logsdon, Glennis A; Schneider, Valerie A; Potapova, Tamara; Wood, Jonathan; Chow, William; Armstrong, Joel; Fredrickson, Jeanne; Pak, Evgenia; Tigyi, Kristof; Kremitzki, Milinn; Markovic, Christopher; Maduro, Valerie; Dutra, Amalia; Bouffard, Gerard G; Chang, Alexander M; Hansen, Nancy F; Wilfert, Amy B; Thibaud-Nissen, Françoise; Schmitt, Anthony D; Belton, Jon-Matthew; Selvaraj, Siddarth; Dennis, Megan Y; Soto, Daniela C; Sahasrabudhe, Ruta; Kaya, Gulhan; Quick, Josh; Loman, Nicholas J; Holmes, Nadine; Loose, Matthew; Surti, Urvashi; Risques, Rosa Ana; Graves Lindsay, Tina A; Fulton, Robert; Hall, Ira; Paten, Benedict; Howe, Kerstin; Timp, Winston; Young, Alice; Mullikin, James C; Pevzner, Pavel A; Gerton, Jennifer L; Sullivan, Beth A; Eichler, Evan E; Phillippy, Adam M
    After two decades of improvements, the current human reference genome (GRCh38) is the most accurate and complete vertebrate genome ever produced. However, no single chromosome has been finished end to end, and hundreds of unresolved gaps persist1,2. Here we present a human genome assembly that surpasses the continuity of GRCh382, along with a gapless, telomere-to-telomere assembly of a human chromosome. This was enabled by high-coverage, ultra-long-read nanopore sequencing of the complete hydatidiform mole CHM13 genome, combined with complementary technologies for quality improvement and validation. Focusing our efforts on the human X chromosome3, we reconstructed the centromeric satellite DNA array (approximately 3.1 Mb) and closed the 29 remaining gaps in the current reference, including new sequences from the human pseudoautosomal regions and from cancer-testis ampliconic gene families (CT-X and GAGE). These sequences will be integrated into future human reference genome releases. In addition, the complete chromosome X, combined with the ultra-long nanopore data, allowed us to map methylation patterns across complex tandem repeats and satellite arrays. Our results demonstrate that finishing the entire human genome is now within reach, and the data presented here will facilitate ongoing efforts to complete the other human chromosomes.