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Kim J, Lee C, Ko BJ, Yoo DA, Won S, Phillippy AM, Fedrigo O, Zhang G, Howe K, Wood J, Durbin R, Formenti G, Brown S, Cantin L, Mello CV, Cho S, Rhie A, Kim H, Jarvis ED. False gene and chromosome losses in genome assemblies caused by GC content variation and repeats. Genome Biol 2022; 23:204. [PMID: 36167554 PMCID: PMC9516821 DOI: 10.1186/s13059-022-02765-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/02/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Many short-read genome assemblies have been found to be incomplete and contain mis-assemblies. The Vertebrate Genomes Project has been producing new reference genome assemblies with an emphasis on being as complete and error-free as possible, which requires utilizing long reads, long-range scaffolding data, new assembly algorithms, and manual curation. A more thorough evaluation of the recent references relative to prior assemblies can provide a detailed overview of the types and magnitude of improvements. RESULTS Here we evaluate new vertebrate genome references relative to the previous assemblies for the same species and, in two cases, the same individuals, including a mammal (platypus), two birds (zebra finch, Anna's hummingbird), and a fish (climbing perch). We find that up to 11% of genomic sequence is entirely missing in the previous assemblies. In the Vertebrate Genomes Project zebra finch assembly, we identify eight new GC- and repeat-rich micro-chromosomes with high gene density. The impact of missing sequences is biased towards GC-rich 5'-proximal promoters and 5' exon regions of protein-coding genes and long non-coding RNAs. Between 26 and 60% of genes include structural or sequence errors that could lead to misunderstanding of their function when using the previous genome assemblies. CONCLUSIONS Our findings reveal novel regulatory landscapes and protein coding sequences that have been greatly underestimated in previous assemblies and are now present in the Vertebrate Genomes Project reference genomes.
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Affiliation(s)
- Juwan Kim
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Chul Lee
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Byung June Ko
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
| | - Dong Ahn Yoo
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Sohyoung Won
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Adam M Phillippy
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Olivier Fedrigo
- Vertebrate Genome Lab, The Rockefeller University, New York City, USA
| | - Guojie Zhang
- BGI-Shenzhen, Shenzhen, 518083, China
- Villum Centre for Biodiversity Genomics, Section for Ecology and Evolution, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650223, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, 650223, China
| | | | | | - Richard Durbin
- Wellcome Sanger Institute, Cambridge, UK
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Giulio Formenti
- Vertebrate Genome Lab, The Rockefeller University, New York City, USA
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York City, USA
| | - Samara Brown
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York City, USA
| | - Lindsey Cantin
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York City, USA
| | - Claudio V Mello
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Seoae Cho
- eGnome, Inc, Seoul, Republic of Korea
| | - Arang Rhie
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Heebal Kim
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea.
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea.
- eGnome, Inc, Seoul, Republic of Korea.
| | - Erich D Jarvis
- Vertebrate Genome Lab, The Rockefeller University, New York City, USA.
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York City, USA.
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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Ko BJ, Lee C, Kim J, Rhie A, Yoo DA, Howe K, Wood J, Cho S, Brown S, Formenti G, Jarvis ED, Kim H. Widespread false gene gains caused by duplication errors in genome assemblies. Genome Biol 2022; 23:205. [PMID: 36167596 PMCID: PMC9516828 DOI: 10.1186/s13059-022-02764-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/02/2022] [Indexed: 12/22/2022] Open
Abstract
Background False duplications in genome assemblies lead to false biological conclusions. We quantified false duplications in popularly used previous genome assemblies for platypus, zebra finch, and Anna’s Hummingbird, and their new counterparts of the same species generated by the Vertebrate Genomes Project, of which the Vertebrate Genomes Project pipeline attempted to eliminate false duplications through haplotype phasing and purging. These assemblies are among the first generated by the Vertebrate Genomes Project where there was a prior chromosomal level reference assembly to compare with. Results Whole genome alignments revealed that 4 to 16% of the sequences are falsely duplicated in the previous assemblies, impacting hundreds to thousands of genes. These lead to overestimated gene family expansions. The main source of the false duplications is heterotype duplications, where the haplotype sequences were relatively more divergent than other parts of the genome leading the assembly algorithms to classify them as separate genes or genomic regions. A minor source is sequencing errors. Ancient ATP nucleotide binding gene families have a higher prevalence of false duplications compared to other gene families. Although present in a smaller proportion, we observe false duplications remaining in the Vertebrate Genomes Project assemblies that can be identified and purged. Conclusions This study highlights the need for more advanced assembly methods that better separate haplotypes and sequence errors, and the need for cautious analyses on gene gains. Supplementary Information The online version contains supplementary material available at 10.1186/s13059-022-02764-1.
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Affiliation(s)
- Byung June Ko
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
| | - Chul Lee
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Juwan Kim
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | - Arang Rhie
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, USA
| | - Dong Ahn Yoo
- Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea
| | | | | | - Seoae Cho
- eGnome, Inc, Seoul, Republic of Korea
| | - Samara Brown
- Laboratory of the Neurogenetics of Language, The Rockefeller University, New York, NY, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Giulio Formenti
- Laboratory of the Neurogenetics of Language, The Rockefeller University, New York, NY, USA
| | - Erich D Jarvis
- Laboratory of the Neurogenetics of Language, The Rockefeller University, New York, NY, USA. .,Howard Hughes Medical Institute, Chevy Chase, MD, USA.
| | - Heebal Kim
- Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea. .,Interdisciplinary Program in Bioinformatics, Seoul National University, Seoul, Republic of Korea. .,eGnome, Inc, Seoul, Republic of Korea.
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