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Feigin C, Frankenberg S, Pask A. A Chromosome-Scale Hybrid Genome Assembly of the Extinct Tasmanian Tiger (Thylacinus cynocephalus). Genome Biol Evol 2022; 14:evac048. [PMID: 35349647 PMCID: PMC9007325 DOI: 10.1093/gbe/evac048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
The extinct Tasmanian tiger or thylacine (Thylacinus cynocephalus) was a large marsupial carnivore native to Australia. Once ranging across parts of the mainland, the species remained only on the island of Tasmania by the time of European colonization. It was driven to extinction in the early 20th century and is an emblem of native species loss in Australia. The thylacine was a striking example of convergent evolution with placental canids, with which it shared a similar skull morphology. Consequently, it has been the subject of extensive study. While the original thylacine assemblies published in 2018 enabled the first exploration of the species' genome biology, further progress is hindered by the lack of high-quality genomic resources. Here, we present a new chromosome-scale hybrid genome assembly for the thylacine, which compares favorably with many recent de novo marsupial genomes. In addition, we provide homology-based gene annotations, characterize the repeat content of the thylacine genome, and show that consistent with demographic decline, the species possessed a low rate of heterozygosity even compared to extant, threatened marsupials.
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Affiliation(s)
- Charles Feigin
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
- Department of Molecular Biology, Princeton University, New Jersey, USA
| | - Stephen Frankenberg
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Andrew Pask
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
- Department of Sciences, Museums Victoria, Carlton, Victoria, Australia
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Lin J, Duchêne D, Carøe C, Smith O, Ciucani MM, Niemann J, Richmond D, Greenwood AD, MacPhee R, Zhang G, Gopalakrishnan S, Gilbert MTP. Probing the genomic limits of de-extinction in the Christmas Island rat. Curr Biol 2022:S0960-9822(22)00249-4. [PMID: 35271794 DOI: 10.1016/j.cub.2022.02.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 01/24/2022] [Accepted: 02/07/2022] [Indexed: 12/17/2022]
Abstract
Three principal methods are under discussion as possible pathways to “true” de-extinction; i.e., back-breeding, cloning, and genetic engineering.1,2 Of these, while the latter approach is most likely to apply to the largest number of extinct species, its potential is constrained by the degree to which the extinct species genome can be reconstructed. We explore this question using the extinct Christmas Island rat (Rattus macleari) as a model, an endemic rat species that was driven extinct between 1898 and 1908.3, 4, 5 We first re-sequenced its genome to an average of >60× coverage, then mapped it to the reference genomes of different Rattus species. We then explored how evolutionary divergence from the extant reference genome affected the fraction of the Christmas Island rat genome that could be recovered. Our analyses show that even when the extremely high-quality Norway brown rat (R. norvegicus) is used as a reference, nearly 5% of the genome sequence is unrecoverable, with 1,661 genes recovered at lower than 90% completeness, and 26 completely absent. Furthermore, we find the distribution of regions affected is not random, but for example, if 90% completeness is used as the cutoff, genes related to immune response and olfaction are excessively affected. Ultimately, our approach demonstrates the importance of applying similar analyses to candidates for de-extinction through genome editing in order to provide critical baseline information about how representative the edited form would be of the extinct species. Evolutionary divergence limits the completeness of extinct species genomes The extinct Christmas Island rat was re-sequenced to ca. 60× coverage Nevertheless, 4.85% of the Norway brown rat genome remains absent after mapping Absences are not random; immune response and olfaction are excessively affected
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Straube N, Lyra ML, Paijmans JLA, Preick M, Basler N, Penner J, Rödel MO, Westbury MV, Haddad CFB, Barlow A, Hofreiter M. Successful application of ancient DNA extraction and library construction protocols to museum wet collection specimens. Mol Ecol Resour 2021; 21:2299-2315. [PMID: 34036732 DOI: 10.1111/1755-0998.13433] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 05/09/2021] [Accepted: 05/14/2021] [Indexed: 01/02/2023]
Abstract
Millions of scientific specimens are housed in museum collections, a large part of which are fluid preserved. The use of formaldehyde as fixative and subsequent storage in ethanol is especially common in ichthyology and herpetology. This type of preservation damages DNA and reduces the chance of successful retrieval of genetic data. We applied ancient DNA extraction and single stranded library construction protocols to a variety of vertebrate samples obtained from wet collections and of different ages. Our results show that almost all samples tested yielded endogenous DNA. Archival DNA extraction was successful across different tissue types as well as using small amounts of tissue. Conversion of archival DNA fragments into single-stranded libraries resulted in usable data even for samples with initially undetectable DNA amounts. Subsequent target capture approaches for mitochondrial DNA using homemade baits on a subset of 30 samples resulted in almost complete mitochondrial genome sequences in several instances. Thus, application of ancient DNA methodology makes wet collection specimens, including type material as well as rare, old or extinct species, accessible for genetic and genomic analyses. Our results, accompanied by detailed step-by-step protocols, are a large step forward to open the DNA archive of museum wet collections for scientific studies.
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Affiliation(s)
- Nicolas Straube
- University Museum of Bergen, Bergen, Norway.,SNSB Bavarian State Collection of Zoology, München, Germany
| | - Mariana L Lyra
- Departamento de Biodiversidade, Instituto de Biociências and Centro de Aquicultura (CAUNESP), Laboratório de Herpetologia, Universidade Estadual Paulista - UNESP, Rio Claro, SP, Brazil.,Zoological Institute, Braunschweig University of Technology, Braunschweig, Germany
| | - Johanna L A Paijmans
- Department of Mathematics and Natural Sciences, Evolutionary Adaptive Genomics, Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Michaela Preick
- Department of Mathematics and Natural Sciences, Evolutionary Adaptive Genomics, Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Nikolas Basler
- Department of Mathematics and Natural Sciences, Evolutionary Adaptive Genomics, Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Johannes Penner
- Museum für Naturkunde- Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany.,Chair of Wildlife Ecology and Management, Albert Ludwigs University Freiburg, Freiburg, Germany
| | - Mark-Oliver Rödel
- Museum für Naturkunde- Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
| | - Michael V Westbury
- Section for Evolutionary Genomics, The GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Célio F B Haddad
- Departamento de Biodiversidade, Instituto de Biociências and Centro de Aquicultura (CAUNESP), Laboratório de Herpetologia, Universidade Estadual Paulista - UNESP, Rio Claro, SP, Brazil
| | - Axel Barlow
- Department of Mathematics and Natural Sciences, Evolutionary Adaptive Genomics, Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Michael Hofreiter
- Department of Mathematics and Natural Sciences, Evolutionary Adaptive Genomics, Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
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