1
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Saraceno C, Timoshevskiy VA, Smith JJ. Functional analyses of the polycomb-group genes in sea lamprey embryos undergoing programmed DNA loss. J Exp Zool B Mol Dev Evol 2024; 342:260-270. [PMID: 37902302 DOI: 10.1002/jez.b.23225] [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] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/22/2023] [Accepted: 10/03/2023] [Indexed: 10/31/2023]
Abstract
During early development, sea lamprey embryos undergo programmatic elimination of DNA from somatic progenitor cells in a process termed programmed genome rearrangement (PGR). Eliminated DNA eventually becomes condensed into micronuclei, which are then physically degraded and permanently lost from the cell. Previous studies indicated that many of the genes eliminated during PGR have mammalian homologs that are bound by polycomb repressive complex (PRC) in embryonic stem cells. To test whether PRC components play a role in the faithful elimination of germline-specific sequences, we used a combination of CRISPR/Cas9 and lightsheet microscopy to investigate the impact of gene knockouts on early development and the progression through stages of DNA elimination. Analysis of knockout embryos for the core PRC2 subunits EZH, SUZ12, and EED show that disruption of all three genes results in an increase in micronucleus number, altered distribution of micronuclei within embryos, and an increase in micronucleus volume in mutant embryos. While the upstream events of DNA elimination are not strongly impacted by loss of PRC2 components, this study suggests that PRC2 plays a role in the later stages of elimination related to micronucleus condensation and degradation. These findings also suggest that other genes/epigenetic pathways may work in parallel during DNA elimination to mediate chromatin structure, accessibility, and the ultimate loss of germline-specific DNA.
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Affiliation(s)
- Cody Saraceno
- Department of Biology, University of Kentucky, Lexington, Kentucky, USA
| | | | - Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, Kentucky, USA
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2
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Marlétaz F, Timoshevskaya N, Timoshevskiy VA, Parey E, Simakov O, Gavriouchkina D, Suzuki M, Kubokawa K, Brenner S, Smith JJ, Rokhsar DS. The hagfish genome and the evolution of vertebrates. Nature 2024; 627:811-820. [PMID: 38262590 PMCID: PMC10972751 DOI: 10.1038/s41586-024-07070-3] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 01/15/2024] [Indexed: 01/25/2024]
Abstract
As the only surviving lineages of jawless fishes, hagfishes and lampreys provide a crucial window into early vertebrate evolution1-3. Here we investigate the complex history, timing and functional role of genome-wide duplications4-7 and programmed DNA elimination8,9 in vertebrates in the light of a chromosome-scale genome sequence for the brown hagfish Eptatretus atami. Combining evidence from syntenic and phylogenetic analyses, we establish a comprehensive picture of vertebrate genome evolution, including an auto-tetraploidization (1RV) that predates the early Cambrian cyclostome-gnathostome split, followed by a mid-late Cambrian allo-tetraploidization (2RJV) in gnathostomes and a prolonged Cambrian-Ordovician hexaploidization (2RCY) in cyclostomes. Subsequently, hagfishes underwent extensive genomic changes, with chromosomal fusions accompanied by the loss of genes that are essential for organ systems (for example, genes involved in the development of eyes and in the proliferation of osteoclasts); these changes account, in part, for the simplification of the hagfish body plan1,2. Finally, we characterize programmed DNA elimination in hagfish, identifying protein-coding genes and repetitive elements that are deleted from somatic cell lineages during early development. The elimination of these germline-specific genes provides a mechanism for resolving genetic conflict between soma and germline by repressing germline and pluripotency functions, paralleling findings in lampreys10,11. Reconstruction of the early genomic history of vertebrates provides a framework for further investigations of the evolution of cyclostomes and jawed vertebrates.
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Affiliation(s)
- Ferdinand Marlétaz
- Centre for Life's Origins and Evolution, Department of Genetics, Evolution and Environment, University College London, London, UK.
- Molecular Genetics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
| | | | | | - Elise Parey
- Centre for Life's Origins and Evolution, Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Oleg Simakov
- Molecular Genetics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Department for Neurosciences and Developmental Biology, University of Vienna, Vienna, Austria
| | - Daria Gavriouchkina
- Molecular Genetics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- UK Dementia Research Institute, University College London, London, UK
| | - Masakazu Suzuki
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, Japan
| | - Kaoru Kubokawa
- Ocean Research Institute, The University of Tokyo, Tokyo, Japan
| | - Sydney Brenner
- Comparative and Medical Genomics Laboratory, Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore, Singapore
| | - Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, KY, USA.
| | - Daniel S Rokhsar
- Molecular Genetics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, USA.
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3
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Timoshevskaya N, Eşkut KI, Timoshevskiy VA, Robb SMC, Holt C, Hess JE, Parker HJ, Baker CF, Miller AK, Saraceno C, Yandell M, Krumlauf R, Narum SR, Lampman RT, Gemmell NJ, Mountcastle J, Haase B, Balacco JR, Formenti G, Pelan S, Sims Y, Howe K, Fedrigo O, Jarvis ED, Smith JJ. An improved germline genome assembly for the sea lamprey Petromyzon marinus illuminates the evolution of germline-specific chromosomes. Cell Rep 2023; 42:112263. [PMID: 36930644 PMCID: PMC10166183 DOI: 10.1016/j.celrep.2023.112263] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 10/17/2022] [Accepted: 02/28/2023] [Indexed: 03/17/2023] Open
Abstract
Programmed DNA loss is a gene silencing mechanism that is employed by several vertebrate and nonvertebrate lineages, including all living jawless vertebrates and songbirds. Reconstructing the evolution of somatically eliminated (germline-specific) sequences in these species has proven challenging due to a high content of repeats and gene duplications in eliminated sequences and a corresponding lack of highly accurate and contiguous assemblies for these regions. Here, we present an improved assembly of the sea lamprey (Petromyzon marinus) genome that was generated using recently standardized methods that increase the contiguity and accuracy of vertebrate genome assemblies. This assembly resolves highly contiguous, somatically retained chromosomes and at least one germline-specific chromosome, permitting new analyses that reconstruct the timing, mode, and repercussions of recruitment of genes to the germline-specific fraction. These analyses reveal major roles of interchromosomal segmental duplication, intrachromosomal duplication, and positive selection for germline functions in the long-term evolution of germline-specific chromosomes.
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Affiliation(s)
| | - Kaan I Eşkut
- Department of Biology, University of Kentucky, Lexington, KY 40506, USA
| | | | - Sofia M C Robb
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Carson Holt
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Jon E Hess
- Columbia River Inter-Tribal Fish Commission, Portland, OR 97232, USA
| | - Hugo J Parker
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Cindy F Baker
- National Institute of Water and Atmospheric Research Limited (NIWA), Hamilton, Waikato 3261, New Zealand
| | - Allison K Miller
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, Otago 9054, New Zealand
| | - Cody Saraceno
- Department of Biology, University of Kentucky, Lexington, KY 40506, USA
| | - Mark Yandell
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Robb Krumlauf
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy & Cell Biology, The University of Kansas School of Medicine, Kansas City, KS 66160, USA
| | - Shawn R Narum
- Columbia River Inter-Tribal Fish Commission, Hagerman, ID 83332, USA
| | - Ralph T Lampman
- Yakama Nation Fisheries Resource Management Program, Pacific Lamprey Project, Toppenish, WA 98948, USA
| | - Neil J Gemmell
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, Otago 9054, New Zealand
| | | | - Bettina Haase
- Vertebrate Genome Lab, The Rockefeller University, New York, NY 10065, USA
| | - Jennifer R Balacco
- Vertebrate Genome Lab, The Rockefeller University, New York, NY 10065, USA
| | - Giulio Formenti
- Vertebrate Genome Lab, The Rockefeller University, New York, NY 10065, USA; Laboratory of Neurogenetics of Language, The Rockefeller University, New York, NY 10065, USA
| | - Sarah Pelan
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, UK
| | - Ying Sims
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, UK
| | - Kerstin Howe
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, UK
| | - Olivier Fedrigo
- Vertebrate Genome Lab, The Rockefeller University, New York, NY 10065, USA
| | - Erich D Jarvis
- Vertebrate Genome Lab, The Rockefeller University, New York, NY 10065, USA; Laboratory of Neurogenetics of Language, The Rockefeller University, New York, NY 10065, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
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4
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Abstract
Over the last few decades, an increasing number of vertebrate taxa have been identified that undergo programmed genome rearrangement, or programmed DNA loss, during development. In these organisms, the genome of germ cells is often reproducibly different from the genome of all other cells within the body. Although we clearly have not identified all vertebrate taxa that undergo programmed genome loss, the list of species known to undergo loss now represents ∼10% of vertebrate species, including several basally diverging lineages. Recent studies have shed new light on the targets and mechanisms of DNA loss and their association with canonical modes of DNA silencing. Ultimately, expansion of these studies into a larger collection of taxa will aid in reconstructing patterns of shared/independent ancestry of programmed DNA loss in the vertebrate lineage, as well as more recent evolutionary events that have shaped the structure and content of eliminated DNA.
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Affiliation(s)
- Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA; , ,
| | | | - Cody Saraceno
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA; , ,
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5
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Sharma A, Kinney NA, Timoshevskiy VA, Sharakhova MV, Sharakhov IV. Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex. Genes (Basel) 2020; 11:E327. [PMID: 32204543 PMCID: PMC7140835 DOI: 10.3390/genes11030327] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [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] [Received: 02/19/2020] [Revised: 03/13/2020] [Accepted: 03/16/2020] [Indexed: 12/31/2022] Open
Abstract
Heterochromatin is identified as a potential factor driving diversification of species. To understand the magnitude of heterochromatin variation within the Anopheles gambiae complex of malaria mosquitoes, we analyzed metaphase chromosomes in An. arabiensis, An. coluzzii, An. gambiae, An. merus, and An. quadriannulatus. Using fluorescence in situ hybridization (FISH) with ribosomal DNA (rDNA), a highly repetitive fraction of DNA, and heterochromatic Bacterial Artificial Chromosome (BAC) clones, we established the correspondence of pericentric heterochromatin between the metaphase and polytene X chromosomes of An. gambiae. We then developed chromosome idiograms and demonstrated that the X chromosomes exhibit qualitative differences in their pattern of heterochromatic bands and position of satellite DNA (satDNA) repeats among the sibling species with postzygotic isolation, An. arabiensis, An. merus, An. quadriannulatus, and An. coluzzii or An. gambiae. The identified differences in the size and structure of the X chromosome heterochromatin point to a possible role of repetitive DNA in speciation of mosquitoes. We found that An. coluzzii and An. gambiae, incipient species with prezygotic isolation, share variations in the relative positions of the satDNA repeats and the proximal heterochromatin band on the X chromosomes. This previously unknown genetic polymorphism in malaria mosquitoes may be caused by a differential amplification of DNA repeats or an inversion in the sex chromosome heterochromatin.
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Affiliation(s)
- Atashi Sharma
- Department of Entomology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA; (A.S.); (V.A.T.); (M.V.S.)
| | - Nicholas A. Kinney
- Genomics Bioinformatics and Computational Biology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA;
| | - Vladimir A. Timoshevskiy
- Department of Entomology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA; (A.S.); (V.A.T.); (M.V.S.)
| | - Maria V. Sharakhova
- Department of Entomology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA; (A.S.); (V.A.T.); (M.V.S.)
- Laboratory of Evolutionary Genomics of Insects, the Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 634050 Tomsk, Russia
| | - Igor V. Sharakhov
- Department of Entomology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA; (A.S.); (V.A.T.); (M.V.S.)
- Genomics Bioinformatics and Computational Biology, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA;
- Laboratory of Evolutionary Genomics of Insects, the Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
- Department of Cytology and Genetics, Tomsk State University, 634050 Tomsk, Russia
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6
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Timoshevskiy VA, Timoshevskaya NY, Smith JJ. Germline-Specific Repetitive Elements in Programmatically Eliminated Chromosomes of the Sea Lamprey ( Petromyzon marinus). Genes (Basel) 2019; 10:E832. [PMID: 31652530 PMCID: PMC6826781 DOI: 10.3390/genes10100832] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [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: 09/12/2019] [Revised: 10/17/2019] [Accepted: 10/19/2019] [Indexed: 12/26/2022] Open
Abstract
The sea lamprey (Petromyzon marinus) is one of few vertebrate species known to reproducibly eliminate large fractions of its genome during normal embryonic development. This germline-specific DNA is lost in the form of large fragments, including entire chromosomes, and available evidence suggests that DNA elimination acts as a permanent silencing mechanism that prevents the somatic expression of a specific subset of "germline" genes. However, reconstruction of eliminated regions has proven to be challenging due to the complexity of the lamprey karyotype. We applied an integrative approach aimed at further characterization of the large-scale structure of eliminated segments, including: (1) in silico identification of germline-enriched repeats; (2) mapping the chromosomal location of specific repetitive sequences in germline metaphases; and (3) 3D DNA/DNA-hybridization to embryonic lagging anaphases, which permitted us to both verify the specificity of elements to physically eliminated chromosomes and characterize the subcellular organization of these elements during elimination. This approach resulted in the discovery of several repetitive elements that are found exclusively on the eliminated chromosomes, which subsequently permitted the identification of 12 individual chromosomes that are programmatically eliminated during early embryogenesis. The fidelity and specificity of these highly abundant sequences, their distinctive patterning in eliminated chromosomes, and subcellular localization in elimination anaphases suggest that these sequences might contribute to the specific targeting of chromosomes for elimination or possibly in molecular interactions that mediate their decelerated poleward movement in chromosome elimination anaphases, isolation into micronuclei and eventual degradation.
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Affiliation(s)
| | | | - Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
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7
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Smith JJ, Timoshevskaya N, Timoshevskiy VA, Keinath MC, Hardy D, Voss SR. A chromosome-scale assembly of the axolotl genome. Genome Res 2019; 29:317-324. [PMID: 30679309 PMCID: PMC6360810 DOI: 10.1101/gr.241901.118] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 11/26/2018] [Indexed: 01/14/2023]
Abstract
The axolotl (Ambystoma mexicanum) provides critical models for studying regeneration, evolution, and development. However, its large genome (∼32 Gb) presents a formidable barrier to genetic analyses. Recent efforts have yielded genome assemblies consisting of thousands of unordered scaffolds that resolve gene structures, but do not yet permit large-scale analyses of genome structure and function. We adapted an established mapping approach to leverage dense SNP typing information and for the first time assemble the axolotl genome into 14 chromosomes. Moreover, we used fluorescence in situ hybridization to verify the structure of these 14 scaffolds and assign each to its corresponding physical chromosome. This new assembly covers 27.3 Gb and encompasses 94% of annotated gene models on chromosomal scaffolds. We show the assembly's utility by resolving genome-wide orthologies between the axolotl and other vertebrates, identifying the footprints of historical introgression events that occurred during the development of axolotl genetic stocks, and precisely mapping several phenotypes including a large deletion underlying the cardiac mutant. This chromosome-scale assembly will greatly facilitate studies of the axolotl in biological research.
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Affiliation(s)
- Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA
| | | | | | - Melissa C Keinath
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA.,Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Drew Hardy
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky 40506, USA.,Ambystoma Genetic Stock Center, University of Kentucky, Lexington, Kentucky 40506, USA
| | - S Randal Voss
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky 40506, USA.,Ambystoma Genetic Stock Center, University of Kentucky, Lexington, Kentucky 40506, USA.,Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky 40506, USA
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8
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Sharakhova MV, Artemov GN, Timoshevskiy VA, Sharakhov IV. Physical Genome Mapping Using Fluorescence In Situ Hybridization with Mosquito Chromosomes. Methods Mol Biol 2019; 1858:177-194. [PMID: 30414118 DOI: 10.1007/978-1-4939-8775-7_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The development of genomic resources and tools is an important step in designing novel approaches to genetic control of mosquitoes. Physical genome maps enhance the quality of the genome assemblies, improve gene annotation, and provide a better framework for comparative and population genomics studies in mosquitoes. In this chapter, we describe protocols for an important procedure in physical genome mapping-fluorescence in situ hybridization (FISH). We provide details on (1) dissection of salivary glands, ovaries, and imaginal discs for obtaining high-quality polytene or mitotic chromosome preparations; (2) DNA-labeling procedures and extraction of repetitive DNA fractions; and (3) approaches to FISH on polytene and mitotic chromosomes.
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Affiliation(s)
- Maria V Sharakhova
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA.
| | - Gleb N Artemov
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Vladimir A Timoshevskiy
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Igor V Sharakhov
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
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9
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Timoshevskiy VA, Lampman RT, Hess JE, Porter LL, Smith JJ. Deep ancestry of programmed genome rearrangement in lampreys. Dev Biol 2017; 429:31-34. [PMID: 28669817 PMCID: PMC5554715 DOI: 10.1016/j.ydbio.2017.06.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 05/16/2017] [Accepted: 06/28/2017] [Indexed: 11/27/2022]
Abstract
In most multicellular organisms, the structure and content of the genome is rigorously maintained over the course of development. However some species have evolved genome biologies that permit, or require, developmentally regulated changes in the physical structure and content of the genome (programmed genome rearrangement: PGR). Relatively few vertebrates are known to undergo PGR, although all agnathans surveyed to date (several hagfish and one lamprey: Petromyzon marinus) show evidence of large scale PGR. To further resolve the ancestry of PGR within vertebrates, we developed probes that allow simultaneous tracking of nearly all sequences eliminated by PGR in P. marinus and a second lamprey species (Entosphenus tridentatus). These comparative analyses reveal conserved subcellular structures (lagging chromatin and micronuclei) associated with PGR and provide the first comparative embryological evidence in support of the idea that PGR represents an ancient and evolutionarily stable strategy for regulating inherent developmental/genetic conflicts between germline and soma.
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Affiliation(s)
| | - Ralph T Lampman
- Yakama Nation Fisheries Resource Management Program, Toppenish, WA 98948, USA
| | - Jon E Hess
- Columbia River Inter-Tribal Fish Commission, Portland, OR 97232, USA
| | - Laurie L Porter
- Columbia River Inter-Tribal Fish Commission, Portland, OR 97232, USA
| | - Jeramiah J Smith
- University of Kentucky, Department of Biology, Lexington, KY 40506, USA.
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10
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Timoshevskiy VA, Herdy JR, Keinath MC, Smith JJ. Cellular and Molecular Features of Developmentally Programmed Genome Rearrangement in a Vertebrate (Sea Lamprey: Petromyzon marinus). PLoS Genet 2016; 12:e1006103. [PMID: 27341395 PMCID: PMC4920378 DOI: 10.1371/journal.pgen.1006103] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 05/13/2016] [Indexed: 11/21/2022] Open
Abstract
The sea lamprey (Petromyzon marinus) represents one of the few vertebrate species known to undergo large-scale programmatic elimination of genomic DNA over the course of its normal development. Programmed genome rearrangements (PGRs) result in the reproducible loss of ~20% of the genome from somatic cell lineages during early embryogenesis. Studies of PGR hold the potential to provide novel insights related to the maintenance of genome stability during the cell cycle and coordination between mechanisms responsible for the accurate distribution of chromosomes into daughter cells, yet little is known regarding the mechanistic basis or cellular context of PGR in this or any other vertebrate lineage. Here we identify epigenetic silencing events that are associated with the programmed elimination of DNA and describe the spatiotemporal dynamics of PGR during lamprey embryogenesis. In situ analyses reveal that the earliest DNA methylation (and to some extent H3K9 trimethylation) events are limited to specific extranuclear structures (micronuclei) containing eliminated DNA. During early embryogenesis a majority of micronuclei (~60%) show strong enrichment for repressive chromatin modifications (H3K9me3 and 5meC). These analyses also led to the discovery that eliminated DNA is packaged into chromatin that does not migrate with somatically retained chromosomes during anaphase, a condition that is superficially similar to lagging chromosomes observed in some cancer subtypes. Closer examination of “lagging” chromatin revealed distributions of repetitive elements, cytoskeletal contacts and chromatin contacts that provide new insights into the cellular mechanisms underlying the programmed loss of these segments. Our analyses provide additional perspective on the cellular and molecular context of PGR, identify new structures associated with elimination of DNA and reveal that PGR is completed over the course of several successive cell divisions. Lampreys possess a fascinating genome biology wherein large portions of the genome, including large numbers of genes, are programmatically deleted during development. The lamprey therefore represents a uniquely informative system with respect to several broad areas of biology, including genome stability/rearrangement, epigenetic silencing, and the establishment and maintenance of pluripotency. However, little is known regarding the cellular context or mechanism of deletion, partly due to the challenges of observing rearrangements in situ. Here we present analyses and new techniques that significantly advance our understanding of the subcellular context of programmed rearrangements and interactions between programmed deletion and canonical DNA silencing mechanisms. These analyses demonstrate that DNA elimination occurs earlier in embryogenesis than was previously recognized and reveal several new cellular and molecular aspects of programmed DNA loss. Specifically we show that eliminated DNA exhibits a unique migration pattern during cell division, is packaged into discreet subcellular structures later in the cell cycle, and undergoes epigenetic silencing through DNA and histone methylation. These observations provide new insight into the mechanisms underlying programmed DNA loss and suggest a functional link between programmed DNA loss and other, more conserved gene silencing pathways.
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Affiliation(s)
| | - Joseph R. Herdy
- Department of Biology, University of Kentucky, Lexington, Kentucky, United States of America
- Laboratory of Genetics, The Salk Institute, La Jolla, California, United States of America
| | - Melissa C. Keinath
- Department of Biology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Jeramiah J. Smith
- Department of Biology, University of Kentucky, Lexington, Kentucky, United States of America
- * E-mail:
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11
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Dickson LB, Sharakhova MV, Timoshevskiy VA, Fleming KL, Caspary A, Sylla M, Black WC. Reproductive Incompatibility Involving Senegalese Aedes aegypti (L) Is Associated with Chromosome Rearrangements. PLoS Negl Trop Dis 2016; 10:e0004626. [PMID: 27105225 PMCID: PMC4841568 DOI: 10.1371/journal.pntd.0004626] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 03/23/2016] [Indexed: 01/16/2023] Open
Abstract
Aedes aegypti, the primary vector of dengue, yellow fever and Zika flaviviruses, consists of at least two subspecies. Aedes aegypti (Aaa) is light in color, has pale scales on the first abdominal tergite, oviposits in artificial containers, and preferentially feeds on humans. Aedes aegypti formosus (Aaf), has a dark cuticle, is restricted to sub-Saharan Africa, has no pale scales on the first abdominal tergite and frequently oviposits in natural containers. Scale patterns correlate with cuticle color in East Africa but not in Senegal, West Africa where black cuticle mosquitoes display a continuum of scaling patterns and breed domestically indoors. An earlier laboratory study did not indicate any pre- or postzygotic barriers to gene flow between Aaa and Aaf in East Africa. However, similar attempts to construct F1 intercross families between Aaa laboratory strains and Senegal Ae. aegypti (SenAae) failed due to poor F1 oviposition and low F2 egg-to-adult survival. Insemination and assortative mating experiments failed to identify prezygotic mating barriers. Backcrosses were performed to test for postzygotic isolation patterns consistent with Haldane’s rule modified for species, like Aedes, that have an autosomal sex determining locus (SDL). Egg-pupal survival was predicted to be low in females mated to hybrid F1 males but average when a male mates with a hybrid F1 female. Survival was in fact significantly reduced when females mated to hybrid males but egg-pupal survival was significantly increased when males were mated to hybrid F1 females. These observations are therefore inconclusive with regards to Haldane’s rule. Basic cytogenetic analyses and Fluorescent In Situ Hybridization (FISH) experiments were performed to compare SenAae strains with the IB12 strain of Aaa that was used for genome sequencing and physical mapping. Some SenAae strains had longer chromosomes than IB12 and significantly different centromeric indices on chromosomes 1 and 3. DAPI staining was used to identify AT-rich regions, chromomycin A3 following pretreatment with barium hydroxide stained for GC-rich regions and stained the ribosomal RNA locus and YOYO-1 was used to test for differential staining. Chromosome patterns in SenAae strains revealed by these three stains differed from those in IB12. For FISH, 40 BAC clones previously physically mapped on Aaa chromosomes were used to test for chromosome rearrangements in SenAae relative to IB12. Differences in the order of markers identified two chromosomal rearrangements between IB12 and SenAae strains. The first rearrangement involves two overlapping pericentric (containing the centromere) inversions in chromosome 3 or an insertion of a large fragment into the 3q arm. The second rearrangement is close to the centromere on the p arm of chromosome 2. Linkage analysis of the SDL and the white-eye locus identified a likely chromosomal rearrangement on chromosome 1. The reproductive incompatibility observed within SenAae and between SenAae and Aaa may be generally associated with chromosome rearrangements on all three chromosomes and specifically caused by pericentric inversions on chromosomes 2 and 3. Aedes aegypti is one of the best studied mosquito species and it is the principal vector of dengue, Zika, and yellow fever flaviviruses and the Chikungunya alphavirus. Aedes aegypti occurs throughout all tropical and subtropical regions of the world, and previous population genetic studies have shown that the highest genetic diversity occurs in Africa. Aedes aegypti from Senegal, West Africa (SenAae) have a low oviposition rate; those that do oviposit have a low fecundity and poor egg-to-adult survival. Furthermore rearrangements were detected on all three chromosomes in SenAae. These observations are consistent with the presence of at least two cryptic subspecies of Ae. aegypti in Senegal arising from reproductive isolation due to chromosome rearrangements. Genetic control strategies are being considered for the suppression of Ae. aegypti populations worldwide. Barriers to gene flow in African Ae. aegypti populations could compromise these future control efforts.
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Affiliation(s)
- Laura B. Dickson
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Maria V. Sharakhova
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Vladimir A. Timoshevskiy
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Karen L. Fleming
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Alex Caspary
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Massamba Sylla
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - William C. Black
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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Hall AB, Papathanos PA, Sharma A, Cheng C, Akbari OS, Assour L, Bergman NH, Cagnetti A, Crisanti A, Dottorini T, Fiorentini E, Galizi R, Hnath J, Jiang X, Koren S, Nolan T, Radune D, Sharakhova MV, Steele A, Timoshevskiy VA, Windbichler N, Zhang S, Hahn MW, Phillippy AM, Emrich SJ, Sharakhov IV, Tu ZJ, Besansky NJ. Radical remodeling of the Y chromosome in a recent radiation of malaria mosquitoes. Proc Natl Acad Sci U S A 2016; 113:E2114-23. [PMID: 27035980 PMCID: PMC4839409 DOI: 10.1073/pnas.1525164113] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Y chromosomes control essential male functions in many species, including sex determination and fertility. However, because of obstacles posed by repeat-rich heterochromatin, knowledge of Y chromosome sequences is limited to a handful of model organisms, constraining our understanding of Y biology across the tree of life. Here, we leverage long single-molecule sequencing to determine the content and structure of the nonrecombining Y chromosome of the primary African malaria mosquito, Anopheles gambiae We find that the An. gambiae Y consists almost entirely of a few massively amplified, tandemly arrayed repeats, some of which can recombine with similar repeats on the X chromosome. Sex-specific genome resequencing in a recent species radiation, the An. gambiae complex, revealed rapid sequence turnover within An. gambiae and among species. Exploiting 52 sex-specific An. gambiae RNA-Seq datasets representing all developmental stages, we identified a small repertoire of Y-linked genes that lack X gametologs and are not Y-linked in any other species except An. gambiae, with the notable exception of YG2, a candidate male-determining gene. YG2 is the only gene conserved and exclusive to the Y in all species examined, yet sequence similarity to YG2 is not detectable in the genome of a more distant mosquito relative, suggesting rapid evolution of Y chromosome genes in this highly dynamic genus of malaria vectors. The extensive characterization of the An. gambiae Y provides a long-awaited foundation for studying male mosquito biology, and will inform novel mosquito control strategies based on the manipulation of Y chromosomes.
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Affiliation(s)
- Andrew Brantley Hall
- The Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Philippos-Aris Papathanos
- Section of Genomics and Genetics, Department of Experimental Medicine, University of Perugia, 06132 Perugia, Italy; Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Atashi Sharma
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Changde Cheng
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556
| | - Omar S Akbari
- Department of Entomology, Riverside Center for Disease Vector Research, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521
| | - Lauren Assour
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Nicholas H Bergman
- National Biodefense Analysis and Countermeasures Center, Frederick, MD 21702
| | - Alessia Cagnetti
- Section of Genomics and Genetics, Department of Experimental Medicine, University of Perugia, 06132 Perugia, Italy
| | - Andrea Crisanti
- Section of Genomics and Genetics, Department of Experimental Medicine, University of Perugia, 06132 Perugia, Italy; Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Tania Dottorini
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Elisa Fiorentini
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Roberto Galizi
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Jonathan Hnath
- National Biodefense Analysis and Countermeasures Center, Frederick, MD 21702
| | - Xiaofang Jiang
- The Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Sergey Koren
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Tony Nolan
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Diane Radune
- National Biodefense Analysis and Countermeasures Center, Frederick, MD 21702
| | - Maria V Sharakhova
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; Laboratory of Evolutionary Cytogenetics, Tomsk State University, Tomsk 634050, Russia
| | - Aaron Steele
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Vladimir A Timoshevskiy
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Nikolai Windbichler
- Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Simo Zhang
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405
| | - Matthew W Hahn
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405; Department of Biology, Indiana University, Bloomington, IN 47405
| | - Adam M Phillippy
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Scott J Emrich
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556; Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Igor V Sharakhov
- The Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; Laboratory of Evolutionary Cytogenetics, Tomsk State University, Tomsk 634050, Russia;
| | - Zhijian Jake Tu
- The Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Nora J Besansky
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556;
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Keinath MC, Timoshevskiy VA, Timoshevskaya NY, Tsonis PA, Voss SR, Smith JJ. Initial characterization of the large genome of the salamander Ambystoma mexicanum using shotgun and laser capture chromosome sequencing. Sci Rep 2015; 5:16413. [PMID: 26553646 PMCID: PMC4639759 DOI: 10.1038/srep16413] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 10/14/2015] [Indexed: 12/22/2022] Open
Abstract
Vertebrates exhibit substantial diversity in genome size, and some of the largest genomes exist in species that uniquely inform diverse areas of basic and biomedical research. For example, the salamander Ambystoma mexicanum (the Mexican axolotl) is a model organism for studies of regeneration, development and genome evolution, yet its genome is ~10× larger than the human genome. As part of a hierarchical approach toward improving genome resources for the species, we generated 600 Gb of shotgun sequence data and developed methods for sequencing individual laser-captured chromosomes. Based on these data, we estimate that the A. mexicanum genome is ~32 Gb. Notably, as much as 19 Gb of the A. mexicanum genome can potentially be considered single copy, which presumably reflects the evolutionary diversification of mobile elements that accumulated during an ancient episode of genome expansion. Chromosome-targeted sequencing permitted the development of assemblies within the constraints of modern computational platforms, allowed us to place 2062 genes on the two smallest A. mexicanum chromosomes and resolves key events in the history of vertebrate genome evolution. Our analyses show that the capture and sequencing of individual chromosomes is likely to provide valuable information for the systematic sequencing, assembly and scaffolding of large genomes.
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Affiliation(s)
- Melissa C Keinath
- Department of Biology, University of Kentucky, Lexington, KY, 40506, USA
| | | | | | | | - S Randal Voss
- Department of Biology, University of Kentucky, Lexington, KY, 40506, USA.,Spinal Cord and Brain and Injury Research Center, University of Kentucky, Lexington, KY, 40506, USA
| | - Jeramiah J Smith
- Department of Biology, University of Kentucky, Lexington, KY, 40506, USA
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Hall AB, Basu S, Jiang X, Qi Y, Timoshevskiy VA, Biedler JK, Sharakhova MV, Elahi R, Anderson MAE, Chen XG, Sharakhov IV, Adelman ZN, Tu Z. SEX DETERMINATION. A male-determining factor in the mosquito Aedes aegypti. Science 2015; 348:1268-70. [PMID: 25999371 DOI: 10.1126/science.aaa2850] [Citation(s) in RCA: 194] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 05/07/2015] [Indexed: 12/27/2022]
Abstract
Sex determination in the mosquito Aedes aegypti is governed by a dominant male-determining factor (M factor) located within a Y chromosome-like region called the M locus. Here, we show that an M-locus gene, Nix, functions as an M factor in A. aegypti. Nix exhibits persistent M linkage and early embryonic expression, two characteristics required of an M factor. Nix knockout with clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 resulted in largely feminized genetic males and the production of female isoforms of two key regulators of sexual differentiation: doublesex and fruitless. Ectopic expression of Nix resulted in genetic females with nearly complete male genitalia. Thus, Nix is both required and sufficient to initiate male development. This study provides a foundation for mosquito control strategies that convert female mosquitoes into harmless males.
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Affiliation(s)
- Andrew Brantley Hall
- Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Sanjay Basu
- Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Xiaofang Jiang
- Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Yumin Qi
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Vladimir A Timoshevskiy
- Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - James K Biedler
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Maria V Sharakhova
- Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Rubayet Elahi
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA
| | - Michelle A E Anderson
- Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Xiao-Guang Chen
- School of Public Health and Tropical Medicine, Southern Medical University, Guangdong, People's Republic of China
| | - Igor V Sharakhov
- Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Zach N Adelman
- Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA. Department of Entomology, Virginia Tech, Blacksburg, VA, USA.
| | - Zhijian Tu
- Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA. Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA.
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15
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Naumenko AN, Timoshevskiy VA, Kinney NA, Kokhanenko AA, deBruyn BS, Lovin DD, Stegniy VN, Severson DW, Sharakhov IV, Sharakhova MV. Correction: Mitotic-Chromosome-Based Physical Mapping of the Culex quinquefasciatus Genome. PLoS One 2015; 10:e0127565. [PMID: 25954932 PMCID: PMC4425355 DOI: 10.1371/journal.pone.0127565] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Naumenko AN, Timoshevskiy VA, Kinney NA, Kokhanenko AA, deBruyn BS, Lovin DD, Stegniy VN, Severson DW, Sharakhov IV, Sharakhova MV. Mitotic-chromosome-based physical mapping of the Culex quinquefasciatus genome. PLoS One 2015; 10:e0115737. [PMID: 25768920 PMCID: PMC4358980 DOI: 10.1371/journal.pone.0115737] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 11/21/2014] [Indexed: 11/28/2022] Open
Abstract
The genome assembly of southern house mosquito Cx. quinquefasciatus is represented by a high number of supercontigs with no order or orientation on the chromosomes. Although cytogenetic maps for the polytene chromosomes of this mosquito have been developed, their utilization for the genome mapping remains difficult because of the low number of high-quality spreads in chromosome preparations. Therefore, a simple and robust mitotic-chromosome-based approach for the genome mapping of Cx. quinquefasciatus still needs to be developed. In this study, we performed physical mapping of 37 genomic supercontigs using fluorescent in situ hybridization on mitotic chromosomes from imaginal discs of 4th instar larvae. The genetic linkage map nomenclature was adopted for the chromosome numbering based on the direct positioning of 58 markers that were previously genetically mapped. The smallest, largest, and intermediate chromosomes were numbered as 1, 2, and 3, respectively. For idiogram development, we analyzed and described in detail the morphology and proportions of the mitotic chromosomes. Chromosomes were subdivided into 19 divisions and 72 bands of four different intensities. These idiograms were used for mapping the genomic supercontigs/genetic markers. We also determined the presence of length polymorphism in the q arm of sex-determining chromosome 1 in Cx. quinquefasciatus related to the size of ribosomal locus. Our physical mapping and previous genetic linkage mapping resulted in the chromosomal assignment of 13% of the total genome assembly to the chromosome bands. We provided the first detailed description, nomenclature, and idiograms for the mitotic chromosomes of Cx. quinquefasciatus. Further application of the approach developed in this study will help to improve the quality of the southern house mosquito genome.
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Affiliation(s)
- Anastasia N. Naumenko
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Vladimir A. Timoshevskiy
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Nicholas A. Kinney
- Department of Genomics, Bioinformatics, and Computational Biology, Virginia Tech, Blacksburg, Virginia, United States of America
| | | | - Becky S. deBruyn
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Diane D. Lovin
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | | | - David W. Severson
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Igor V. Sharakhov
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Maria V. Sharakhova
- Department of Entomology and Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
- Institute of Biology and Biophysics, Tomsk State University, Tomsk, Russia
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Hall AB, Timoshevskiy VA, Sharakhova MV, Jiang X, Basu S, Anderson MAE, Hu W, Sharakhov IV, Adelman ZN, Tu Z. Insights into the preservation of the homomorphic sex-determining chromosome of Aedes aegypti from the discovery of a male-biased gene tightly linked to the M-locus. Genome Biol Evol 2014; 6:179-91. [PMID: 24398378 PMCID: PMC3914700 DOI: 10.1093/gbe/evu002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [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] [Indexed: 01/05/2023] Open
Abstract
The preservation of a homomorphic sex-determining chromosome in some organisms without transformation into a heteromorphic sex chromosome is a long-standing enigma in evolutionary biology. A dominant sex-determining locus (or M-locus) in an undifferentiated homomorphic chromosome confers the male phenotype in the yellow fever mosquito Aedes aegypti. Genetic evidence suggests that the M-locus is in a nonrecombining region. However, the molecular nature of the M-locus has not been characterized. Using a recently developed approach based on Illumina sequencing of male and female genomic DNA, we identified a novel gene, myo-sex, that is present almost exclusively in the male genome but can sporadically be found in the female genome due to recombination. For simplicity, we define sequences that are primarily found in the male genome as male-biased. Fluorescence in situ hybridization (FISH) on A. aegypti chromosomes demonstrated that the myo-sex probe localized to region 1q21, the established location of the M-locus. Myo-sex is a duplicated myosin heavy chain gene that is highly expressed in the pupa and adult male. Myo-sex shares 83% nucleotide identity and 97% amino acid identity with its closest autosomal paralog, consistent with ancient duplication followed by strong purifying selection. Compared with males, myo-sex is expressed at very low levels in the females that acquired it, indicating that myo-sex may be sexually antagonistic. This study establishes a framework to discover male-biased sequences within a homomorphic sex-determining chromosome and offers new insights into the evolutionary forces that have impeded the expansion of the nonrecombining M-locus in A. aegypti.
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Timoshevskiy VA, Kinney NA, deBruyn BS, Mao C, Tu Z, Severson DW, Sharakhov IV, Sharakhova MV. Genomic composition and evolution of Aedes aegypti chromosomes revealed by the analysis of physically mapped supercontigs. BMC Biol 2014; 12:27. [PMID: 24731704 PMCID: PMC4021624 DOI: 10.1186/1741-7007-12-27] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND An initial comparative genomic study of the malaria vector Anopheles gambiae and the yellow fever mosquito Aedes aegypti revealed striking differences in the genome assembly size and in the abundance of transposable elements between the two species. However, the chromosome arms homology between An. gambiae and Ae. aegypti, as well as the distribution of genes and repetitive elements in chromosomes of Ae. aegypti, remained largely unexplored because of the lack of a detailed physical genome map for the yellow fever mosquito. RESULTS Using a molecular landmark-guided fluorescent in situ hybridization approach, we mapped 624 Mb of the Ae. aegypti genome to mitotic chromosomes. We used this map to analyze the distribution of genes, tandem repeats and transposable elements along the chromosomes and to explore the patterns of chromosome homology and rearrangements between Ae. aegypti and An. gambiae. The study demonstrated that the q arm of the sex-determining chromosome 1 had the lowest gene content and the highest density of minisatellites. A comparative genomic analysis with An. gambiae determined that the previously proposed whole-arm synteny is not fully preserved; a number of pericentric inversions have occurred between the two species. The sex-determining chromosome 1 had a higher rate of genome rearrangements than observed in autosomes 2 and 3 of Ae. aegypti. CONCLUSIONS The study developed a physical map of 45% of the Ae. aegypti genome and provided new insights into genomic composition and evolution of Ae. aegypti chromosomes. Our data suggest that minisatellites rather than transposable elements played a major role in rapid evolution of chromosome 1 in the Aedes lineage. The research tools and information generated by this study contribute to a more complete understanding of the genome organization and evolution in mosquitoes.
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Affiliation(s)
| | | | | | | | | | | | | | - Maria V Sharakhova
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA.
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Timoshevskiy VA, Severson DW, deBruyn BS, Black WC, Sharakhov IV, Sharakhova MV. An integrated linkage, chromosome, and genome map for the yellow fever mosquito Aedes aegypti. PLoS Negl Trop Dis 2013; 7:e2052. [PMID: 23459230 PMCID: PMC3573077 DOI: 10.1371/journal.pntd.0002052] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 12/21/2012] [Indexed: 11/18/2022] Open
Abstract
Background Aedes aegypti, the yellow fever mosquito, is an efficient vector of arboviruses and a convenient model system for laboratory research. Extensive linkage mapping of morphological and molecular markers localized a number of quantitative trait loci (QTLs) related to the mosquito's ability to transmit various pathogens. However, linking the QTLs to Ae. aegypti chromosomes and genomic sequences has been challenging because of the poor quality of polytene chromosomes and the highly fragmented genome assembly for this species. Methodology/Principal Findings Based on the approach developed in our previous study, we constructed idiograms for mitotic chromosomes of Ae. aegypti based on their banding patterns at early metaphase. These idiograms represent the first cytogenetic map developed for mitotic chromosomes of Ae. aegypti. One hundred bacterial artificial chromosome clones carrying major genetic markers were hybridized to the chromosomes using fluorescent in situ hybridization. As a result, QTLs related to the transmission of the filarioid nematode Brugia malayi, the avian malaria parasite Plasmodium gallinaceum, and the dengue virus, as well as sex determination locus and 183 Mbp of genomic sequences were anchored to the exact positions on Ae. aegypti chromosomes. A linear regression analysis demonstrated a good correlation between positions of the markers on the physical and linkage maps. As a result of the recombination rate variation along the chromosomes, 12 QTLs on the linkage map were combined into five major clusters of QTLs on the chromosome map. Conclusion This study developed an integrated linkage, chromosome, and genome map—iMap—for the yellow fever mosquito. Our discovery of the localization of multiple QTLs in a few major chromosome clusters suggests a possibility that the transmission of various pathogens is controlled by the same genomic loci. Thus, the iMap will facilitate the identification of genomic determinants of traits responsible for susceptibility or refractoriness of the mosquito to diverse pathogens. About half of the human population is under risk of dengue infection. Because of the absence of a vaccine or drug treatment, the prevention of this disease largely relies on controlling its major vector mosquito Aedes aegypti. Availability of the complete genome sequence for this mosquito offers the potential to help in the identification of novel disease control strategies. An efficient vector of arboviruses, Ae. aegypti is also a convenient model for laboratory studies. A number of genetic loci related to the remarkable ability of this mosquito to transmit various pathogens were genetically mapped to the three linkage groups corresponding to the three individual chromosomes of the mosquito. However, the exact physical positions of the genetic loci and genomic sequences on the chromosomes were unknown. In this study, we developed maps for mitotic chromosomes of Ae. aegypti and localized 100 clones carrying major genetic markers, which were previously used for mapping genetic loci associated with the pathogens' transmission. Finally, linkage, chromosome, and genome maps of Ae. aegypti were integrated. Anchoring of the genomic sequences associated with genetic markers to the chromosomes of Ae. aegypti will help to identify candidate genes that might be utilized for developing advanced genome-based strategies for vector control.
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Affiliation(s)
- Vladimir A. Timoshevskiy
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - David W. Severson
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Becky S. deBruyn
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - William C. Black
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Igor V. Sharakhov
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Maria V. Sharakhova
- Department of Entomology, Fralin Life Science Institute, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail:
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Abstract
Fluorescent in situ hybridization (FISH) is a technique routinely used by many laboratories to determine the chromosomal position of DNA and RNA probes. One important application of this method is the development of high-quality physical maps useful for improving the genome assemblies for various organisms. The natural banding pattern of polytene and mitotic chromosomes provides guidance for the precise ordering and orientation of the genomic supercontigs. Among the three mosquito genera, namely Anopheles, Aedes, and Culex, a well-established chromosome-based mapping technique has been developed only for Anopheles, whose members possess readable polytene chromosomes. As a result of genome mapping efforts, 88% of the An. gambiae genome has been placed to precise chromosome positions. Two other mosquito genera, Aedes and Culex, have poorly polytenized chromosomes because of significant overrepresentation of transposable elements in their genomes. Only 31 and 9% of the genomic supercontings have been assigned without order or orientation to chromosomes of Ae. aegypti and Cx. quinquefasciatus, respectively. Mitotic chromosome preparation for these two species had previously been limited to brain ganglia and cell lines. However, chromosome slides prepared from the brain ganglia of mosquitoes usually contain low numbers of metaphase plates. Also, although a FISH technique has been developed for mitotic chromosomes from a cell line of Ae. aegypti, the accumulation of multiple chromosomal rearrangements in cell line chromosomes makes them useless for genome mapping. Here we describe a simple, robust technique for obtaining high-quality mitotic chromosome preparations from imaginal discs (IDs) of 4th instar larvae which can be used for all three genera of mosquitoes. A standard FISH protocol is optimized for using BAC clones of genomic DNA as a probe on mitotic chromosomes of Ae. aegypti and Cx. quinquefasciatus, and for utilizing an intergenic spacer (IGS) region of ribosomal DNA (rDNA) as a probe on An. gambiae chromosomes. In addition to physical mapping, the developed technique can be applied to population cytogenetics and chromosome taxonomy/systematics of mosquitoes and other insect groups.
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