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Souza GM, Kretschmer R, Toma GA, de Oliveira AM, Deon GA, Setti PG, Zeni Dos Santos R, Goes CAG, Del Valle Garnero A, Gunski RJ, de Oliveira EHC, Porto-Foresti F, Liehr T, Utsunomia R, de Bello Cioffi M. Satellitome analysis on the pale-breasted thrush Turdus leucomelas (Passeriformes; Turdidae) uncovers the putative co-evolution of sex chromosomes and satellite DNAs. Sci Rep 2024; 14:20656. [PMID: 39232109 PMCID: PMC11375038 DOI: 10.1038/s41598-024-71635-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 08/29/2024] [Indexed: 09/06/2024] Open
Abstract
Do all birds' sex chromosomes follow the same canonical one-way direction of evolution? We combined cytogenetic and genomic approaches to analyze the process of the W chromosomal differentiation in two selected Passeriform species, named the Pale-breasted Thrush Turdus leucomelas and the Rufous-bellied thrush T. rufiventris. We characterized the full catalog of satellite DNAs (satellitome) of T. leucomelas, and the 10 TleSatDNA classes obtained together with 16 microsatellite motifs were in situ mapped in both species. Additionally, using Comparative Genomic Hybridization (CGH) assays, we investigated their intragenomic variations. The W chromosomes of both species did not accumulate higher amounts of both heterochromatin and repetitive sequences. However, while T. leucomelas showed a heterochromatin-poor W chromosome with a very complex evolutionary history, T. rufiventris showed a small and partially heterochromatic W chromosome that represents a differentiated version of its original autosomal complement (Z chromosome). The combined approach of CGH and sequential satDNA mapping suggest the occurrence of a former W-autosomal translocation event in T. leucomelas, which had an impact on the W chromosome in terms of sequence gains and losses. At the same time, an autosome, which is present in both males and females in a polymorphic state, lost sequences and integrated previously W-specific ones. This putative W-autosomal translocation, however, did not result in the emergence of a multiple-sex chromosome system. Instead, the generation of a neo-W chromosome suggests an unexpected evolutionary trajectory that deviates from the standard canonical model of sex chromosome evolution.
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Affiliation(s)
- Guilherme Mota Souza
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Rafael Kretschmer
- Departamento de Ecologia, Zoologia e Genética, Instituto de Biologia, Universidade Federal de Pelotas, Pelotas, RS, 96010-610, Brazil
| | - Gustavo Akira Toma
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Alan Moura de Oliveira
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Geize Aparecida Deon
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Princia Grejo Setti
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
| | | | | | | | - Ricardo José Gunski
- Universidade Federal do Pampa, Campus São Gabriel, São Gabriel, RS, 97307-020, Brazil
| | - Edivaldo Herculano Correa de Oliveira
- Seção de Meio Ambiente, Instituto Evandro Chagas, Ananindeua, PA, 67030-000, Brazil
- Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Fabio Porto-Foresti
- Faculdade de Ciências, Universidade Estadual Paulista, Bauru, SP, 17033-360, Brazil
| | - Thomas Liehr
- Institut für Humangenetik, Universitätsklinikum Jena, Friedrich-Schiller Universität, 07747, Jena, Germany.
| | - Ricardo Utsunomia
- Faculdade de Ciências, Universidade Estadual Paulista, Bauru, SP, 17033-360, Brazil
| | - Marcelo de Bello Cioffi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, 13565-905, Brazil
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Diversity of Underwater Vocalizations in Chinese Soft-Shelled Turtle ( Pelodiscus sinensis). Animals (Basel) 2023; 13:ani13050812. [PMID: 36899669 PMCID: PMC10000088 DOI: 10.3390/ani13050812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 02/11/2023] [Accepted: 02/21/2023] [Indexed: 02/26/2023] Open
Abstract
Sound communication is important for underwater species. The wild population of the Chinese soft-shelled turtle (Pelodiscus sinensis) is listed as vulnerable. However, its vocalization, which can serve as the basis for ecological and evolutionary research, has not been studied. Here, we performed underwater recordings of 23 Chinese soft-shelled turtles of different ages and sexes and identified 720 underwater calls. The turtle calls were manually divided into 10 call types according to visual and aural inspection properties. The similarity test indicated that the manual division was reliable. We described the acoustic properties of the calls and the statistical analysis showed that the peak frequency of calls was significantly different between adult females and males, and also between subadults and adults. Similar to other aquatic turtles that prefer to live in deep water, Chinese soft-shelled turtles have a high vocal diversity and many harmonic calls, indicating that this highly aquatic species developed a variety of vocalizations to enhance their underwater communication, which helped them adapt to the complex and dim underwater environment. Furthermore, the turtles showed a tendency for vocalization to become more diverse with age.
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Conservation of Major Satellite DNAs in Snake Heterochromatin. Animals (Basel) 2023; 13:ani13030334. [PMID: 36766223 PMCID: PMC9913375 DOI: 10.3390/ani13030334] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023] Open
Abstract
Repetitive DNA sequences constitute a sizeable portion of animal genomes, and tandemly organized satellite DNAs are a major part of them. They are usually located in constitutive heterochromatin clusters in or near the centromeres or telomeres, and less frequently in the interstitial parts of chromosome arms. They are also frequently accumulated in sex chromosomes. The function of these clusters is to sustain the architecture of the chromosomes and the nucleus, and to regulate chromosome behavior during mitosis and meiosis. The study of satellite DNA diversity is important for understanding sex chromosome evolution, interspecific hybridization, and speciation. In this work, we identified four satellite DNA families in the genomes of two snakes from different families: Daboia russelii (Viperidae) and Pantherophis guttatus (Colubridae) and determine their chromosomal localization. We found that one family is localized in the centromeres of both species, whereas the others form clusters in certain chromosomes or subsets of chromosomes. BLAST with snake genome assemblies showed the conservation of such clusters, as well as a subtle presence of the satellites in the interspersed manner outside the clusters. Overall, our results show high conservation of satellite DNA in snakes and confirm the "library" model of satellite DNA evolution.
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Kulak M, Komissarov A, Fillon V, Tsukanova K, Saifitdinova A, Galkina S. Genome organization of major tandem repeats and their specificity for heterochromatin of macro- and microchromosomes in Japanese quail. Genome 2022; 65:391-403. [PMID: 35776982 DOI: 10.1139/gen-2022-0012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tandemly repeated DNAs form heterochromatic regions of chromosomes, including the vital centromeric chromatin. Despite the progress in new genomic technologies tandem repeats remain poorly deciphered and need targeted analysis in the species of interest. The Japanese quail is one of the highest-producing poultry species as well as a model organism. Its genome differs by a noticeable accumulation of heterochromatin, which led to an increase by 1/7 compared to the chicken genome size. Prominent heterochromatin blocks occupy the short arms of acrocentric macrochromosomes and of microchromosomes. We have applied de novo repeat finder approach to unassembled raw reads of the Japanese quail genome. We identified the 20 most common tandem repeats with the abundance >1 Mb, which represent about 4.8% of the genome. We found that tandem repeat CjapSAT primarily contribute to the centromeric regions of the macrochromosomes CJA1-8. Cjap31B together with previously characterized BglII make up centromere regions of microchromosomes and W chromosome. Other repeats populate heterochromatin of microchromosomal short arms in unequal proportions, as revealed by FISH. The Cjap84A, Cjap408A and CjapSAT repeat sequences show similarities with retrotransposon motifs. This suggests that retroelements may have played a crucial role in the distribution of repeats throughout the Japanese quail genome.
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Affiliation(s)
- Maria Kulak
- Saint Petersburg State University, Saint Petersburg, Russian Federation;
| | | | - Valerie Fillon
- INRA Toulouse-Occitanie, Castanet Tolosan, Occitanie, France;
| | - Kseniya Tsukanova
- Saint Petersburg State University, Saint Petersburg, Russian Federation;
| | - Alsu Saifitdinova
- Herzen State Pedagogical University of Russia, 104720, Saint Petersburg, Russian Federation;
| | - Svetlana Galkina
- Saint Petersburg State University, Saint Petersburg, Russian Federation;
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Srikulnath K, Ahmad SF, Singchat W, Panthum T. Why Do Some Vertebrates Have Microchromosomes? Cells 2021; 10:2182. [PMID: 34571831 PMCID: PMC8466491 DOI: 10.3390/cells10092182] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/17/2021] [Accepted: 08/17/2021] [Indexed: 12/27/2022] Open
Abstract
With more than 70,000 living species, vertebrates have a huge impact on the field of biology and research, including karyotype evolution. One prominent aspect of many vertebrate karyotypes is the enigmatic occurrence of tiny and often cytogenetically indistinguishable microchromosomes, which possess distinctive features compared to macrochromosomes. Why certain vertebrate species carry these microchromosomes in some lineages while others do not, and how they evolve remain open questions. New studies have shown that microchromosomes exhibit certain unique characteristics of genome structure and organization, such as high gene densities, low heterochromatin levels, and high rates of recombination. Our review focuses on recent concepts to expand current knowledge on the dynamic nature of karyotype evolution in vertebrates, raising important questions regarding the evolutionary origins and ramifications of microchromosomes. We introduce the basic karyotypic features to clarify the size, shape, and morphology of macro- and microchromosomes and report their distribution across different lineages. Finally, we characterize the mechanisms of different evolutionary forces underlying the origin and evolution of microchromosomes.
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Affiliation(s)
- Kornsorn Srikulnath
- Animal Genomics and Bioresource Research Center (AGB Research Center), Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (T.P.)
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- The International Undergraduate Program in Bioscience and Technology, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Amphibian Research Center, Hiroshima University, 1-3-1, Kagamiyama, Higashihiroshima 739-8526, Japan
| | - Syed Farhan Ahmad
- Animal Genomics and Bioresource Research Center (AGB Research Center), Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (T.P.)
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- The International Undergraduate Program in Bioscience and Technology, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Worapong Singchat
- Animal Genomics and Bioresource Research Center (AGB Research Center), Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (T.P.)
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Thitipong Panthum
- Animal Genomics and Bioresource Research Center (AGB Research Center), Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (T.P.)
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
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Impact of Repetitive DNA Elements on Snake Genome Biology and Evolution. Cells 2021; 10:cells10071707. [PMID: 34359877 PMCID: PMC8303610 DOI: 10.3390/cells10071707] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 12/11/2022] Open
Abstract
The distinctive biology and unique evolutionary features of snakes make them fascinating model systems to elucidate how genomes evolve and how variation at the genomic level is interlinked with phenotypic-level evolution. Similar to other eukaryotic genomes, large proportions of snake genomes contain repetitive DNA, including transposable elements (TEs) and satellite repeats. The importance of repetitive DNA and its structural and functional role in the snake genome, remain unclear. This review highlights the major types of repeats and their proportions in snake genomes, reflecting the high diversity and composition of snake repeats. We present snakes as an emerging and important model system for the study of repetitive DNA under the impact of sex and microchromosome evolution. We assemble evidence to show that certain repetitive elements in snakes are transcriptionally active and demonstrate highly dynamic lineage-specific patterns as repeat sequences. We hypothesize that particular TEs can trigger different genomic mechanisms that might contribute to driving adaptive evolution in snakes. Finally, we review emerging approaches that may be used to study the expression of repetitive elements in complex genomes, such as snakes. The specific aspects presented here will stimulate further discussion on the role of genomic repeats in shaping snake evolution.
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Liu J, Wang Z, Li J, Xu L, Liu J, Feng S, Guo C, Chen S, Ren Z, Rao J, Wei K, Chen Y, Jarvis ED, Zhang G, Zhou Q. A new emu genome illuminates the evolution of genome configuration and nuclear architecture of avian chromosomes. Genome Res 2021; 31:497-511. [PMID: 33408157 PMCID: PMC7919449 DOI: 10.1101/gr.271569.120] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 12/30/2020] [Indexed: 01/30/2023]
Abstract
Emu and other ratites are more informative than any other birds in reconstructing the evolution of the ancestral avian or vertebrate karyotype because of their much slower rate of genome evolution. Here, we generated a new chromosome-level genome assembly of a female emu, and estimated the tempo of chromosome evolution across major avian phylogenetic branches, by comparing it to chromosome-level genome assemblies of 11 other bird and one turtle species. We found ratites exhibited the lowest numbers of intra- and inter-chromosomal changes among birds since their divergence with turtles. The small-sized and gene-rich emu microchromosomes have frequent inter-chromosomal contacts that are associated with housekeeping genes, which appears to be driven by clustering their centromeres in the nuclear interior, away from the macrochromosomes in the nuclear periphery. Unlike nonratite birds, only less than one-third of the emu W Chromosome regions have lost homologous recombination and diverged between the sexes. The emu W is demarcated into a highly heterochromatic region (WS0) and another recently evolved region (WS1) with only moderate sequence divergence with the Z Chromosome. WS1 has expanded its inactive chromatin compartment, increased chromatin contacts within the region, and decreased contacts with the nearby regions, possibly influenced by the spreading of heterochromatin from WS0. These patterns suggest that alteration of chromatin conformation comprises an important early step of sex chromosome evolution. Overall, our results provide novel insights into the evolution of avian genome structure and sex chromosomes in three-dimensional space.
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Affiliation(s)
- Jing Liu
- MOE Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna 1090, Austria
| | - Zongji Wang
- MOE Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna 1090, Austria
- Institute of Animal Sex and Development, Zhejiang Wanli University, Ningbo 315100, China
| | - Jing Li
- MOE Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Luohao Xu
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna 1090, Austria
| | - Jiaqi Liu
- Wuhan Gooalgene Technology Company, Wuhan 430070, China
| | - Shaohong Feng
- BGI-Shenzhen, Beishan Industrial Zone, Shenzhen 518083, China
| | - Chunxue Guo
- BGI-Shenzhen, Beishan Industrial Zone, Shenzhen 518083, China
| | - Shengchan Chen
- Longteng Ecological Culture Company, Limited, Zhashui 711400, China
| | - Zhanjun Ren
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China
| | - Jinpeng Rao
- Center for Reproductive Medicine, The 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310052, China
| | - Kai Wei
- Center for Reproductive Medicine, The 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310052, China
| | - Yuezhou Chen
- Jianzhou Poultry Industry Company, Limited, Yong'an 366000, China
| | - Erich D Jarvis
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York, New York 10065, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Guojie Zhang
- China National GeneBank, BGI-Shenzhen, Shenzhen 518120, China
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
- Section for Ecology and Evolution, Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming 650223, China
| | - Qi Zhou
- MOE Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna 1090, Austria
- Center for Reproductive Medicine, The 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310052, China
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Ahmad SF, Singchat W, Jehangir M, Panthum T, Srikulnath K. Consequence of Paradigm Shift with Repeat Landscapes in Reptiles: Powerful Facilitators of Chromosomal Rearrangements for Diversity and Evolution. Genes (Basel) 2020; 11:E827. [PMID: 32708239 PMCID: PMC7397244 DOI: 10.3390/genes11070827] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 07/16/2020] [Accepted: 07/17/2020] [Indexed: 12/24/2022] Open
Abstract
Reptiles are notable for the extensive genomic diversity and species richness among amniote classes, but there is nevertheless a need for detailed genome-scale studies. Although the monophyletic amniotes have recently been a focus of attention through an increasing number of genome sequencing projects, the abundant repetitive portion of the genome, termed the "repeatome", remains poorly understood across different lineages. Consisting predominantly of transposable elements or mobile and satellite sequences, these repeat elements are considered crucial in causing chromosomal rearrangements that lead to genomic diversity and evolution. Here, we propose major repeat landscapes in representative reptilian species, highlighting their evolutionary dynamics and role in mediating chromosomal rearrangements. Distinct karyotype variability, which is typically a conspicuous feature of reptile genomes, is discussed, with a particular focus on rearrangements correlated with evolutionary reorganization of micro- and macrochromosomes and sex chromosomes. The exceptional karyotype variation and extreme genomic diversity of reptiles are used to test several hypotheses concerning genomic structure, function, and evolution.
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Affiliation(s)
- Syed Farhan Ahmad
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (M.J.); (T.P.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Worapong Singchat
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (M.J.); (T.P.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Maryam Jehangir
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (M.J.); (T.P.)
- Integrative Genomics Lab-LGI, Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, São Paulo State University (UNESP), Botucatu 18618-689, Brazil
| | - Thitipong Panthum
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (M.J.); (T.P.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Kornsorn Srikulnath
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; (S.F.A.); (W.S.); (M.J.); (T.P.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University, Kasetsart University, Bangkok 10900, Thailand
- Center of Excellence on Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok 10900, Thailand
- Omics Center for Agriculture, Bioresources, Food and Health, Kasetsart University (OmiKU), Bangkok 10900, Thailand
- Amphibian Research Center, Hiroshima University, 1-3-1, Kagamiyama, Higashihiroshima 739-8526, Japan
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Molecular cytogenetic characterization of repetitive sequences comprising centromeric heterochromatin in three Anseriformes species. PLoS One 2019; 14:e0214028. [PMID: 30913221 PMCID: PMC6435179 DOI: 10.1371/journal.pone.0214028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/05/2019] [Indexed: 01/22/2023] Open
Abstract
The highly repetitive DNA sequence of centromeric heterochromatin is an effective molecular cytogenetic marker for investigating genomic compartmentalization between macrochromosomes and microchromosomes in birds. We isolated four repetitive sequence families of centromeric heterochromatin from three Anseriformes species, viz., domestic duck (Anas platyrhynchos, APL), bean goose (Anser fabalis, AFA), and whooper swan (Cygnus cygnus, CCY), and characterized the sequences by molecular cytogenetic approach. The 190-bp APL-HaeIII and 101-bp AFA-HinfI-S sequences were localized in almost all chromosomes of A. platyrhynchos and A. fabalis, respectively. However, the 192-bp AFA-HinfI-L and 290-bp CCY-ApaI sequences were distributed in almost all microchromosomes of A. fabalis and in approximately 10 microchromosomes of C. cygnus, respectively. APL-HaeIII, AFA-HinfI-L, and CCY-ApaI showed partial sequence homology with the chicken nuclear-membrane-associated (CNM) repeat families, which were localized primarily to the centromeric regions of microchromosomes in Galliformes, suggesting that ancestral sequences of the CNM repeat families are observed in the common ancestors of Anseriformes and Galliformes. These results collectively provide the possibility that homogenization of centromeric heterochromatin occurred between microchromosomes in Anseriformes and Galliformes; however, homogenization between macrochromosomes and microchromosomes also occurred in some centromeric repetitive sequences.
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Prakhongcheep O, Thapana W, Suntronpong A, Singchat W, Pattanatanang K, Phatcharakullawarawat R, Muangmai N, Peyachoknagul S, Matsubara K, Ezaz T, Srikulnath K. Lack of satellite DNA species-specific homogenization and relationship to chromosomal rearrangements in monitor lizards (Varanidae, Squamata). BMC Evol Biol 2017; 17:193. [PMID: 28814266 PMCID: PMC5559828 DOI: 10.1186/s12862-017-1044-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 08/08/2017] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Satellite DNAs (stDNAs) are highly repeated sequences that constitute large portions of any genome. The evolutionary dynamics of stDNA (e.g. copy number, nucleotide sequence, location) can, therefore, provide an insight into genome organization and evolution. We investigated the evolutionary origin of VSAREP stDNA in 17 monitor lizards (seven Asian, five Australian, and five African) at molecular and cytogenetic level. RESULTS Results revealed that VSAREP is conserved in the genome of Asian and Australian varanids, but not in African varanids, suggesting that these sequences are either differentiated or lost in the African varanids. Phylogenetic and arrangement network analyses revealed the existence of at least four VSAREP subfamilies. The similarity of each sequence unit within the same VSAREP subfamily from different species was higher than those of other VSAREP subfamilies belonging to the same species. Additionally, all VSAREP subfamilies isolated from the three Australian species (Varanus rosenbergi, V. gouldii, and V. acanthurus) were co-localized near the centromeric or pericentromeric regions of the macrochromosomes, except for chromosomes 3 and 4 in each Australian varanid. However, their chromosomal arrangements were different among species. CONCLUSIONS The VSAREP stDNA family lack homogenized species-specific nucleotide positions in varanid lineage. Most VSAREP sequences were shared among varanids within the four VSAREP subfamilies. This suggests that nucleotide substitutions in each varanid species accumulated more slowly than homogenization rates in each VSAREP subfamily, resulting in non-species-specific evolution of stDNA profiles. Moreover, changes in location of VSAREP stDNA in each Australian varanid suggests a correlation with chromosomal rearrangements, leading to karyotypic differences among these species.
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Affiliation(s)
- Ornjira Prakhongcheep
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Animal Breeding and Genetics Consortium - Kasetsart University (ABG - KU), 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU), Kasetsart University, Bangkok, 10900, Thailand
| | - Watcharaporn Thapana
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Animal Breeding and Genetics Consortium - Kasetsart University (ABG - KU), 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU), Kasetsart University, Bangkok, 10900, Thailand
| | - Aorarat Suntronpong
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Animal Breeding and Genetics Consortium - Kasetsart University (ABG - KU), 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
| | - Worapong Singchat
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Animal Breeding and Genetics Consortium - Kasetsart University (ABG - KU), 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
| | - Khampee Pattanatanang
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Real Zoo, The Sky Shopping Center, Ayutthaya, 13210, Thailand
| | | | - Narongrit Muangmai
- Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
| | - Surin Peyachoknagul
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU), Kasetsart University, Bangkok, 10900, Thailand
- Department of Biology, Faculty of Science, Naresuan University, Phitsanulok, 65000, Thailand
| | - Kazumi Matsubara
- Wildlife Genetics Laboratory, Institute for Applied Ecology, University of Canberra, Canberra, ACT 2600, Australia
| | - Tariq Ezaz
- Wildlife Genetics Laboratory, Institute for Applied Ecology, University of Canberra, Canberra, ACT 2600, Australia
| | - Kornsorn Srikulnath
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand.
- Animal Breeding and Genetics Consortium - Kasetsart University (ABG - KU), 50 Ngamwongwan, Chatuchak, Bangkok, 10900, Thailand.
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU), Kasetsart University, Bangkok, 10900, Thailand.
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11
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Srikulnath K, Thapana W, Muangmai N. Role of Chromosome Changes in Crocodylus Evolution and Diversity. Genomics Inform 2015; 13:102-11. [PMID: 26865840 PMCID: PMC4742319 DOI: 10.5808/gi.2015.13.4.102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 11/03/2015] [Accepted: 11/16/2015] [Indexed: 01/21/2023] Open
Abstract
The karyotypes of most species of crocodilians were studied using conventional and molecular cytogenetics. These provided an important contribution of chromosomal rearrangements for the evolutionary processes of Crocodylia and Sauropsida (birds and reptiles). The karyotypic features of crocodilians contain small diploid chromosome numbers (30~42), with little interspecific variation of the chromosome arm number (fundamental number) among crocodiles (56~60). This suggested that centric fusion and/or fission events occurred in the lineage, leading to crocodilian evolution and diversity. The chromosome numbers of Alligator, Caiman, Melanosuchus, Paleosuchus, Gavialis, Tomistoma, Mecistops, and Osteolaemus were stable within each genus, whereas those of Crocodylus (crocodylians) varied within the taxa. This agreed with molecular phylogeny that suggested a highly recent radiation of Crocodylus species. Karyotype analysis also suggests the direction of molecular phylogenetic placement among Crocodylus species and their migration from the Indo-Pacific to Africa and The New World. Crocodylus species originated from an ancestor in the Indo-Pacific around 9~16 million years ago (MYA) in the mid-Miocene, with a rapid radiation and dispersion into Africa 8~12 MYA. This was followed by a trans-Atlantic dispersion to the New World between 4~8 MYA in the Pliocene. The chromosomes provided a better understanding of crocodilian evolution and diversity, which will be useful for further study of the genome evolution in Crocodylia.
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Affiliation(s)
- Kornsorn Srikulnath
- Laboratory of Animal Cytogenetics and Comparative Genomics, Department of Genetics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Watcharaporn Thapana
- Laboratory of Animal Cytogenetics and Comparative Genomics, Department of Genetics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Narongrit Muangmai
- Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, Bangkok 10900, Thailand
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12
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Matsubara K, Uno Y, Srikulnath K, Seki R, Nishida C, Matsuda Y. Molecular cloning and characterization of satellite DNA sequences from constitutive heterochromatin of the habu snake (Protobothrops flavoviridis, Viperidae) and the Burmese python (Python bivittatus, Pythonidae). Chromosoma 2015. [DOI: 10.1007/s00412-015-0529-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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13
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Chaiprasertsri N, Uno Y, Peyachoknagul S, Prakhongcheep O, Baicharoen S, Charernsuk S, Nishida C, Matsuda Y, Koga A, Srikulnath K. Highly species-specific centromeric repetitive DNA sequences in lizards: molecular cytogenetic characterization of a novel family of satellite DNA sequences isolated from the water monitor lizard (Varanus salvator macromaculatus, Platynota). J Hered 2014; 104:798-806. [PMID: 24129994 DOI: 10.1093/jhered/est061] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Two novel repetitive DNA sequences, VSAREP1 and VSAREP2, were isolated from the water monitor lizard (Varanus salvator macromaculatus, Platynota) and characterized using molecular cytogenetics. The respective lengths and guanine-cytosine (GC) contents of the sequences were 190 bp and 57.5% for VSAREP1 and 185 bp and 59.7% for VSAREP2, and both elements were tandemly arrayed as satellite DNA in the genome. VSAREP1 and VSAREP2 were each located at the C-positive heterochromatin in the pericentromeric region of chromosome 2q, the centromeric region of chromosome 5, and 3 pairs of microchromosomes. This suggests that genomic compartmentalization between macro- and microchromosomes might not have occurred in the centromeric repetitive sequences of V. salvator macromaculatus. These 2 sequences did only hybridize to genomic DNA of V. salvator macromaculatus, but no signal was observed even for other squamate reptiles, including Varanus exanthematicus, which is a closely related species of V. salvator macromaculatus. These results suggest that these sequences were differentiated rapidly or were specifically amplified in the V. salvator macromaculatus genome.
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Affiliation(s)
- Nampech Chaiprasertsri
- the Laboratory of Animal Cytogenetics and Comparative Genomics, Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
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14
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Nishida C, Ishishita S, Yamada K, Griffin DK, Matsuda Y. Dynamic chromosome reorganization in the osprey ( Pandion haliaetus , Pandionidae, Falconiformes): relationship between chromosome size and the chromosomal distribution of centromeric repetitive DNA sequences. Cytogenet Genome Res 2014; 142:179-89. [PMID: 24513810 DOI: 10.1159/000358407] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2013] [Indexed: 11/19/2022] Open
Abstract
The osprey (Pandion haliaetus) has a diploid number of 74 chromosomes, consisting of a large number of medium-sized macrochromosomes and relatively few microchromosomes; this differs greatly from the typical avian karyotype. Chromosome painting with chicken DNA probes revealed that the karyotype of P. haliaetus differs from the chicken karyotype by at least 14 fission events involving macrochromosomes (chicken chromosomes 1-9 and Z) and at most 15 fusions of microchromosomes, suggesting that considerable karyotype reorganization occurred in P. haliaetus in a similar manner previously reported for Accipitridae. A distinct difference was observed, however, between Accipitridae and Pandionidae with respect to the pattern of chromosome rearrangements that occurred after fissions of macrochromosomes. Metacentric or submetacentric chromosomes 1-5 in P. haliaetus appear to have been formed by centric fusion of chromosome segments derived from macrochromosomal fissions. By contrast, many pairs of bi-armed chromosomes in Accipitridae species seem to result from pericentric inversions that occurred in the fission-derived chromosomes. Two families of repetitive sequences were isolated; the 173-bp PHA-HaeIII sequence occurred on all chromosomes, whereas intense signals from the 742-bp PHA-NsiI sequence were localized to all acrocentric chromosomes, with weak signals on most of the bi-armed chromosomes. Two repetitive sequences cohybridized in the centromeric heterochromatin; however, the sequences differed in unit size, nucleotide sequence and GC content. The results suggest that the 2 sequence families originated from different ancestral sequences and were homogenized independently in centromeres, and that a chromosome size-dependent compartmentalization may have been lost in P. haliaetus.
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Affiliation(s)
- C Nishida
- Department of Natural History Sciences, Hokkaido University, Sapporo, Japan
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15
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Developmental diseases and the hypothetical Master Development Program. Med Hypotheses 2010; 74:564-73. [DOI: 10.1016/j.mehy.2009.09.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 09/17/2009] [Indexed: 11/24/2022]
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16
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Chapus C, Edwards SV. Genome evolution in Reptilia: in silico chicken mapping of 12,000 BAC-end sequences from two reptiles and a basal bird. BMC Genomics 2009; 10 Suppl 2:S8. [PMID: 19607659 PMCID: PMC2966332 DOI: 10.1186/1471-2164-10-s2-s8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND With the publication of the draft chicken genome and the recent production of several BAC clone libraries from non-avian reptiles and birds, it is now possible to undertake more detailed comparative genomic studies in Reptilia. Of interest in particular are the genomic events that transformed the large, repeat-rich genomes of mammals and non-avian reptiles into the minimalist chicken genome. We have used paired BAC end sequences (BESs) from the American alligator (Alligator mississippiensis), painted turtle (Chrysemys picta) and emu (Dromaius novaehollandiae) to investigate patterns of sequence divergence, gene and retroelement content, and microsynteny between these species and chicken. RESULTS From a total of 11,967 curated BESs, we successfully mapped 725, 773 and 2597 sequences in alligator, turtle, and emu, respectively, to sites in the draft chicken genome using a stringent BLAST protocol. Most commonly, sequences mapped to a single site in the chicken genome. Of 1675, 1828 and 2936 paired BESs obtained for alligator, turtle, and emu, respectively, a total of 34 (alligator, 2%), 24 (turtle, 1.3%) and 479 (emu, 16.3%) pairs were found to map with high confidence and in the correct orientation and with BAC-sized intermarker distances to single chicken chromosomes, including 25 such paired hits in emu mapping to the chicken Z chromosome. By determining the insert sizes of a subset of BAC clones from these three species, we also found a significant correlation between the intermarker distance in alligator and turtle and in chicken, with slopes as expected on the basis of the ratio of the genome sizes. CONCLUSION Our results suggest that a large number of small-scale chromosomal rearrangements and deletions in the lineage leading to chicken have drastically reduced the number of detected syntenies observed between the chicken and alligator, turtle, and emu genomes and imply that small deletions occurring widely throughout the genomes of reptilian and avian ancestors led to the ~50% reduction in genome size observed in birds compared to reptiles. We have also mapped and identified likely gene regions in hundreds of new BAC clones from these species.
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Affiliation(s)
- Charles Chapus
- Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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17
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Genomic organization of repetitive DNAs in the cichlid fish Astronotus ocellatus. Genetica 2008; 136:461-9. [DOI: 10.1007/s10709-008-9346-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 12/11/2008] [Indexed: 01/20/2023]
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18
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Molecular structures of centromeric heterochromatin and karyotypic evolution in the Siamese crocodile (Crocodylus siamensis) (Crocodylidae, Crocodylia). Chromosome Res 2008; 16:1119-32. [DOI: 10.1007/s10577-008-1263-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 08/20/2008] [Accepted: 08/20/2008] [Indexed: 10/21/2022]
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Kawai A, Nishida-Umehara C, Ishijima J, Tsuda Y, Ota H, Matsuda Y. Different origins of bird and reptile sex chromosomes inferred from comparative mapping of chicken Z-linked genes. Cytogenet Genome Res 2007; 117:92-102. [PMID: 17675849 DOI: 10.1159/000103169] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 11/16/2006] [Indexed: 11/19/2022] Open
Abstract
Recent progress of chicken genome projects has revealed that bird ZW and mammalian XY sex chromosomes were derived from different autosomal pairs of the common ancestor; however, the evolutionary relationship between bird and reptilian sex chromosomes is still unclear. The Chinese soft-shelled turtle (Pelodiscus sinensis) exhibits genetic sex determination, but no distinguishable (heteromorphic) sex chromosomes have been identified. In order to investigate this further, we performed molecular cytogenetic analyses of this species, and thereby identified ZZ/ZW-type micro-sex chromosomes. In addition, we cloned reptile homologues of chicken Z-linked genes from three reptilian species, the Chinese soft-shelled turtle and the Japanese four-striped rat snake (Elaphe quadrivirgata), which have heteromorphic sex chromosomes, and the Siam crocodile (Crocodylus siamensis), which exhibits temperature-dependent sex determination and lacks sex chromosomes. We then mapped them to chromosomes of each species using FISH. The linkage of the genes has been highly conserved in all species: the chicken Z chromosome corresponded to the turtle chromosome 6q, snake chromosome 2p and crocodile chromosome 3. The order of the genes was identical among the three species. The absence of homology between the bird Z chromosome and the snake and turtle Z sex chromosomes suggests that the origin of the sex chromosomes and the causative genes of sex determination are different between birds and reptiles.
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Affiliation(s)
- A Kawai
- Laboratory of Animal Cytogenetics, Division of Biosciences, Graduate School of Science, Hokkaido University, Sapporo, Japan
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Kuraku S, Ishijima J, Nishida-Umehara C, Agata K, Kuratani S, Matsuda Y. cDNA-based gene mapping and GC3 profiling in the soft-shelled turtle suggest a chromosomal size-dependent GC bias shared by sauropsids. Chromosome Res 2006; 14:187-202. [PMID: 16544192 DOI: 10.1007/s10577-006-1035-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 01/10/2006] [Indexed: 10/24/2022]
Abstract
Mammalian and avian genomes comprise several classes of chromosomal segments that vary dramatically in GC-content. Especially in chicken, microchromosomes exhibit a higher GC-content and a higher gene density than macrochromosomes. To understand the evolutionary history of the intra-genome GC heterogeneity in amniotes, it is necessary to examine the equivalence of this GC heterogeneity at the nucleotide level between these animals including reptiles, from which birds diverged. We isolated cDNAs for 39 protein-coding genes from the Chinese soft-shelled turtle, Pelodiscus sinensis, and performed chromosome mapping of 31 genes. The GC-content of exonic third positions (GC3) of P. sinensis genes showed a heterogeneous distribution, and exhibited a significant positive correlation with that of chicken and human orthologs, indicating that the last common ancestor of extant amniotes had already established a GC-compartmentalized genomic structure. Furthermore, chromosome mapping in P. sinensis revealed that microchromosomes tend to contain more GC-rich genes than GC-poor genes, as in chicken. These results illustrate two modes of genome evolution in amniotes: mammals elaborated the genomic configuration in which GC-rich and GC-poor regions coexist in individual chromosomes, whereas sauropsids (reptiles and birds) refined the chromosomal size-dependent GC compartmentalization in which GC-rich genomic fractions tend to be confined to microchromosomes.
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Affiliation(s)
- Shigehiro Kuraku
- Laboratory for Evolutionary Morphology, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
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