1
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Peel E, Silver L, Brandies P, Zhu Y, Cheng Y, Hogg CJ, Belov K. Best genome sequencing strategies for annotation of complex immune gene families in wildlife. Gigascience 2022; 11:giac100. [PMID: 36310247 PMCID: PMC9618407 DOI: 10.1093/gigascience/giac100] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 08/10/2022] [Accepted: 09/29/2022] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND The biodiversity crisis and increasing impact of wildlife disease on animal and human health provides impetus for studying immune genes in wildlife. Despite the recent boom in genomes for wildlife species, immune genes are poorly annotated in nonmodel species owing to their high level of polymorphism and complex genomic organisation. Our research over the past decade and a half on Tasmanian devils and koalas highlights the importance of genomics and accurate immune annotations to investigate disease in wildlife. Given this, we have increasingly been asked the minimum levels of genome quality required to effectively annotate immune genes in order to study immunogenetic diversity. Here we set out to answer this question by manually annotating immune genes in 5 marsupial genomes and 1 monotreme genome to determine the impact of sequencing data type, assembly quality, and automated annotation on accurate immune annotation. RESULTS Genome quality is directly linked to our ability to annotate complex immune gene families, with long reads and scaffolding technologies required to reassemble immune gene clusters and elucidate evolution, organisation, and true gene content of the immune repertoire. Draft-quality genomes generated from short reads with HiC or 10× Chromium linked reads were unable to achieve this. Despite mammalian BUSCOv5 scores of up to 94.1% amongst the 6 genomes, automated annotation pipelines incorrectly annotated up to 59% of manually annotated immune genes regardless of assembly quality or method of automated annotation. CONCLUSIONS Our results demonstrate that long reads and scaffolding technologies, alongside manual annotation, are required to accurately study the immune gene repertoire of wildlife species.
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Affiliation(s)
- Emma Peel
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, University of Sydney, Sydney NSW 2006, Australia
| | - Luke Silver
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Parice Brandies
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Ying Zhu
- Sichuan Provincial Academy of Natural Resource Sciences, Chengdu, Sichuan 610000, China
| | - Yuanyuan Cheng
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Carolyn J Hogg
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, University of Sydney, Sydney NSW 2006, Australia
| | - Katherine Belov
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, University of Sydney, Sydney NSW 2006, Australia
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2
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Zhou Y, Shearwin-Whyatt L, Li J, Song Z, Hayakawa T, Stevens D, Fenelon JC, Peel E, Cheng Y, Pajpach F, Bradley N, Suzuki H, Nikaido M, Damas J, Daish T, Perry T, Zhu Z, Geng Y, Rhie A, Sims Y, Wood J, Haase B, Mountcastle J, Fedrigo O, Li Q, Yang H, Wang J, Johnston SD, Phillippy AM, Howe K, Jarvis ED, Ryder OA, Kaessmann H, Donnelly P, Korlach J, Lewin HA, Graves J, Belov K, Renfree MB, Grutzner F, Zhou Q, Zhang G. Platypus and echidna genomes reveal mammalian biology and evolution. Nature 2021; 592:756-762. [PMID: 33408411 PMCID: PMC8081666 DOI: 10.1038/s41586-020-03039-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 07/30/2020] [Indexed: 12/13/2022]
Abstract
Egg-laying mammals (monotremes) are the only extant mammalian outgroup to therians (marsupial and eutherian animals) and provide key insights into mammalian evolution1,2. Here we generate and analyse reference genomes of the platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus), which represent the only two extant monotreme lineages. The nearly complete platypus genome assembly has anchored almost the entire genome onto chromosomes, markedly improving the genome continuity and gene annotation. Together with our echidna sequence, the genomes of the two species allow us to detect the ancestral and lineage-specific genomic changes that shape both monotreme and mammalian evolution. We provide evidence that the monotreme sex chromosome complex originated from an ancestral chromosome ring configuration. The formation of such a unique chromosome complex may have been facilitated by the unusually extensive interactions between the multi-X and multi-Y chromosomes that are shared by the autosomal homologues in humans. Further comparative genomic analyses unravel marked differences between monotremes and therians in haptoglobin genes, lactation genes and chemosensory receptor genes for smell and taste that underlie the ecological adaptation of monotremes.
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Affiliation(s)
- Yang Zhou
- BGI-Shenzhen, Shenzhen, China
- Villum Center for Biodiversity Genomics, Section for Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Linda Shearwin-Whyatt
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | - Jing Li
- MOE Laboratory of Biosystems Homeostasis and Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Zhenzhen Song
- BGI-Shenzhen, Shenzhen, China
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen, China
| | - Takashi Hayakawa
- Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan
- Japan Monkey Centre, Inuyama, Japan
| | - David Stevens
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | - Jane C Fenelon
- School of BioSciences, The University of Melbourne, Melbourne, Victoria, Australia
| | - Emma Peel
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Yuanyuan Cheng
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Filip Pajpach
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | - Natasha Bradley
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | | | - Masato Nikaido
- School of Life Science and Technology, Tokyo Institute of Technology, Tokyo, Japan
| | - Joana Damas
- The Genome Center, University of California, Davis, CA, USA
| | - Tasman Daish
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | - Tahlia Perry
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
| | - Zexian Zhu
- MOE Laboratory of Biosystems Homeostasis and Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Yuncong Geng
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Arang Rhie
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ying Sims
- Tree of Life Programme, Wellcome Sanger Institute, Cambridge, UK
| | - Jonathan Wood
- Tree of Life Programme, Wellcome Sanger Institute, Cambridge, UK
| | - Bettina Haase
- The Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA
| | | | - Olivier Fedrigo
- The Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA
| | - Qiye Li
- BGI-Shenzhen, Shenzhen, China
| | - Huanming Yang
- BGI-Shenzhen, Shenzhen, China
- James D. Watson Institute of Genome Sciences, Hangzhou, China
- University of the Chinese Academy of Sciences, Beijing, China
- Guangdong Provincial Academician Workstation of BGI Synthetic Genomics, BGI-Shenzhen, Shenzhen, China
| | - Jian Wang
- BGI-Shenzhen, Shenzhen, China
- James D. Watson Institute of Genome Sciences, Hangzhou, China
| | - Stephen D Johnston
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, Queensland, Australia
| | - Adam M Phillippy
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Kerstin Howe
- Tree of Life Programme, Wellcome Sanger Institute, Cambridge, UK
| | - Erich D Jarvis
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York, NY, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | | | - Henrik Kaessmann
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Peter Donnelly
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | | | - Harris A Lewin
- The Genome Center, University of California, Davis, CA, USA
- Department of Evolution and Ecology, College of Biological Sciences, University of California, Davis, CA, USA
- Department of Reproduction and Population Health, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Jennifer Graves
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory, Australia
- School of Life Sciences, La Trobe University, Melbourne, Victoria, Australia
| | - Katherine Belov
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Marilyn B Renfree
- School of BioSciences, The University of Melbourne, Melbourne, Victoria, Australia
| | - Frank Grutzner
- School of Biological Sciences, The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia.
| | - Qi Zhou
- MOE Laboratory of Biosystems Homeostasis and Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China.
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria.
- Center for Reproductive Medicine, The 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
| | - Guojie Zhang
- BGI-Shenzhen, Shenzhen, China.
- Villum Center for Biodiversity Genomics, Section for Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China.
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Abstract
Abstract
Tachyglossus aculeatus (Shaw, 1792) is a monotreme commonly called the short-beaked echidna. Although considered Australia’s most common native mammal because of its continent-wide distribution, its population numbers everywhere are low. It is easily distinguished from all other native Australian mammals because of its spine-covered body, hairless beak, and unique “rolling” gait. The five subspecies, one of which is found in Papua New Guinea, show variations in fur density, spine diameter, length, and number of grooming claws. The Kangaroo Island short-beaked echidna Tachyglossus aculeatus multiaculeatus is listed as “Endangered” but all other Tachyglossus are listed as “Least Concern” in the 2016 International Union for Conservation of Nature and Natural Resources Red List.
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Affiliation(s)
- Peggy D Rismiller
- Pelican Lagoon Research & Wildlife Centre, Penneshaw, South Australia, Australia
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Frank Grutzner
- The Environment Institute, The University of Adelaide, Adelaide, South Australia, Australia
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4
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Abduriyim S, Zou D, Zhao H. Origin and evolution of the major histocompatibility complex class I region in eutherian mammals. Ecol Evol 2019; 9:7861-7874. [PMID: 31346446 PMCID: PMC6636196 DOI: 10.1002/ece3.5373] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 05/27/2019] [Accepted: 05/27/2019] [Indexed: 01/09/2023] Open
Abstract
Major histocompatibility complex (MHC) genes in vertebrates are vital in defending against pathogenic infections. To gain new insights into the evolution of MHC Class I (MHCI) genes and test competing hypotheses on the origin of the MHCI region in eutherian mammals, we studied available genome assemblies of nine species in Afrotheria, Xenarthra, and Laurasiatheria, and successfully characterized the MHCI region in six species. The following numbers of putatively functional genes were detected: in the elephant, four, one, and eight in the extended class I region, and κ and β duplication blocks, respectively; in the tenrec, one in the κ duplication block; and in the four bat species, one or two in the β duplication block. Our results indicate that MHCI genes in the κ and β duplication blocks may have originated in the common ancestor of eutherian mammals. In the elephant, tenrec, and all four bats, some MHCI genes occurred outside the MHCI region, suggesting that eutherians may have a more complex MHCI genomic organization than previously thought. Bat-specific three- or five-amino-acid insertions were detected in the MHCI α1 domain in all four bats studied, suggesting that pathogen defense in bats relies on MHCIs having a wider peptide-binding groove, as previously assayed by a bat MHCI gene with a three-amino-acid insertion showing a larger peptide repertoire than in other mammals. Our study adds to knowledge on the diversity of eutherian MHCI genes, which may have been shaped in a taxon-specific manner.
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Affiliation(s)
- Shamshidin Abduriyim
- Department of Ecology, Hubei Key Laboratory of Cell Homeostasis, College of Life ScienceWuhan UniversityWuhanChina
| | - Da‐Hu Zou
- Department of Ecology, Hubei Key Laboratory of Cell Homeostasis, College of Life ScienceWuhan UniversityWuhanChina
| | - Huabin Zhao
- Department of Ecology, Hubei Key Laboratory of Cell Homeostasis, College of Life ScienceWuhan UniversityWuhanChina
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5
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Perry T, Toledo-Flores D, Kang WX, Ferguson A, Laming B, Tsend-Ayush E, Lim SL, Grützner F. Non-invasive genetic sexing technique for analysis of short-beaked echidna (Tachyglossus aculeatus) populations. Reprod Fertil Dev 2019; 31:1289-1295. [PMID: 31158328 DOI: 10.1071/rd18142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/04/2019] [Indexed: 11/23/2022] Open
Abstract
Identifying male and female echidnas is challenging due to the lack of external genitalia or any other differing morphological features. This limits studies of wild populations and is a major problem for echidna captive management and breeding. Non-invasive genetic approaches to determine sex minimise the need for handling animals and are used extensively in other mammals. However, currently available approaches cannot be applied to monotremes because their sex chromosomes share no homology with sex chromosomes in other mammals. In this study we used recently identified X and Y chromosome-specific sequences to establish a non-invasive polymerase chain reaction-based technique to determine the sex of echidnas. Genomic DNA was extracted from echidna hair follicles followed by amplification of two Y chromosome (male-specific) genes (mediator complex subunit 26 Y-gametolog (CRSPY) and anti-Müllerian hormone Y-gametolog (AMHY)) and the X chromosome gene (anti-Müllerian hormone X-gametolog (AMHX)). Using this technique, we identified the sex of 10 juvenile echidnas born at Perth Zoo, revealing that eight of the 10 echidnas were female. Future use of the genetic sexing technique in echidnas will inform captive management, continue breeding success and can be used to investigate sex ratios and population dynamics in wild populations.
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Affiliation(s)
- Tahlia Perry
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Deborah Toledo-Flores
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Wan X Kang
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Arthur Ferguson
- Perth Zoo, 20 Labouchere Road, South Perth, WA 6151, Australia
| | - Belinda Laming
- Perth Zoo, 20 Labouchere Road, South Perth, WA 6151, Australia
| | - Enkhjargal Tsend-Ayush
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Shu L Lim
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Frank Grützner
- The Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia; and Corresponding author.
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6
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de Sá ALA, Breaux B, Burlamaqui TCT, Deiss TC, Sena L, Criscitiello MF, Schneider MPC. The Marine Mammal Class II Major Histocompatibility Complex Organization. Front Immunol 2019; 10:696. [PMID: 31019512 PMCID: PMC6459222 DOI: 10.3389/fimmu.2019.00696] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/13/2019] [Indexed: 12/17/2022] Open
Abstract
Sirenians share with cetaceans and pinnipeds several convergent traits selected for the aquatic lifestyle. Living in water poses new challenges not only for locomotion and feeding but also for combating new pathogens, which may render the immune system one of the best tools aquatic mammals have for dealing with aquatic microbial threats. So far, only cetaceans have had their class II Major Histocompatibility Complex (MHC) organization characterized, despite the importance of MHC genes for adaptive immune responses. This study aims to characterize the organization of the marine mammal class II MHC using publicly available genomes. We located class II sequences in the genomes of one sirenian, four pinnipeds and eight cetaceans using NCBI-BLAST and reannotated the sequences using local BLAST search with exon and intron libraries. Scaffolds containing class II sequences were compared using dotplot analysis and introns were used for phylogenetic analysis. The manatee class II region shares overall synteny with other mammals, however most DR loci were translocated from the canonical location, past the extended class II region. Detailed analysis of the genomes of closely related taxa revealed that this presumed translocation is shared with all other living afrotherians. Other presumptive chromosome rearrangements in Afrotheria are the deletion of DQ loci in Afrosoricida and deletion of DP in E. telfairi. Pinnipeds share the main features of dog MHC: lack of a functional pair of DPA/DPB genes and inverted DRB locus between DQ and DO subregions. All cetaceans share the Cetartiodactyla inversion separating class II genes into two subregions: class IIa, with DR and DQ genes, and class IIb, with non-classic genes and a DRB pseudogene. These results point to three distinct and unheralded class II MHC structures in marine mammals: one canonical organization but lacking DP genes in pinnipeds; one bearing an inversion separating IIa and IIb subregions lacking DP genes found in cetaceans; and one with a translocation separating the most diverse class II gene from the MHC found in afrotherians and presumptive functional DR, DQ, and DP genes. Future functional research will reveal how these aquatic mammals cope with pathogen pressures with these divergent MHC organizations.
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Affiliation(s)
- André Luiz Alves de Sá
- Laboratory of Applied Genetics, Socio-Environmental and Water Resources Institute, Federal Rural University of the Amazon, Belém, Brazil.,Laboratory of Genomics and Biotechnology, Biological Sciences Institute, Federal University of Pará, Belém, Brazil
| | - Breanna Breaux
- Comparative Immunogenetics Laboratory, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | | | - Thaddeus Charles Deiss
- Comparative Immunogenetics Laboratory, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Leonardo Sena
- Center of Biodiversity Advanced Studies, Biological Sciences Institute, Federal University of Pará, Belém, Brazil
| | - Michael Frederick Criscitiello
- Comparative Immunogenetics Laboratory, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States
| | - Maria Paula Cruz Schneider
- Laboratory of Genomics and Biotechnology, Biological Sciences Institute, Federal University of Pará, Belém, Brazil
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7
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Maeda T, Suetake H, Odaka T, Miyadai T. Original Ligand for LTβR Is LIGHT: Insight into Evolution of the LT/LTβR System. THE JOURNAL OF IMMUNOLOGY 2018; 201:202-214. [PMID: 29769272 DOI: 10.4049/jimmunol.1700900] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 04/25/2018] [Indexed: 01/23/2023]
Abstract
The lymphotoxin (LT)/LTβ receptor (LTβR) axis is crucial for the regulation of immune responses and development of lymphoid tissues in mammals. Despite the importance of this pathway, the existence and function of LT and LTβR remain obscure for nonmammalian species. In this study, we report a nonmammalian LTβR and its ligand. We demonstrate that TNF-New (TNFN), which has been considered orthologous to mammalian LT, was expressed on the cell surface as a homomer in vitro. This different protein structure indicates that TNFN is not orthologous to mammalian LTα and LTβ. Additionally, we found that LTβR was conserved in teleosts, but the soluble form of recombinant fugu LTβR did not bind to membrane TNFN under the circumstance tested. Conversely, the LTβR recombinant bound to another ligand, LIGHT, similar to that of mammals. These findings indicate that teleost LTβR is originally a LIGHT receptor. In the cytoplasmic region of fugu LTβR, recombinant fugu LTβR bound to the adaptor protein TNFR-associated factor (TRAF) 2, but little to TRAF3. This difference suggests that teleost LTβR could potentially activate the classical NF-κB pathway with a novel binding domain, but would have little ability to activate an alternative one. Collectively, our results suggested that LIGHT was the original ligand for LTβR, and that the teleost immune system lacked the LT/LTβR pathway. Acquisition of the LT ligand and TRAF binding domain after lobe-finned fish may have facilitated the sophistication of the immune system and lymphoid tissues.
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Affiliation(s)
- Tomoki Maeda
- Graduate School of Biosciences and Biotechnology, Fukui Prefectural University, Fukui 917-0003, Japan.,Japan Society for the Promotion of Science, Tokyo 102-0083, Japan; and
| | - Hiroaki Suetake
- Faculty of Marine Science and Technology, Fukui Prefectural University, Fukui 917-0003, Japan
| | - Tomoyuki Odaka
- Faculty of Marine Science and Technology, Fukui Prefectural University, Fukui 917-0003, Japan
| | - Toshiaki Miyadai
- Faculty of Marine Science and Technology, Fukui Prefectural University, Fukui 917-0003, Japan
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8
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Deakin JE. Implications of monotreme and marsupial chromosome evolution on sex determination and differentiation. Gen Comp Endocrinol 2017; 244:130-138. [PMID: 26431612 DOI: 10.1016/j.ygcen.2015.09.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 09/15/2015] [Accepted: 09/26/2015] [Indexed: 12/30/2022]
Abstract
Studies of chromosomes from monotremes and marsupials endemic to Australasia have provided important insight into the evolution of their genomes as well as uncovering fundamental differences in their sex determination/differentiation pathways. Great advances have been made this century into solving the mystery of the complicated sex chromosome system in monotremes. Monotremes possess multiple different X and Y chromosomes and a candidate sex determining gene has been identified. Even greater advancements have been made for marsupials, with reconstruction of the ancestral karyotype enabling the evolutionary history of marsupial chromosomes to be determined. Furthermore, the study of sex chromosomes in intersex marsupials has afforded insight into differences in the sexual differentiation pathway between marsupials and eutherians, together with experiments showing the insensitivity of the mammary glands, pouch and scrotum to exogenous hormones, led to the hypothesis that there is a gene (or genes) on the X chromosome responsible for the development of either pouch or scrotum. This review highlights the major advancements made towards understanding chromosome evolution and how this has impacted on our understanding of sex determination and differentiation in these interesting mammals.
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Affiliation(s)
- Janine E Deakin
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia.
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9
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Ng JHJ, Tachedjian M, Deakin J, Wynne JW, Cui J, Haring V, Broz I, Chen H, Belov K, Wang LF, Baker ML. Evolution and comparative analysis of the bat MHC-I region. Sci Rep 2016; 6:21256. [PMID: 26876644 PMCID: PMC4753418 DOI: 10.1038/srep21256] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 01/20/2016] [Indexed: 12/22/2022] Open
Abstract
Bats are natural hosts to numerous viruses and have ancient origins, having diverged from other eutherian mammals early in evolution. These characteristics place them in an important position to provide insights into the evolution of the mammalian immune system and antiviral immunity. We describe the first detailed partial map of a bat (Pteropus alecto) MHC-I region with comparative analysis of the MHC-I region and genes. The bat MHC-I region is highly condensed, yet relatively conserved in organisation, and is unusual in that MHC-I genes are present within only one of the three highly conserved class I duplication blocks. We hypothesise that MHC-I genes first originated in the β duplication block, and subsequently duplicated in a step-wise manner across the MHC-I region during mammalian evolution. Furthermore, bat MHC-I genes contain unique insertions within their peptide-binding grooves potentially affecting the peptide repertoire presented to T cells, which may have implications for the ability of bats to control infection without overt disease.
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Affiliation(s)
- Justin H. J. Ng
- CSIRO Health and Biosecurity Business Unit, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
- Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia
- Program in Emerging Infectious Diseases, Duke-National University of Singapore Medical School, Singapore 169857
| | - Mary Tachedjian
- CSIRO Health and Biosecurity Business Unit, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Janine Deakin
- Institute for Applied Ecology, The University of Canberra, ACT 2617, Australia
| | - James W. Wynne
- CSIRO Health and Biosecurity Business Unit, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Jie Cui
- Program in Emerging Infectious Diseases, Duke-National University of Singapore Medical School, Singapore 169857
| | - Volker Haring
- CSIRO, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Ivano Broz
- CSIRO, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Honglei Chen
- CSIRO, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
| | - Katherine Belov
- Faculty of Veterinary Science, University of Sydney, NSW 2006, Australia
| | - Lin-Fa Wang
- Program in Emerging Infectious Diseases, Duke-National University of Singapore Medical School, Singapore 169857
| | - Michelle L. Baker
- CSIRO Health and Biosecurity Business Unit, Australian Animal Health Laboratory, Geelong, VIC 3220, Australia
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10
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Deakin JE, Graves JAM, Rens W. The evolution of marsupial and monotreme chromosomes. Cytogenet Genome Res 2012; 137:113-29. [PMID: 22777195 DOI: 10.1159/000339433] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Marsupial and monotreme mammals fill an important gap in vertebrate phylogeny between reptile-mammal divergence 310 million years ago (mya) and the eutherian (placental) mammal radiation 105 mya. They possess many unique features including their distinctive chromosomes, which in marsupials are typically very large and well conserved between species. In contrast, monotreme genomes are divided into several large chromosomes and many smaller chromosomes, with a complicated sex chromosome system that forms a translocation chain in male meiosis. The application of molecular cytogenetic techniques has greatly advanced our understanding of the evolution of marsupial chromosomes and allowed the reconstruction of the ancestral marsupial karyotype. Chromosome painting and gene mapping have played a vital role in piecing together the puzzle of monotreme karyotypes, particularly their complicated sex chromosome system. Here, we discuss the significant insight into karyotype evolution afforded by the combination of recently sequenced marsupial and monotreme genomes with cytogenetic analysis, which has provided a greater understanding of the events that have shaped not only marsupial and monotreme genomes, but the genomes of all mammals.
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Affiliation(s)
- J E Deakin
- Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT, Australia.
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11
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Hrdličková R, Nehyba J, Lim SL, Grützner F, Bose HR. Insights into the evolution of mammalian telomerase: platypus TERT shares similarities with genes of birds and other reptiles and localizes on sex chromosomes. BMC Genomics 2012; 13:216. [PMID: 22655747 PMCID: PMC3546421 DOI: 10.1186/1471-2164-13-216] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 05/04/2012] [Indexed: 01/05/2023] Open
Abstract
Background The TERT gene encodes the catalytic subunit of the telomerase complex and is responsible for maintaining telomere length. Vertebrate telomerase has been studied in eutherian mammals, fish, and the chicken, but less attention has been paid to other vertebrates. The platypus occupies an important evolutionary position, providing unique insight into the evolution of mammalian genes. We report the cloning of a platypus TERT (OanTERT) ortholog, and provide a comparison with genes of other vertebrates. Results The OanTERT encodes a protein with a high sequence similarity to marsupial TERT and avian TERT. Like the TERT of sauropsids and marsupials, as well as that of sharks and echinoderms, OanTERT contains extended variable linkers in the N-terminal region suggesting that they were present already in basal vertebrates and lost independently in ray-finned fish and eutherian mammals. Several alternatively spliced OanTERT variants structurally similar to avian TERT variants were identified. Telomerase activity is expressed in all platypus tissues like that of cold-blooded animals and murine rodents. OanTERT was localized on pseudoautosomal regions of sex chromosomes X3/Y2, expanding the homology between human chromosome 5 and platypus sex chromosomes. Synteny analysis suggests that TERT co-localized with sex-linked genes in the last common mammalian ancestor. Interestingly, female platypuses express higher levels of telomerase in heart and liver tissues than do males. Conclusions OanTERT shares many features with TERT of the reptilian outgroup, suggesting that OanTERT represents the ancestral mammalian TERT. Features specific to TERT of eutherian mammals have, therefore, evolved more recently after the divergence of monotremes.
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Affiliation(s)
- Radmila Hrdličková
- Section of Molecular Genetics and Microbiology, School of Biological Science, University of Texas at Austin, 78712-1095, USA
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12
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Tsend-Ayush E, Kortschak RD, Bernard P, Lim SL, Ryan J, Rosenkranz R, Borodina T, Dohm JC, Himmelbauer H, Harley VR, Grützner F. Identification of mediator complex 26 (Crsp7) gametologs on platypus X1 and Y5 sex chromosomes: a candidate testis-determining gene in monotremes? Chromosome Res 2012; 20:127-38. [DOI: 10.1007/s10577-011-9270-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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13
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Livernois AM, Graves JAM, Waters PD. The origin and evolution of vertebrate sex chromosomes and dosage compensation. Heredity (Edinb) 2011; 108:50-8. [PMID: 22086077 DOI: 10.1038/hdy.2011.106] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In mammals, birds, snakes and many lizards and fish, sex is determined genetically (either male XY heterogamy or female ZW heterogamy), whereas in alligators, and in many reptiles and turtles, the temperature at which eggs are incubated determines sex. Evidently, different sex-determining systems (and sex chromosome pairs) have evolved independently in different vertebrate lineages. Homology shared by Xs and Ys (and Zs and Ws) within species demonstrates that differentiated sex chromosomes were once homologous, and that the sex-specific non-recombining Y (or W) was progressively degraded. Consequently, genes are left in single copy in the heterogametic sex, which results in an imbalance of the dosage of genes on the sex chromosomes between the sexes, and also relative to the autosomes. Dosage compensation has evolved in diverse species to compensate for these dose differences, with the stringency of compensation apparently differing greatly between lineages, perhaps reflecting the concentration of genes on the original autosome pair that required dosage compensation. We discuss the organization and evolution of amniote sex chromosomes, and hypothesize that dosage insensitivity might predispose an autosome to evolving function as a sex chromosome.
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Affiliation(s)
- A M Livernois
- Evolution Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
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14
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Siddle HV, Deakin JE, Coggill P, Whilming LG, Harrow J, Kaufman J, Beck S, Belov K. The tammar wallaby major histocompatibility complex shows evidence of past genomic instability. BMC Genomics 2011; 12:421. [PMID: 21854592 PMCID: PMC3179965 DOI: 10.1186/1471-2164-12-421] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 08/19/2011] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND The major histocompatibility complex (MHC) is a group of genes with a variety of roles in the innate and adaptive immune responses. MHC genes form a genetically linked cluster in eutherian mammals, an organization that is thought to confer functional and evolutionary advantages to the immune system. The tammar wallaby (Macropus eugenii), an Australian marsupial, provides a unique model for understanding MHC gene evolution, as many of its antigen presenting genes are not linked to the MHC, but are scattered around the genome. RESULTS Here we describe the 'core' tammar wallaby MHC region on chromosome 2q by ordering and sequencing 33 BAC clones, covering over 4.5 MB and containing 129 genes. When compared to the MHC region of the South American opossum, eutherian mammals and non-mammals, the wallaby MHC has a novel gene organization. The wallaby has undergone an expansion of MHC class II genes, which are separated into two clusters by the class III genes. The antigen processing genes have undergone duplication, resulting in two copies of TAP1 and three copies of TAP2. Notably, Kangaroo Endogenous Retroviral Elements are present within the region and may have contributed to the genomic instability. CONCLUSIONS The wallaby MHC has been extensively remodeled since the American and Australian marsupials last shared a common ancestor. The instability is characterized by the movement of antigen presenting genes away from the core MHC, most likely via the presence and activity of retroviral elements. We propose that the movement of class II genes away from the ancestral class II region has allowed this gene family to expand and diversify in the wallaby. The duplication of TAP genes in the wallaby MHC makes this species a unique model organism for studying the relationship between MHC gene organization and function.
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Affiliation(s)
- Hannah V Siddle
- Faculty of Veterinary Science, University of Sydney, NSW 2006, AUSTRALIA
- University of Cambridge, Department of Pathology, Cambridge CB2 1QP, UK
| | - Janine E Deakin
- ARC Centre of Excellence for Kangaroo Genomics, Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia
| | - Penny Coggill
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton Hall, Hinxton, Cambridgeshire, CB10 1SA, UK
| | - Laurens G Whilming
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton Hall, Hinxton, Cambridgeshire, CB10 1SA, UK
| | - Jennifer Harrow
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton Hall, Hinxton, Cambridgeshire, CB10 1SA, UK
| | - Jim Kaufman
- University of Cambridge, Department of Pathology, Cambridge CB2 1QP, UK
| | - Stephan Beck
- UCL Cancer Institute, University College London, London WC1E 6BT, UK
| | - Katherine Belov
- Faculty of Veterinary Science, University of Sydney, NSW 2006, AUSTRALIA
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15
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Sex chromosome evolution in amniotes: applications for bacterial artificial chromosome libraries. J Biomed Biotechnol 2010; 2011:132975. [PMID: 20981143 PMCID: PMC2957134 DOI: 10.1155/2011/132975] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 09/27/2010] [Indexed: 11/18/2022] Open
Abstract
Variability among sex chromosome pairs in amniotes denotes a dynamic history. Since amniotes diverged from a common ancestor, their sex chromosome pairs and, more broadly, sex-determining mechanisms have changed reversibly and frequently. These changes have been studied and characterized through the use of many tools and experimental approaches but perhaps most effectively through applications for bacterial artificial chromosome (BAC) libraries. Individual BAC clones carry 100–200 kb of sequence from one individual of a target species that can be isolated by screening, mapped onto karyotypes, and sequenced. With these techniques, researchers have identified differences and similarities in sex chromosome content and organization across amniotes and have addressed hypotheses regarding the frequency and direction of past changes. Here, we review studies of sex chromosome evolution in amniotes and the ways in which the field of research has been affected by the advent of BAC libraries.
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16
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Daish T, Casey A, Grützner F. Platypus chain reaction: directional and ordered meiotic pairing of the multiple sex chromosome chain in Ornithorhynchus anatinus. Reprod Fertil Dev 2010; 21:976-84. [PMID: 19874721 DOI: 10.1071/rd09085] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 06/25/2009] [Indexed: 12/28/2022] Open
Abstract
Monotremes are phylogenetically and phenotypically unique animals with an unusually complex sex chromosome system that is composed of ten chromosomes in platypus and nine in echidna. These chromosomes are alternately linked (X1Y1, X2Y2, ...) at meiosis via pseudoautosomal regions and segregate to form spermatozoa containing either X or Y chromosomes. The physical and epigenetic mechanisms involved in pairing and assembly of the complex sex chromosome chain in early meiotic prophase I are completely unknown. We have analysed the pairing dynamics of specific sex chromosome pseudoautosomal regions in platypus spermatocytes during prophase of meiosis I. Our data show a highly coordinated pairing process that begins at the terminal Y5 chromosome and completes with the union of sex chromosomes X1Y1. The consistency of this ordered assembly of the chain is remarkable and raises questions about the mechanisms and factors that regulate the differential pairing of sex chromosomes and how this relates to potential meiotic silencing mechanisms and alternate segregation.
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Affiliation(s)
- Tasman Daish
- Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, North Terrace, Adelaide, SA 5005, Australia
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17
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Abstract
Sex chromosomes have evolved multiple times in many taxa. The recent explosion in the availability of whole genome sequences from a variety of organisms makes it possible to investigate sex chromosome evolution within and across genomes. Comparative genomic studies have shown that quite distant species may share fundamental properties of sex chromosome evolution, while very similar species can evolve unique sex chromosome systems. Furthermore, within-species genomic analyses can illuminate chromosome-wide sequence and expression polymorphisms. Here, we explore recent advances in the study of vertebrate sex chromosomes achieved using genomic analyses.
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Affiliation(s)
- Melissa A Wilson
- Center for Comparative Genomics and Bioinformatics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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18
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Identification of natural killer cell receptor clusters in the platypus genome reveals an expansion of C-type lectin genes. Immunogenetics 2009; 61:565-79. [PMID: 19597809 DOI: 10.1007/s00251-009-0386-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 06/24/2009] [Indexed: 02/03/2023]
Abstract
Natural killer (NK) cell receptors belong to two unrelated, but functionally analogous gene families: the immunoglobulin superfamily, situated in the leukocyte receptor complex (LRC) and the C-type lectin superfamily, located in the natural killer complex (NKC). Here, we describe the largest NK receptor gene expansion seen to date. We identified 213 putative C-type lectin NK receptor homologs in the genome of the platypus. Many have arisen as the result of a lineage-specific expansion. Orthologs of OLR1, CD69, KLRE, CLEC12B, and CLEC16p genes were also identified. The NKC is split into at least two regions of the genome: 34 genes map to chromosome 7, two map to a small autosome, and the remainder are unanchored in the current genome assembly. No NK receptor genes from the LRC were identified. The massive C-type lectin expansion and lack of Ig-domain-containing NK receptors represents the most extreme polarization of NK receptors found to date. We have used this new data from platypus to trace the possible evolutionary history of the NK receptor clusters.
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19
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Comparative genomic analysis of the major histocompatibility complex class I region in the teleost genus Oryzias. Immunogenetics 2009; 61:385-99. [DOI: 10.1007/s00251-009-0371-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 03/20/2009] [Indexed: 11/27/2022]
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20
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Daish T, Grützner F. Location, location, location! Monotremes provide unique insights into the evolution of sex chromosome silencing in mammals. DNA Cell Biol 2009; 28:91-100. [PMID: 19196046 DOI: 10.1089/dna.2008.0818] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Platypus and echidnas are the only living representative of the egg-laying mammals that diverged 166 million years ago from the mammalian lineage. Despite occupying a key spot in mammalian phylogeny, research on monotremes has been limited by access to material and lack of molecular genetic resources. This has changed recently, and the sequencing of the platypus genome has promoted monotremes into a generally accessible tool in comparative genomics. The most extraordinary aspect of the monotreme genome is an amazingly complex sex chromosomes system that shares extensive homology with bird sex chromosomes and no homology with sex chromosomes of other mammals. This raises important questions about dosage compensation of the five pairs of sex chromosomes in females and meiotic silencing in males, and we are only beginning to unravel possible mechanisms and pathways that may be involved. The homology between monotreme and bird sex chromosomes makes comparison between those species worthwhile, also as they provide a well-defined example where the same sex chromosomes changed from female heterogamety (chicken) to male heterogamety (monotremes). We summarize recent research on monotreme and chicken sex chromosomes and discuss possible mechanisms that may contribute to sex chromosome silencing in monotremes.
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Affiliation(s)
- Tasman Daish
- Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia.
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21
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Tsukamoto K, Sakaizumi M, Hata M, Sawara Y, Eah J, Kim CB, Nonaka M. Dichotomous haplotypic lineages of the immunoproteasome subunit genes, PSMB8 and PSMB10, in the MHC class I region of a Teleost Medaka, Oryzias latipes. Mol Biol Evol 2009; 26:769-81. [PMID: 19126869 DOI: 10.1093/molbev/msn305] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Sequence comparison of the medaka, Oryzias latipes, major histocompatibility complex (MHC) class I region between two inbred strains, the HNI (derived from the Northern Population) and the Hd-rR (from the Southern Population), revealed a approximately 100 kb highly divergent segment encompassing two MHC class IA genes, Orla-UAA and Orla-UBA, and two immunoproteasome beta subunit genes, PSMB8 and PSMB10. To elucidate the genetic diversity of this region, we analyzed polymorphisms of the PSMB8 and PSMB10 genes using wild populations of medaka from three genetically different groups: the Northern Population, the Southern Population, and the China-West Korean Population. A total of 1,245 specimens from 10 localities were analyzed, and all the PSMB8 and PSMB10 alleles were classified into the N (fixed in the HNI strain) or the d (fixed in the Hd-rR strain) lineage. Polymerase chain reaction analysis of the region from PSMB8 to PSMB10 indicated that the two allelic lineages of these genes are segregating together constituting dichotomous haplotypic lineages. Both haplotypic lineages were identified in all three groups, although the frequency of d haplotypic lineage (73-100%) was much higher than that of N haplotypic lineage (0-27%) in all analyzed populations. The two allelic lineages of the PSMB8 gene showed curious substitutions at the 31st and 53rd residues of the mature peptide, which are likely involved in formation of the S1 pocket, suggesting that these alleles have a functional difference in cleavage specificity. These results indicate that the two medaka MHC haplotypic lineages encompassing the PSMB8 and PSMB10 genes are maintained in wild populations by a balancing selection.
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Affiliation(s)
- Kentaro Tsukamoto
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
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22
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Abstract
The sequencing of the platypus genome has spurred investigations into the characterisation of the monotreme immune response. As the most divergent of extant mammals, the characterisation of the monotreme immune repertoire allows us to trace the evolutionary history of immunity in mammals and provide insights into the immune gene complement of ancestral mammals. The immune system of monotremes has remained largely uncharacterised due to the lack of specific immunological reagents and limited access to animals for experimentation. Early immunological studies focussed on the anatomy and physiology of the lymphoid system in the platypus. More recent molecular studies have focussed on characterisation of individual immunoglobulin, T-cell receptor and MHC genes in both the platypus and short-beaked echidna. Here, we review the published literature on the monotreme immune gene repertoire and provide new data generated from genome analysis on cytokines, Fc receptors and immunoglobulins. We present an overview of key gene families responsible for innate and adaptive immunity including the cathelicidins, defensins, T-cell receptors and the major histocompatibility complex (MHC) Class I and Class II antigens. We comment on the usefulness of these sequences for future studies into immunity, health and disease in monotremes.
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23
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Abstract
The three extant genera of the prototherian mammals, Ornithorhynchus (platypus), Tachyglossus (Australian echidna) and Zaglossus (New Guinea echidna), all have a mechanism of sex determination at odds with that seen in eutherian and metatherian mammals. Indeed, they stand apart from all vertebrates. Instead of the XX/XY, X1X2Y or ZZ/ZW systems seen in the majority of vertebrates the monotremes have a chain of nine (or ten) chromosomes present during meiosis in the male. This is believed to be the consequence of a presumed series of reciprocal translocations involving four autosomal pairs and the original X and Y chromosomes. The presence of this chain in all three genera indicates that a similar chain occurred in their common ancestor. This paper provides an overview of the search to unravel the mystery of this chain and to determine the identity of the sex chromosomes and members of the chain. The development of new techniques has hugely facilitated clarification of the findings of the earlier researchers. As a result, the chromosomes of the platypus and the echidna have now been individually described, the chain elements and/or sex chromosomes have been identified unambiguously and their order in the chain has been determined. The research reviewed here has also provided insights into the evolution of mammalian sex chromosomes and given new directions for unravelling dosage compensation and sex-determination mechanisms in mammals.
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24
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Baker ML, Melman SD, Huntley J, Miller RD. Evolution of the opossum major histocompatibility complex: evidence for diverse alternative splice patterns and low polymorphism among class I genes. Immunology 2008; 128:e418-31. [PMID: 19191910 DOI: 10.1111/j.1365-2567.2008.02994.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The opossum major histocompatibility complex (MHC) shares a similar organization with that of non-mammals while containing a diverse set of class I genes more like that of eutherian (placental) mammals. There are 11 class I loci in the opossum MHC region, seven of which are known to be transcribed. The previously described Monodelphis domestica (Modo)-UA1 and Modo-UG display characteristics consistent with their being classical and non-classical class I genes, respectively. Here we describe the characteristics of the remaining five transcribed class I loci (Modo-UE, -UK, -UI, -UJ and -UM). All five genes have peptide-binding grooves with low or no polymorphism, contain unpaired cysteines with the potential to produce homodimer formation and display genomic organizational features that would be unusual for classical class I loci. In addition, Modo-UJ and -UM were expressed in alternatively spliced mRNA forms, including a potentially soluble isoform of Modo-UJ. Thus, the MHC region of the opossum contains a single class I gene that is clearly classical and six other class I genes each with its own unique characteristics that probably perform roles other than or in addition to antigen presentation.
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Affiliation(s)
- Michelle L Baker
- Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, NM, USA.
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25
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Niwa H, Sekita Y, Tsend-Ayush E, Grützner F. Platypus Pou5f1 reveals the first steps in the evolution of trophectoderm differentiation and pluripotency in mammals. Evol Dev 2008; 10:671-82. [DOI: 10.1111/j.1525-142x.2008.00280.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Tsend-Ayush E, Dodge N, Mohr J, Casey A, Himmelbauer H, Kremitzki CL, Schatzkamer K, Graves T, Warren WC, Grützner F. Higher-order genome organization in platypus and chicken sperm and repositioning of sex chromosomes during mammalian evolution. Chromosoma 2008; 118:53-69. [PMID: 18726609 DOI: 10.1007/s00412-008-0177-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 07/18/2008] [Accepted: 07/21/2008] [Indexed: 10/21/2022]
Abstract
In mammals, chromosomes occupy defined positions in sperm, whereas previous work in chicken showed random chromosome distribution. Monotremes (platypus and echidnas) are the most basal group of living mammals. They have elongated sperm like chicken and a complex sex chromosome system with homology to chicken sex chromosomes. We used platypus and chicken genomic clones to investigate genome organization in sperm. In chicken sperm, about half of the chromosomes investigated are organized non-randomly, whereas in platypus chromosome organization in sperm is almost entirely non-random. The use of genomic clones allowed us to determine chromosome orientation and chromatin compaction in sperm. We found that in both species chromosomes maintain orientation of chromosomes in sperm independent of random or non-random positioning along the sperm nucleus. The distance of loci correlated with the total length of sperm nuclei, suggesting that chromatin extension depends on sperm elongation. In platypus, most sex chromosomes cluster in the posterior region of the sperm nucleus, presumably the result of postmeiotic association of sex chromosomes. Chicken and platypus autosomes sharing homology with the human X chromosome located centrally in both species suggesting that this is the ancestral position. This suggests that in some therian mammals a more anterior position of the X chromosome has evolved independently.
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Affiliation(s)
- Enkhjargal Tsend-Ayush
- School of Molecular & Biomedical Science, The University of Adelaide, Adelaide, SA, Australia
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27
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Rens W, O'Brien PCM, Grützner F, Clarke O, Graphodatskaya D, Tsend-Ayush E, Trifonov VA, Skelton H, Wallis MC, Johnston S, Veyrunes F, Graves JAM, Ferguson-Smith MA. The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z. Genome Biol 2008; 8:R243. [PMID: 18021405 PMCID: PMC2258203 DOI: 10.1186/gb-2007-8-11-r243] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/02/2007] [Indexed: 11/10/2022] Open
Abstract
A comparative study of the karyotype of the short-beaked echidna shows that monotremes appear to have a unique XY sex chromosome system that shares some homology with the avian Z. Background Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. Results Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1. Conclusion Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.
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Affiliation(s)
- Willem Rens
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES, UK.
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28
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Veyrunes F, Waters PD, Miethke P, Rens W, McMillan D, Alsop AE, Grützner F, Deakin JE, Whittington CM, Schatzkamer K, Kremitzki CL, Graves T, Ferguson-Smith MA, Warren W, Marshall Graves JA. Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes. Genome Res 2008; 18:965-73. [PMID: 18463302 DOI: 10.1101/gr.7101908] [Citation(s) in RCA: 225] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In therian mammals (placentals and marsupials), sex is determined by an XX female: XY male system, in which a gene (SRY) on the Y affects male determination. There is no equivalent in other amniotes, although some taxa (notably birds and snakes) have differentiated sex chromosomes. Birds have a ZW female: ZZ male system with no homology with mammal sex chromosomes, in which dosage of a Z-borne gene (possibly DMRT1) affects male determination. As the most basal mammal group, the egg-laying monotremes are ideal for determining how the therian XY system evolved. The platypus has an extraordinary sex chromosome complex, in which five X and five Y chromosomes pair in a translocation chain of alternating X and Y chromosomes. We used physical mapping to identify genes on the pairing regions between adjacent X and Y chromosomes. Most significantly, comparative mapping shows that, contrary to earlier reports, there is no homology between the platypus and therian X chromosomes. Orthologs of genes in the conserved region of the human X (including SOX3, the gene from which SRY evolved) all map to platypus chromosome 6, which therefore represents the ancestral autosome from which the therian X and Y pair derived. Rather, the platypus X chromosomes have substantial homology with the bird Z chromosome (including DMRT1) and to segments syntenic with this region in the human genome. Thus, platypus sex chromosomes have strong homology with bird, but not to therian sex chromosomes, implying that the therian X and Y chromosomes (and the SRY gene) evolved from an autosomal pair after the divergence of monotremes only 166 million years ago. Therefore, the therian X and Y are more than 145 million years younger than previously thought.
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Affiliation(s)
- Frédéric Veyrunes
- Research School of Biological Sciences, Australian National University, Canberra 2601, Australia
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29
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McMillan D, Miethke P, Alsop AE, Rens W, O'Brien P, Trifonov V, Veyrunes F, Schatzkamer K, Kremitzki CL, Graves T, Warren W, Grützner F, Ferguson-Smith MA, Graves JAM. Characterizing the chromosomes of the platypus (Ornithorhynchus anatinus). Chromosome Res 2008; 15:961-74. [PMID: 18185982 DOI: 10.1007/s10577-007-1186-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 10/20/2007] [Accepted: 10/20/2007] [Indexed: 01/27/2023]
Abstract
Like the unique platypus itself, the platypus genome is extraordinary because of its complex sex chromosome system, and is controversial because of difficulties in identification of small autosomes and sex chromosomes. A 6-fold shotgun sequence of the platypus genome is now available and is being assembled with the help of physical mapping. It is therefore essential to characterize the chromosomes and resolve the ambiguities and inconsistencies in identifying autosomes and sex chromosomes. We have used chromosome paints and DAPI banding to identify and classify pairs of autosomes and sex chromosomes. We have established an agreed nomenclature and identified anchor BAC clones for each chromosome that will ensure unambiguous gene localizations.
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Affiliation(s)
- Daniel McMillan
- Comparative Genomics Group, Research School of Biological Sciences, The Australian National University, Canberra, ACT 2601, Australia
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