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Antigen Presentation and Autophagy in Teleost Adaptive Immunity. Int J Mol Sci 2022; 23:ijms23094899. [PMID: 35563287 PMCID: PMC9103719 DOI: 10.3390/ijms23094899] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 01/27/2023] Open
Abstract
Infectious diseases are a burden for aquaculture. Antigen processing and presentation (APP) to the immune effector cells that fight pathogens is key in the adaptive immune response. At the core of the adaptive immunity that appeared in lower vertebrates during evolution are the variable genes encoding the major histocompatibility complex (MHC). MHC class I molecules mainly present peptides processed in the cytosol by the proteasome and transported to the cell surface of all cells through secretory compartments. Professional antigen-presenting cells (pAPC) also express MHC class II molecules, which normally present peptides processed from exogenous antigens through lysosomal pathways. Autophagy is an intracellular self-degradation process that is conserved in all eukaryotes and is induced by starvation to contribute to cellular homeostasis. Self-digestion during autophagy mainly occurs by the fusion of autophagosomes, which engulf portions of cytosol and fuse with lysosomes (macroautophagy) or assisted by chaperones (chaperone-mediated autophagy, CMA) that deliver proteins to lysosomes. Thus, during self-degradation, antigens can be processed to be presented by the MHC to immune effector cells, thus, linking autophagy to APP. This review is focused on the essential components of the APP that are conserved in teleost fish and the increasing evidence related to the modulation of APP and autophagy during pathogen infection.
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Almeida T, Ohta Y, Gaigher A, Muñoz-Mérida A, Neves F, Castro LFC, Machado AM, Esteves PJ, Veríssimo A, Flajnik MF. A Highly Complex, MHC-Linked, 350 Million-Year-Old Shark Nonclassical Class I Lineage. THE JOURNAL OF IMMUNOLOGY 2021; 207:824-836. [PMID: 34301841 DOI: 10.4049/jimmunol.2000851] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 05/09/2021] [Indexed: 11/19/2022]
Abstract
Cartilaginous fish, or Chondrichthyes, are the oldest extant vertebrates to possess the MHC and the Ig superfamily-based Ag receptors, the defining genes of the gnathostome adaptive immune system. In this work, we have identified a novel MHC lineage, UEA, a complex multigene nonclassical class I family found in sharks (division Selachii) but not detected in chimaeras (subclass Holocephali) or rays (division Batoidea). This new lineage is distantly related to the previously reported nonclassical class I lineage UCA, which appears to be present only in dogfish sharks (order Squaliformes). UEA lacks conservation of the nine invariant residues in the peptide (ligand)-binding regions (PBR) that bind to the N and C termini of bound peptide in most vertebrate classical class I proteins, which are replaced by relatively hydrophobic residues compared with the classical UAA. In fact, UEA and UCA proteins have the most hydrophobic-predicted PBR of all identified chondrichthyan class I molecules. UEA genes detected in the whale shark and bamboo shark genome projects are MHC linked. Consistent with UEA comprising a very large gene family, we detected weak expression in different tissues of the nurse shark via Northern blotting and RNA sequencing. UEA genes fall into three sublineages with unique characteristics in the PBR. UEA shares structural and genetic features with certain nonclassical class I genes in other vertebrates, such as the highly complex XNC nonclassical class I genes in Xenopus, and we anticipate that each shark gene, or at least each sublineage, will have a unique function, perhaps in bacterial defense.
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Affiliation(s)
- Tereza Almeida
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal.,Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal.,Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, MD; and
| | - Yuko Ohta
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, MD; and
| | - Arnaud Gaigher
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal
| | - Antonio Muñoz-Mérida
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal
| | - Fabiana Neves
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal
| | - L Filipe C Castro
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal.,Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Porto, Portugal
| | - André M Machado
- Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Porto, Portugal
| | - Pedro J Esteves
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal.,Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal
| | - Ana Veríssimo
- CIBIO-InBIO, Centro de Investigacão em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Porto, Portugal
| | - Martin F Flajnik
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, MD; and
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3
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MHC class I evolution; from Northern pike to salmonids. BMC Ecol Evol 2021; 21:3. [PMID: 33514321 PMCID: PMC7853315 DOI: 10.1186/s12862-020-01736-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 12/13/2020] [Indexed: 11/29/2022] Open
Abstract
Background Salmonids are of major importance both as farmed and wild animals. With the changing environment comes changes in pathogenic pressures so understanding the immune system of all salmonid species is of essence. Major histocompatibility complex (MHC) genes are key players in the adaptive immune system signalling infection to responding T-cells populations. Classical MHC class I (MHCI) genes, defined by high polymorphism, broad expression patterns and peptide binding ability, have a key role in inducing immunity. In salmonids, the fourth whole genome duplication that occurred 94 million years ago has provided salmonids with duplicate MHCI regions, while Northern Pike, a basal sister clade to salmonids, represent a species which has not experienced this whole genome duplication. Results Comparing the gene organization and evolution of MHC class I gene sequences in Northern pike versus salmonids displays a complex picture of how many of these genes evolved. Regional salmonid Ia and Ib Z lineage gene duplicates are not orthologs to the Northern pike Z lineage sequences. Instead, salmonids have experienced unique gene duplications in both duplicate regions as well as in the Salmo and Oncorhynchus branch. Species-specific gene duplications are even more pronounced for some L lineage genes. Conclusions Although both Northern pike as well as salmonids have expanded their U and Z lineage genes, these gene duplications occurred separately in pike and in salmonids. However, the similarity between these duplications suggest the transposable machinery was present in a common ancestor. The salmonid MHCIa and MHCIb regions were formed during the 94 MYA since the split from pike and before the Oncorhynchus and Salmo branch separated. As seen in tetrapods, the non-classical U lineage genes are diversified duplicates of their classical counterpart. One MHCI lineage, the L lineage, experienced massive species-specific gene duplications after Oncorhynchus and Salmo split approximately 25 MYA. Based on what we currently know about L lineage genes, this large variation in number of L lineage genes also signals a large functional diversity in salmonids.
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Abstract
Based on analysis of available genome sequences, five gene lineages of MHC class I molecules (MHC I-U, -Z, -S, -L and -P) and one gene lineage of MHC class II molecules (MHC II-D) have been identified in Osteichthyes. In the latter lineage, three MHC II molecule sublineages have been identified (MHC II-A, -B and -E). As regards MHC class I molecules in Osteichthyes, it is important to take note of the fact that the lineages U and Z in MHC I genes have been identified in almost all fish species examined so far. Phylogenetic studies into MHC II molecule genes of sublineages A and B suggest that they may be descended from the genes of the sublineage named A/B that have been identified in spotted gar (Lepisosteus oculatus). The sublineage E genes of MHC II molecules, which represent the group of non-polymorphic genes with poor expression in the tissues connected with the immune system, are present in primitive fish, i.e. in paddlefish, sturgeons and spotted gar (Lepisosteus oculatus), as well as in cyprinids (Cyprinidae), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss). Full elucidation of the details relating to the organisation and functioning of the particular components of the major histocompatibility complex in Osteichthyes can advance the understanding of the evolution of the MHC molecule genes and the immune mechanism.
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Abstract
Recent decades, there is significant progress in understanding the mechanisms of tumor progression and immune evasion. The newly discovered protein NLRC5 is demonstrated to participate in regulating cancer immune escape through enhancing MHC class I genes expression in certain tumors. Nevertheless, increasing evidence has revealed that NLRC5 is up-regulated in some other tumors and promote tumor development and progression. The purpose of this review is to describe the role of NLRC5 in tumors and discuss whether NLRC5 can be a potential target in cancer treatment.
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Affiliation(s)
- Feng Tang
- Department of Neurosurgery, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, 230601, Anhui, China.
- Cerebral Vascular Disease Research Center, Anhui Medical University, Hefei, 230601, China.
| | - Yadi Xu
- Department of Neurosurgery, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, 230601, Anhui, China
- Cerebral Vascular Disease Research Center, Anhui Medical University, Hefei, 230601, China
| | - Bing Zhao
- Department of Neurosurgery, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, 230601, Anhui, China.
- Cerebral Vascular Disease Research Center, Anhui Medical University, Hefei, 230601, China.
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Chen H, Huang S, Jiang Y, Han F, Ni Q, Yao Y, Xu H, Mishra S, Zhang M. The MHC Class Ia Genes in Chenfu's Treefrog ( Zhangixalus chenfui) Evolved via Gene Duplication, Recombination, and Selection. Animals (Basel) 2019; 10:ani10010034. [PMID: 31877958 PMCID: PMC7023105 DOI: 10.3390/ani10010034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/19/2019] [Accepted: 12/19/2019] [Indexed: 01/29/2023] Open
Abstract
Simple Summary Amphibians, the first terrestrial vertebrates, provide materials for adaptive evolutionary studies, such as the evolution of the major histocompatibility complex (MHC). To date, various MHC evolutionary mechanisms have been identified in frogs, but more research is needed to determine the evolutionary mechanisms of the frog MHC. The main purpose of this study was to evaluate polymorphisms in the MHC class Ia genes of the Chenfu’s Treefrog. The MHC class Ia genes of the Chenfu’s Treefrog have high polymorphism. The mechanisms responsible for the formation of the polymorphisms include gene duplication, recombination, and selection. Abstract The molecular mechanisms underlying the evolution of adaptive immunity-related proteins can be deduced by a thorough examination of the major histocompatibility complex (MHC). Currently, in vertebrates, there is a relatively large amount of research on MHCs in mammals and birds. However, research related to amphibian MHC genes and knowledge about the evolutionary patterns is limited. This study aimed to isolate the MHC class I genes from Chenfu’s Treefrog (Zhangixalus chenfui) and reveal the underlying evolutionary processes. A total of 23 alleles spanning the coding region of MHC class Ia genes were identified in 13 individual samples. Multiple approaches were used to test and identify recombination from the 23 alleles. Amphibian MHC class Ia alleles, from NCBI, were used to construct the phylogenetic relationships in MEGA. Additionally, the partition strategy was adopted to construct phylogenetic relationships using MrBayes and MEGA. The sites of positive selection were identified by FEL, PAML, and MEME. In Chenfu’s Treefrog, we found that: (1) recombination usually takes place between whole exons of MHC class Ia genes; (2) there are at least 3 loci for MHC class Ia, and (3) the diversity of genes in MHC class Ia can be attributed to recombination, gene duplication, and positive selection. We characterized the evolutionary mechanisms underlying MHC class Ia genes in Chenfu’s Treefrog, and in so doing, broadened the knowledge of amphibian MHC systems.
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Wang B, Du HH, Huang HQ, Xian JA, Xia ZH, Hu YH. Major histocompatibility complex class I (MHC Iα) of Japanese flounder (Paralichthys olivaceus) plays a critical role in defense against intracellular pathogen infection. FISH & SHELLFISH IMMUNOLOGY 2019; 94:122-131. [PMID: 31491527 DOI: 10.1016/j.fsi.2019.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/11/2019] [Accepted: 09/02/2019] [Indexed: 06/10/2023]
Abstract
The major histocompatibility complex (MHC) is a highly polymorphic region of the vertebrate genome that plays a critical role in initiating immune responses towards invading pathogens. It is well known that MHC I molecules play a central role in the immune response to viruses. However, rare literatures were reported the role of MHC I in the resistance to intracellular bacteria. Sequences of MHC Iα were identified in multiple teleost species, including Japanese flounder (Paralichthys olivaceus), however, the immunological function of MHC Iα remain largely unknown. In this study, we examined the expression profile and biological activity of an MHC Iα homologue, PoMHC Iα, from P. olivaceus. Structural analysis showed that PoMHC Iα possesses conserved structural characteristics of MHC Iα proteins, including MHC_I domain, IGc1 domain, transmembrane region. Expression of PoMHC Iα was upregulated in a time-dependent manner by extracellular and intracellular bacterial pathogens and viral pathogen infection. Different expression patterns were exhibited in response to the infection of different types of microbial pathogens in different immune tissues. Recombinant PoMHC Iα increased the capability of host cells to defense against intracellular pathogen Edwardsiella tarda infection and enhanced the expression of immune related genes. The knockdown of PoMHC Iα attenuated the ability of cells to eliminate E. tarda, which was sustained by the in vivo results that overexpression of PoMHC Iα promoted the host defense against invading E. tarda. Antigen uptake assay indicated PoMHC Iα participated in cells antigen presentation. Collectively, this study is the first report that MHC Iα plays an important role in immune defense against intracellular bacterial pathogen in teleost. Taken together, these findings add new insights into the biological function of teleost MHC Iα and emphasize the importance of MHC I gene products for the control of E. tarda infection.
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Affiliation(s)
- Bo Wang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Institute of Tropical Agriculture and Forestry, Hainan University, Haikou, 570228, China; Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China
| | - He-He Du
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China; Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China
| | - Hui-Qin Huang
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China; Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China
| | - Jian-An Xian
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China; Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China
| | - Zhi-Hui Xia
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Institute of Tropical Agriculture and Forestry, Hainan University, Haikou, 570228, China
| | - Yong-Hua Hu
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao, China; Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China.
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8
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Major Histocompatibility Complex (MHC) Genes and Disease Resistance in Fish. Cells 2019; 8:cells8040378. [PMID: 31027287 PMCID: PMC6523485 DOI: 10.3390/cells8040378] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 04/12/2019] [Accepted: 04/23/2019] [Indexed: 12/20/2022] Open
Abstract
Fascinating about classical major histocompatibility complex (MHC) molecules is their polymorphism. The present study is a review and discussion of the fish MHC situation. The basic pattern of MHC variation in fish is similar to mammals, with MHC class I versus class II, and polymorphic classical versus nonpolymorphic nonclassical. However, in many or all teleost fishes, important differences with mammalian or human MHC were observed: (1) The allelic/haplotype diversification levels of classical MHC class I tend to be much higher than in mammals and involve structural positions within but also outside the peptide binding groove; (2) Teleost fish classical MHC class I and class II loci are not linked. The present article summarizes previous studies that performed quantitative trait loci (QTL) analysis for mapping differences in teleost fish disease resistance, and discusses them from MHC point of view. Overall, those QTL studies suggest the possible importance of genomic regions including classical MHC class II and nonclassical MHC class I genes, whereas similar observations were not made for the genomic regions with the highly diversified classical MHC class I alleles. It must be concluded that despite decades of knowing MHC polymorphism in jawed vertebrate species including fish, firm conclusions (as opposed to appealing hypotheses) on the reasons for MHC polymorphism cannot be made, and that the types of polymorphism observed in fish may not be explained by disease-resistance models alone.
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9
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Ballingall KT, Bontrop RE, Ellis SA, Grimholt U, Hammond JA, Ho CS, Kaufman J, Kennedy LJ, Maccari G, Miller D, Robinson J, Marsh SGE. Comparative MHC nomenclature: report from the ISAG/IUIS-VIC committee 2018. Immunogenetics 2018; 70:625-632. [PMID: 30039257 DOI: 10.1007/s00251-018-1073-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 07/13/2018] [Indexed: 12/24/2022]
Abstract
Significant progress has been made over the last decade in defining major histocompatibility complex (MHC) diversity at the nucleotide, allele, haplotype, diplotype, and population levels in many non-human species. Much of this progress has been driven by the increased availability and reduced costs associated with nucleotide sequencing technologies. This report provides an update on the activities of the comparative MHC nomenclature committee which is a standing committee of both the International Society for Animal Genetics (ISAG) and the International Union of Immunological Societies (IUIS) where it operates under the umbrella of the Veterinary Immunology Committee (VIC). A previous report from this committee in 2006 defined the role of the committee in providing guidance in the development of a standardized nomenclature for genes and alleles at MHC loci in non-human species. It described the establishment of the Immuno Polymorphism Database, IPD-MHC, which continues to provide public access to high quality MHC sequence data across a range of species. In this report, guidelines for the continued development of a universal MHC nomenclature framework are described, summarizing the continued development of each species section within the IPD-MHC project.
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Affiliation(s)
- Keith T Ballingall
- Moredun Research Institute, Midlothian, UK and Chair of the Comparative MHC Nomenclature Committee, Edinburgh, Scotland, UK.
| | | | | | | | | | | | | | - Lorna J Kennedy
- Centre for Integrated Genomic Medical Research, Manchester, UK
| | - Giuseppe Maccari
- The Pirbright Institute, Pirbright, Surrey, UK.,Anthony Nolan Research Institute, London, UK
| | - Donald Miller
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - James Robinson
- Anthony Nolan Research Institute, London, UK.,UCL Cancer Institute, Royal Free Campus, London, UK
| | - Steven G E Marsh
- Anthony Nolan Research Institute, London, UK.,UCL Cancer Institute, Royal Free Campus, London, UK
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Dijkstra JM, Grimholt U. Major histocompatibility complex (MHC) fragment numbers alone - in Atlantic cod and in general - do not represent functional variability. F1000Res 2018; 7:963. [PMID: 30135730 DOI: 10.12688/f1000research.15386.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/21/2018] [Indexed: 12/16/2022] Open
Abstract
This correspondence concerns a publication by Malmstrøm et al. in Nature Genetics in October 2016. Malmstrøm et al. made an important contribution to fish phylogeny research by using low-coverage genome sequencing for comparison of 66 teleost (modern bony) fish species, with 64 of those 66 belonging to the species-rich clade Neoteleostei, and with 27 of those 64 belonging to the order Gadiformes. For these 66 species, Malmstrøm et al. estimated numbers of genes belonging to the major histocompatibility complex (MHC) class I lineages U and Z and concluded that in teleost fish these combined numbers are positively associated with, and a driving factor of, the rates of establishment of new fish species (speciation rates). They also claimed that functional genes for the MHC class II system molecules MHC IIA, MHC IIB, CD4 and CD74 were lost in early Gadiformes. Our main criticisms are (1) that the authors did not provide sufficient evidence for presence or absence of intact functional MHC class I or MHC class II system genes, (2) that they did not discuss that an MHC subpopulation gene number alone is a very incomplete measure of MHC variance, and (3) that the MHC system is more likely to reduce speciation rates than to enhance them. Furthermore, their use of the Ornstein-Uhlenbeck model is a typical example of overly naïve use of that model system. In short, we conclude that their new model of MHC class I evolution, reflected in their title "Evolution of the immune system influences speciation rates in teleost fish", is unsubstantiated, and that their "pinpointing" of the functional loss of the MHC class II system and all the important MHC class II system genes to the onset of Gadiformes is preliminary, because they did not sufficiently investigate the species at the clade border.
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Affiliation(s)
- Johannes M Dijkstra
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, 470-1192, Japan
| | - Unni Grimholt
- Fish Research Group, Norwegian Veterinary Institute, Oslo, Oslo N-0106, Norway
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11
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Dijkstra JM, Grimholt U. Major histocompatibility complex (MHC) fragment numbers alone - in Atlantic cod and in general - do not represent functional variability. F1000Res 2018; 7:963. [PMID: 30135730 PMCID: PMC6081975 DOI: 10.12688/f1000research.15386.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/04/2018] [Indexed: 12/14/2022] Open
Abstract
This correspondence concerns a publication by Malmstrøm
et al. in Nature Genetics in October 2016. Malmstrøm
et al. made an important contribution to fish phylogeny research by using low-coverage genome sequencing for comparison of 66 teleost (modern bony) fish species, with 64 of those 66 belonging to the species-rich clade Neoteleostei, and with 27 of those 64 belonging to the order Gadiformes. For these 66 species, Malmstrøm
et al. estimated numbers of genes belonging to the major histocompatibility complex (MHC) class I lineages U and Z and concluded that in teleost fish these combined numbers are positively associated with, and a driving factor of, the rates of establishment of new fish species (speciation rates). They also claimed that functional genes for the MHC class II system molecules MHC IIA, MHC IIB, CD4 and CD74 were lost in early Gadiformes. Our main criticisms are (1) that the authors did not provide sufficient evidence for presence or absence of intact functional MHC class I or MHC class II system genes, (2) that they did not discuss that an MHC subpopulation gene number alone is a very incomplete measure of MHC variance, and (3) that the MHC system is more likely to reduce speciation rates than to enhance them. Furthermore, their use of the Ornstein-Uhlenbeck model is a typical example of overly naïve use of that model system. In short, we conclude that their new model of MHC class I evolution, reflected in their title “Evolution of the immune system influences speciation rates in teleost fish”, is unsubstantiated, and that their “pinpointing” of the functional loss of the MHC class II system and all the important MHC class II system genes to the onset of Gadiformes is preliminary, because they did not sufficiently investigate the species at the clade border.
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Affiliation(s)
- Johannes M Dijkstra
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, 470-1192, Japan
| | - Unni Grimholt
- Fish Research Group, Norwegian Veterinary Institute, Oslo, Oslo N-0106, Norway
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12
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Whole genome duplications have provided teleosts with many roads to peptide loaded MHC class I molecules. BMC Evol Biol 2018; 18:25. [PMID: 29471808 PMCID: PMC5824609 DOI: 10.1186/s12862-018-1138-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 02/15/2018] [Indexed: 12/31/2022] Open
Abstract
Background In sharks, chickens, rats, frogs, medaka and zebrafish there is haplotypic variation in MHC class I and closely linked genes involved in antigen processing, peptide translocation and peptide loading. At least in chicken, such MHCIa haplotypes of MHCIa, TAP2 and Tapasin are shown to influence the repertoire of pathogen epitopes being presented to CD8+ T-cells with subsequent effect on cell-mediated immune responses. Results Examining MHCI haplotype variation in Atlantic salmon using transcriptome and genome resources we found little evidence for polymorphism in antigen processing genes closely linked to the classical MHCIa genes. Looking at other genes involved in MHCI assembly and antigen processing we found retention of functional gene duplicates originating from the second vertebrate genome duplication event providing cyprinids, salmonids, and neoteleosts with the potential of several different peptide-loading complexes. One of these gene duplications has also been retained in the tetrapod lineage with orthologs in frogs, birds and opossum. Conclusion We postulate that the unique salmonid whole genome duplication (SGD) is responsible for eliminating haplotypic content in the paralog MHCIa regions possibly due to frequent recombination and reorganization events at early stages after the SGD. In return, multiple rounds of whole genome duplications has provided Atlantic salmon, other teleosts and even lower vertebrates with alternative peptide loading complexes. How this affects antigen presentation remains to be established. Electronic supplementary material The online version of this article (10.1186/s12862-018-1138-9) contains supplementary material, which is available to authorized users.
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13
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Didinger C, Eimes JA, Lillie M, Waldman B. Multiple major histocompatibility complex class I genes in Asian anurans: Ontogeny and phylogeny. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2017; 70:69-79. [PMID: 28027939 DOI: 10.1016/j.dci.2016.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 06/06/2023]
Abstract
Amphibians, as the first terrestrial vertebrates, offer a window into early major histocompatibility complex (MHC) evolution. We characterized the MHC class I of two Korean amphibians, the Asiatic toad (Bufo gargarizans) and the Japanese tree frog (Hyla japonica). We found at least four transcribed MHC class I (MHC I) loci, the highest number confirmed in any anuran to date. Furthermore, we identified MHC I transcripts in terrestrial adults, and possibly in aquatic larvae, of both species. We conducted a phylogenetic analysis based on MHC I sequence data and found that B. gargarizans and H. japonica cluster together in the superfamily Nobleobatrachia. We further identified three supertypes shared by the two species. Our results reveal substantial variation in the number of MHC I loci in anurans and suggest that certain supertypes have particular physiochemical properties that may confer pathogen resistance.
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Affiliation(s)
- Chelsea Didinger
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea
| | - John A Eimes
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea
| | - Mette Lillie
- Department of Medical Biochemistry and Microbiology (IMBIM), Genomics, Uppsala University, Box 582, 75123 Uppsala, Sweden
| | - Bruce Waldman
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea.
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Grimholt U. MHC and Evolution in Teleosts. BIOLOGY 2016; 5:biology5010006. [PMID: 26797646 PMCID: PMC4810163 DOI: 10.3390/biology5010006] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 01/12/2016] [Accepted: 01/13/2016] [Indexed: 12/18/2022]
Abstract
Major histocompatibility complex (MHC) molecules are key players in initiating immune responses towards invading pathogens. Both MHC class I and class II genes are present in teleosts, and, using phylogenetic clustering, sequences from both classes have been classified into various lineages. The polymorphic and classical MHC class I and class II gene sequences belong to the U and A lineages, respectively. The remaining class I and class II lineages contain nonclassical gene sequences that, despite their non-orthologous nature, may still hold functions similar to their mammalian nonclassical counterparts. However, the fact that several of these nonclassical lineages are only present in some teleost species is puzzling and questions their functional importance. The number of genes within each lineage greatly varies between teleost species. At least some gene expansions seem reasonable, such as the huge MHC class I expansion in Atlantic cod that most likely compensates for the lack of MHC class II and CD4. The evolutionary trigger for similar MHC class I expansions in tilapia, for example, which has a functional MHC class II, is not so apparent. Future studies will provide us with a more detailed understanding in particular of nonclassical MHC gene functions.
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Affiliation(s)
- Unni Grimholt
- Department of Virology, Norwegian Veterinary Institute, Ullevaalsveien 68, Oslo N-0106, Norway.
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15
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Grimholt U, Tsukamoto K, Azuma T, Leong J, Koop BF, Dijkstra JM. A comprehensive analysis of teleost MHC class I sequences. BMC Evol Biol 2015; 15:32. [PMID: 25888517 PMCID: PMC4364491 DOI: 10.1186/s12862-015-0309-1] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 02/16/2015] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND MHC class I (MHCI) molecules are the key presenters of peptides generated through the intracellular pathway to CD8-positive T-cells. In fish, MHCI genes were first identified in the early 1990's, but we still know little about their functional relevance. The expansion and presumed sub-functionalization of cod MHCI and access to many published fish genome sequences provide us with the incentive to undertake a comprehensive study of deduced teleost fish MHCI molecules. RESULTS We expand the known MHCI lineages in teleosts to five with identification of a new lineage defined as P. The two lineages U and Z, which both include presumed peptide binding classical/typical molecules besides more derived molecules, are present in all teleosts analyzed. The U lineage displays two modes of evolution, most pronouncedly observed in classical-type alpha 1 domains; cod and stickleback have expanded on one of at least eight ancient alpha 1 domain lineages as opposed to many other teleosts that preserved a number of these ancient lineages. The Z lineage comes in a typical format present in all analyzed ray-finned fish species as well as lungfish. The typical Z format displays an unprecedented conservation of almost all 37 residues predicted to make up the peptide binding groove. However, also co-existing atypical Z sub-lineage molecules, which lost the presumed peptide binding motif, are found in some fish like carps and cavefish. The remaining three lineages, L, S and P, are not predicted to bind peptides and are lost in some species. CONCLUSIONS Much like tetrapods, teleosts have polymorphic classical peptide binding MHCI molecules, a number of classical-similar non-classical MHCI molecules, and some members of more diverged MHCI lineages. Different from tetrapods, however, is that in some teleosts the classical MHCI polymorphism incorporates multiple ancient MHCI domain lineages. Also different from tetrapods is that teleosts have typical Z molecules, in which the residues that presumably form the peptide binding groove have been almost completely conserved for over 400 million years. The reasons for the uniquely teleost evolution modes of peptide binding MHCI molecules remain an enigma.
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Affiliation(s)
| | - Kentaro Tsukamoto
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, 470-1192, Japan.
| | - Teruo Azuma
- Fisheries Technology Division, National Research Institute of Fisheries Engineering, 7620-7, Hasaki, Kamisu-shi, Ibaraki, Japan.
| | - Jong Leong
- Centre for Biomedical Research, Department of Biology, University of Victoria, PO Box 3020 STN CSC, Victoria, Canada.
| | - Ben F Koop
- Centre for Biomedical Research, Department of Biology, University of Victoria, PO Box 3020 STN CSC, Victoria, Canada.
| | - Johannes M Dijkstra
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, 470-1192, Japan.
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16
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Dirscherl H, McConnell SC, Yoder JA, de Jong JLO. The MHC class I genes of zebrafish. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 46:11-23. [PMID: 24631581 PMCID: PMC4031684 DOI: 10.1016/j.dci.2014.02.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 02/26/2014] [Accepted: 02/28/2014] [Indexed: 05/17/2023]
Abstract
Major histocompatibility complex (MHC) molecules play a central role in the immune response and in the recognition of non-self. Found in all jawed vertebrate species, including zebrafish and other teleosts, MHC genes are considered the most polymorphic of all genes. In this review we focus on the multi-faceted diversity of zebrafish MHC class I genes, which are classified into three sequence lineages: U, Z, and L. We examine the polygenic, polymorphic, and haplotypic diversity of the zebrafish MHC class I genes, discussing known and postulated functional differences between the different class I lineages. In addition, we provide the first comprehensive nomenclature for the L lineage genes in zebrafish, encompassing at least 15 genes, and characterize their sequence properties. Finally, we discuss how recent findings have shed new light on the remarkably diverse MHC loci of this species.
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Affiliation(s)
- Hayley Dirscherl
- Department of Molecular Biomedical Sciences, North Carolina State University, 1060 William Moore Drive, Raleigh, NC 27607, USA; The Joint Biomedical Engineering Graduate Program, University of North Carolina-North Carolina State University, Raleigh, NC, USA
| | - Sean C McConnell
- Section of Hematology-Oncology and Stem Cell Transplant, Department of Pediatrics, The University of Chicago, KCBD 5120, Chicago, IL 60637, USA
| | - Jeffrey A Yoder
- Department of Molecular Biomedical Sciences, North Carolina State University, 1060 William Moore Drive, Raleigh, NC 27607, USA; Center for Comparative Medicine and Translational Research, North Carolina State University, 1060 William Moore Drive, Raleigh, NC 27607, USA.
| | - Jill L O de Jong
- Section of Hematology-Oncology and Stem Cell Transplant, Department of Pediatrics, The University of Chicago, KCBD 5120, Chicago, IL 60637, USA.
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17
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Somamoto T, Koppang EO, Fischer U. Antiviral functions of CD8(+) cytotoxic T cells in teleost fish. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 43:197-204. [PMID: 23938605 DOI: 10.1016/j.dci.2013.07.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 07/24/2013] [Accepted: 07/24/2013] [Indexed: 06/02/2023]
Abstract
Cytotoxic T-cells (CTLs) play a pivotal role in eliminating viruses in mammalian adaptive immune system. Many recent studies on T-cell immunity of fish have suggested that teleost CTLs are also important for antiviral immunity. Cellular functional studies using clonal ginbuan crucian carp and rainbow trout have provided in vivo and in vitro evidence that in many respects, virus-specific CTLs of fish have functions similar to those of mammalian CTLs. In addition, mRNA expression profiles of CTL-related molecules, such as CD8, TCR and MHC class I, have shown that in a wide range of fish species, CTLs are involved in antiviral adaptive immunity. These findings are a basis to formulate possible vaccination strategies to trigger effective antiviral CTL responses in teleost fish. This review describes recent advances in our understanding of antiviral CTL functions in teleost fish and discusses vaccination strategies for efficiently inducing CTL activities.
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Affiliation(s)
- Tomonori Somamoto
- Laboratory of Marine Biochemistry, Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
| | - Erling Olaf Koppang
- Section of Anatomy and Pathology, Institute of Basic Science and Aquatic Medicine, Norwegian School of Veterinary Science, Ullevålsveien 72, 0033 Oslo, Norway
| | - Uwe Fischer
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Infectology, 17493 Greifswald-Insel Riems, Germany
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18
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McConnell SC, Restaino AC, de Jong JL. Multiple divergent haplotypes express completely distinct sets of class I MHC genes in zebrafish. Immunogenetics 2014; 66:199-213. [PMID: 24291825 PMCID: PMC3965299 DOI: 10.1007/s00251-013-0749-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Accepted: 11/16/2013] [Indexed: 12/12/2022]
Abstract
The zebrafish is an important animal model for stem cell biology, cancer, and immunology research. Histocompatibility represents a key intersection of these disciplines; however, histocompatibility in zebrafish remains poorly understood. We examined a set of diverse zebrafish class I major histocompatibility complex (MHC) genes that segregate with specific haplotypes at chromosome 19, and for which donor-recipient matching has been shown to improve engraftment after hematopoietic transplantation. Using flanking gene polymorphisms, we identified six distinct chromosome 19 haplotypes. We describe several novel class I U lineage genes and characterize their sequence properties, expression, and haplotype distribution. Altogether, ten full-length zebrafish class I genes were analyzed, mhc1uba through mhc1uka. Expression data and sequence properties indicate that most are candidate classical genes. Several substitutions in putative peptide anchor residues, often shared with deduced MHC molecules from additional teleost species, suggest flexibility in antigen binding. All ten zebrafish class I genes were uniquely assigned among the six haplotypes, with dominant or codominant expression of one to three genes per haplotype. Interestingly, while the divergent MHC haplotypes display variable gene copy number and content, the different genes appear to have ancient origin, with extremely high levels of sequence diversity. Furthermore, haplotype variability extends beyond the MHC genes to include divergent forms of psmb8. The many disparate haplotypes at this locus therefore represent a remarkable form of genomic region configuration polymorphism. Defining the functional MHC genes within these divergent class I haplotypes in zebrafish will provide an important foundation for future studies in immunology and transplantation.
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Affiliation(s)
- Sean C. McConnell
- Department of Pediatrics, Section of Hematology/Oncology, University of Chicago, Knapp Center for Biomedical Discovery, 900 E. 57St, Chicago, IL 60637
| | - Anthony C. Restaino
- Department of Pediatrics, Section of Hematology/Oncology, University of Chicago, Knapp Center for Biomedical Discovery, 900 E. 57St, Chicago, IL 60637
| | - Jill L.O. de Jong
- Department of Pediatrics, Section of Hematology/Oncology, University of Chicago, Knapp Center for Biomedical Discovery, 900 E. 57St, Chicago, IL 60637
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19
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Characterization of the Z lineage Major histocompatability complex class I genes in zebrafish. Immunogenetics 2013; 66:185-98. [PMID: 24287892 DOI: 10.1007/s00251-013-0748-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 11/11/2013] [Indexed: 02/01/2023]
Abstract
Zebrafish (Danio rerio) are a valuable model for studying immunity, infection, and hematopoietic disease and have recently been employed for transplantation assays. However, the lack of syngeneic zebrafish creates challenges with identifying immune-matched individuals. The MHC class I genes, which mediate allogeneic recognition in mammals, have been grouped into three broad lineages in zebrafish: the classical U genes on chromosome 19, the Z genes which have been reported to map to chromosome 1, and the L genes that map to multiple loci. Transplantations between individual zebrafish that are matched at the U locus fail to consistently engraft suggesting that additional loci contribute to allogeneic recognition. Although two full-length zebrafish Z transcripts have been described, the genomic organization and diversity of these genes have not been reported. Herein we define ten Z genes on chromosomes 1 and 3 and on an unplaced genomic scaffold. We report that neither of the Z transcripts previously described match the current genome assembly and classify these transcripts as additional gene loci. We characterize full-length transcripts for 9 of these 12 genes. We demonstrate a high level of expression variation of the Z genes between individual zebrafish suggestive of haplotypic variation. We report low level sequence variation for individual Z genes between individual zebrafish reflecting a possible nonclassical function, although these molecules may still contribute to allogeneic recognition. Finally, we present a gene nomenclature system for the Z genes consistent with MHC nomenclature in other species and with the zebrafish gene nomenclature guidelines.
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20
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Evolution of MHC class I in the order Crocodylia. Immunogenetics 2013; 66:53-65. [PMID: 24253731 DOI: 10.1007/s00251-013-0746-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022]
Abstract
The major histocompatibility complex (MHC) is a dynamic genomic region with an essential role in the adaptive immunity of jawed vertebrates. The evolution of the MHC has been dominated by gene duplication and gene loss, commonly known as the birth-and-death process. Evolutionary studies of the MHC have mostly focused on model species. However, the investigation of this region in non-avian reptiles is still in its infancy. To provide insights into the evolutionary mechanisms that have shaped the diversity of this region in the Order Crocodylia, we investigated MHC class I exon 3, intron 3, and exon 4 across 20 species of the families Alligatoridae and Crocodilidae. We generated 124 DNA sequences and identified 31 putative functional variants as well as 14 null variants. Phylogenetic analyses revealed three gene groups, all of which were present in Crocodilidae but only one in Alligatoridae. Within these groups, variants generally appear to cluster at the genus or family level rather than in species-specific groups. In addition, we found variation in gene copy number and some indication of interlocus recombination. These results suggest that MHC class I in Crocodylia underwent independent events of gene duplication, particularly in Crocodilidae. These findings enhance our understanding of MHC class I evolution and provide a preliminary framework for comparative studies of other non-avian reptiles as well as diversity assessment within Crocodylia.
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Bannai HP, Nonaka M. Comprehensive analysis of medaka major histocompatibility complex (MHC) class II genes: implications for evolution in teleosts. Immunogenetics 2013; 65:883-95. [PMID: 23989892 DOI: 10.1007/s00251-013-0731-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 08/19/2013] [Indexed: 12/29/2022]
Abstract
The major histocompatibility complex (MHC) class II molecules play central roles in adaptive immunity by regulating immune response via the activation of CD4 T cells. The full complement of the MHC class II genes has been elucidated only in mammalian species to date. To understand the evolution of these genes, we performed their first comprehensive analysis in nonmammalian species using a teleost, medaka (Oryzias latipes). Based on a database search, cDNA cloning, and genomic PCR, medaka was shown to possess five pairs of expressed class II genes, comprising one IIA and one IIB gene. Each pair was located on a different chromosome and was not linked to the class I genes. Only one pair showed a high degree of polymorphism and was considered to be classical class II genes, whereas the other four pairs were nonclassical. Phylogenetic analysis of all medaka class II genes and most reported teleost class II genes revealed that the IIA and IIB genes formed separate clades, each containing three well-corresponding lineages. One lineage contained three medaka genes and all known classical class II genes of Ostariophysi and Euteleostei and was presumed to be an original lineage of the teleost MHC class II genes. The other two lineages contained one nonclassical medaka gene each and some Euteleostei genes. These results indicate that multiple lineages of the teleost MHC class II genes have been conserved for hundreds of millions of years and that the tightly linked IIA and IIB genes have undergone concerted evolution.
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Affiliation(s)
- Hidemi P Bannai
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan
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22
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Zhao M, Wang Y, Shen H, Li C, Chen C, Luo Z, Wu H. Evolution by selection, recombination, and gene duplication in MHC class I genes of two Rhacophoridae species. BMC Evol Biol 2013; 13:113. [PMID: 23734729 PMCID: PMC3684511 DOI: 10.1186/1471-2148-13-113] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 05/29/2013] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Comparison of major histocompatibility complex (MHC) genes across vertebrate species can reveal molecular mechanisms underlying the evolution of adaptive immunity-related proteins. As the first terrestrial tetrapods, amphibians deserve special attention because of their exposure to probably increased spectrum of microorganisms compared with ancestral aquatic fishes. Knowledge regarding the evolutionary patterns and mechanisms associated with amphibian MHC genes remains limited. The goal of the present study was to isolate MHC class I genes from two Rhacophoridae species (Rhacophorus omeimontis and Polypedates megacephalus) and examine their evolution. RESULTS We identified 27 MHC class I alleles spanning the region from exon 2 to 4 in 38 tree frogs. The available evidence suggests that these 27 sequences all belong to classical MHC class I (MHC Ia) genes. Although several anuran species only display one MHC class Ia locus, at least two or three loci were observed in P. megacephalus and R. omeimontis, indicating that the number of MHC class Ia loci varies among anuran species. Recombination events, which mainly involve the entire exons, played an important role in shaping the genetic diversity of the 27 MHC class Ia alleles. In addition, signals of positive selection were found in Rhacophoridae MHC class Ia genes. Amino acid sites strongly suggested by program to be under positive selection basically accorded with the putative antigen binding sites deduced from crystal structure of human HLA. Phylogenetic relationships among MHC class I alleles revealed the presence of trans-species polymorphisms. CONCLUSIONS In the two Rhacophoridae species (1) there are two or three MHC class Ia loci; (2) recombination mainly occurs between the entire exons of MHC class Ia genes; (3) balancing selection, gene duplication and recombination all contribute to the diversity of MHC class Ia genes. These findings broaden our knowledge on the evolution of amphibian MHC systems.
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Affiliation(s)
- Mian Zhao
- Molecular and Behavioural Ecology Research Group, College of Life Sciences, Central China Normal University, 152 Luoyulu, Hongshan District, Wuhan 430079, China
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23
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Pinto RD, Randelli E, Buonocore F, Pereira PJB, dos Santos NMS. Molecular cloning and characterization of sea bass (Dicentrarchus labrax, L.) MHC class I heavy chain and β2-microglobulin. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2013; 39:234-254. [PMID: 23116964 DOI: 10.1016/j.dci.2012.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 10/10/2012] [Accepted: 10/11/2012] [Indexed: 06/01/2023]
Abstract
In this work, the gene and cDNA of sea bass (Dicentrarchus labrax) β2-microglobulin (Dila-β2m) and several cDNAs of MHC class I heavy chain (Dila-UA) were characterized. While Dila-β2m is single-copy, numerous Dila-UA transcripts were identified per individual with variability at the peptide-binding domain (PBD), but also with unexpected diversity from the connective peptide (CP) through the 3' untranslated region (UTR). Phylogenetic analysis segregates Dila-β2m and Dila-UA into each subfamily cluster, placing them in the fish class and branching Dila-MHC-I with lineage U. The α1 domains resemble those of the recently proposed L1 trans-species lineage. Although no Dila-specific α1, α2 or α3 sub-lineages could be observed, two highly distinct sub-lineages were identified at the CP/TM/CYT regions. The three-dimensional homology model of sea bass MHC-I complex is consistent with other characterized vertebrate structures. Furthermore, basal tissue-specific expression profiles were determined for both molecules, and expression of β2m was evaluated after poly I:C stimulus. Results suggest these molecules are orthologues of other β2m and teleost classical MHC-I and their basic structure is evolutionarily conserved, providing relevant information for further studies on antigen presentation in this fish species.
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Affiliation(s)
- Rute D Pinto
- Fish Immunology and Vaccinology Group, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, Porto, Portugal.
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MHC class I of saltwater crocodiles (Crocodylus porosus): polymorphism and balancing selection. Immunogenetics 2012; 64:825-38. [PMID: 22864956 DOI: 10.1007/s00251-012-0637-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 07/17/2012] [Indexed: 10/28/2022]
Abstract
Saltwater crocodiles are in high demand for the production of luxury fashion items. However, their susceptibility to disease incurs substantial losses and it is hoped to be able to genetically select these animals for disease resistance. So far, this has only been enabled by phenotypic selection. Investigating the major histocompatibility complex (MHC) could provide insight into the ability of an individual to respond to pathogens acting as a selective pressure on the host. Here, we assessed genetic diversity and a role of selection in shaping the diversity of MHC class I exon 3 among 42 saltwater crocodiles from nine river basins in the Northern Territory, Australia. We generated 640 sequences using cloning and sequencing methods and identified 43 MHC variants among them. Phylogenetic analyses clustered these variants into two major clades, which may suggest two gene lineages. We found the number of variants within an individual varying between one and seven, indicating that there are at least four gene loci in this species. Selection detection analyses revealed an elevated ratio of nonsynonymous to synonymous substitutions (mean = 1.152 per codon), suggesting balancing selection. Population differentiation analyses revealed that the MHC did not show structuring among the river basins, and there were some shared variants among them. This may be a result of possible gene flow and/or similar selection pressures among populations. These findings provide background knowledge to identify potential MHC markers, which could be used for selecting genetically variable individuals for future disease associations. All MHC class I exon 3 sequences reported in this paper were submitted to the GenBank database with following accession numbers: HQ008785-HQ008789, HQ008791-HQ008798, HQ008808-HQ008815, HQ008824, HQ008826-HQ008830, HQ008835, HQ008839, HQ008842-HQ008850, and JX023536-JX023540.
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