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Yan J, Song C, Liang J, La Y, Lai J, Pan R, Huang Z, Li B, Zhang P. Moderate Genetic Diversity of MHC Genes in an Isolated Small Population of Black-and-White Snub-Nosed Monkeys ( Rhinopithecus bieti). Animals (Basel) 2024; 14:2276. [PMID: 39123802 PMCID: PMC11310952 DOI: 10.3390/ani14152276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 08/01/2024] [Accepted: 08/01/2024] [Indexed: 08/12/2024] Open
Abstract
Genetic diversity is an essential indicator that echoes the natural selection and environmental adaptation of a species. Isolated small populations are vulnerable to genetic drift, inbreeding, and limited gene flow; thus, assessing their genetic diversity is critical in conservation. In this study, we studied the genetic diversity of black-and-white snub-nosed monkeys (Rhinopithecus bieti) using neutral microsatellites and five adaptive major histocompatibility complex (MHC) genes. Two DQA1 alleles, two DQB1 alleles, two DRB1 alleles, two DRB5 alleles, and three DPB1 alleles were isolated from a population. The results indicate that neutral microsatellites demonstrate a high degree of heterozygosity and polymorphism, while adaptive MHC genes display a high degree of heterozygosity and moderate polymorphism. The results also show that balancing selection has prominently influenced the MHC diversity of the species during evolution: (1) significant positive selection is identified at several amino acid sites (primarily at and near antigen-binding sites) of the DRB1, DRB5, and DQB1 genes; (2) phylogenetic analyses display the patterns of trans-species evolution for all MHC loci. This study provides valuable genetic diversity insights into black-and-white snub-nosed monkeys, which dwell at the highest altitude and have experienced the harshest environmental selection of all primates globally since the Pleistocene. Such results provide valuable scientific evidence and a reference for making or amending conservation strategies for this endangered primate species.
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Affiliation(s)
- Jibing Yan
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
| | - Chunmei Song
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
| | - Jiaqi Liang
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
| | - Yanni La
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
| | - Jiandong Lai
- Baima Snow Mountain National Nature Reserve Administrative Bureau, Diqing 674500, China;
| | - Ruliang Pan
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
- International Center of Biodiversity and Primat Conservation, Dali University, Dali 671003, China
- School of Human Sciences, The University of Western Australia, Perth, WA 6009, Australia
| | - Zhipang Huang
- Institute of Eastern-Himalaya Biodiversity Research, Dali University, Dali 671003, China;
| | - Baoguo Li
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
- Shaanxi Institute of Zoology, Xi’an 710032, China
- College of Life Science, Yanan University, Yanan 710032, China
| | - Pei Zhang
- Shaanxi Key Laboratory of Animal Conservation, College of Life Sciences, Northwest University, Xi’an 710069, China; (J.Y.); (C.S.); (J.L.); (Y.L.); (R.P.)
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Fu M. Evolutionary analysis of major histocompatibility complex variants in chytrid-resistant and susceptible amphibians. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2024; 118:105544. [PMID: 38216106 DOI: 10.1016/j.meegid.2023.105544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/09/2023] [Accepted: 12/17/2023] [Indexed: 01/14/2024]
Abstract
An amphibian emerging infectious disease (EID), chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), originated in Asia but primarily led to declines and extinctions in amphibian populations outside of Asia. Host major histocompatibility complex (MHC) molecules exhibit high polymorphism, and the evolution of MHC can be influenced by recombination and pathogens. Previous studies have indicated that host MHC class II is associated with Bd resistance. In this study, I conducted recombination and selection tests on functional MHC IIß1 alleles from an Asian Bd-resistant anuran species (Bufo gargarizans) and an Australasian Bd-susceptible species (Litoria caerulea). Recombination at the same site was identified in both species, supporting the hypothesis that recombination contributes to MHC IIß1 diversity in amphibians. Positive selection was observed in MHC IIß1 alleles in both species. In L. caerulea, at least four amino acid sites were identified under significant positive selection in the MHC IIß1, whereas these sites were either negatively selected or conserved in B. gargarizans. This suggests these sites might be selected for Bd resistance. Hydrophobicity was detected in certain amino acid sites relating to Bd resistance, suggesting this physicochemical property may be a factor selected to counteract Bd infection. These findings of this study provide an evolutionary basis for understanding how amphibian MHC IIß1 may undergo selection in response to chytrid infection.
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Affiliation(s)
- Minjie Fu
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea; Research Institute of Basic Sciences, Seoul National University, Seoul 08826, Republic of Korea.
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Lau Q, Igawa T, Kosch TA, Dharmayanthi AB, Berger L, Skerratt LF, Satta Y. Conserved Evolution of MHC Supertypes among Japanese Frogs Suggests Selection for Bd Resistance. Animals (Basel) 2023; 13:2121. [PMID: 37443920 DOI: 10.3390/ani13132121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/16/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
The chytrid fungus Batrachochytrium dendrobatidis (Bd) is a major threat to amphibians, yet there are no reports of major disease impacts in East Asian frogs. Genetic variation of the major histocompatibility complex (MHC) has been associated with resistance to Bd in frogs from East Asia and worldwide. Using transcriptomic data collated from 11 Japanese frog species (one individual per species), we isolated MHC class I and IIb sequences and validated using molecular cloning. We then compared MHC from Japanese frogs and other species worldwide, with varying Bd susceptibility. Supertyping analysis, which groups MHC alleles based on physicochemical properties of peptide binding sites, identified that all examined East Asian frogs contained at least one MHC-IIb allele belonging to supertype ST-1. This indicates that, despite the large divergence times between some Japanese frogs (up to 145 million years), particular functional properties in the peptide binding sites of MHC-II are conserved among East Asian frogs. Furthermore, preliminary analysis using NetMHCIIpan-4.0, which predicts potential Bd-peptide binding ability, suggests that MHC-IIb ST-1 and ST-2 have higher overall peptide binding ability than other supertypes, irrespective of whether the peptides are derived from Bd, other fungi, or bacteria. Our findings suggest that MHC-IIb among East Asian frogs may have co-evolved under the same selective pressure. Given that Bd originated in this region, it may be a major driver of MHC evolution in East Asian frogs.
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Affiliation(s)
- Quintin Lau
- Research Center for Integrative Evolutionary Science, Sokendai (The Graduate University for Advanced Studies), Hayama 240-0115, Japan
| | - Takeshi Igawa
- Amphibian Research Center, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Tiffany A Kosch
- One Health Research Group, Faculty of Science, University of Melbourne, Parkville 3010, Australia
| | - Anik B Dharmayanthi
- Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN), Bogor 16911, Indonesia
| | - Lee Berger
- One Health Research Group, Faculty of Science, University of Melbourne, Parkville 3010, Australia
| | - Lee F Skerratt
- One Health Research Group, Faculty of Science, University of Melbourne, Parkville 3010, Australia
| | - Yoko Satta
- Research Center for Integrative Evolutionary Science, Sokendai (The Graduate University for Advanced Studies), Hayama 240-0115, Japan
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Winternitz J, Chakarov N, Rinaud T, Ottensmann M, Krüger O. High functional allelic diversity and copy number in both MHC classes in the common buzzard. BMC Ecol Evol 2023; 23:24. [PMID: 37355591 PMCID: PMC10290333 DOI: 10.1186/s12862-023-02135-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 06/12/2023] [Indexed: 06/26/2023] Open
Abstract
BACKGROUND The major histocompatibility complex (MHC), which encodes molecules that recognize various pathogens and parasites and initiates the adaptive immune response in vertebrates, is renowned for its exceptional polymorphism and is a model of adaptive gene evolution. In birds, the number of MHC genes and sequence diversity varies greatly among taxa, believed due to evolutionary history and differential selection pressures. Earlier characterization studies and recent comparative studies suggest that non-passerine species have relatively few MHC gene copies compared to passerines. Additionally, comparative studies that have looked at partial MHC sequences have speculated that non-passerines have opposite patterns of selection on MHC class I (MHC-I) and class II (MHC-II) loci than passerines: namely, greater sequence diversity and signals of selection on MHC-II than MHC-I. However, new sequencing technology is revealing much greater MHC variation than previously expected while also facilitating full sequence variant detection directly from genomic data. Our study aims to take advantage of high-throughput sequencing methods to fully characterize both classes and domains of MHC of a non-passerine bird of prey, the common buzzard (Buteo buteo), to test predictions of MHC variation and differential selection on MHC classes. RESULTS Using genetic, genomic, and transcriptomic high-throughput sequencing data, we established common buzzards have at least three loci that produce functional alleles at both MHC classes. In total, we characterize 91 alleles from 113 common buzzard chicks for MHC-I exon 3 and 41 alleles from 125 chicks for MHC-IIB exon 2. Among these alleles, we found greater sequence polymorphism and stronger diversifying selection at MHC-IIB exon 2 than MHC-I exon 3, suggesting differential selection pressures on MHC classes. However, upon further investigation of the entire peptide-binding groove by including genomic data from MHC-I exon 2 and MHC-IIA exon 2, this turned out to be false. MHC-I exon 2 was as polymorphic as MHC-IIB exon 2 and MHC-IIA exon 2 was essentially invariant. Thus, comparisons between MHC-I and MHC-II that included both domains of the peptide-binding groove showed no differences in polymorphism nor diversifying selection between the classes. Nevertheless, selection analysis indicates balancing selection has been acting on common buzzard MHC and phylogenetic inference revealed that trans-species polymorphism is present between common buzzards and species separated for over 33 million years for class I and class II. CONCLUSIONS We characterize and confirm the functionality of unexpectedly high copy number and allelic diversity in both MHC classes of a bird of prey. While balancing selection is acting on both classes, there is no evidence of differential selection pressure on MHC classes in common buzzards and this result may hold more generally once more data for understudied MHC exons becomes available.
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Affiliation(s)
- Jamie Winternitz
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Nayden Chakarov
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Tony Rinaud
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Meinolf Ottensmann
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Oliver Krüger
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
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Expression Changes of MHC and Other Immune Genes in Frog Skin during Ontogeny. Animals (Basel) 2020; 10:ani10010091. [PMID: 31935873 PMCID: PMC7022564 DOI: 10.3390/ani10010091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/30/2019] [Accepted: 12/31/2019] [Indexed: 01/03/2023] Open
Abstract
Simple Summary Tadpoles undergo many changes in physiology and immunology until metamorphosis into adult frogs. Major histocompatibility complex (MHC) molecules are an important part of vertebrate adaptive immunity, and our study measured the expression of two MHC genes (MHC class I and II) in skin during six tadpole stages of the Montane Brown frog (Rana ornativentris). First, using a qPCR method, we found that both MHC class I and II expression significantly increased between stage 24/25 (‘early’) and stage 28 (‘mid’) tadpole skin. Then, we conducted next-generation sequencing for ‘early’, ‘mid’ and ‘late’ stage tadpole skin mRNA of both R. ornativentris and a model species, Xenopus tropicalis, and confirmed that MHC expression increased from the ‘mid’ stage. We also performed further analyses of transcriptome data and found that several immune-related gene ontology terms were upregulated from the ‘mid’ tadpole stage. Our findings probably support that both MHC class I and II have a functional role during tadpole development. Abstract Anuran amphibians undergo major physiological and immunological changes following metamorphosis. Genes of the major histocompatibility complex (MHC) code for receptors important for vertebrate adaptive immunity. We used qPCR to measure skin MHC expression in six different ontological stages of Rana ornativentris (n = 10 per stage); normalized MHC class I and II expression at the mRNA level was significantly higher in stage 28 (mid-larval) compared to stages 24/25 (early-larval) tadpoles. Subsequent transcriptomic analyses of three tadpole (early-, mid-, and late-larval) stages of R. ornativentris and model species Xenopus tropicalis focused on mRNA expression of immune-related genes in the skin. Normalized expression of most MHC class I and II transcripts in both species were significantly higher in mid- and late-larval stages compared to early-larval stage. In addition, gene ontology (GO) analyses of differentially expressed transcripts revealed several immune-related GO terms that were significantly upregulated from the mid-larval stage. Our study provides evidence that both MHC class I and II is expressed during development in both R. ornativentris and X. tropicalis.
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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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Lau Q, Igawa T, Kosch TA, Satta Y. Selective constraint acting on TLR2 and TLR4 genes of Japanese Rana frogs. PeerJ 2018; 6:e4842. [PMID: 29844986 PMCID: PMC5971840 DOI: 10.7717/peerj.4842] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/06/2018] [Indexed: 12/22/2022] Open
Abstract
Toll-like receptors (TLRs) are an important component of innate immunity, the first line of pathogen defence. One of the major roles of TLRs includes recognition of pathogen-associated molecular patterns. Amphibians are currently facing population declines and even extinction due to chytridiomycosis caused by the Batrachochytrium dendrobatidis (Bd) fungus. Evidence from other vertebrates shows that TLR2 and TLR4 are involved in innate immunity against various fungi. Such genes therefore may play a functional role in amphibian-chytridiomycosis dynamics. Frogs from East Asia appear to be tolerant to Bd, so we examined the genetic diversity that underlies TLR2 and TLR4 from three Japanese Ranidae frog species, Rana japonica, R. ornativentris and R. tagoi tagoi (n = 5 per species). We isolated 27 TLR2 and 20 TLR4 alleles and found that these genes are evolutionarily conserved, with overall evidence supporting purifying selection. In contrast, site-by-site analysis of selection identified several specific codon sites under positive selection, some of which were located in the variable leucine rich repeat domains. In addition, preliminary expression levels of TLR2 and TLR4 from transcriptome data showed overall low expression. Although it remains unclear whether infectious pathogens are a selective force acting on TLRs of Japanese frogs, our results support that certain sites in TLRs of these species may have experienced pathogen-mediated selection.
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Affiliation(s)
- Quintin Lau
- Department of Evolutionary Studies of Biosystems, Sokendai (Graduate University for Advanced Studies), Hayama, Kanagawa, Japan
| | - Takeshi Igawa
- Amphibian Research Center, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Tiffany A Kosch
- One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University of North Queensland, Townsville, Queensland, Australia
| | - Yoko Satta
- Department of Evolutionary Studies of Biosystems, Sokendai (Graduate University for Advanced Studies), Hayama, Kanagawa, Japan
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Genetic variation and selection of MHC class I loci differ in two congeneric frogs. Genetica 2018; 146:125-136. [PMID: 29450668 DOI: 10.1007/s10709-018-0016-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 02/09/2018] [Indexed: 10/18/2022]
Abstract
Major histocompatibility complex (MHC) genes encode proteins in the acquired immune response pathway that often show distinctive selection-driven patterns in wild vertebrate populations. We examined genetic variation and signatures of selection in the MHC class I alpha 1 (A1)- and alpha 2 (A2)-domain encoding exons of two frog congeners [Agalychnis callidryas (n = 20) and A. lemur (n = 20)] from a single locality in Panama. We also investigated how historical demographic processes may have impacted MHC genetic diversity by analyzing a neutral mitochondrial marker. We found that both MHC domains were highly variable in both species, with both species likely expressing three loci. Our analyses revealed different signatures of selection between the two species, most notably that the A. callidryas A2 domain had experienced positive selection while the A2 domain of A. lemur had not. Diversifying selection acted on the same number of A1 and A2 allelic lineages, but on a higher percentage of A1 sites compared to A2 sites. Neutrality tests of mitochondrial haplotypes predominately indicated that the two species were at genetic equilibrium when the samples were collected. In addition, two historical tests of demography indicated both species have had relatively stable population sizes over the past 100,000 years; thus large population size changes are unlikely to have greatly influenced MHC diversity in either species during this time period. In conclusion, our results suggest that the impact of selection on MHC diversity varied between these two closely related species, likely due to a combination of distinct ecological conditions and past pathogenic pressures.
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Lau Q, Igawa T, Minei R, Kosch TA, Satta Y. Transcriptome analyses of immune tissues from three Japanese frogs (genus Rana ) reveals their utility in characterizing major histocompatibility complex class II. BMC Genomics 2017; 18:994. [PMID: 29281968 PMCID: PMC5745589 DOI: 10.1186/s12864-017-4404-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 12/19/2017] [Indexed: 01/05/2023] Open
Abstract
Background In Japan and East Asia, endemic frogs appear to be tolerant or not susceptible to chytridiomycosis, a deadly amphibian disease caused by the chytrid fungus Batrachochytridium dendrobatidis (Bd). Japanese frogs may have evolved mechanisms of immune resistance to pathogens such as Bd. This study characterizes immune genes expressed in various tissues of healthy Japanese Rana frogs. Results We generated transcriptome data sets of skin, spleen and blood from three adult Japanese Ranidae frogs (Japanese brown frog Rana japonica, the montane brown frog Rana ornativentris, and Tago’s brown frog Rana tagoi tagoi) as well as whole body of R. japonica and R. ornativentris tadpoles. From this, we identified tissue- and stage-specific differentially expressed genes; in particular, the spleen was most enriched for immune-related genes. A specific immune gene, major histocompatibility complex class IIB (MHC-IIB), was further characterized due to its role in pathogen recognition. We identified a total of 33 MHC-IIB variants from the three focal species (n = 7 individuals each), which displayed evolutionary signatures related to increased MHC variation, including balancing selection. Our supertyping analyses of MHC-IIB variants from Japanese frogs and previously studied frog species identified potential physiochemical properties of MHC-II that may be important for recognizing and binding chytrid-related antigens. Conclusions This is one of the first studies to generate transcriptomic resources for Japanese frogs, and contributes to further understanding the immunogenetic factors associated with resistance to infectious diseases in amphibians such as chytridiomycosis. Notably, MHC-IIB supertyping analyses identified unique functional properties of specific MHC-IIB alleles that may partially contribute to Bd resistance, and such properties provide a springboard for future experimental validation. Electronic supplementary material The online version of this article (10.1186/s12864-017-4404-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Quintin Lau
- Department of Evolutionary Studies of Biosystems, Sokendai, The Graduate University for Advanced Studies, Kamiyamaguchi 1560-35, Hayama, Kanagawa, 240-0193, Japan.
| | - Takeshi Igawa
- Amphibian Research Center, Hiroshima University, 1-3-1, Higashi-Hiroshima, Hiroshima, 739-8526, Japan
| | - Ryuhei Minei
- Department of Bioscience, Nagahama Institute of Bio-Science and Technology, Tamura-cho 1266, Nagahama, Shiga, 526-0829, Japan
| | - Tiffany A Kosch
- One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, 4811, Australia
| | - Yoko Satta
- Department of Evolutionary Studies of Biosystems, Sokendai, The Graduate University for Advanced Studies, Kamiyamaguchi 1560-35, Hayama, Kanagawa, 240-0193, Japan
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Major histocompatibility complex variation and the evolution of resistance to amphibian chytridiomycosis. Immunogenetics 2017; 69:529-536. [PMID: 28695290 DOI: 10.1007/s00251-017-1008-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 05/29/2017] [Indexed: 01/06/2023]
Abstract
Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has been implicated in population declines and species extinctions of amphibians around the world. Susceptibility to the disease varies both within and among species, most likely attributable to heritable immunogenetic variation. Analyses of transcriptional expression in hosts following their infection by Bd reveal complex responses. Species resistant to Bd generally show evidence of stronger innate and adaptive immune system responses. Major histocompatibility complex (MHC) class I and class II genes of some susceptible species are up-regulated following host infection by Bd, but resistant species show no comparable changes in transcriptional expression. Bd-resistant species share similar pocket conformations within the MHC-II antigen-binding groove. Among susceptible species, survivors of epizootics bear alleles encoding these conformations. Individuals with homozygous resistance alleles appear to benefit by enhanced resistance, especially in environmental conditions that promote pathogen virulence. Subjects that are repeatedly infected and subsequently cleared of Bd can develop an acquired immune response to the pathogen. Strong directional selection for MHC alleles that encode resistance to Bd may deplete genetic variation necessary to respond to other pathogens. Resistance to chytridiomycosis incurs life-history costs that require further study.
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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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