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Wang X, Heckel G. Genome-wide relaxation of selection and the evolution of the island syndrome in Orkney voles. Genome Res 2024; 34:851-862. [PMID: 38955466 PMCID: PMC11293545 DOI: 10.1101/gr.278487.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 05/14/2024] [Indexed: 07/04/2024]
Abstract
Island populations often experience different ecological and demographic conditions than their counterparts on the continent, resulting in divergent evolutionary forces affecting their genomes. Random genetic drift and selection both may leave their imprints on island populations, although the relative impact depends strongly on the specific conditions. Here we address their contributions to the island syndrome in a rodent with an unusually clear history of isolation. Common voles (Microtus arvalis) were introduced by humans on the Orkney archipelago north of Scotland >5000 years ago and rapidly evolved to exceptionally large size. Our analyses show that the genomes of Orkney voles were dominated by genetic drift, with extremely low diversity, variable Tajima's D, and very high divergence from continental conspecifics. Increased d N/d S ratios over a wide range of genes in Orkney voles indicated genome-wide relaxation of purifying selection. We found evidence of hard sweeps on key genes of the lipid metabolism pathway only in continental voles. The marked increase of body size in Orkney-a typical phenomenon of the island syndrome-may thus be associated to the relaxation of positive selection on genes related to this pathway. On the other hand, a hard sweep on immune genes of Orkney voles likely reflects the divergent ecological conditions and possibly the history of human introduction. The long-term isolated Orkney voles show that adaptive changes may still impact the evolutionary trajectories of such populations despite the pervasive consequences of genetic drift at the genome level.
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Affiliation(s)
- Xuejing Wang
- Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Gerald Heckel
- Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland;
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
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2
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Infection with a Recently Discovered Gammaherpesvirus Variant in European Badgers, Meles meles, is Associated with Higher Relative Viral Loads in Blood. Pathogens 2022; 11:pathogens11101154. [PMID: 36297210 PMCID: PMC9606972 DOI: 10.3390/pathogens11101154] [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: 08/29/2022] [Revised: 09/29/2022] [Accepted: 10/03/2022] [Indexed: 11/30/2022] Open
Abstract
Herpesviruses are ubiquitous pathogens infecting most animals. Although host immunity continually coevolves to combat virulence, viral variants with enhanced transmissibility or virulence occasionally emerge, resulting in disease burdens in host populations. Mustelid gammaherpesvirus 1 (MusGHV-1) is the only herpesvirus species identified thus far in European badgers, Meles meles. No MusGHV-1 associated pathomorbidity has been reported, but reactivation of MusGHV-1 in genital tracts is linked to impaired female reproductive success. An analysis of a short sequence from the highly conserved DNA polymerase (DNApol) gene previously identified two variants in a single host population. Here we compared genetic variance in blood samples from 66 known individuals of this same free-ranging badger population using a partial sequence comprising 2874 nucleotides of the DNApol gene, among which we identified 15 nucleotide differences resulting in 5 amino acid differences. Prevalence was 86% (59/66) for the common and 17% (11/66) for the novel variant, with 6% (4/66) of badgers presenting with coinfection. MusGHV-1 variants were distributed unevenly across the population, with individuals infected with the novel genotype clustered in 3 of 25 contiguous social groups. Individuals infected with the novel variant had significantly higher MusGHV-1 viral loads in their blood (p = 0.002) after adjusting for age (juveniles > adults, p < 0.001) and season (summer > spring and autumn, p = 0.005; mixed-effect linear regression), likely indicating higher virulence of the novel variant. Further genome-wide analyses of MusGHV-1 host resistance genes and host phenotypic variations are required to clarify the drivers and sequelae of this new MusGHV-1 variant.
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3
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Scherman K, Råberg L, Westerdahl H. Borrelia Infection in Bank Voles Myodes glareolus Is Associated With Specific DQB Haplotypes Which Affect Allelic Divergence Within Individuals. Front Immunol 2021; 12:703025. [PMID: 34381454 PMCID: PMC8350566 DOI: 10.3389/fimmu.2021.703025] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/01/2021] [Indexed: 11/17/2022] Open
Abstract
The high polymorphism of Major Histocompatibility Complex (MHC) genes is generally considered to be a result of pathogen-mediated balancing selection. Such selection may operate in the form of heterozygote advantage, and/or through specific MHC allele–pathogen interactions. Specific MHC allele–pathogen interactions may promote polymorphism via negative frequency-dependent selection (NFDS), or selection that varies in time and/or space because of variability in the composition of the pathogen community (fluctuating selection; FS). In addition, divergent allele advantage (DAA) may act on top of these forms of balancing selection, explaining the high sequence divergence between MHC alleles. DAA has primarily been thought of as an extension of heterozygote advantage. However, DAA could also work in concert with NFDS though this is yet to be tested explicitly. To evaluate the importance of DAA in pathogen-mediated balancing selection, we surveyed allelic polymorphism of MHC class II DQB genes in wild bank voles (Myodes glareolus) and tested for associations between DQB haplotypes and infection by Borrelia afzelii, a tick-transmitted bacterium causing Lyme disease in humans. We found two significant associations between DQB haplotypes and infection status: one haplotype was associated with lower risk of infection (resistance), while another was associated with higher risk of infection (susceptibility). Interestingly, allelic divergence within individuals was higher for voles with the resistance haplotype compared to other voles. In contrast, allelic divergence was lower for voles with the susceptibility haplotype than other voles. The pattern of higher allelic divergence in individuals with the resistance haplotype is consistent with NFDS favouring divergent alleles in a natural population, hence selection where DAA works in concert with NFDS.
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Affiliation(s)
- Kristin Scherman
- Molecular Ecology and Evolution Lab, Department of Biology, Lund University, Lund, Sweden
| | - Lars Råberg
- Functional Zoology, Department of Biology, Lund University, Lund, Sweden
| | - Helena Westerdahl
- Molecular Ecology and Evolution Lab, Department of Biology, Lund University, Lund, Sweden
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4
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Quéméré E, Hessenauer P, Galan M, Fernandez M, Merlet J, Chaval Y, Morellet N, Verheyden H, Gilot-Fromont E, Charbonnel N. Pathogen-mediated selection favours the maintenance of innate immunity gene polymorphism in a widespread wild ungulate. J Evol Biol 2021; 34:1156-1166. [PMID: 34062025 DOI: 10.1111/jeb.13876] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 05/07/2021] [Accepted: 05/15/2021] [Indexed: 12/11/2022]
Abstract
Toll-like receptors (TLR) play a central role in recognition and host frontline defence against a wide range of pathogens. A number of recent studies have shown that TLR genes (Tlrs) often exhibit large polymorphism in natural populations. Yet, there is little knowledge on how this polymorphism is maintained and how it influences disease susceptibility in the wild. In previous work, we showed that some Tlrs exhibit similarly high levels of genetic diversity as genes of the Major Histocompatibility Complex (MHC), and signatures of contemporary balancing selection in roe deer (Capreolus capreolus), the most abundant cervid species in Europe. Here, we investigated the evolutionary mechanisms by which pathogen-mediated selection could shape this innate immunity genetic diversity by examining the relationships between Tlr (Tlr2, Tlr4 and Tlr5) genotypes (heterozygosity status and presence of specific alleles) and infections with Toxoplasma and Chlamydia, two widespread intracellular pathogens known to cause reproductive failure in ungulates. We showed that Toxoplasma and Chlamydia exposures vary significantly across years and landscape features with few co-infection events detected and that the two pathogens exert antagonistic selection on Tlr2 polymorphism. By contrast, we found limited support for Tlr heterozygote advantage. Our study confirmed the importance of looking beyond Mhc genes in wildlife immunogenetic studies. It also emphasized the necessity to consider multiple pathogen challenges and their spatiotemporal variation to improve our understanding of vertebrate defence evolution against pathogens.
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Affiliation(s)
- Erwan Quéméré
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France.,ESE, Ecology and Ecosystems Health, INRAE, Rennes, France
| | | | - Maxime Galan
- Département de Foresterie, Université Laval, Quebec, QC, Canada
| | - Marie Fernandez
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France
| | - Joël Merlet
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France
| | - Yannick Chaval
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France
| | - Nicolas Morellet
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France
| | - Hélène Verheyden
- Université de Toulouse, INRAE, CEFS, Castanet-Tolosan, France.,LTSER ZA PYRénées GARonne, Auzeville-Tolosane, France
| | - Emmanuelle Gilot-Fromont
- Université de Lyon, Université Lyon 1, UMR CNRS 5558, Villeurbanne, France.,Université de Lyon, VetAgro Sup, Marcy l'Etoile, France
| | - Nathalie Charbonnel
- CBGP, INRAE, CIRAD, IRD, Institut Agro, Univ Montpellier, Montpellier, France
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5
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Zhu Y, Grueber C, Li Y, He M, Hu L, He K, Liu H, Zhang H, Wu H. MHC-associated Baylisascaris schroederi load informs the giant panda reintroduction program. INTERNATIONAL JOURNAL FOR PARASITOLOGY-PARASITES AND WILDLIFE 2020; 12:113-120. [PMID: 32528846 PMCID: PMC7283101 DOI: 10.1016/j.ijppaw.2020.05.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/24/2020] [Accepted: 05/24/2020] [Indexed: 12/27/2022]
Abstract
Reintroducing captive giant pandas (Ailuropoda melanoleuca) to the wild is the ultimate goal of their ex situ conservation. Choosing higher fitness candidates to train prior to release is the first step in the giant panda reintroduction program. Disease resistance is one important index of individual fitness and presumed to be related to variation at major histocompatibility complex genes (MHC). Here, we used seven polymorphic functional MHC genes (Aime-C, Aime-I, Aime-L, Aime-DQA1, Aime-DQA2, Aime-DQB1 and Aime-DRB3) and estimate their relationship with Baylisascaris schroederi (Ascarididae) infection in giant panda. We found that DQA1 heterozygous pandas were less frequently infected than homozygotes. The presence of one MHC genotype and one MHC allele were also associated with B. schroederi infection: Aime-C*0203 and Aime-L*08 were both associated with B. schroederi resistance. Our results indicate that both heterozygosity and certain MHC variants are important for panda disease resistance, and should therefore be considered in future reintroduction programs for this species alongside conventional selection criteria (such as physical condition and pedigree-based information). MHC heterozygous pandas were less frequently infected by Baylisascaris schroederi than homozygotes. Presence of Aime-C*0203 and Aime-L*08 are associated with Baylisascaris schroederi resistance. MHC types are important for panda parasite resistance.
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Affiliation(s)
- Ying Zhu
- Sichuan Province Laboratory for Natural Resources Protection and Sustainable Utilization, Sichuan Provincial Academy of Natural Resource Sciences, Chengdu, China.,Faculty of Science, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia
| | - Catherine Grueber
- Faculty of Science, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia
| | - Yudong Li
- Sichuan Province Laboratory for Natural Resources Protection and Sustainable Utilization, Sichuan Provincial Academy of Natural Resource Sciences, Chengdu, China
| | - Ming He
- China Conservation and Research Center for the Giant Panda, Dujiangyan, Sichuan, China
| | - Lan Hu
- China Conservation and Research Center for the Giant Panda, Dujiangyan, Sichuan, China
| | - Ke He
- College of Animal Sciences & Technology, Zhejiang A & F University, Hangzhou, China
| | - Hongyi Liu
- College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Hemin Zhang
- China Conservation and Research Center for the Giant Panda, Dujiangyan, Sichuan, China
| | - Honglin Wu
- China Conservation and Research Center for the Giant Panda, Dujiangyan, Sichuan, China
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6
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Kloch A, Biedrzycka A. Post-glacial phylogeography and variation in innate immunity loci in a sylvatic rodent, bank vole Myodes glareolus. Mamm Biol 2020. [DOI: 10.1007/s42991-020-00016-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
AbstractIn the northern hemisphere, the spatial structure of many taxa has been shaped by migration patterns after the last glaciation, and phylogeography based on mtDNA variation may reflect the post-glacial demography. The mtDNA lineages are expected to differ in their adaptations to local conditions but little is known about the impact of these conditions on functional genetic variation. Here, we answer this question through an analysis of geographic variation and selection patterns in seven innate immunity genes in free-living bank voles Myodes glareolus from 10 localities across species range assigned to different lineages based on mtDNA. We found clear discrepancies between population structure in mtDNA and each of the studied innate immunity genes. There was no uniform pattern of spatial variation at immunity loci, they differed in the levels of polymorphism, and the results of neutrality tests were not consistent over loci. Each locus comprised a few common haplotypes shared between mitochondrial lineages and studied locations, plus numerous haplotypes unique for each studied site. Our results suggest that the diversity of innate immunity genes cannot be explained solely in terms of demographic processes, and that the observed polymorphism may be attributed to local selection. The strength and direction of selection differed between loci, even within the same gene family, which underlines how crucial it is to take a complex approach while studying the selection patterns acting on immune-related genes.
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Portanier E, Garel M, Devillard S, Maillard D, Poissant J, Galan M, Benabed S, Poirel MT, Duhayer J, Itty C, Bourgoin G. Both candidate gene and neutral genetic diversity correlate with parasite resistance in female Mediterranean mouflon. BMC Ecol 2019; 19:12. [PMID: 30836982 PMCID: PMC6402107 DOI: 10.1186/s12898-019-0228-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 02/23/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Parasite infections can have substantial impacts on population dynamics and are accordingly a key challenge for wild population management. Here we studied genetic mechanisms driving parasite resistance in a large herbivore through a comprehensive approach combining measurements of neutral (16 microsatellites) and adaptive (MHC DRB1 exon 2) genetic diversity and two types of gastrointestinal parasites (nematodes and coccidia). RESULTS While accounting for other extrinsic and intrinsic predictors known to impact parasite load, we show that both neutral genetic diversity and DRB1 are associated with resistance to gastrointestinal nematodes. Intermediate levels of multi-locus heterozygosity maximized nematodes resistance, suggesting that both in- and outbreeding depression might occur in the population. DRB1 heterozygosity and specific alleles effects were detected, suggesting the occurrence of heterozygote advantage, rare-allele effects and/or fluctuating selection. On the contrary, no association was detected between genetic diversity and resistance to coccidia, indicating that different parasite classes are impacted by different genetic drivers. CONCLUSIONS This study provides important insights for large herbivores and wild sheep pathogen management, and in particular suggests that factors likely to impact genetic diversity and allelic frequencies, including global changes, are also expected to impact parasite resistance.
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Affiliation(s)
- Elodie Portanier
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Évolutive, 69100 Villeurbanne, France
- Office National de la Chasse et de la Faune Sauvage, Unité Ongulés Sauvages, 5 allée de Bethléem, Z.I. Mayencin, 38610 Gières, France
- Université de Lyon, VetAgro Sup, Campus Vétérinaire de Lyon, 1 Avenue Bourgelat, BP 83, 69280 Marcy l’Etoile, France
| | - Mathieu Garel
- Office National de la Chasse et de la Faune Sauvage, Unité Ongulés Sauvages, 5 allée de Bethléem, Z.I. Mayencin, 38610 Gières, France
| | - Sébastien Devillard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Évolutive, 69100 Villeurbanne, France
| | - Daniel Maillard
- Office National de la Chasse et de la Faune Sauvage, Unité Ongulés Sauvages, 5 allée de Bethléem, Z.I. Mayencin, 38610 Gières, France
| | - Jocelyn Poissant
- Department of Ecosystem and Public Health, University of Calgary, Calgary, Canada
| | - Maxime Galan
- CBGP, INRA, CIRAD, IRD, Montpellier SupAgro, Université de Montpellier, 34980 Montferrier Sur Lez, France
| | - Slimania Benabed
- Université de Lyon, VetAgro Sup, Campus Vétérinaire de Lyon, 1 Avenue Bourgelat, BP 83, 69280 Marcy l’Etoile, France
| | - Marie-Thérèse Poirel
- Université de Lyon, VetAgro Sup, Campus Vétérinaire de Lyon, 1 Avenue Bourgelat, BP 83, 69280 Marcy l’Etoile, France
| | - Jeanne Duhayer
- Office National de la Chasse et de la Faune Sauvage, Unité Ongulés Sauvages, 5 allée de Bethléem, Z.I. Mayencin, 38610 Gières, France
| | - Christian Itty
- Office National de la Chasse et de la Faune Sauvage, Unité Ongulés Sauvages, 5 allée de Bethléem, Z.I. Mayencin, 38610 Gières, France
| | - Gilles Bourgoin
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Évolutive, 69100 Villeurbanne, France
- Université de Lyon, VetAgro Sup, Campus Vétérinaire de Lyon, 1 Avenue Bourgelat, BP 83, 69280 Marcy l’Etoile, France
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8
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Kaesler E, Kappeler PM, Brameier M, Demeler J, Kraus C, Rakotoniaina JH, Hämäläinen AM, Huchard E. Shared evolutionary origin of major histocompatibility complex polymorphism in sympatric lemurs. Mol Ecol 2017; 26:5629-5645. [PMID: 28833696 DOI: 10.1111/mec.14336] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 07/12/2017] [Accepted: 08/05/2017] [Indexed: 12/11/2022]
Abstract
Genes of the major histocompatibility complex (MHC) play a central role in adaptive immune responses of vertebrates. They exhibit remarkable polymorphism, often crossing species boundaries with similar alleles or allelic motifs shared across species. This pattern may reflect parallel parasite-mediated selective pressures, either favouring the long maintenance of ancestral MHC allelic lineages across successive speciation events by balancing selection ("trans-species polymorphism"), or alternatively favouring the independent emergence of functionally similar alleles post-speciation via convergent evolution. Here, we investigate the origins of MHC similarity across several species of dwarf and mouse lemurs (Cheirogaleidae). We examined MHC class II variation in two highly polymorphic loci (DRB, DQB) and evaluated the overlap of gut-parasite communities in four sympatric lemurs. We tested for parasite-MHC associations across species to determine whether similar parasite pressures may select for similar MHC alleles in different species. Next, we integrated our MHC data with those previously obtained from other Cheirogaleidae to investigate the relative contribution of convergent evolution and co-ancestry to shared MHC polymorphism by contrasting patterns of codon usage at functional vs. neutral sites. Our results indicate that parasites shared across species may select for functionally similar MHC alleles, implying that the dynamics of MHC-parasite co-evolution should be envisaged at the community level. We further show that balancing selection maintaining trans-species polymorphism, rather than convergent evolution, is the primary mechanism explaining shared MHC sequence motifs between species that diverged up to 30 million years ago.
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Affiliation(s)
- Eva Kaesler
- Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung, Verhaltensökologie & Soziobiologie, Göttingen, Germany
| | - Peter M Kappeler
- Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung, Verhaltensökologie & Soziobiologie, Göttingen, Germany.,Johann Friedrich Blumenbach Institut für Zoologie & Anthropologie, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Markus Brameier
- Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung, Göttingen, Germany
| | - Janina Demeler
- Institut für Parasitologie und Tropenveterinärmedizin, Berlin, Germany
| | - Cornelia Kraus
- Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung, Verhaltensökologie & Soziobiologie, Göttingen, Germany.,Johann Friedrich Blumenbach Institut für Zoologie & Anthropologie, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Josué H Rakotoniaina
- Johann Friedrich Blumenbach Institut für Zoologie & Anthropologie, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Anni M Hämäläinen
- Johann Friedrich Blumenbach Institut für Zoologie & Anthropologie, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Elise Huchard
- Institute for Evolutionary Biology, Montpellier (ISEM, UMR 5554), CNRS, Université Montpellier, Montpellier Cedex 5, France
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Abstract
Genotype calling plays important roles in population-genomic studies, which have been greatly accelerated by sequencing technologies. To take full advantage of the resultant information, we have developed maximum-likelihood (ML) methods for calling genotypes from high-throughput sequencing data. As the statistical uncertainties associated with sequencing data depend on depths of coverage, we have developed two types of genotype callers. One approach is appropriate for low-coverage sequencing data, and incorporates population-level information on genotype frequencies and error rates pre-estimated by an ML method. Performance evaluation using computer simulations and human data shows that the proposed framework yields less biased estimates of allele frequencies and more accurate genotype calls than current widely used methods. Another type of genotype caller applies to high-coverage sequencing data, requires no prior genotype-frequency estimates, and makes no assumption on the number of alleles at a polymorphic site. Using computer simulations, we determine the depth of coverage necessary to accurately characterize polymorphisms using this second method. We applied the proposed method to high-coverage (mean 18×) sequencing data of 83 clones from a population of Daphnia pulex. The results show that the proposed method enables conservative and reasonably powerful detection of polymorphisms with arbitrary numbers of alleles. We have extended the proposed method to the analysis of genomic data for polyploid organisms, showing that calling accurate polyploid genotypes requires much higher coverage than diploid genotypes.
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10
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Hablützel PI, Grégoir AF, Vanhove MPM, Volckaert FAM, Raeymaekers JAM. Weak link between dispersal and parasite community differentiation or immunogenetic divergence in two sympatric cichlid fishes. Mol Ecol 2016; 25:5451-5466. [PMID: 27596520 DOI: 10.1111/mec.13833] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 02/03/2023]
Abstract
Geographical isolation, habitat variation and trophic specialization have contributed to a large extent to the astonishing diversity of cichlid fishes in the Great East African lakes. Because parasite communities often vary across space and environments, parasites can accompany and potentially enhance cichlid species diversification. However, host dispersal may reduce opportunities for parasite-driven evolution by homogenizing parasite communities and allele frequencies of immunity genes. To test for the relationships between parasite community variation, host dispersal and parasite-induced host evolution, we studied two sympatric cichlid species with contrasting dispersal capacities along the shores of southern Lake Tanganyika. Whereas the philopatric Tropheus moorii evolved into several genetically differentiated colour morphs, Simochromis diagramma is phenotypically rather uniform across its distribution range and shows only weak population structure. Populations of both species were infected with divergent parasite communities and harbour differentiated variant pools of an important set of immune genes, the major histocompatibility complex (MHC). The overall extent of geographical variation of parasites and MHC genes was similar between host species. This indicates that immunogenetic divergence among populations of Lake Tanganyika cichlids can occur even in species that are strongly dispersing. However, because this also includes species that are phenotypically uniform, parasite-induced evolution may not represent a key factor underlying species diversification in this system.
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Affiliation(s)
- P I Hablützel
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Ch. de Bériotstraat 32, B-3000, Leuven, Belgium.
| | - A F Grégoir
- Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. de Bériotstraat 32, B-3000, Leuven, Belgium
| | - M P M Vanhove
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Ch. de Bériotstraat 32, B-3000, Leuven, Belgium.,Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37, Brno, Czech Republic
| | - F A M Volckaert
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Ch. de Bériotstraat 32, B-3000, Leuven, Belgium
| | - J A M Raeymaekers
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Ch. de Bériotstraat 32, B-3000, Leuven, Belgium.,Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, N-7491, Trondheim, Norway
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11
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Seifertová M, Jarkovský J, Šimková A. Does the parasite-mediated selection drive the MHC class IIB diversity in wild populations of European chub (Squalius cephalus)? Parasitol Res 2015; 115:1401-15. [PMID: 26693717 DOI: 10.1007/s00436-015-4874-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 12/07/2015] [Indexed: 11/29/2022]
Abstract
The genes of major histocompatibility complex (MHC) provide an excellent opportunity to study host-parasite relationships because they are expected to evolve in response to parasites and variation in parasite communities. In this study, we investigated the potential role of parasite-mediated selection acting on MHC class IIB (DAB) genes in European chub (Squalius cephalus) natural populations. We found significant differences between populations in metazoan parasites, neutral and adaptive genetic diversities. The analyses based on pairwise data revealed that populations with dissimilar MHC allelic profiles were geographically distant populations with significantly different diversity in microsatellites and a dissimilar composition of parasite communities. The results from the generalized estimating equations method (GEE) on the level of individuals revealed that metazoan parasite load in European chub was influenced by the diversity of DAB alleles as well as by the diversity of neutral genetic markers and host traits reflecting condition and immunocompetence. The multivariate co-inertia analysis showed specific associations between DAB alleles and parasite species. DAB1-like alleles were more involved in associations with ectoparasites, while DAB3-like alleles were positively associated with endoparasites which could suggest potential differences between DAB genes caused by different selection pressure. Our study revealed that parasite-mediated selection is not the only variable affecting MHC diversity in European chub; however, we strongly support the role of neutral processes as the main driver of DAB diversity across populations. In addition, our study contributes to the understanding of the evolution of MHC genes in wild living fish.
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Affiliation(s)
- Mária Seifertová
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137, Brno, Czech Republic.
| | - Jiří Jarkovský
- Institute of Biostatistics and Analyses, Faculty of Medicine and Faculty of Science, Masaryk University, Kamenice 126/3, 625 00, Brno, Czech Republic
| | - Andrea Šimková
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137, Brno, Czech Republic
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Bateson ZW, Whittingham LA, Johnson JA, Dunn PO. Contrasting patterns of selection and drift between two categories of immune genes in prairie-chickens. Mol Ecol 2015; 24:6095-106. [PMID: 26547898 DOI: 10.1111/mec.13459] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 10/31/2015] [Accepted: 11/03/2015] [Indexed: 12/22/2022]
Abstract
Immune-receptor genes of the adaptive immune system, such as the major histocompatibility complex (MHC), are involved in recognizing specific pathogens and are known to have high rates of adaptive evolution, presumably as a consequence of rapid co-evolution between hosts and pathogens. In contrast, many 'mediating' genes of the immune system do not interact directly with specific pathogens and are involved in signalling (e.g. cytokines) or controlling immune cell growth. As a consequence, we might expect stronger selection at immune-receptor than mediating genes, but these two types of genes have not been compared directly in wild populations. Here, we tested the hypothesis that selection differs between MHC (class I and II) and mediating genes by comparing levels of population differentiation across the range of greater prairie-chickens (Tympanuchus cupido). As predicted, there was stronger population differentiation and isolation by distance at immune receptor (MHC) than at either mediating genes or neutral microsatellites, suggesting a stronger role of local adaptation at the MHC. In contrast, mediating genes displayed weaker differentiation between populations than neutral microsatellites, consistent with selection favouring similar alleles across populations for mediating genes. In addition to selection, drift also had a stronger effect on immune receptor (MHC) than mediating genes as indicated by the stronger decline of MHC variation in relation to population size. This is the first study in the wild to show that the effects of selection and drift on immune genes vary across populations depending on their functional role.
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Affiliation(s)
- Zachary W Bateson
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Linda A Whittingham
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Jeff A Johnson
- Department of Biological Sciences, Institute of Applied Sciences, University of North Texas, Denton, TX, USA
| | - Peter O Dunn
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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13
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Vayssier-Taussat M, Kazimirova M, Hubalek Z, Hornok S, Farkas R, Cosson JF, Bonnet S, Vourch G, Gasqui P, Mihalca AD, Plantard O, Silaghi C, Cutler S, Rizzoli A. Emerging horizons for tick-borne pathogens: from the 'one pathogen-one disease' vision to the pathobiome paradigm. Future Microbiol 2015; 10:2033-43. [PMID: 26610021 DOI: 10.2217/fmb.15.114] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ticks, as vectors of several notorious zoonotic pathogens, represent an important and increasing threat for human and animal health in Europe. Recent applications of new technology revealed the complexity of the tick microbiome, which may affect its vectorial capacity. Appreciation of these complex systems is expanding our understanding of tick-borne pathogens, leading us to evolve a more integrated view that embraces the 'pathobiome'; the pathogenic agent integrated within its abiotic and biotic environments. In this review, we will explore how this new vision will revolutionize our understanding of tick-borne diseases. We will discuss the implications in terms of future research approaches that will enable us to efficiently prevent and control the threat posed by ticks.
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Affiliation(s)
| | - Maria Kazimirova
- Institute of Zoology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Zdenek Hubalek
- Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
| | - Sándor Hornok
- Department of Parasitology & Zoology, Faculty of Veterinary Science, Szent István University, Budapest, Hungary
| | - Robert Farkas
- Department of Parasitology & Zoology, Faculty of Veterinary Science, Szent István University, Budapest, Hungary
| | | | - Sarah Bonnet
- INRA, UMR BIPAR, INRA, ANSES, ENVA Maisons-Alfort, France
| | - Gwenaël Vourch
- INRA, UR 346 Epidémiologie Animale, Saint Genès Champanelle, France
| | - Patrick Gasqui
- INRA, UR 346 Epidémiologie Animale, Saint Genès Champanelle, France
| | - Andrei Daniel Mihalca
- University of Agricultural Sciences & Veterinary Medicine Cluj-Napoca, Department of Parasitology & Parasitic Diseases, Cluj-Napoca, Romania
| | | | - Cornelia Silaghi
- National Centre for Vector Entomology, Institute of Parasitology, Vetsuisse-Faculty, University of Zurich, Zürich, Switzerland
| | - Sally Cutler
- University of East London, School of Health, Sport & Bioscience, London, UK
| | - Annapaola Rizzoli
- Fondazione Edmund Mach, Research & Innovation Centre, San Michele all'Adige, Trento, Italy
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14
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Vaumourin E, Vourc'h G, Gasqui P, Vayssier-Taussat M. The importance of multiparasitism: examining the consequences of co-infections for human and animal health. Parasit Vectors 2015; 8:545. [PMID: 26482351 PMCID: PMC4617890 DOI: 10.1186/s13071-015-1167-9] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/14/2015] [Indexed: 11/23/2022] Open
Abstract
Most parasites co-occur with other parasites, although the importance of such multiparasitism has only recently been recognised. Co-infections may result when hosts are independently infected by different parasites at the same time or when interactions among parasite species facilitate co-occurrence. Such interactions can have important repercussions on human or animal health because they can alter host susceptibility, infection duration, transmission risks, and clinical symptoms. These interactions may be synergistic or antagonistic and thus produce diverse effects in infected humans and animals. Interactions among parasites strongly influence parasite dynamics and therefore play a major role in structuring parasite populations (both within and among hosts) as well as host populations. However, several methodological challenges remain when it comes to detecting parasite interactions. The goal of this review is to summarise current knowledge on the causes and consequences of multiparasitism and to discuss the different methods and tools that researchers have developed to study the factors that lead to multiparasitism. It also identifies new research directions to pursue.
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Affiliation(s)
- Elise Vaumourin
- UR346 Animal Epidemiology Research Unit, INRA, Saint Genès Champanelle, France. .,USC BIPAR, INRA-ANSES-ENVA, Maisons-Alfort, France.
| | - Gwenaël Vourc'h
- UR346 Animal Epidemiology Research Unit, INRA, Saint Genès Champanelle, France.
| | - Patrick Gasqui
- UR346 Animal Epidemiology Research Unit, INRA, Saint Genès Champanelle, France.
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15
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Stutz WE, Schmerer M, Coates JL, Bolnick DI. Among-lake reciprocal transplants induce convergent expression of immune genes in threespine stickleback. Mol Ecol 2015; 24:4629-46. [PMID: 26118468 DOI: 10.1111/mec.13295] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/22/2015] [Accepted: 06/24/2015] [Indexed: 12/25/2022]
Abstract
Geographic variation in parasite communities can drive evolutionary divergence in host immune genes. However, biotic and abiotic environmental variation can also induce plastic differences in immune function among populations. At present, there is little information concerning the relative magnitudes of heritable vs. induced immune divergence in natural populations. We examined immune gene expression profiles of threespine stickleback (Gasterosteus aculeatus) from six lakes on Vancouver Island, British Columbia. Parasite community composition differs between lake types (large or small, containing limnetic- or benthic-like stickleback) and between watersheds. We observed corresponding differences in immune gene expression profiles among wild-caught stickleback, using a set of seven immune genes representing distinct branches of the immune system. To evaluate the role of environmental effects on this differentiation, we experimentally transplanted wild-caught fish into cages in their native lake, or into a nearby foreign lake. Transplanted individuals' immune gene expression converged on patterns typical of their destination lake, deviating from their native expression profile. Transplant individuals' source population had a much smaller effect, suggesting relatively weak genetic underpinning of population differences in immunity, as viewed through gene expression. This strong environmental regulation of immune gene expression provides a counterpoint to the large emerging literature documenting microevolution and genetic diversification of immune function. Our findings illustrate the value of studying immunity in natural environmental settings where the immune system has evolved and actively functions.
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Affiliation(s)
- William E Stutz
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
| | - Matthew Schmerer
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
| | - Jessica L Coates
- Department of Biology, Spelman College, 350 Spelman Lane SW, Atlanta, GA, 30314, USA
| | - Daniel I Bolnick
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA.,Howard Hughes Medical Institute, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
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16
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Bichet C, Moodley Y, Penn DJ, Sorci G, Garnier S. Genetic structure in insular and mainland populations of house sparrows (Passer domesticus) and their hemosporidian parasites. Ecol Evol 2015; 5:1639-52. [PMID: 25937907 PMCID: PMC4409412 DOI: 10.1002/ece3.1452] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 02/08/2015] [Indexed: 11/07/2022] Open
Abstract
Small and isolated populations usually exhibit low levels of genetic variability, and thus, they are expected to have a lower capacity to adapt to changes in environmental conditions, such as exposure to pathogens and parasites. Comparing the genetic variability of selectively neutral versus functional loci allows one to assess the evolutionary history of populations and their future evolutionary potential. The genes of the major histocompatibility complex (MHC) control immune recognition of parasites, and their unusually high diversity is genes which is likely driven by parasite-mediated balancing selection. Here, we examined diversity and differentiation of neutral microsatellite loci and functional MHC class I genes in house sparrows (Passer domesticus), living in six insular and six mainland populations, and we aimed to determine whether their diversity or differentiation correlates with the diversity and the prevalence of infection of hemosporidian parasites. We found that island bird populations tended to have lower neutral genetic variability, whereas MHC variability gene was similar between island and mainland populations. Similarly, island populations tended to show greater genetic differentiation than mainland populations, especially at microsatellite markers. The maintenance of MHC genetic diversity and its less marked structure in the island populations could be attributed to balancing-selection. The greater MHC differentiation among populations was negatively correlated with similarity in blood parasites (prevalence and diversity of parasite strains) between populations. Even at low prevalence and small geographical scale, haemosporidian parasites might contribute to structure the variability of immune genes among populations of hosts.
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Affiliation(s)
- Coraline Bichet
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France ; Laboratoire LBBE, UMR CNRS 5558, Université Claude Bernard Lyon 1 bâtiment Mendel, 43 boulevard du 11 novembre 1918, 69622, Villeurbanne Cedex, France
| | - Yoshan Moodley
- Department of Zoology, University of Venda Private Bag X5050, Thohoyandou, 0950, South Africa ; Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria
| | - Dustin J Penn
- Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria
| | - Gabriele Sorci
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France
| | - Stéphane Garnier
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France
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17
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Kuduk K, Babik W, Bellemain E, Valentini A, Zedrosser A, Taberlet P, Kindberg J, Swenson JE, Radwan J. No evidence for the effect of MHC on male mating success in the brown bear. PLoS One 2014; 9:e113414. [PMID: 25470381 PMCID: PMC4254848 DOI: 10.1371/journal.pone.0113414] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 10/23/2014] [Indexed: 11/19/2022] Open
Abstract
Mate choice is thought to contribute to the maintenance of the spectacularly high polymorphism of the Major Histocompatibility Complex (MHC) genes, along with balancing selection from parasites, but the relative contribution of the former mechanism is debated. Here, we investigated the association between male MHC genotype and mating success in the brown bear. We analysed fragments of sequences coding for the peptide-binding region of the highly polymorphic MHC class I and class II DRB genes, while controlling for genome-wide effects using a panel of 18 microsatellite markers. Male mating success did not depend on the number of alleles shared with the female or amino-acid distance between potential mates at either locus. Furthermore, we found no indication of female mating preferences for MHC similarity being contingent on the number of alleles the females carried. Finally, we found no significant association between the number of MHC alleles a male carried and his mating success. Thus, our results provided no support for the role of mate choice in shaping MHC polymorphism in the brown bear.
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Affiliation(s)
- Katarzyna Kuduk
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, 30-387, Kraków, Poland
| | - Wieslaw Babik
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, 30-387, Kraków, Poland
| | - Eva Bellemain
- SPYGEN, Savoie Technolac - Bât. Koala 17, rue du Lac Saint-André - BP 274, 73375, Le Bourget-du-Lac Cedex, France
| | - Alice Valentini
- SPYGEN, Savoie Technolac - Bât. Koala 17, rue du Lac Saint-André - BP 274, 73375, Le Bourget-du-Lac Cedex, France
| | - Andreas Zedrosser
- Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432, Ås, Norway
- Institute for Wildlife Biology and Game Management, University of Natural Resources and Life Sciences, AT-1180, Vienna, Austria
| | - Pierre Taberlet
- CNRS, LECA, F-38000, Grenoble, France
- Université Grenoble Alpes, LECA, F-38000, Grenoble, France
| | - Jonas Kindberg
- Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden
| | - Jon E. Swenson
- Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432, Ås, Norway
- Norwegian Institute for Nature Research, NO-7485, Trondheim, Norway
| | - Jacek Radwan
- Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, 30-387, Kraków, Poland
- * E-mail:
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18
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Ruiz-López MJ, Monello RJ, Schuttler SG, Lance SL, Gompper ME, Eggert LS. Major Histocompatibility Complex, demographic, and environmental predictors of antibody presence in a free-ranging mammal. INFECTION GENETICS AND EVOLUTION 2014; 28:317-27. [PMID: 25446941 DOI: 10.1016/j.meegid.2014.10.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/30/2014] [Accepted: 10/16/2014] [Indexed: 10/24/2022]
Abstract
Major Histocompatibility Complex (MHC) variability plays a key role in pathogen resistance, but its relative importance compared to environmental and demographic factors that also influence resistance is unknown. We analyzed the MHC II DRB exon 2 for 165 raccoons (Procyon lotor) in Missouri (USA). For each animal we also determined the presence of immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to two highly virulent pathogens, canine distemper virus (CDV) and parvovirus. We investigated the role of MHC polymorphism and other demographic and environmental factors previously associated with predicting seroconversion. In addition, using an experimental approach, we studied the relative importance of resource availability and contact rates. We found important associations between IgG antibody presence and several MHC alleles and supertypes but not between IgM antibody presence and MHC. No effect of individual MHC diversity was found. For CDV, supertype S8, one allele within S8 (Prlo-DRB(∗)222), and a second allele (Prlo-DRB(∗)204) were positively associated with being IgG+, while supertype S4 and one allele within the supertype (Prlo-DRB(∗)210) were negatively associated with being IgG+. Age, year, and increased food availability were also positively associated with being IgG+, but allele Prlo-DRB(∗)222 was a stronger predictor. For parvovirus, only one MHC allele was negatively associated with being IgG+ and age and site were stronger predictors of seroconversion. Our results show that negative-frequency dependent selection is likely acting on the raccoon MHC and that while the role of MHC in relation to other factors depends on the pathogen of interest, it may be one of the most important factors predicting successful immune response.
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Affiliation(s)
- María José Ruiz-López
- Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, MO 65211, USA.
| | - Ryan J Monello
- Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Stephanie G Schuttler
- Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, MO 65211, USA; Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Stacey L Lance
- Savannah River Ecology Laboratory, P O Drawer E, Aiken, SC 29802, USA
| | - Matthew E Gompper
- Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Lori S Eggert
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
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19
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Herdegen M, Babik W, Radwan J. Selective pressures on MHC class II genes in the guppy (Poecilia reticulata) as inferred by hierarchical analysis of population structure. J Evol Biol 2014; 27:2347-59. [PMID: 25244157 DOI: 10.1111/jeb.12476] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 08/08/2014] [Accepted: 08/11/2014] [Indexed: 11/29/2022]
Abstract
Genes of the major histocompatibility complex, which are the most polymorphic of all vertebrate genes, are a pre-eminent system for the study of selective pressures that arise from host-pathogen interactions. Balancing selection capable of maintaining high polymorphism should lead to the homogenization of MHC allele frequencies among populations, but there is some evidence to suggest that diversifying selection also operates on the MHC. However, the pattern of population structure observed at MHC loci is likely to depend on the spatial and/or temporal scale examined. Here, we investigated selection acting on MHC genes at different geographic scales using Venezuelan guppy populations inhabiting four regions. We found a significant correlation between MHC and microsatellite allelic richness across populations, which suggests the role of genetic drift in shaping MHC diversity. However, compared to microsatellites, more MHC variation was explained by differences between populations within larger geographic regions and less by the differences between the regions. Furthermore, among proximate populations, variation in MHC allele frequencies was significantly higher compared to microsatellites, indicating that selection acting on MHC may increase population structure at small spatial scales. However, in populations that have significantly diverged at neutral markers, the population-genetic signature of diversifying selection may be eradicated in the long term by that of balancing selection, which acts to preserve rare alleles and thus maintain a common pool of MHC alleles.
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Affiliation(s)
- M Herdegen
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
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20
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Cutrera AP, Zenuto RR, Lacey EA. Interpopulation differences in parasite load and variable selective pressures on MHC genes inCtenomys talarum. J Mammal 2014. [DOI: 10.1644/13-mamm-a-120] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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21
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Role of selection versus neutral processes determining genetic variation in a small mammal along a climatic gradient in southern Africa. Evol Ecol 2014. [DOI: 10.1007/s10682-014-9731-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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22
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Immunogenetic factors affecting susceptibility of humans and rodents to hantaviruses and the clinical course of hantaviral disease in humans. Viruses 2014; 6:2214-41. [PMID: 24859344 PMCID: PMC4036553 DOI: 10.3390/v6052214] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 03/17/2014] [Accepted: 05/16/2014] [Indexed: 12/11/2022] Open
Abstract
We reviewed the associations of immunity-related genes with susceptibility of humans and rodents to hantaviruses, and with severity of hantaviral diseases in humans. Several class I and class II HLA haplotypes were linked with severe or benign hantavirus infections, and these haplotypes varied among localities and hantaviruses. The polymorphism of other immunity-related genes including the C4A gene and a high-producing genotype of TNF gene associated with severe PUUV infection. Additional genes that may contribute to disease or to PUUV infection severity include non-carriage of the interleukin-1 receptor antagonist (IL-1RA) allele 2 and IL-1β (-511) allele 2, polymorphisms of plasminogen activator inhibitor (PAI-1) and platelet GP1a. In addition, immunogenetic studies have been conducted to identify mechanisms that could be linked with the persistence/clearance of hantaviruses in reservoirs. Persistence was associated during experimental infections with an upregulation of anti-inflammatory responses. Using natural rodent population samples, polymorphisms and/or expression levels of several genes have been analyzed. These genes were selected based on the literature of rodent or human/hantavirus interactions (some Mhc class II genes, Tnf promoter, and genes encoding the proteins TLR4, TLR7, Mx2 and β3 integrin). The comparison of genetic differentiation estimated between bank vole populations sampled over Europe, at neutral and candidate genes, has allowed to evidence signatures of selection for Tnf, Mx2 and the Drb Mhc class II genes. Altogether, these results corroborated the hypothesis of an evolution of tolerance strategies in rodents. We finally discuss the importance of these results from the medical and epidemiological perspectives.
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23
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Vaumourin E, Vourc'h G, Telfer S, Lambin X, Salih D, Seitzer U, Morand S, Charbonnel N, Vayssier-Taussat M, Gasqui P. To be or not to be associated: power study of four statistical modeling approaches to identify parasite associations in cross-sectional studies. Front Cell Infect Microbiol 2014; 4:62. [PMID: 24860791 PMCID: PMC4030204 DOI: 10.3389/fcimb.2014.00062] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 04/23/2014] [Indexed: 01/08/2023] Open
Abstract
A growing number of studies are reporting simultaneous infections by parasites in many different hosts. The detection of whether these parasites are significantly associated is important in medicine and epidemiology. Numerous approaches to detect associations are available, but only a few provide statistical tests. Furthermore, they generally test for an overall detection of association and do not identify which parasite is associated with which other one. Here, we developed a new approach, the association screening approach, to detect the overall and the detail of multi-parasite associations. We studied the power of this new approach and of three other known ones (i.e., the generalized chi-square, the network and the multinomial GLM approaches) to identify parasite associations either due to parasite interactions or to confounding factors. We applied these four approaches to detect associations within two populations of multi-infected hosts: (1) rodents infected with Bartonella sp., Babesia microti and Anaplasma phagocytophilum and (2) bovine population infected with Theileria sp. and Babesia sp. We found that the best power is obtained with the screening model and the generalized chi-square test. The differentiation between associations, which are due to confounding factors and parasite interactions was not possible. The screening approach significantly identified associations between Bartonella doshiae and B. microti, and between T. parva, T. mutans, and T. velifera. Thus, the screening approach was relevant to test the overall presence of parasite associations and identify the parasite combinations that are significantly over- or under-represented. Unraveling whether the associations are due to real biological interactions or confounding factors should be further investigated. Nevertheless, in the age of genomics and the advent of new technologies, it is a considerable asset to speed up researches focusing on the mechanisms driving interactions between parasites.
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Affiliation(s)
- Elise Vaumourin
- INRA, UR346 Epidémiologie Animale Saint Genès Champanelle, France ; INRA-Anses-ENVA, USC BIPAR Maisons-Alfort, France
| | - Gwenaël Vourc'h
- INRA, UR346 Epidémiologie Animale Saint Genès Champanelle, France
| | - Sandra Telfer
- School of Biological Sciences, University of Aberdeen Aberdeen, UK
| | - Xavier Lambin
- School of Biological Sciences, University of Aberdeen Aberdeen, UK
| | - Diaeldin Salih
- Department of Ticks and Tick-borne Diseases, Veterinary Research Institute Khartoum, Sudan
| | - Ulrike Seitzer
- Division of Veterinary-Infection Biology and Immunology, Research Center Borstel Borstel, Germany
| | - Serge Morand
- Institut des Sciences de l'Evolution (CNRS /IRD / UM2), University of Montpellier 2 Montpellier, France ; Animal et Gestion Intégrée des Risques, CIRAD Montpellier, France
| | - Nathalie Charbonnel
- INRA, UMR CBGP (INRA / IRD / CIRAD / Montpellier SupAgro) Montpellier, France
| | | | - Patrick Gasqui
- INRA, UR346 Epidémiologie Animale Saint Genès Champanelle, France
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Winternitz JC, Wares JP, Yabsley MJ, Altizer S. Wild cyclic voles maintain high neutral and MHC diversity without strong evidence for parasite-mediated selection. Evol Ecol 2014. [DOI: 10.1007/s10682-014-9709-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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25
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Zhang M, He H. Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China. BMC Evol Biol 2013; 13:149. [PMID: 23848494 PMCID: PMC3720540 DOI: 10.1186/1471-2148-13-149] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 06/27/2013] [Indexed: 11/21/2022] Open
Abstract
Background Genes of the major histocompatibility complex (MHC) exhibit high levels of variability, which is believed to have arisen through pathogen-mediated selection. We investigated the relationship between parasite load and genetic diversity at selectively neutral, non-coding markers (microsatellites) and adaptive genetic variation at a functionally important part of the MHC in six independent natural populations of Brandt’s voles (Lasiopodomys brandtii) from two regions of the Xilingol Grassland area of Inner Mongolia. Results Two-hundred and fifty-two voles were screened for gastrointestinal parasites, and were assessed for genetic variation. Parasite screening was done through non-invasive fecal egg counts, while allelic diversity was determined via single-stranded conformation polymorphism and DNA sequencing. We detected eight distinct helminth egg morphotypes. A total of 10 microsatellite loci were genotyped and 19 unique MHC class II B alleles were isolated. The rate of nonsynonymous substitutions (dN) exceeded the rate of synonymous substitutions (dS) at putative antigen binding sites of DRB. Neutral and adaptive genetic diversity differed between the six vole populations. To test the main pathogen-driven selection hypotheses for the maintenance of host MHC diversity and parasite species-specific co-evolutionary effects, multivariate approaches (generalized linear mixed models) were used to test for associations between the MHC class II DRB genotype and infections with nematodes. We found no evidence for heterozygote advantage, and overall heterozygosity was lower than expected in the MHC alleles. We identified an association between the parasite load and specific MHC alleles in the voles, and this pattern varied between geographic regions. Conclusions The results suggest that MHC variability in Brandt’s voles is maintained by rare allele advantage and fluctuating selection, but the data failed to show any heterozygote advantage effect. Our results add to a growing body of evidence showing that the mode and relative strength of pathogen-driven selection acting on MHC diversity varies within specific wild populations. In addition, our study contributes to the understanding of what maintains MHC diversity, of host-pathogen coevolution and of how genetic diversity is maintained in voles.
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Affiliation(s)
- Min Zhang
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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Pavey SA, Sevellec M, Adam W, Normandeau E, Lamaze FC, Gagnaire PA, Filteau M, Hebert FO, Maaroufi H, Bernatchez L. Nonparallelism in MHCIIβ diversity accompanies nonparallelism in pathogen infection of lake whitefish (Coregonus clupeaformis) species pairs as revealed by next-generation sequencing. Mol Ecol 2013; 22:3833-49. [DOI: 10.1111/mec.12358] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/03/2013] [Accepted: 04/08/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Scott A. Pavey
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Maelle Sevellec
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - William Adam
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Eric Normandeau
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Fabien C. Lamaze
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Pierre-Alexandre Gagnaire
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
- Institut des Sciences de l'Evolution - Montpellier (ISEM); Universite Montpellier II; Place Eugene Bataillon 34095 Montpellier Cedex France
| | - Marie Filteau
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Francois Olivier Hebert
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Halim Maaroufi
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
- Plate-forme de Bio-informatique and Institut de Biologie Intégrative et des Systèmes; Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Louis Bernatchez
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
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27
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Vaumourin E, Gasqui P, Buffet JP, Chapuis JL, Pisanu B, Ferquel E, Vayssier-Taussat M, Vourc'h G. A probabilistic model in cross-sectional studies for identifying interactions between two persistent vector-borne pathogens in reservoir populations. PLoS One 2013; 8:e66167. [PMID: 23840418 PMCID: PMC3688727 DOI: 10.1371/journal.pone.0066167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 05/03/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In natural populations, individuals are infected more often by several pathogens than by just one. In such a context, pathogens can interact. This interaction could modify the probability of infection by subsequent pathogens. Identifying when pathogen associations correspond to biological interactions is a challenge in cross-sectional studies where the sequence of infection cannot be demonstrated. METHODOLOGY/PRINCIPAL FINDINGS Here we modelled the probability of an individual being infected by one and then another pathogen, using a probabilistic model and maximum likelihood statistics. Our model was developed to apply to cross-sectional data, vector-borne and persistent pathogens, and to take into account confounding factors. Our modelling approach was more powerful than the commonly used Chi-square test of independence. Our model was applied to detect potential interaction between Borrelia afzelii and Bartonella spp. that infected a bank vole population at 11% and 57% respectively. No interaction was identified. CONCLUSIONS/SIGNIFICANCE The modelling approach we proposed is powerful and can identify the direction of potential interaction. Such an approach can be adapted to other types of pathogens, such as non-persistents. The model can be used to identify when co-occurrence patterns correspond to pathogen interactions, which will contribute to understanding how organism communities are assembled and structured. In the long term, the model's capacity to better identify pathogen interactions will improve understanding of infectious risk.
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Affiliation(s)
- Elise Vaumourin
- INRA, UR346 Epidémiologie Animale, Saint Genès Champanelle, France.
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28
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Sepil I, Lachish S, Sheldon BC. Mhc-linked survival and lifetime reproductive success in a wild population of great tits. Mol Ecol 2012. [DOI: 10.1111/mec.12123] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Irem Sepil
- Department of Zoology; Edward Grey Institute; University of Oxford; South Parks Road Oxford OX1 3PS UK
| | - Shelly Lachish
- Department of Zoology; Edward Grey Institute; University of Oxford; South Parks Road Oxford OX1 3PS UK
| | - Ben C. Sheldon
- Department of Zoology; Edward Grey Institute; University of Oxford; South Parks Road Oxford OX1 3PS UK
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29
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Affiliation(s)
- Thomas A. White
- Department of Ecology and Evolutionary Biology; Cornell University; Corson Hall Ithaca New York 14853-2701 USA
- CMPG Lab; Institute of Ecology and Evolution; University of Bern; Baltzerstrasse 6 CH-3012 Bern Switzerland
| | - Sarah E. Perkins
- Cardiff School of Biosciences; Biomedical Sciences Building Museum Avenue Cardiff CF10 3AX UK
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30
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MHC influences infection with parasites and winter survival in the root vole Microtus oeconomus. Evol Ecol 2012. [DOI: 10.1007/s10682-012-9611-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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31
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McMullan M, van Oosterhout C. Inference of selection based on temporal genetic differentiation in the study of highly polymorphic multigene families. PLoS One 2012; 7:e42119. [PMID: 22900006 PMCID: PMC3416836 DOI: 10.1371/journal.pone.0042119] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 07/02/2012] [Indexed: 01/12/2023] Open
Abstract
The co-evolutionary arms race between host immune genes and parasite virulence genes is known as Red Queen dynamics. Temporal fluctuations in allele frequencies, or the ‘turnover’ of alleles at immune genes, are concordant with predictions of the Red Queen hypothesis. Such observations are often taken as evidence of host-parasite co-evolution. Here, we use computer simulations of the Major Histocompatibility Complex (MHC) of guppies (Poecilia reticulata) to study the turnover rate of alleles (temporal genetic differentiation, G'ST). Temporal fluctuations in MHC allele frequencies can be ≥≤order of magnitude larger than changes observed at neutral loci. Although such large fluctuations in the MHC are consistent with Red Queen dynamics, simulations show that other demographic and population genetic processes can account for this observation, these include: (1) overdominant selection, (2) fluctuating population size within a metapopulation, and (3) the number of novel MHC alleles introduced by immigrants when there are multiple duplicated genes. Synergy between these forces combined with migration rate and the effective population size can drive the rapid turnover in MHC alleles. We posit that rapid allelic turnover is an inherent property of highly polymorphic multigene families and that it cannot be taken as evidence of Red Queen dynamics. Furthermore, combining temporal samples in spatial FST outlier analysis may obscure the signal of selection.
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Affiliation(s)
- Mark McMullan
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.
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32
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Kuduk K, Johanet A, Allainé D, Cohas A, Radwan J. Contrasting patterns of selection acting on MHC class I and class II DRB genes in the Alpine marmot (Marmota marmota). J Evol Biol 2012; 25:1686-93. [PMID: 22594882 DOI: 10.1111/j.1420-9101.2012.02537.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The major histocompatibility complex (MHC) genes code for proteins that play a critical role in the immune system response. The MHC genes are among the most polymorphic genes in vertebrates, presumably due to balancing selection. The two MHC classes appear to differ in the rate of evolution, but the reasons for this variation are not well understood. Here, we investigate the level of polymorphism and the evolution of sequences that code for the peptide-binding regions of MHC class I and class II DRB genes in the Alpine marmot (Marmota marmota). We found evidence for four expressed MHC class I loci and two expressed MHC class II loci. MHC genes in marmots were characterized by low polymorphism, as one to eight alleles per putative locus were detected in 38 individuals from three French Alps populations. The generally limited degree of polymorphism, which was more pronounced in class I genes, is likely due to bottleneck the populations undergone. Additionally, gene duplication within each class might have compensated for the loss of polymorphism at particular loci. The two gene classes showed different patterns of evolution. The most polymorphic of the putative loci, Mama-DRB1, showed clear evidence of historical positive selection for amino acid replacements. However, no signal of positive selection was evident in the MHC class I genes. These contrasting patterns of sequence evolution may reflect differences in selection pressures acting on class I and class II genes.
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Affiliation(s)
- K Kuduk
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, Kraków, Poland
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33
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Lillie M, Woodward RE, Sanderson CE, Eldridge MDB, Belov K. Diversity at the major histocompatibility complex Class II in the platypus, Ornithorhynchus anatinus. J Hered 2012; 103:467-78. [PMID: 22563128 DOI: 10.1093/jhered/ess012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The platypus (Ornithorhynchus anatinus) is the sole survivor of a previously widely distributed and diverse lineage of ornithorhynchid monotremes. Its dependence on healthy water systems imposes an inherent sensitivity to habitat degradation and climate change. Here, we compare genetic diversity at the major histocompatibility complex (MHC) Class II-DZB gene and 3 MHC-associated microsatellite markers with diversity at 6 neutral microsatellite markers in 70 platypuses from across their range, including the mainland of Australia and the isolated populations of Tasmania, King Island, and Kangaroo Island. Overall, high DZB diversity was observed in the platypus, with 57 DZB β1 alleles characterized. Significant positive selection was detected within the DZB peptide-binding region, promoting variation in this domain. Low levels of genetic diversity were detected at all markers in the 2 island populations, King Island (endemic) and Kangaroo Island (introduced), with the King Island platypuses monomorphic at the DZB locus. Loss of MHC diversity on King Island is of concern, as the population may have compromised immunological fitness and reduced ability to resist changing environmental conditions.
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Affiliation(s)
- Mette Lillie
- Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia
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34
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Froeschke G, Sommer S. Insights into the complex associations between MHC class II DRB polymorphism and multiple gastrointestinal parasite infestations in the striped mouse. PLoS One 2012; 7:e31820. [PMID: 22389675 PMCID: PMC3289624 DOI: 10.1371/journal.pone.0031820] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 01/13/2012] [Indexed: 11/19/2022] Open
Abstract
Differences in host susceptibility to different parasite types are largely based on the degree of matching between immune genes and parasite antigens. Specifically the variable genes of the major histocompatibility complex (MHC) play a major role in the defence of parasites. However, underlying genetic mechanisms in wild populations are still not well understood because there is a lack of studies which deal with multiple parasite infections and their competition within. To gain insights into these complex associations, we implemented the full record of gastrointestinal nematodes from 439 genotyped individuals of the striped mouse, Rhabdomys pumilio. We used two different multivariate approaches to test for associations between MHC class II DRB genotype and multiple nematodes with regard to the main pathogen-driven selection hypotheses maintaining MHC diversity and parasite species-specific co-evolutionary effects. The former includes investigations of a 'heterozygote advantage', or its specific form a 'divergent-allele advantage' caused by highly dissimilar alleles as well as possible effects of specific MHC-alleles selected by a 'rare allele advantage' (= negative 'frequency-dependent selection'). A combination of generalized linear mixed models (GLMMs) and co-inertia (COIA) analyses made it possible to consider multiple parasite species despite the risk of type I errors on the population and on the individual level. We could not find any evidence for a 'heterozygote' advantage but support for 'divergent-allele' advantage and infection intensity. In addition, both approaches demonstrated high concordance of positive as well as negative associations between specific MHC alleles and certain parasite species. Furthermore, certain MHC alleles were associated with more than one parasite species, suggesting a many-to-many gene-parasite co-evolution. The most frequent allele Rhpu-DRB*38 revealed a pleiotropic effect, involving three nematode species. Our study demonstrates the co-existence of specialist and generalist MHC alleles in terms of parasite detection which may be an important feature in the maintenance of MHC polymorphism.
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Affiliation(s)
| | - Simone Sommer
- Evolutionary Genetics, Leibniz-Institute for Zoo and Wildlife Research (IZW), Berlin, Germany
- * E-mail:
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MALÉ PIERREJEANG, MARTIN JEANFRANÇOIS, GALAN MAXIME, DEFFONTAINE VALÉRIE, BRYJA JOSEF, COSSON JEANFRANÇOIS, MICHAUX JOHAN, CHARBONNEL NATHALIE. Discongruence of Mhc and cytochrome b phylogeographical patterns in Myodes glareolus (Rodentia: Cricetidae). Biol J Linn Soc Lond 2012. [DOI: 10.1111/j.1095-8312.2011.01799.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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36
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Biedrzycka A, Kloch A, Buczek M, Radwan J. Major histocompatibility complex DRB genes and blood parasite loads in fragmented populations of the spotted suslik Spermophilus suslicus. Mamm Biol 2011. [DOI: 10.1016/j.mambio.2011.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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37
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Bordes F, Morand S. The impact of multiple infections on wild animal hosts: a review. Infect Ecol Epidemiol 2011; 1:IEE-1-7346. [PMID: 22957114 PMCID: PMC3426331 DOI: 10.3402/iee.v1i0.7346] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/11/2011] [Accepted: 08/25/2011] [Indexed: 12/23/2022] Open
Abstract
Field parasitological studies consistently demonstrate the reality of polyparasitism in natural systems. However, only recently, studies from ecological and evolutionary fields have emphasised a broad spectrum of potential multiple infections-related impacts. The main goal of our review is to reunify the different approaches on the impacts of polyparasitism, not only from laboratory or human medical studies but also from field or theoretical studies. We put forward that ecological and epidemiological determinants to explain the level of polyparasitism, which regularly affects not only host body condition, survival or reproduction but also host metabolism, genetics or immune investment. Despite inherent limitations of all these studies, multiple infections should be considered more systematically in wildlife to better appreciate the importance of parasite diversity in wildlife, cumulative effects of parasitism on the ecology and evolution of their hosts.
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Affiliation(s)
- Frédéric Bordes
- Institut des Sciences de l'Evolution, CNRS-UM2, CC65, Université de Montpellier, Montpellier, France
| | - Serge Morand
- Institut des Sciences de l'Evolution, CNRS-UM2, CC65, Université de Montpellier, Montpellier, France
- UR22 AGIRs, CIRAD, Campus International de Baillarguet, 34398, Montpellier, France
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38
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de Eyto E, McGinnity P, Huisman J, Coughlan J, Consuegra S, Farrell K, O'Toole C, Tufto J, Megens HJ, Jordan W, Cross T, Stet RJM. Varying disease-mediated selection at different life-history stages of Atlantic salmon in fresh water. Evol Appl 2011; 4:749-62. [PMID: 25568020 PMCID: PMC3352546 DOI: 10.1111/j.1752-4571.2011.00197.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 06/10/2011] [Indexed: 02/03/2023] Open
Abstract
Laboratory studies on associations between disease resistance and susceptibility and major histocompatibility (MH) genes in Atlantic salmon Salmo salar have shown the importance of immunogenetics in understanding the capacity of populations to fight specific diseases. However, the occurrence and virulence of pathogens may vary spatially and temporally in the wild, making it more complicated to predict the overall effect that MH genes exert on fitness of natural populations and over several life-history stages. Here we show that MH variability is a significant determinant of salmon survival in fresh water, by comparing observed and expected genotype frequencies at MH and control microsatellite loci at parr and migrant stages in the wild. We found that additive allelic effects at immunogenetic loci were more likely to determine survival than dominance deviation, and that selection on certain MH alleles varied with life stage, possibly owing to varying pathogen prevalence and/or virulence over time. Our results highlight the importance of preserving genetic diversity (particularly at MH loci) in wild populations, so that they have the best chance of adapting to new and increased disease challenges as a result of projected climate warming and increasing aquaculture.
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Affiliation(s)
| | - Philip McGinnity
- Department of Zoology, Ecology and Plant Science/Aquaculture and Fisheries Development Centre, University College Cork Distillery Fields, North Mall, Cork, Ireland
| | - Jisca Huisman
- Department of Biology, Norwegian University of Science and Technology Trondheim, Norway
| | - Jamie Coughlan
- Department of Zoology, Ecology and Plant Science/Aquaculture and Fisheries Development Centre, University College Cork Distillery Fields, North Mall, Cork, Ireland
| | - Sofia Consuegra
- Aberystwyth University, Institute of Biological, Environmental & Rural Sciences Aberystwyth, UK
| | | | - Ciar O'Toole
- Department of Zoology, Ecology and Plant Science/Aquaculture and Fisheries Development Centre, University College Cork Distillery Fields, North Mall, Cork, Ireland
| | - Jarle Tufto
- Department of Mathematical Sciences, Norwegian University of Science and Technology Trondheim, Norway
| | - Hendrik-Jan Megens
- Department of Animal Sciences, Wageningen University Wageningen, the Netherlands
| | - William Jordan
- Institute of Zoology, Zoological Society of London Regent's Park, London, UK
| | - Tom Cross
- Department of Zoology, Ecology and Plant Science/Aquaculture and Fisheries Development Centre, University College Cork Distillery Fields, North Mall, Cork, Ireland
| | - Rene J M Stet
- Scottish Fish Immunology Research Centre, University of Aberdeen Zoology Building, Tillydrone Avenue, Aberdeen, UK
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39
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Depleted genetic variation of the European ground squirrel in Central Europe in both microsatellites and the major histocompatibility complex gene: implications for conservation. CONSERV GENET 2011. [DOI: 10.1007/s10592-011-0213-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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40
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Cutrera AP, Zenuto RR, Lacey EA. MHC variation, multiple simultaneous infections and physiological condition in the subterranean rodent Ctenomys talarum. INFECTION GENETICS AND EVOLUTION 2011; 11:1023-36. [PMID: 21497205 DOI: 10.1016/j.meegid.2011.03.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 02/28/2011] [Accepted: 03/24/2011] [Indexed: 01/15/2023]
Abstract
Parasites and pathogens can play a significant role in shaping the genetic diversity of host populations, particularly at genes associated with host immune response. To explore this relationship in a natural population of vertebrates, we characterized Major Histocompatibility Complex (MHC) variation in the subterranean rodent Ctenomys talarum (the talas tuco-tuco) as a function of parasite load and ability to mount an adaptive immune response against a novel antigen. Specifically, we quantified genotypic diversity at the MHC class II DRB locus in relation to (1) natural variation in infection by multiple genera of parasites (potential agents of selection on MHC genes) and (2) antibody production in response to injection with sheep red blood cells (a measure of immunocompetence). Data were analyzed using co-inertia multivariate statistics, with epidemiological proxies for individual condition (hematocrit, leukocyte profile, body weight) and risk of parasite exposure (season of capture, sex). A significant excess of DRB heterozygotes was evident in the study population. Co-inertia analyses revealed significant associations between specific DRB alleles and both parasite load and intensity of humoral immune response against sheep red blood cells. The presence of specific DRB aminoacid sequences appeared to be more strongly associated with parasite load and response to a novel antigen than was heterozygosity at the DRB locus. These data suggest a role for parasite-driven balancing selection in maintaining MHC variation in natural populations of C. talarum. At the same time, these findings underscore the importance of using diverse parameters to study interactions among physiological conditions, immunocompetence, and MHC diversity in free-living animals that are confronted with multiple simultaneous immune challenges.
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Affiliation(s)
- Ana Paula Cutrera
- Laboratorio de Ecofisiología, Departamento de Biología, Universidad Nacional de Mar del Plata, CONICET, CC 1245, Mar del Plata, Argentina.
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41
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Ardia DR, Parmentier HK, Vogel LA. The role of constraints and limitation in driving individual variation in immune response. Funct Ecol 2011. [DOI: 10.1111/j.1365-2435.2010.01759.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Daniel R. Ardia
- Department of Biology, Franklin & Marshall College, Lancaster, Pennsylvania 17604, USA
| | - Henk K. Parmentier
- Adaptation Physiology Group, Department of Animal Sciences, Wageningen Institute of Animal Sciences, Marijkeweg 40, 6709 PG Wageningen, The Netherlands
| | - Laura A. Vogel
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790, USA
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42
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Eizaguirre C, Lenz TL. Major histocompatibility complex polymorphism: dynamics and consequences of parasite-mediated local adaptation in fishes. JOURNAL OF FISH BIOLOGY 2010; 77:2023-2047. [PMID: 21133915 DOI: 10.1111/j.1095-8649.2010.02819.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Parasitism is a common form of life and represents a strong selective pressure for host organisms. In response to this evolutionary pressure, vertebrates have developed genetically coded defences such as the major histocompatibility complex (MHC). Mechanisms of parasite-mediated selection not only maintain outstanding polymorphism in these genes but have also been proposed to further promote host population divergence and ultimately speciation because it can drive evolution of local adaptation in which MHC genes play a crucial role. This review first highlights the dynamics and complexity of parasite-mediated selection in natural systems, which not only depends on dominating parasite strategies and on the taxonomic diversity of the parasite community but also includes the differences in parasite communities between habitats and niches, creating divergent selection on locally adapted populations. Then the different ways in which MHC genes potentially allow vertebrates to respond to these dynamics and to adapt locally are outlined. Finally, it is proposed that varying selection strength in time and space may lead to variation in the strength of precopulatory reproductive isolation which has evolved to maintain local adaptation.
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Affiliation(s)
- C Eizaguirre
- Leibniz Institute for Marine Sciences (IFM GEOMAR), Department of Evolutionary Ecology of Marine Fishes, Düsternbrooker Weg 20, 24105, Kiel, Germany.
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43
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Garamszegi LZ, Nunn CL. Parasite-mediated evolution of the functional part of the MHC in primates. J Evol Biol 2010; 24:184-95. [PMID: 21091566 DOI: 10.1111/j.1420-9101.2010.02156.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The major histocompatibility complex (MHC) is a key model of genetic polymorphism, but the mechanisms underlying its extreme variability are debated. Most hypotheses for MHC diversity focus on pathogen-driven selection and predict that MHC polymorphism evolves under the pressure of a diverse parasite fauna. Several studies reported that certain alleles offer protection against certain parasites, yet it remains unclear whether variation in parasite pressure more generally covaries with allelic diversity and rates of molecular evolution of MHC across species. We tested this prediction in a comparative study of 41 primate species. We characterized polymorphism of the exon 2 of DRB region of the MHC class II. Our phylogenetic analyses controlled for the potential effects of neutral mutation rate, population size, geographic origin and body mass and revealed that nematode species richness associates positively with nonsynonymous nucleotide substitution rate at the functional part of the molecule. We failed to find evidence for allelic diversity being strongly related to parasite species richness. Continental distribution was a strong predictor of both allelic diversity and substitution rate, with higher values in Malagasy and Neotropical primates. These results indicate that parasite pressure can influence the different estimates of MHC polymorphism, whereas geography plays an independent role in the natural history of MHC.
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Affiliation(s)
- L Z Garamszegi
- Department of Evolutionary Ecology, Estación Biológica de Doñana-CSIC, Seville, Spain.
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44
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Cížková D, Gouy de Bellocq J, Baird SJE, Piálek J, Bryja J. Genetic structure and contrasting selection pattern at two major histocompatibility complex genes in wild house mouse populations. Heredity (Edinb) 2010; 106:727-40. [PMID: 20823902 DOI: 10.1038/hdy.2010.112] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The mammalian major histocompatibility complex (MHC) is a tightly linked cluster of immune genes, and is often thought of as inherited as a unit. This has led to the hope that studying a single MHC gene will reveal patterns of evolution representative of the MHC as a whole. In this study we analyse a 1000-km transect of MHC variation traversing the European house mouse hybrid zone to compare signals of selection and patterns of diversification at two closely linked MHC class II genes, H-2Aa and H-2Eb. We show that although they are 0.01 cM apart (that is, recombination is expected only once in 10 000 meioses), disparate evolutionary patterns were detected. H-2Aa shows higher allelic polymorphism, faster allelic turnover due to higher mutation rates, stronger positive selection at antigen-binding sites and higher population structuring than H-2Eb. H-2Eb alleles are maintained in the gene pool for longer, including over separation of the subspecies, some H-2Eb alleles are positively and others negatively selected and some of the alleles are not expressed. We conclude that studies on MHC genes in wild-living vertebrates can give substantially different results depending on the MHC gene examined and that the level of polymorphism in a related species is a poor criterion for gene choice.
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Affiliation(s)
- D Cížková
- Department of Population Biology, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech Republic.
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45
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Oppelt C, Starkloff A, Rausch P, Von Holst D, Rödel HG. Major histocompatibility complex variation and age-specific endoparasite load in subadult European rabbits. Mol Ecol 2010; 19:4155-67. [PMID: 20723049 DOI: 10.1111/j.1365-294x.2010.04766.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Genes of the major histocompatibility complex (MHC) play a fundamental role in the vertebrate immune response and are amongst the most polymorphic genes in vertebrate genomes. It is generally agreed that the highly polymorphic nature of the MHC is maintained through host-parasite co-evolution. Two nonexclusive mechanisms of selection are supposed to act on MHC genes: superiority of MHC heterozygous individuals (overdominance) and an advantage for rare MHC alleles. However, the precise mechanisms and their relative importance are still unknown. Here, we examined MHC dependent parasite load in European rabbits (Oryctolagus cuniculus) from a distinct population with low MHC diversity (three alleles, six genotypes). Using a multivariate approach, we tested for associations of individual MHC class II DRB constitution and the rabbits' intestinal burden with nematodes and coccidia. Rabbits having a particular allele showed lower infestations with hepatic coccidia (E. stiedai). However, a comparison of all six genotypes in the population revealed that carriers of this allele only benefit when they are heterozygous, and furthermore, MHC heterozygosity in general did not affect individual parasite load. In conclusion, this study suggests an immunogenetic basis of European rabbit resistance to hepatic coccidiosis, which can strongly limit survival to maturity in this species. Our study gives a complex picture of MHC-parasite correlations, unveiling the limits of the classical hypotheses of how MHC polymorphism is maintained in natural systems.
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Affiliation(s)
- Claus Oppelt
- Department of Animal Physiology, University of Bayreuth, D-95440 Bayreuth, GermanyLimnological Institute, University of Konstanz, D-78464 Konstanz, Germany
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Schwensow N, Dausmann K, Eberle M, Fietz J, Sommer S. Functional associations of similar MHC alleles and shared parasite species in two sympatric lemurs. INFECTION GENETICS AND EVOLUTION 2010; 10:662-8. [PMID: 20363374 DOI: 10.1016/j.meegid.2010.03.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 03/25/2010] [Accepted: 03/26/2010] [Indexed: 11/18/2022]
Abstract
Several recent studies of animals in their natural surroundings found evidence for effects of certain major histocompatibility complex (MHC) immune gene alleles on the parasite load. However, in multi-infected individuals the particular selection pressure exerted by specific parasites has rarely been explored. In this study we took advantage of the parasitological and genetic data of two previously investigated Malagasy lemur species (Cheirogaleus medius and Microcebus murinus). We investigated whether the two sympatric and ecologically similar primates are infected by similar parasite species and explored if certain parasites are associated with particular MHC alleles. Our study revealed that most of the parasite egg morphotypes were found in both hosts. In each lemur species we identified one MHC allele which was positively associated with Ascaris-infection. Interestingly, these MHC alleles were very similar to each other but differed from all other investigated MHC alleles in an amino acid substitution in a putative functional important antigen binding site. Thus, our study gives first intriguing evidence for a direct connection between certain antigen binding sites of MHC molecules with a particular parasite in two wild primate populations. This may indicate that indeed certain parasites exert direct selective pressure on the MHC of wild living hosts.
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Affiliation(s)
- Nina Schwensow
- Leibniz Institute for Zoo and Wildlife Research, Dept. Evolutionary Genetics, Alfred-Kowalke-Strasse 17, D-10315 Berlin, Germany
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Charbonnel N, Bryja J, Galan M, Deter J, Tollenaere C, Chaval Y, Morand S, Cosson JF. Negative relationships between cellular immune response, Mhc class II heterozygosity and secondary sexual trait in the montane water vole. Evol Appl 2010; 3:279-90. [PMID: 25567924 PMCID: PMC3352462 DOI: 10.1111/j.1752-4571.2009.00108.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 11/10/2009] [Indexed: 11/26/2022] Open
Abstract
Heterogeneities in immune responsiveness may affect key epidemiological parameters and the dynamics of pathogens. The roles of immunogenetics in these variations remain poorly explored. We analysed the influence of Major histocompatibility complex (Mhc) genes and epigamic traits on the response to phytohaemagglutinin in males from cyclic populations of the montane water vole (Arvicola scherman). Besides, we tested the relevance of lateral scent glands as honest signals of male quality. Our results did not corroborate neither the hypotheses of genome-wide heterozygosity-fitness correlation nor the Mhc heterozygote advantage. We found a negative relationship between Mhc hetetozygosity and response to phytohaemagglutinin, mediated by a specific Mhc homozygous genotype. Our results therefore support the hypothesis of the Arte-Dqa-05 homozygous genotype being a ‘good’ Mhc variant in terms of immunogenetic quality. The development of the scent glands seems to be an honest signal for mate choice as it is negatively correlated with helminth load. The ‘good gene’ hypothesis was not validated as Arte-Dqa-05 homozygous males did not exhibit larger glands. Besides, the negative relationship observed between the size of these glands and the response to phytohaemagglutinin, mainly for Mhc homozygotes, corroborates the immunocompetence handicap hypothesis. The Mhc variants associated with larger glands remain yet to be determined.
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Affiliation(s)
- Nathalie Charbonnel
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France
| | - Josef Bryja
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France ; Department of Population Biology, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic Studenec, Czech Republic
| | - Maxime Galan
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France
| | - Julie Deter
- IFREMER, Département Environnement, Microbiologie et Phycotoxines, Laboratoire de Microbiologie, ZI de la pointe du diable Plouzané, France
| | - Charlotte Tollenaere
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France
| | - Yannick Chaval
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France
| | - Serge Morand
- Université Montpellier II, CNRS, Institut des Sciences de l'Evolution de Montpellier Montpellier Cedex, France
| | - Jean-François Cosson
- Centre de Biologie et Gestion des Populations UMR (INRA/IRD/Cirad/Montpellier SupAgro), INRA-EFPA Montferrier sur Lez Cedex, France
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48
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Spurgin LG, Richardson DS. How pathogens drive genetic diversity: MHC, mechanisms and misunderstandings. Proc Biol Sci 2010; 277:979-88. [PMID: 20071384 DOI: 10.1098/rspb.2009.2084] [Citation(s) in RCA: 518] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Major histocompatibility complex (MHC) genes have been put forward as a model for studying how genetic diversity is maintained in wild populations. Pathogen-mediated selection (PMS) is believed to generate the extraordinary levels of MHC diversity observed. However, establishing the relative importance of the three proposed mechanisms of PMS (heterozygote advantage, rare-allele advantage and fluctuating selection) has proved extremely difficult. Studies have attempted to differentiate between mechanisms of PMS using two approaches: (i) comparing MHC diversity with that expected under neutrality and (ii) relating MHC diversity to pathogen regime. Here, we show that in many cases the same predictions arise from the different mechanisms under these approaches, and that most studies that have inferred one mechanism of selection have not fully considered the alternative explanations. We argue that, while it may be possible to demonstrate that particular mechanisms of PMS are occurring, resolving their relative importance within a system is probably impossible. A more realistic target is to continue to demonstrate when and where the different mechanisms of PMS occur, with the aim of determining their relative importance across systems. We put forward what we believe to be the most promising approaches that will allow us to progress towards achieving this.
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Affiliation(s)
- Lewis G Spurgin
- Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich, UK
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Evans ML, Neff BD. Major histocompatibility complex heterozygote advantage and widespread bacterial infections in populations of Chinook salmon (Oncorhynchus tshawytscha). Mol Ecol 2009; 18:4716-29. [PMID: 19821902 DOI: 10.1111/j.1365-294x.2009.04374.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite growing evidence for parasite-mediated selection on the vertebrate major histocompatibility complex (MHC), little is known about variation in the bacterial parasite community within and among host populations or its influence on MHC evolution. In this study, we characterize variation in the parasitic bacterial community associated with Chinook salmon (Oncorhynchus tshawytscha) fry in five populations in British Columbia (BC), Canada across 2 years, and examine whether bacterial infections are a potential source of selection on the MHC. We found an unprecedented diversity of bacteria infecting fry with a total of 55 unique bacteria identified. Bacterial infection rates varied from 9% to 29% among populations and there was a significant isolation by distance relationship in bacterial community phylogenetic similarity across the populations. Spatial variation in the frequency of infections and in the phylogenetic similarity of bacterial communities may result in differential parasite-mediated selection at the MHC across populations. Across all populations, we found evidence of a heterozygote advantage at the MHC class II, which may be a source of balancing selection on this locus. Interestingly, a co-inertia analysis indicated only susceptibility associations between a few of the MHC class I and II alleles and specific bacterial parasites; there was no evidence that any of the alleles provided resistance to the bacteria. Our results reveal a complex bacterial community infecting populations of a fish and underscore the importance of considering the role of multiple pathogens in the evolution of host adaptations.
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Affiliation(s)
- Melissa L Evans
- Department of Biology, University of Western Ontario, 1151 Richmond St. N, London, ON, N6A 5B7, Canada
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50
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CENTENO-CUADROS A, DELIBES M, GODOY JA. Phylogeography of Southern Water Vole (Arvicola sapidus): evidence for refugia within the Iberian glacial refugium? Mol Ecol 2009; 18:3652-67. [DOI: 10.1111/j.1365-294x.2009.04297.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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