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Lam DK, Frantz AC, Burke T, Geffen E, Sin SYW. Both selection and drift drive the spatial pattern of adaptive genetic variation in a wild mammal. Evolution 2023; 77:221-238. [PMID: 36626810 DOI: 10.1093/evolut/qpac014] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 10/03/2022] [Accepted: 11/04/2022] [Indexed: 01/12/2023]
Abstract
The major histocompatibility complex (MHC) has been intensively studied for the relative effects of different evolutionary forces in recent decades. Pathogen-mediated balancing selection is generally thought to explain the high polymorphism observed in MHC genes, but it is still unclear to what extent MHC diversity is shaped by selection relative to neutral drift. In this study, we genotyped MHC class II DRB genes and 15 neutral microsatellite loci across 26 geographic populations of European badgers (Meles meles) covering most of their geographic range. By comparing variation of microsatellite and diversity of MHC at different levels, we demonstrate that both balancing selection and drift have shaped the evolution of MHC genes. When only MHC allelic identity was investigated, the spatial pattern of MHC variation was similar to that of microsatellites. By contrast, when functional aspects of the MHC diversity (e.g., immunological supertypes) were considered, balancing selection appears to decrease genetic structuring across populations. Our comprehensive sampling and analytical approach enable us to conclude that the likely mechanisms of selection are heterozygote advantage and/or rare-allele advantage. This study is a clear demonstration of how both balancing selection and genetic drift simultaneously affect the evolution of MHC genes in a widely distributed wild mammal.
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Affiliation(s)
- Derek Kong Lam
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Alain C Frantz
- Musée National d'Histoire Naturelle, Luxembourg, Luxembourg
| | - Terry Burke
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Sheffield, United Kingdom
| | - Eli Geffen
- School of Zoology, Tel Aviv University, Tel Aviv, Israel
| | - Simon Yung Wa Sin
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
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2
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Addressing conservation measures through fine-tuned species distribution models for an Italian endangered endemic anuran. Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2022.e02302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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3
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Cortazar-Chinarro M, Meurling S, Schroyens L, Siljestam M, Richter-Boix A, Laurila A, Höglund J. Major Histocompatibility Complex Variation and Haplotype Associated Survival in Response to Experimental Infection of Two Bd-GPL Strains Along a Latitudinal Gradient. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.915271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
While both innate and adaptive immune system mechanisms have been implicated in resistance against the chytrid fungus Batrachochytrium dendrobatidis (Bd), studies on the role of specific MHC haplotypes on Bd infection are rare. Here, we studied variation in MHC Class IIB loci in the common toad Bufo bufo along a latitudinal gradient across Sweden. In general, Swedish toad populations had few MHC Class IIB haplotypes and MHC diversity declined from south (13 haplotypes) to the north (four haplotypes). The low diversity may compromise the ability of northern populations to fight emerging disease, such as Bd. In a laboratory experiment, we infected newly metamorphosed toads with two strains of the Global Pandemic Lineage of the fungus (Bd-GPL) and compared survival with sham controls. Bd-infected toads had lower survival compared to controls. Moreover, survival was dependent on the Bd-strain and northern toads had lower Bd-mediated survival than southern individuals. MHC diversity was lower in northern toads. All northern experimental animals were monomorphic for a single MHC haplotype, whereas we found seven different haplotypes in southern experimental animals. In southern toads, survival was dependent on both Bd-strain and MHC haplotype suggesting differential infection dynamics depending on both Bd-strain and host immune system characteristics.
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Martin KR, Mansfield KL, Savage AE. Adaptive evolution of major histocompatibility complex class I immune genes and disease associations in coastal juvenile sea turtles. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211190. [PMID: 35154791 PMCID: PMC8825991 DOI: 10.1098/rsos.211190] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 01/06/2022] [Indexed: 05/12/2023]
Abstract
Characterizing polymorphism at the major histocompatibility complex (MHC) genes is key to understanding the vertebrate immune response to disease. Despite being globally afflicted by the infectious tumour disease fibropapillomatosis (FP), immunogenetic variation in sea turtles is minimally explored. We sequenced the α 1 peptide-binding region of MHC class I genes (162 bp) from 268 juvenile green (Chelonia mydas) and 88 loggerhead (Caretta caretta) sea turtles in Florida, USA. We recovered extensive variation (116 alleles) and trans-species polymorphism. Supertyping analysis uncovered three functional MHC supertypes corresponding to the three well-supported clades in the phylogeny. We found significant evidence of positive selection at seven amino acid sites in the class I exon. Random forest modelling and risk ratio analysis of Ch. mydas alleles uncovered one allele weakly associated with smooth FP tumour texture, which may be associated with disease outcome. Our study represents the first characterization of MHC class I diversity in Ch. mydas and the largest sample of sea turtles used to date in any study of adaptive genetic variation, revealing tremendous genetic variation and high adaptive potential to viral pathogen threats. The novel associations we identified between MHC diversity and FP outcomes in sea turtles further highlight the importance of evaluating genetic predictors of disease, including MHC and other functional markers.
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Affiliation(s)
- Katherine R. Martin
- Department of Biology, University of Central Florida, 4110 Libra Drive, Orlando, FL 32816, USA
| | - Katherine L. Mansfield
- Department of Biology, University of Central Florida, 4110 Libra Drive, Orlando, FL 32816, USA
| | - Anna E. Savage
- Department of Biology, University of Central Florida, 4110 Libra Drive, Orlando, FL 32816, USA
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Cheng Y, Grueber C, Hogg CJ, Belov K. Improved high-throughput MHC typing for non-model species using long-read sequencing. Mol Ecol Resour 2021; 22:862-876. [PMID: 34551192 PMCID: PMC9293008 DOI: 10.1111/1755-0998.13511] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 08/26/2021] [Accepted: 09/06/2021] [Indexed: 11/29/2022]
Abstract
The major histocompatibility complex (MHC) plays a critical role in the vertebrate immune system. Accurate MHC typing is critical to understanding not only host fitness and disease susceptibility, but also the mechanisms underlying host‐pathogen co‐evolution. However, due to the high degree of gene duplication and diversification of MHC genes, it is often technically challenging to accurately characterise MHC genetic diversity in non‐model species. Here we conducted a systematic review to identify common issues associated with current widely used MHC typing approaches. Then to overcome these challenges, we developed a long‐read based MHC typing method along with a new analysis pipeline. Our approach enables the sequencing of fully phased MHC alleles spanning all key functional domains and the separation of highly similar alleles as well as the removal of technical artefacts such as PCR heteroduplexes and chimeras. Using this approach, we performed population‐scale MHC typing in the Tasmanian devil (Sarcophilus harrisii), revealing previously undiscovered MHC functional diversity in this endangered species. Our new method provides a better solution for addressing research questions that require high MHC typing accuracy. Since the method is not limited by species or the number of genes analysed, it will be applicable for studying not only the MHC but also other complex gene families.
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Affiliation(s)
- Yuanyuan Cheng
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Catherine Grueber
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Carolyn J Hogg
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia.,San Diego Zoo Wildlife Alliance, San Diego, California, USA
| | - Katherine Belov
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
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Talarico L, Marta S, Rossi AR, Crescenzo S, Petrosino G, Martinoli M, Tancioni L. Balancing selection, genetic drift, and human-mediated introgression interplay to shape MHC (functional) diversity in Mediterranean brown trout. Ecol Evol 2021; 11:10026-10041. [PMID: 34367556 PMCID: PMC8328470 DOI: 10.1002/ece3.7760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 05/14/2021] [Accepted: 05/17/2021] [Indexed: 12/19/2022] Open
Abstract
The extraordinary polymorphism of major histocompatibility complex (MHC) genes is considered a paradigm of pathogen-mediated balancing selection, although empirical evidence is still scarce. Furthermore, the relative contribution of balancing selection to shape MHC population structure and diversity, compared to that of neutral forces, as well as its interaction with other evolutionary processes such as hybridization, remains largely unclear. To investigate these issues, we analyzed adaptive (MHC-DAB gene) and neutral (11 microsatellite loci) variation in 156 brown trout (Salmo trutta complex) from six wild populations in central Italy exposed to introgression from domestic hatchery lineages (assessed with the LDH gene). MHC diversity and structuring correlated with those at microsatellites, indicating the substantial role of neutral forces. However, individuals carrying locally rare MHC alleles/supertypes were in better body condition (a proxy of individual fitness/parasite load) regardless of the zygosity status and degree of sequence dissimilarity of MHC, hence supporting balancing selection under rare allele advantage, but not heterozygote advantage or divergent allele advantage. The association between specific MHC supertypes and body condition confirmed in part this finding. Across populations, MHC allelic richness increased with increasing admixture between native and domestic lineages, indicating introgression as a source of MHC variation. Furthermore, introgression across populations appeared more pronounced for MHC than microsatellites, possibly because initially rare MHC variants are expected to introgress more readily under rare allele advantage. Providing evidence for the complex interplay among neutral evolutionary forces, balancing selection, and human-mediated introgression in shaping the pattern of MHC (functional) variation, our findings contribute to a deeper understanding of the evolution of MHC genes in wild populations exposed to anthropogenic disturbance.
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Affiliation(s)
- Lorenzo Talarico
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
| | - Silvio Marta
- Department of Environmental Science and PolicyUniversity of MilanMilanItaly
| | - Anna Rita Rossi
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Simone Crescenzo
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Gerardo Petrosino
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Marco Martinoli
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
- Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria (CREA)Centro di Zootecnia e AcquacolturaMonterotondoItaly
| | - Lorenzo Tancioni
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
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Cortázar-Chinarro M, Meyer-Lucht Y, Van der Valk T, Richter-Boix A, Laurila A, Höglund J. Antimicrobial peptide and sequence variation along a latitudinal gradient in two anurans. BMC Genet 2020; 21:38. [PMID: 32228443 PMCID: PMC7106915 DOI: 10.1186/s12863-020-00839-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 03/06/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND While there is evidence of both purifying and balancing selection in immune defense genes, large-scale genetic diversity in antimicrobial peptides (AMPs), an important part of the innate immune system released from dermal glands in the skin, has remained uninvestigated. Here we describe genetic diversity at three AMP loci (Temporin, Brevinin and Palustrin) in two ranid frogs (Rana arvalis and R. temporaria) along a 2000 km latitudinal gradient. We amplified and sequenced part of the Acidic Propiece domain and the hypervariable Mature Peptide domain (~ 150-200 bp) in the three genes using Illumina Miseq and expected to find decreased AMP genetic variation towards the northern distribution limit of the species similarly to studies on MHC genetic patterns. RESULTS We found multiple loci for each AMP and relatively high gene diversity, but no clear pattern of geographic genetic structure along the latitudinal gradient. We found evidence of trans-specific polymorphism in the two species, indicating a common evolutionary origin of the alleles. Temporin and Brevinin did not form monophyletic clades suggesting that they belong to the same gene family. By implementing codon evolution models we found evidence of strong positive selection acting on the Mature Peptide. We also found evidence of diversifying selection as indicated by divergent allele frequencies among populations and high Theta k values. CONCLUSION Our results suggest that AMPs are an important source of adaptive diversity, minimizing the chance of microorganisms developing resistance to individual peptides.
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Affiliation(s)
- Maria Cortázar-Chinarro
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.
| | - Yvonne Meyer-Lucht
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.,Centre for Paleogenetics Svante Arrhenius väg 20C, SE-106 91, Stockholm, Sweden
| | - Tom Van der Valk
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden
| | - Alex Richter-Boix
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden
| | - Anssi Laurila
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden
| | - Jacob Höglund
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden
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Talarico L, Babik W, Marta S, Pietrocini V, Mattoccia M. MHC structuring and divergent allele advantage in a urodele amphibian: a hierarchical multi-scale approach. Heredity (Edinb) 2019; 123:593-607. [PMID: 31036951 PMCID: PMC6972932 DOI: 10.1038/s41437-019-0221-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 03/31/2019] [Accepted: 03/31/2019] [Indexed: 12/27/2022] Open
Abstract
Proteins encoded by extraordinarily polymorphic major histocompatibility complex (MHC) genes are involved in the adaptive immune response. Balancing selection is believed to maintain MHC polymorphism in the long term, although neutral processes also play a role in shaping MHC diversity. However, the relative contribution of these processes is poorly understood. Here we characterized MHC class II variation of a low-dispersal, pond-breeding newt (Triturus carnifex) over a restricted, geographically structured area. We aimed to (1) evaluate the contribution of selection and neutral processes to shaping MHC diversity at two geographic scales, and (2) test for signatures of divergent allele advantage (DAA), which is a potentially important mechanism of balancing selection. The dominant role of selection in shaping MHC variation was suggested by the lack of correlation between MHC and neutral (microsatellite) variation. Although most variation occurred within populations for both types of markers, they differed in the extent of structuring at the two spatial scales. MHC structuring was more pronounced at local scales, suggesting the role of local selection, while structuring was not detectable at a larger scale, possibly due to the effect of balancing selection. Microsatellites showed the opposite pattern. As expected under DAA, the observed genotypes combined more sequence diversity than expected under a random association of alleles. Thus, DAA may contribute to maintaining MHC polymorphism, which is ancient, as supported by signatures of historical positive selection and trans-species polymorphism. Our results point to the importance of a multi-scale approach in studying MHC variation, especially in low-dispersal taxa, which are genetically structured at fine spatial scales.
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Affiliation(s)
- Lorenzo Talarico
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy.
| | - Wiesław Babik
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, Kraków, 30-387, Poland
| | - Silvio Marta
- Department of Environmental Sciences and Policy, University of Milan, Via G. Celoria 26, Milan, 20133, Italy
| | - Venusta Pietrocini
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy
| | - Marco Mattoccia
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy
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Hernández-Gómez O, Kimble SJ, Hua J, Wuerthner VP, Jones DK, Mattes BM, Cothran RD, Relyea RA, Meindl GA, Hoverman JT. Local adaptation of the MHC class IIβ gene in populations of wood frogs (Lithobates sylvaticus) correlates with proximity to agriculture. INFECTION GENETICS AND EVOLUTION 2019; 73:197-204. [DOI: 10.1016/j.meegid.2019.04.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/26/2019] [Accepted: 04/29/2019] [Indexed: 11/16/2022]
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