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Olayemi A, Schmid DW, Fleischer R, Wilhelm K, Heni AC, Mueller-Klein N, Haikukutu L, Fichet-Calvet E, Günther S, Sommer S. MHC-I alleles mediate clearance and antibody response to the zoonotic Lassa virus in Mastomys rodent reservoirs. PLoS Negl Trop Dis 2024; 18:e0011984. [PMID: 38421939 PMCID: PMC10903922 DOI: 10.1371/journal.pntd.0011984] [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: 04/18/2023] [Accepted: 02/09/2024] [Indexed: 03/02/2024] Open
Abstract
West African Mastomys rodents are the primary reservoir of the zoonotic Lassa virus (LASV). The virus causes haemorrhagic Lassa fever and considerable mortality in humans. To date, the role of Mastomys immunogenetics in resistance to, and persistence of, LASV infections is largely unknown. Here, we investigated the role of Major Histocompatibility Complex class I (MHC-I) on LASV infection status (i.e., active vs. cleared infection, determined via PCR and an immunofluorescence assay on IgG antibodies, respectively) in Mastomys natalensis and M. erythroleucus sampled within southwestern Nigeria. We identified more than 190 and 90 MHC-I alleles by Illumina high throughput-sequencing in M. natalensis and M. erythroleucus, respectively, with different MHC allele compositions and frequencies between LASV endemic and non-endemic sites. In M. natalensis, the MHC allele ManaMHC-I*006 was negatively associated with active infections (PCR-positive) and positively associated with cleared infections (IgG-positive) simultaneously, suggesting efficient immune responses that facilitate LASV clearance in animals carrying this allele. Contrarily, alleles ManaMHC-I*008 and ManaMHC-I*021 in M. natalensis, and MaerMHC-I*008 in M. erythroleucus, were positively associated with active infection, implying susceptibility. Alleles associated with susceptibility shared a glutamic acid at the positively selected codon 57, while ManaMHC-I*006 featured an arginine. There was no link between number of MHC alleles per Mastomys individual and LASV prevalence. Thus, specific alleles, but not MHC diversity per se, seem to mediate antibody responses to viremia. We conclude that co-evolution with LASV likely shaped the MHC-I diversity of the main LASV reservoirs in southwestern Nigeria, and that information on reservoir immunogenetics may hold insights into transmission dynamics and zoonotic spillover risks.
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Affiliation(s)
- Ayodeji Olayemi
- Natural History Museum, Obafemi Awolowo University, Ile Ife, Osun State, Nigeria
| | - Dominik Werner Schmid
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | - Ramona Fleischer
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | - Kerstin Wilhelm
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | | | - Nadine Mueller-Klein
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | - Lavinia Haikukutu
- Department of Wildlife Management, Sokoine University of Agriculture, Morogoro, Tanzania
| | - Elisabeth Fichet-Calvet
- Department of Zoonoses Control, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Stephan Günther
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Simone Sommer
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
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Arbanasić H, Medrano-González L, Hrenar T, Mikelić A, Gomerčić T, Svetličić I, Pavlinec Ž, Đuras M, Galov A. Recent selection created distinctive variability patterns on MHC class II loci in three dolphin species from the Mediterranean Sea. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2024; 150:105079. [PMID: 37832898 DOI: 10.1016/j.dci.2023.105079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 10/10/2023] [Accepted: 10/10/2023] [Indexed: 10/15/2023]
Abstract
The major histocompatibility complex (MHC) includes highly polymorphic genes involved in antigen presentation, which is crucial for adaptive immune response. They represent fitness related genetic markers particularly informative for populations exposed to environmental challenges. Here we analyse the diversity and evolutionary traits of MHC class II DQA and DQB genes in the dolphins Stenella coeruleoalba and Grampus griseus from the Mediterranean Sea. We found substantial nucleotide and functional diversity, as well as strong evidence of balancing selection indicated by allele and supertype frequencies, Tajima's D statistics and dN/dS tests. The Risso's dolphin, considered the least abundant in the region, showed the effect of divergent allele advantage at the nucleotide and functional-peptide levels. An outstanding polymorphism was found in the striped dolphin, particularly intriguing in the DQA gene where the Ewens-Watterson test detected a selection sweep that occurred in recent history. We hypothesize that morbillivirus, which has recurrently invaded Mediterranean populations over the last decades, exerted the detected selective pressure.
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Affiliation(s)
- Haidi Arbanasić
- Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
| | - Luis Medrano-González
- Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, 04510, Mexico.
| | - Tomica Hrenar
- Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
| | - Ana Mikelić
- Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
| | - Tomislav Gomerčić
- Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, 10000, Zagreb, Croatia.
| | - Ida Svetličić
- Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
| | - Željko Pavlinec
- Croatian Academy of Sciences and Arts, Trg Nikole Šubića Zrinskog 11, 10000, Zagreb, Croatia.
| | - Martina Đuras
- Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, 10000, Zagreb, Croatia.
| | - Ana Galov
- Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
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Mellinger S, Stervander M, Lundberg M, Drews A, Westerdahl H. Improved haplotype resolution of highly duplicated MHC genes in a long-read genome assembly using MiSeq amplicons. PeerJ 2023; 11:e15480. [PMID: 37456901 PMCID: PMC10349553 DOI: 10.7717/peerj.15480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/08/2023] [Indexed: 07/18/2023] Open
Abstract
Long-read sequencing offers a great improvement in the assembly of complex genomic regions, such as the major histocompatibility complex (MHC) region, which can contain both tandemly duplicated MHC genes (paralogs) and high repeat content. The MHC genes have expanded in passerine birds, resulting in numerous MHC paralogs, with relatively high sequence similarity, making the assembly of the MHC region challenging even with long-read sequencing. In addition, MHC genes show rather high sequence divergence between alleles, making diploid-aware assemblers incorrectly classify haplotypes from the same locus as sequences originating from different genomic regions. Consequently, the number of MHC paralogs can easily be over- or underestimated in long-read assemblies. We therefore set out to verify the MHC diversity in an original and a haplotype-purged long-read assembly of one great reed warbler Acrocephalus arundinaceus individual (the focal individual) by using Illumina MiSeq amplicon sequencing. Single exons, representing MHC class I (MHC-I) and class IIB (MHC-IIB) alleles, were sequenced in the focal individual and mapped to the annotated MHC alleles in the original long-read genome assembly. Eighty-four percent of the annotated MHC-I alleles in the original long-read genome assembly were detected using 55% of the amplicon alleles and likewise, 78% of the annotated MHC-IIB alleles were detected using 61% of the amplicon alleles, indicating an incomplete annotation of MHC genes. In the haploid genome assembly, each MHC-IIB gene should be represented by one allele. The parental origin of the MHC-IIB amplicon alleles in the focal individual was determined by sequencing MHC-IIB in its parents. Two of five larger scaffolds, containing 6-19 MHC-IIB paralogs, had a maternal and paternal origin, respectively, as well as a high nucleotide similarity, which suggests that these scaffolds had been incorrectly assigned as belonging to different loci in the genome rather than as alternate haplotypes of the same locus. Therefore, the number of MHC-IIB paralogs was overestimated in the haploid genome assembly. Based on our findings we propose amplicon sequencing as a suitable complement to long-read sequencing for independent validation of the number of paralogs in general and for haplotype inference in multigene families in particular.
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Affiliation(s)
- Samantha Mellinger
- Department of Biology, Molecular Ecology and Evolution Lab, Lund University, Lund, Sweden
| | - Martin Stervander
- Department of Biology, Molecular Ecology and Evolution Lab, Lund University, Lund, Sweden
- Department of Biology and Environmental Science, Faculty of Health and Life Sciences, Linnaeus University, Kalmar, Sweden
- Bird Group, Natural History Museum, Tring, Hertfordshire, United Kingdom
| | - Max Lundberg
- Department of Biology, Molecular Ecology and Evolution Lab, Lund University, Lund, Sweden
| | - Anna Drews
- Department of Biology, Molecular Ecology and Evolution Lab, Lund University, Lund, Sweden
| | - Helena Westerdahl
- Department of Biology, Molecular Ecology and Evolution Lab, Lund University, Lund, Sweden
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Winternitz J, Chakarov N, Rinaud T, Ottensmann M, Krüger O. High functional allelic diversity and copy number in both MHC classes in the common buzzard. BMC Ecol Evol 2023; 23:24. [PMID: 37355591 PMCID: PMC10290333 DOI: 10.1186/s12862-023-02135-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 06/12/2023] [Indexed: 06/26/2023] Open
Abstract
BACKGROUND The major histocompatibility complex (MHC), which encodes molecules that recognize various pathogens and parasites and initiates the adaptive immune response in vertebrates, is renowned for its exceptional polymorphism and is a model of adaptive gene evolution. In birds, the number of MHC genes and sequence diversity varies greatly among taxa, believed due to evolutionary history and differential selection pressures. Earlier characterization studies and recent comparative studies suggest that non-passerine species have relatively few MHC gene copies compared to passerines. Additionally, comparative studies that have looked at partial MHC sequences have speculated that non-passerines have opposite patterns of selection on MHC class I (MHC-I) and class II (MHC-II) loci than passerines: namely, greater sequence diversity and signals of selection on MHC-II than MHC-I. However, new sequencing technology is revealing much greater MHC variation than previously expected while also facilitating full sequence variant detection directly from genomic data. Our study aims to take advantage of high-throughput sequencing methods to fully characterize both classes and domains of MHC of a non-passerine bird of prey, the common buzzard (Buteo buteo), to test predictions of MHC variation and differential selection on MHC classes. RESULTS Using genetic, genomic, and transcriptomic high-throughput sequencing data, we established common buzzards have at least three loci that produce functional alleles at both MHC classes. In total, we characterize 91 alleles from 113 common buzzard chicks for MHC-I exon 3 and 41 alleles from 125 chicks for MHC-IIB exon 2. Among these alleles, we found greater sequence polymorphism and stronger diversifying selection at MHC-IIB exon 2 than MHC-I exon 3, suggesting differential selection pressures on MHC classes. However, upon further investigation of the entire peptide-binding groove by including genomic data from MHC-I exon 2 and MHC-IIA exon 2, this turned out to be false. MHC-I exon 2 was as polymorphic as MHC-IIB exon 2 and MHC-IIA exon 2 was essentially invariant. Thus, comparisons between MHC-I and MHC-II that included both domains of the peptide-binding groove showed no differences in polymorphism nor diversifying selection between the classes. Nevertheless, selection analysis indicates balancing selection has been acting on common buzzard MHC and phylogenetic inference revealed that trans-species polymorphism is present between common buzzards and species separated for over 33 million years for class I and class II. CONCLUSIONS We characterize and confirm the functionality of unexpectedly high copy number and allelic diversity in both MHC classes of a bird of prey. While balancing selection is acting on both classes, there is no evidence of differential selection pressure on MHC classes in common buzzards and this result may hold more generally once more data for understudied MHC exons becomes available.
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Affiliation(s)
- Jamie Winternitz
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Nayden Chakarov
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Tony Rinaud
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Meinolf Ottensmann
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Oliver Krüger
- Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
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Extensive MHC class IIβ diversity across multiple loci in the small-spotted catshark (Scyliorhinus canicula). Sci Rep 2023; 13:3837. [PMID: 36882519 PMCID: PMC9992475 DOI: 10.1038/s41598-023-30876-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/02/2023] [Indexed: 03/09/2023] Open
Abstract
The major histocompatibility complex (MHC) is a multigene family responsible for pathogen detection, and initiation of adaptive immune responses. Duplication, natural selection, recombination, and their resulting high functional genetic diversity spread across several duplicated loci are the main hallmarks of the MHC. Although these features were described in several jawed vertebrate lineages, a detailed MHC IIβ characterization at the population level is still lacking for chondrichthyans (chimaeras, rays and sharks), i.e. the most basal lineage to possess an MHC-based adaptive immune system. We used the small-spotted catshark (Scyliorhinus canicula, Carcharhiniformes) as a case-study species to characterize MHC IIβ diversity using complementary molecular tools, including publicly available genome and transcriptome datasets, and a newly developed high-throughput Illumina sequencing protocol. We identified three MHC IIβ loci within the same genomic region, all of which are expressed in different tissues. Genetic screening of the exon 2 in 41 individuals of S. canicula from a single population revealed high levels of sequence diversity, evidence for positive selection, and footprints of recombination. Moreover, the results also suggest the presence of copy number variation in MHC IIβ genes. Thus, the small-spotted catshark exhibits characteristics of functional MHC IIβ genes typically observed in other jawed vertebrates.
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Rekdal SL, Anmarkrud JA, Lifjeld JT, Johnsen A. Do female bluethroats without extra-pair offspring have more MHC-compatible social mates? Behav Ecol Sociobiol 2023. [DOI: 10.1007/s00265-023-03311-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
Abstract
Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity in jawed vertebrates, and theory predicts that there should be mate choice for optimizing MHC constitution in the offspring. In a previous study, we demonstrated a non-random female choice of extra-pair males in the bluethroat (Luscinia svecica), yielding offspring that was closer to an intermediate MHC class II (MHCII) allele count than their within-pair halfsiblings. The present study tests whether social pairs with only within-pair young (WPY) in their brood, in the same study population, had a combined MHC-constitution closer to a presumed intermediate optimum, than social pairs with extra-pair young (EPY), with a corresponding pattern in their offspring. As expected, we found that WPY from pure WPY-broods were more MHC-optimal than WPY from mixed broods, but only in broods of young (second year) males. Correspondingly, there was a tendency for social pairs with only WPY in their brood to be more MHC-compatible than social pairs with EPY in their brood, when the male was young. Older bluethroat males have considerably larger testes than young males, and their higher sperm competitiveness could help them secure paternity in their own brood, also when they are not MHC-compatible. In other words, in the sexual conflict over paternity, females may be more likely to realise their preference for a MHC-compatible mate when paired to a young male. As a possible fitness indicator, immune responsiveness to an injected antigen (PHA) was elevated for offspring closer to “the golden mean” in MHCII allele count.
Significance statement
This study contributes to our understanding of MHC-based mate choice in extra-pair mating systems, by showing that female bluethroats (Luscinia svecica) with an MHCII-compatible social mate tend to have no extra-pair young in their brood, but only when the social male is young. This elucidates a possible sexual conflict, in which older social males are able to override female preferences and prevent other males from gaining paternity in their brood through higher sperm production. Studying systems in which extra-pair paternity occurs offers an insight into the genetic benefits of mate choice, as extra-pair males, in contrast to social males, generally contribute only sperm. Further, the strict and thorough genotyping scheme applied in this study enabled us to demonstrate a preference for “the golden mean” in MHC-diversity in a species with one of the highest MHC class II-diversity known to date.
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Worsley SF, Davies CS, Mannarelli ME, Komdeur J, Dugdale HL, Richardson DS. Assessing the causes and consequences of gut mycobiome variation in a wild population of the Seychelles warbler. MICROBIOME 2022; 10:242. [PMID: 36575553 PMCID: PMC9795730 DOI: 10.1186/s40168-022-01432-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/20/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND Considerable research has focussed on the importance of bacterial communities within the vertebrate gut microbiome (GM). However, studies investigating the significance of other microbial kingdoms, such as fungi, are notably lacking, despite their potential to influence host processes. Here, we characterise the fungal GM of individuals living in a natural population of Seychelles warblers (Acrocephalus sechellensis). We evaluate the extent to which fungal GM structure is shaped by environment and host factors, including genome-wide heterozygosity and variation at key immune genes (major histocompatibility complex (MHC) and Toll-like receptor (TLR)). Importantly, we also explore the relationship between fungal GM differences and subsequent host survival. To our knowledge, this is the first time that the genetic drivers and fitness consequences of fungal GM variation have been characterised for a wild vertebrate population. RESULTS Environmental factors, including season and territory quality, explain the largest proportion of variance in the fungal GM. In contrast, neither host age, sex, genome-wide heterozygosity, nor TLR3 genotype was associated with fungal GM differences in Seychelles warblers. However, the presence of four MHC-I alleles and one MHC-II allele was associated with changes in fungal GM alpha diversity. Changes in fungal richness ranged from between 1 and 10 sequencing variants lost or gained; in some cases, this accounted for 20% of the fungal variants carried by an individual. In addition to this, overall MHC-I allelic diversity was associated with small, but potentially important, changes in fungal GM composition. This is evidenced by the fact that fungal GM composition differed between individuals that survived or died within 7 months of being sampled. CONCLUSIONS Our results suggest that environmental factors play a primary role in shaping the fungal GM, but that components of the host immune system-specifically the MHC-may also contribute to the variation in fungal communities across individuals within wild populations. Furthermore, variation in the fungal GM can be associated with differential survival in the wild. Further work is needed to establish the causality of such relationships and, thus, the extent to which components of the GM may impact host evolution. Video Abstract.
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Affiliation(s)
- Sarah F Worsley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK.
| | - Charli S Davies
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
- NERC Biomolecular Analysis Facility, Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - Maria-Elena Mannarelli
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
| | - Jan Komdeur
- Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, P.O. Box 11103, 9700 CC, Groningen, The Netherlands
| | - Hannah L Dugdale
- Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, P.O. Box 11103, 9700 CC, Groningen, The Netherlands
- Faculty of Biological Sciences, School of Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - David S Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK.
- Nature Seychelles, Roche Caiman, Mahé, Republic of Seychelles.
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Evaluation of Genetic Diversity and Parasite-Mediated Selection of MHC Class I Genes in Emberiza godlewskii (Passeriformes: Emberizidae). DIVERSITY 2022. [DOI: 10.3390/d14110925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The major histocompatibility complex (MHC) is a multi-copy immune gene family in vertebrates. Its genes are highly variable and code for antigen-presenting molecules. Characterization of MHC genes in different species and investigating the mechanisms that shape MHC diversity is an important goal in understanding the evolution of biological diversity. Here we developed a next-generation sequencing (NGS) protocol to genotype the MHC class I genes of 326 Godlewski’s buntings (Emberiza godlewskii) sampled in the Western mountain area of Beijing from 2014 to 2016. A total of 184 functional alleles were identified, including both non-classical and classical alleles, clustering into nine supertypes. Compared with other passerine birds, the number of MHC class I alleles per individual in Godlewski’s buntings is high (mean 16.1 ± 3.3, median 16). In addition, we demonstrated signatures of historical and contemporary selection on MHC genes. Reflecting historical selection, ten amino acid sites in the antigen-binding domain showed signatures of balancing selection, eight of which exhibit high amino acid polymorphism. In terms of contemporary selection, we found that specific MHC supertypes were nominally associated with the infection of two malaria parasite lineages. These findings indicate the action of historical and possibly also contemporary balancing selection and suggest negative frequency-dependent or fluctuating selection as possible selection mechanisms.
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Performance Comparison of Different Approaches in Genotyping MHC-DRB: The Contrast between Single-Locus and Multi-Locus Species. Animals (Basel) 2022; 12:ani12182452. [PMID: 36139311 PMCID: PMC9495155 DOI: 10.3390/ani12182452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/12/2022] [Accepted: 09/13/2022] [Indexed: 11/17/2022] Open
Abstract
Major histocompatibility complex (MHC) genes are widely recognised as valuable markers for wildlife genetic studies given their extreme polymorphism and functional importance in fitness-related traits. Newly developed genotyping methods, which rely on the use of next-generation sequencing (NGS), are gradually replacing traditional cloning and Sanger sequencing methods in MHC genotyping studies. Allele calling in NGS methods remains challenging due to extreme polymorphism and locus multiplication in the MHC coupled with allele amplification bias and the generation of artificial sequences. In this study, we compared the performance of molecular cloning with Illumina and Ion Torrent NGS sequencing in MHC-DRB genotyping of single-locus species (roe deer) and species with multiple DRB loci (red deer) in an attempt to adopt a reliable and straightforward method that does not require complex bioinformatic analyses. Our results show that all methods work similarly well in roe deer, but we demonstrate non-consistency in results across methods in red deer. With Illumina sequencing, we detected a maximum number of alleles in 10 red deer individuals (42), while other methods were somewhat less accurate as they scored 69–81% of alleles detected with Illumina sequencing.
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A Review of Suggested Mechanisms of MHC Odor Signaling. BIOLOGY 2022; 11:biology11081187. [PMID: 36009814 PMCID: PMC9405088 DOI: 10.3390/biology11081187] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/26/2022] [Accepted: 08/04/2022] [Indexed: 11/23/2022]
Abstract
Simple Summary Immune genes of the vertebrate MHC vary among individuals. Each individual collection is optimally diverse to provide resistance against some infectious diseases but not too diverse to cause autoimmune diseases. MHC-dependent mate choice aims for optimally complementary MHC alleles. Each potential partner signals through body odor his/her MHC alleles. Identifying the signal molecules was a long-lasting puzzle solved only recently after many deviations as described. Commensal microbiota which are controlled by the individual MHC genes differ among individuals. They were suspected repeatedly to provide the signal, though mice raised germ-free could still smell MHC genes. Carrier hypotheses came in various versions, centered around the specificity of each MHC molecule for binding peptides from diseases, shown to T lymphocytes to induce the immune response. Volatiles of various origins were suggested to fill the place of the peptide and thus reflect the identity of the MHC molecule. Finally, the bound peptides themselves were identified as the sought info-chemicals. Synthesized peptides affect mate choice as predicted. Specific olfactory neurons were shown to react to these peptides but only to the anchors that define the binding specificity. Even eggs choose sperm to produce offspring with optimal MHC, though the signaling pathway needs further research. Abstract Although an individual’s mix of MHC immune genes determines its resistance, finding MHC-dependent mate choice occurred by accident in inbred mice. Inbred mice prefer MHC dissimilar mates, even when the choice was restricted to urine. It took decades to find the info-chemicals, which have to be as polymorphic as the MHC. Microbiota were suggested repeatedly as the origin of the odor signal though germ-free mice maintained normal preference. Different versions of the ‘carrier hypothesis’ suggested MHC molecules carry volatiles after the bound peptide is released. Theory predicted an optimal individual MHC diversity to maximize resistance. The optimally complementary mate should be and is preferred as several studies show. Thus, the odor signal needs to transmit the exact information of the sender’s MHC alleles, as do MHC ligand peptides but not microbiota. The ‘MHC peptide hypothesis’ assumes that olfactory perception of the peptide ligand provides information about the MHC protein in a key-lock fashion. Olfactory neurons react only to the anchors of synthesized MHC peptides, which reflect the binding MHC molecule’s identity. Synthesized peptides supplemented to a male’s signal affect choice in the predicted way, however, not when anchors are mutated. Also, the human brain detects smelled synthesized self-peptides as such. After mate choice, the lottery of meiosis of randomly paired oocyte and sperm haplotypes would often produce MHC non-optimal offspring. In sticklebacks, eggs select MHC-compatible sperm, thus prefer the best combination close to the population optimum.
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Using de novo genome assembly and high-throughput sequencing to characterize the MHC region in a non-model bird, the Eurasian coot. Sci Rep 2022; 12:7031. [PMID: 35488050 PMCID: PMC9054815 DOI: 10.1038/s41598-022-11018-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/01/2022] [Indexed: 11/17/2022] Open
Abstract
Genes of the Major Histocompatibility Complex (MHC) form a key component of vertebrate adaptive immunity, as they code for molecules which bind antigens of intra- and extracellular pathogens (MHC class I and II, respectively) and present them to T cell receptors. In general, MHC genes are hyper-polymorphic and high MHC diversity is often maintained within natural populations (via balancing selection) and within individuals (via gene duplications). Because of its complex architecture with tandems of duplicated genes, characterization of MHC region in non-model vertebrate species still poses a major challenge. Here, we combined de novo genome assembly and high-throughput sequencing to characterize MHC polymorphism in a rallid bird species, the Eurasian coot Fulica atra. An analysis of genome assembly indicated high duplication rate at MHC-I, which was also supported by targeted sequencing of peptide-binding exons (at least five MHC-I loci genotyped). We found high allelic richness at both MHC-I and MHC-II, although signature of diversifying selection and recombination (gene conversion) was much stronger at MHC-II. Our results indicate that Eurasian coot retains extraordinary polymorphism at both MHC classes (when compared to other non-passerine bird species), although they may be subject to different evolutionary mechanism.
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12
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Ratcliffe FC, Garcia de Leaniz C, Consuegra S. MHC class I-α population differentiation in a commercial fish, the European sea bass (Dicentrarchus labrax). Anim Genet 2022; 53:340-351. [PMID: 35274334 PMCID: PMC9314080 DOI: 10.1111/age.13184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 01/13/2022] [Accepted: 02/20/2022] [Indexed: 01/29/2023]
Abstract
Identifying population structuring in highly fecund marine species with high dispersal rates is challenging, but critical for conservation and stock delimitation for fisheries management. European sea bass (Dicentrarchus labrax) is a commercial species of fisheries and aquaculture relevance whose stocks are declining in the North Atlantic, despite management measures to protect them and identifying their fine population structure is needed for managing their exploitation. As for other marine fishes, neutral genetic markers indicate that eastern Atlantic sea bass form a panmictic population and is currently managed as arbitrarily divided stocks. The genes of the major histocompatibility complex (MHC) are key components of the adaptive immune system and ideal candidates to assess fine structuring arising from local selective pressures. We used Illumina sequencing to characterise allelic composition and signatures of selection at the MHC class I-α region of six D. labrax populations across the Atlantic range. We found high allelic diversity driven by positive selection, corresponding to moderate supertype diversity, with 131 alleles clustering into four to eight supertypes, depending on the Bayesian information criterion threshold applied, and a mean number of 13 alleles per individual. Alleles could not be assigned to particular loci, but private alleles allowed us to detect regional genetic structuring not found previously using neutral markers. Our results suggest that MHC markers can be used to detect cryptic population structuring in marine species where neutral markers fail to identify differentiation. This is particularly critical for fisheries management, and of potential use for selective breeding or identifying escapes from sea farms.
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Affiliation(s)
- Frances C Ratcliffe
- Department of Biosciences, College of Science, Swansea University, Swansea, UK
| | | | - Sofia Consuegra
- Department of Biosciences, College of Science, Swansea University, Swansea, UK
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13
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He K, Liang CH, Zhu Y, Dunn P, Zhao A, Minias P. Reconstructing Macroevolutionary Patterns in Avian MHC Architecture With Genomic Data. Front Genet 2022; 13:823686. [PMID: 35251132 PMCID: PMC8893315 DOI: 10.3389/fgene.2022.823686] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/25/2022] [Indexed: 12/28/2022] Open
Abstract
The Major Histocompatibility Complex (MHC) is a hyper-polymorphic genomic region, which forms a part of the vertebrate adaptive immune system and is crucial for intra- and extra-cellular pathogen recognition (MHC-I and MHC-IIA/B, respectively). Although recent advancements in high-throughput sequencing methods sparked research on the MHC in non-model species, the evolutionary history of MHC gene structure is still poorly understood in birds. Here, to explore macroevolutionary patterns in the avian MHC architecture, we retrieved contigs with antigen-presenting MHC and MHC-related genes from available genomes based on third-generation sequencing. We identified: 1) an ancestral avian MHC architecture with compact size and tight linkage between MHC-I, MHC-IIA/IIB and MHC-related genes; 2) three major patterns of MHC-IIA/IIB unit organization in different avian lineages; and 3) lineage-specific gene translocation events (e.g., separation of the antigen-processing TAP genes from the MHC-I region in passerines), and 4) the presence of a single MHC-IIA gene copy in most taxa, showing evidence of strong purifying selection (low dN/dS ratio and low number of positively selected sites). Our study reveals long-term macroevolutionary patterns in the avian MHC architecture and provides the first evidence of important transitions in the genomic arrangement of the MHC region over the last 100 million years of bird evolution.
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Affiliation(s)
- Ke He
- College of Animal Science and Technology, College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Hangzhou, China
- *Correspondence: Ke He, ; Piotr Minias,
| | - Chun-hong Liang
- College of Animal Science and Technology, College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Hangzhou, China
| | - Ying Zhu
- Institute of Qinghai-Tibetan Plateau, Southwest Minzu University, Chengdu, China
| | - Peter Dunn
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Ayong Zhao
- College of Animal Science and Technology, College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Hangzhou, China
| | - Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łodz, Łódź, Poland
- *Correspondence: Ke He, ; Piotr Minias,
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14
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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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15
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Pikus E, Włodarczyk R, Jedlikowski J, Minias P. Urbanization processes drive divergence at the major histocompatibility complex in a common waterbird. PeerJ 2021; 9:e12264. [PMID: 34707940 PMCID: PMC8500109 DOI: 10.7717/peerj.12264] [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: 04/28/2021] [Accepted: 09/16/2021] [Indexed: 11/20/2022] Open
Abstract
Urban sprawl is one of the most common landscape alterations occurring worldwide, and there is a growing list of species that are recognised to have adapted to urban life. To be successful, processes of urban colonization by wildlife require a broad spectrum of phenotypic (e.g., behavioural or physiological) adjustments, but evidence for genetic adaptations is much scarcer. One hypothesis proposes that different pathogen-driven selective pressures between urban and non-urban landscapes leads to adaptations in host immune genes. Here, we examined urbanization-related differentiation at the key pathogen-recognition genes of vertebrate adaptive immunity-the major histocompatibility complex (MHC)-in a common waterbird, the Eurasian coot (Fulica atra). Samples were collected from an old urban population (established before the 1950s), a new urban population (established in the 2000s), and two rural populations from central Poland. We found strong significant divergence (as measured with Jost's D) at the MHC class II between the old urban population and the remaining (new urban and rural) populations. Also, there was a moderate, but significant divergence at the MHC between the new urban population and two rural populations, while no divergence was found between the two rural populations. The total number of MHC alleles and the number of private (population-specific) MHC alleles was lower in old urban populations, as compared to the rural ones. These patterns of differentiation at the MHC were not consistent with patterns found for neutral genetic markers (microsatellites), which showed few differences between the populations. Our results indicate that MHC allele composition depended on the level of anthropogenic disturbance and the time which passed since urban colonization, possibly due to the processes of genotype sorting and local adaptation. As such, our study contributes to the understanding of genetic mechanisms associated with urbanization processes in wildlife.
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Affiliation(s)
- Ewa Pikus
- Department of Biodiversity Studies and Bioeducation, University of Łódź, Łódź, Poland
| | - Radosław Włodarczyk
- Department of Biodiversity Studies and Bioeducation, University of Łódź, Łódź, Poland
| | - Jan Jedlikowski
- Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Piotr Minias
- Department of Biodiversity Studies and Bioeducation, University of Łódź, Łódź, Poland
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16
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Minias P, Drzewińska-Chańko J, Włodarczyk R. Evolution of innate and adaptive immune genes in a non-model waterbird, the common tern. INFECTION GENETICS AND EVOLUTION 2021; 95:105069. [PMID: 34487864 DOI: 10.1016/j.meegid.2021.105069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 08/28/2021] [Accepted: 09/01/2021] [Indexed: 11/25/2022]
Abstract
Toll-like receptors (TLRs) and the Major Histocompatibility Complex (MHC) are the key pathogen-recognition genes of vertebrate immune system and they have a crucial role in the initiation of innate and adaptive immune response, respectively. Recent advancements in sequencing technology sparked research on highly duplicated MHC genes in non-model species, but TLR variation in natural vertebrate populations has remained little studied and comparisons of polymorphism across both TLRs and MHC are scarce. Here, we aimed to compare variation across innate (four TLR loci) and adaptive (MHC class I and class II) immune genes in a non-model avian species, the common tern Sterna hirundo. We detected relatively high allelic richness at TLR genes (9-48 alleles per locus), which was similar to or even higher than the estimated per locus allelic richness at the MHC (24-30 alleles at class I and 13-16 alleles at class II under uniform sample sizes). Despite this, the total number of MHC alleles across all duplicated loci (four class I and three class II) was much higher and MHC alleles showed greater sequence divergence than TLRs. Positive selection targeted relatively more sites at the MHC than TLRs, but the strength of selection (dN/dS ratios) at TLRs was higher when compared to MHC class I. There were also differences in the signature of positive selection and recombination (gene conversion) between MHC class I and II (stronger signature at class II), suggesting that mechanisms maintaining variation at the MHC may vary between both classes. Our study indicates that allelic richness of both innate and adaptive immune receptors may be maintained at relatively high levels in viable avian populations and we recommend a transition from the traditional gene-specific to multi-gene approach in studying molecular evolution of vertebrate immune system.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.
| | - Joanna Drzewińska-Chańko
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland
| | - Radosław Włodarczyk
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland
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17
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Minias P, Włodarczyk R, Remisiewicz M, Cobzaru I, Janiszewski T. Distinct evolutionary trajectories of MHC class I and class II genes in Old World finches and buntings. Heredity (Edinb) 2021; 126:974-990. [PMID: 33824536 PMCID: PMC8178356 DOI: 10.1038/s41437-021-00427-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 03/08/2021] [Accepted: 03/15/2021] [Indexed: 02/01/2023] Open
Abstract
Major histocompatibility complex (MHC) genes code for key proteins of the adaptive immune system, which present antigens from intra-cellular (MHC class I) and extra-cellular (MHC class II) pathogens. Because of their unprecedented diversity, MHC genes have long been an object of scientific interest, but due to methodological difficulties in genotyping of duplicated loci, our knowledge on the evolution of the MHC across different vertebrate lineages is still limited. Here, we compared the evolution of MHC class I and class II genes in three sister clades of common passerine birds, finches (Fringillinae and Carduelinae) and buntings (Emberizidae) using a uniform methodological (genotyping and data processing) approach and uniform sample sizes. Our analyses revealed contrasting evolutionary trajectories of the two MHC classes. We found a stronger signature of pervasive positive selection and higher allele diversity (allele numbers) at the MHC class I than class II. In contrast, MHC class II genes showed greater allele divergence (in terms of nucleotide diversity) and a much stronger recombination (gene conversion) signal. Gene copy numbers at both MHC class I and class II evolved via fluctuating selection and drift (Brownian Motion evolution), but the evolutionary rate was higher at class I. Our study constitutes one of few existing examples, where evolution of MHC class I and class II genes was directly compared using a multi-species approach. We recommend that re-focusing MHC research from single-species and single-class approaches towards multi-species analyses of both MHC classes can substantially increase our understanding MHC evolution in a broad phylogenetic context.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland.
| | - Radosław Włodarczyk
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
| | - Magdalena Remisiewicz
- Bird Migration Research Station, Faculty of Biology, University of Gdańsk, Gdańsk, Poland
| | - Ioana Cobzaru
- Institute of Biology Bucharest, Romanian Academy, Bucharest, Romania
| | - Tomasz Janiszewski
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
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18
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Minias P, He K, Dunn PO. The strength of selection is consistent across both domains of the MHC class I peptide-binding groove in birds. BMC Ecol Evol 2021; 21:80. [PMID: 33964878 PMCID: PMC8106206 DOI: 10.1186/s12862-021-01812-x] [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: 01/04/2021] [Accepted: 04/28/2021] [Indexed: 02/26/2023] Open
Abstract
Background The Major Histocompatibility Complex (MHC) codes for the key vertebrate immune receptors responsible for pathogen recognition. Foreign antigens are recognized via their compatibility to hyper-variable region of the peptide-binding groove (PBR), which consists of two separate protein domains. Specifically, the PBR of the MHC class I receptors, which recognize intra-cellular pathogens, has two α domains encoded by exon 2 (α1) and exon 3 (α2) of the same gene. Most research on avian MHC class I polymorphism has traditionally focused exclusively on exon 3 and comparisons of selection between the two domains have been hampered by the scarcity of molecular data for exon 2. Thus, it is not clear whether the two domains vary in their specificity towards different antigens and whether they are subject to different selective pressure. Results Here, we took advantage of rapidly accumulating genomic resources to test for the differences in selection patterns between both MHC class I domains of the peptide-binding groove in birds. For this purpose, we compiled a dataset of MHC class I exon 2 and 3 sequences for 120 avian species from 46 families. Our phylogenetically-robust approach provided strong evidence for highly consistent levels of selection on the α1 and α2 domains. There were strong correlations in all selection measures (number of positively/negatively selected residues and dN/dS ratios) between both PBR exons. Similar positive associations were found for the level of amino acid polymorphism across the two domains. Conclusions We conclude that the strength of selection and the level of polymorphism are highly consistent between both peptide-binding domains (α1 and α2) of the avian MHC class I. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-021-01812-x.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237, Łódź, Poland.
| | - Ke He
- College of Animal Science and Technology, College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Peter O Dunn
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, USA
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O'Connor EA, Westerdahl H. Trade-offs in expressed major histocompatibility complex diversity seen on a macroevolutionary scale among songbirds. Evolution 2021; 75:1061-1069. [PMID: 33666228 DOI: 10.1111/evo.14207] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 01/07/2021] [Accepted: 02/17/2021] [Indexed: 12/30/2022]
Abstract
To survive organisms must defend themselves against pathogens. Classical Major Histocompatibility Complex (MHC) genes play a key role in pathogen defense by encoding molecules involved in pathogen recognition. MHC gene diversity influences the variety of pathogens individuals can recognize and respond to and has consequently been a popular genetic marker for disease resistance in ecology and evolution. However, MHC diversity is predominantly estimated using genomic DNA (gDNA) with little knowledge of expressed diversity. This limits our ability to interpret the adaptive significance of variation in MHC diversity, especially in species with very many MHC genes such as songbirds. Here, we address this issue using phylogenetic comparative analyses of the number of MHC class I alleles (MHC-I diversity) in gDNA and complementary DNA (cDNA), that is, expressed alleles, across 13 songbird species. We propose three theoretical relationships that could be expected between genomic and expressed MHC-I diversity on a macroevolutionary scale and test which of these are best supported. In doing so, we show that significantly fewer MHC-I alleles than the number available are expressed, suggesting that optimal MHC-I diversity could be achieved by modulating gene expression. Understanding the relationship between genomic and expressed MHC diversity is essential for interpreting variation in MHC diversity in an evolutionary context.
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Affiliation(s)
- Emily A O'Connor
- Molecular Ecology and Evolution Lab, 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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20
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Minias P, Gutiérrez JS, Dunn PO. Avian major histocompatibility complex copy number variation is associated with helminth richness. Biol Lett 2020; 16:20200194. [PMID: 32634375 DOI: 10.1098/rsbl.2020.0194] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Genes of the major histocompatibility complex (MHC) play a key role in the adaptive immunity of vertebrates, as they encode receptors responsible for antigen recognition. Evolutionary history of the MHC proceeded through numerous gene duplications, which increase the spectrum of pathogens recognized by individuals. Although pathogen-mediated selection is believed to be a primary driver of MHC expansion over evolutionary times, empirical evidence for this association is virtually lacking. Here, we used an extensive dataset on MHC class II copy number variation in non-passerine birds to test for an evolutionary correlation with helminth parasite richness. As expected, our phylogenetically-informed modelling revealed a positive association between MHC copy number and total helminth richness, even after controlling for a broad spectrum of ecological and life-history traits. Thus, total helminth richness appears to be the most important correlate of MHC copy number, supporting a leading role of pathogen-mediated selection in the evolution of MHC in birds. Our results provide some of the first, although correlative, evidence linking parasitism to interspecific variation in MHC copy number among birds.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland
| | - Jorge S Gutiérrez
- Department of Anatomy, Cell Biology and Zoology, Faculty of Sciences, University of Extremadura, Badajoz, 06006, Spain
| | - Peter O Dunn
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland.,Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
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21
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Stervander M, Dierickx EG, Thorley J, Brooke MDL, Westerdahl H. High MHC gene copy number maintains diversity despite homozygosity in a Critically Endangered single-island endemic bird, but no evidence of MHC-based mate choice. Mol Ecol 2020; 29:3578-3592. [PMID: 32416000 DOI: 10.1111/mec.15471] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 04/14/2020] [Accepted: 05/04/2020] [Indexed: 12/30/2022]
Abstract
Small population sizes can, over time, put species at risk due to the loss of genetic variation and the deleterious effects of inbreeding. Losing diversity in the major histocompatibility complex (MHC) could be particularly harmful, given its key role in the immune system. Here, we assess MHC class I (MHC-I) diversity and its effects on mate choice and survival in the Critically Endangered Raso lark Alauda razae, a species restricted to the 7 km2 islet of Raso, Cape Verde, since ~1460, whose population size has dropped as low as 20 pairs. Exhaustively genotyping 122 individuals, we find no effect of MHC-I genotype/diversity on mate choice or survival. However, we demonstrate that MHC-I diversity has been maintained through extreme bottlenecks by retention of a high number of gene copies (at least 14), aided by cosegregation of multiple haplotypes comprising 2-8 linked MHC-I loci. Within-locus homozygosity is high, contributing to low population-wide diversity. Conversely, each individual had comparably many alleles, 6-16 (average 11), and the large and divergent haplotypes occur at high frequency in the population, resulting in high within-individual MHC-I diversity. This functional immune gene diversity will be of critical importance for this highly threatened species' adaptive potential.
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Affiliation(s)
- Martin Stervander
- Department of Biology, Lund University, Lund, Sweden.,Department of Biology and Environmental Science, Faculty of Health and Life Sciences, Linnaeus University, Kalmar, Sweden.,Institute of Ecology and Evolution, University of Oregon, Eugene, OR, USA
| | - Elisa G Dierickx
- Department of Zoology, University of Cambridge, Cambridge, UK.,Fauna & Flora International, Cambridge, UK
| | - Jack Thorley
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - M de L Brooke
- Department of Zoology, University of Cambridge, Cambridge, UK
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22
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Not all birds have a single dominantly expressed MHC-I gene: Transcription suggests that siskins have many highly expressed MHC-I genes. Sci Rep 2019; 9:19506. [PMID: 31862923 PMCID: PMC6925233 DOI: 10.1038/s41598-019-55800-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 11/18/2019] [Indexed: 01/03/2023] Open
Abstract
Passerine birds belong to the most species rich bird order and are found in a wide range of habitats. The extremely polymorphic adaptive immune system of passerines, identified through their major histocompatibility complex class I genes (MHC-I), may explain some of this extreme radiation. Recent work has shown that passerines have higher numbers of MHC-I gene copies than other birds, but little is currently known about expression and function of these gene copies. Non-passerine birds have a single highly expressed MHC-I gene copy, a pattern that seems unlikely in passerines. We used high-throughput sequencing to study MHC-I alleles in siskins (Spinus spinus) and determined gene expression, phylogenetic relationships and sequence divergence. We verified between six and 16 MHC-I alleles per individual and 97% of these were expressed. Strikingly, up to five alleles per individual had high expression. Out of 88 alleles 18 were putatively non-classical with low sequence divergence and expression, and found in a single phylogenetic cluster. The remaining 70 alleles were classical, with high sequence divergence and variable degrees of expression. Our results contradict the suggestion that birds only have a single dominantly expressed MHC-I gene by demonstrating several highly expressed MHC-I gene copies in a passerine.
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23
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O'Connor EA, Westerdahl H, Burri R, Edwards SV. Avian MHC Evolution in the Era of Genomics: Phase 1.0. Cells 2019; 8:E1152. [PMID: 31561531 PMCID: PMC6829271 DOI: 10.3390/cells8101152] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/16/2019] [Accepted: 09/20/2019] [Indexed: 12/14/2022] Open
Abstract
Birds are a wonderfully diverse and accessible clade with an exceptional range of ecologies and behaviors, making the study of the avian major histocompatibility complex (MHC) of great interest. In the last 20 years, particularly with the advent of high-throughput sequencing, the avian MHC has been explored in great depth in several dimensions: its ability to explain ecological patterns in nature, such as mating preferences; its correlation with parasite resistance; and its structural evolution across the avian tree of life. Here, we review the latest pulse of avian MHC studies spurred by high-throughput sequencing. Despite high-throughput approaches to MHC studies, substantial areas remain in need of improvement with regard to our understanding of MHC structure, diversity, and evolution. Recent studies of the avian MHC have nonetheless revealed intriguing connections between MHC structure and life history traits, and highlight the advantages of long-term ecological studies for understanding the patterns of MHC variation in the wild. Given the exceptional diversity of birds, their accessibility, and the ease of sequencing their genomes, studies of avian MHC promise to improve our understanding of the many dimensions and consequences of MHC variation in nature. However, significant improvements in assembling complete MHC regions with long-read sequencing will be required for truly transformative studies.
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Affiliation(s)
| | | | - Reto Burri
- Department of Population Ecology, Institute of Ecology & Evolution, Friedrich Schiller University Jena, 07737 Jena, Germany.
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA.
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24
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Qurkhuli T, Schwensow N, Brändel SD, Tschapka M, Sommer S. Can extreme MHC class I diversity be a feature of a wide geographic range? The example of Seba's short-tailed bat (Carollia perspicillata). Immunogenetics 2019; 71:575-587. [PMID: 31520134 PMCID: PMC7079943 DOI: 10.1007/s00251-019-01128-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 08/14/2019] [Indexed: 12/19/2022]
Abstract
The major histocompatibility complex (MHC) is one of the most diverse genetic regions under pathogen-driven selection because of its central role in antigen binding and immunity. The highest MHC variability, both in terms of the number of individual alleles and gene copies, has so far been found in passerine birds; this is probably attributable to passerine adaptation to both a wide geographic range and a diverse array of habitats. If extraordinary high MHC variation and duplication rates are adaptive features under selection during the evolution of ecologically and taxonomically diverse species, then similarly diverse MHC architectures should be found in bats. Bats are an extremely species-rich mammalian group that is globally widely distributed. Many bat species roost in multitudinous groups and have high contact rates with pathogens, conspecifics, and allospecifics. We have characterized the MHC class I diversity in 116 Panamanian Seba's short-tailed bats (Carollia perspicillata), a widely distributed, generalist, neotropical species. We have detected a remarkable individual and population-level diversity of MHC class I genes, with between seven and 22 alleles and a unique genotype in each individual. This diversity is comparable with that reported in passerine birds and, in both taxonomic groups, further variability has evolved through length polymorphisms. Our findings support the hypothesis that, for species with a geographically broader range, high MHC class I variability is particularly adaptive. Investigation of the details of the underlying adaptive processes and the role of the high MHC diversity in pathogen resistance are important next steps for a better understanding of the role of bats in viral evolution and as carriers of several deadly zoonotic viruses.
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Affiliation(s)
- Tamar Qurkhuli
- Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein Allee 11, 89081, Ulm, Germany
| | - Nina Schwensow
- Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein Allee 11, 89081, Ulm, Germany
| | - Stefan Dominik Brändel
- Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein Allee 11, 89081, Ulm, Germany
- Smithsonian Tropical Research Institute, Apartado, 0843-03092, Panamá, República de Panamá
| | - Marco Tschapka
- Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein Allee 11, 89081, Ulm, Germany
- Smithsonian Tropical Research Institute, Apartado, 0843-03092, Panamá, República de Panamá
| | - Simone Sommer
- Institute for Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein Allee 11, 89081, Ulm, Germany.
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25
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Evolution of major histocompatibility complex gene copy number. PLoS Comput Biol 2019; 15:e1007015. [PMID: 31095555 PMCID: PMC6541284 DOI: 10.1371/journal.pcbi.1007015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 05/29/2019] [Accepted: 04/09/2019] [Indexed: 01/05/2023] Open
Abstract
MHC genes, which code for proteins responsible for presenting pathogen-derived antigens to the host immune system, show remarkable copy-number variation both between and within species. However, the evolutionary forces driving this variation are poorly understood. Here, we use computer simulations to investigate whether evolution of the number of MHC variants in the genome can be shaped by the number of pathogen species the host population encounters (pathogen richness). Our model assumed that while increasing a range of pathogens recognised, expressing additional MHC variants also incurs costs such as an increased risk of autoimmunity. We found that pathogen richness selected for high MHC copy number only when the costs were low. Furthermore, the shape of the association was modified by the rate of pathogen evolution, with faster pathogen mutation rates selecting for increased host MHC copy number, but only when pathogen richness was low to moderate. Thus, taking into account factors other than pathogen richness may help explain wide variation between vertebrate species in the number of MHC genes. Within population, variation in the number of unique MHC variants carried by individuals (INV) was observed under most parameter combinations, except at low pathogen richness. This variance gave rise to positive correlations between INV and host immunocompetence (proportion of pathogens recognised). However, within-population variation in host immunocompetence declined with pathogen richness. Thus, counterintuitively, pathogens can contribute more to genetic variance for host fitness in species exposed to fewer pathogen species, with consequences to predictions from “Hamilton-Zuk” theory of sexual selection. Highly polymorphic genes of the Major Histocompatibility Complex (MHC) code for proteins responsible for presenting antigens to lymphocytes, thus initiating adaptive immune response. The polymorphism is driven by coevolution with parasites which are selected to evade recognition by MHC proteins. Expressing many MHC molecules could ensure that an individual could present antigens of most pathogen species encountered, but this comes at a cost, such as enhanced negative selection on lymphocytes leading to holes in T-cell receptor repertoire. Our simulations showed that evolution of the number of MHC genes in the genome is driven by a complex interaction between three factors we explored: pathogen richness, the intrinsic cost of expressing additional MHC variants, and pathogen mutation rate. In contrast to verbal arguments, our results indicate that pathogen richness does not always selects for MHC gene family expansion. Taking into account factors other than pathogen richness, in particular costs of expressing additional MHC variants which are still poorly understood, may help explain striking interspecific variation in the number of MHC genes. Counterintuitively, our results also demonstrated that opportunity for selection on immunocompetence should decrease with MHC gene family expansion.
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26
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Minias P, Pikus E, Anderwald D. Allelic diversity and selection at the MHC class I and class II in a bottlenecked bird of prey, the White-tailed Eagle. BMC Evol Biol 2019; 19:2. [PMID: 30611206 PMCID: PMC6321662 DOI: 10.1186/s12862-018-1338-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 12/17/2018] [Indexed: 01/07/2023] Open
Abstract
Background Genes of the Major Histocompatibility Complex (MHC) are essential for adaptive immune response in vertebrates, as they encode receptors that recognize peptides derived from the processing of intracellular (MHC class I) and extracellular (MHC class II) pathogens. High MHC diversity in natural populations is primarily generated and maintained by pathogen-mediated diversifying and balancing selection. It is, however, debated whether selection at the MHC can counterbalance the effects of drift in bottlenecked populations. The aim of this study was to assess allelic diversity of MHC genes in a recently bottlenecked bird of prey, the White-tailed Eagle Haliaeetus albicilla, as well as to compare mechanisms that shaped the evolution of MHC class I and class II in this species. Results We showed that significant levels of MHC diversity were retained in the core Central European (Polish) population of White-tailed Eagles. Ten MHC class I and 17 MHC class II alleles were recovered in total and individual birds showed high average MHC diversity (3.80 and 6.48 MHC class I and class II alleles per individual, respectively). Distribution of alleles within individuals provided evidence for the presence of at least three class I and five class II loci the White-tailed Eagle, which suggests recent duplication events. MHC class II showed greater sequence polymorphism than MHC class I and there was much stronger signature of diversifying selection acting on MHC class II than class I. Phylogenetic analysis provided evidence for trans-species similarity of class II, but not class I, sequences, which is likely consistent with stronger balancing selection at MHC class II. Conclusions Relatively high MHC diversity retained in the White-tailed Eagles from northern Poland reinforces high conservation value of local eagle populations. At the same time, our study is the first to demonstrate contrasting patterns of allelic diversity and selection at MHC class I and class II in an accipitrid species, supporting the hypothesis that different mechanisms can shape evolutionary trajectories of MHC class I and class II genes. Electronic supplementary material The online version of this article (10.1186/s12862-018-1338-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237, Łódź, Poland.
| | - Ewa Pikus
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 1/3, 90-237, Łódź, Poland
| | - Dariusz Anderwald
- Eagle Conservation Committee, Niepodległości 53/55, 10-044, Olsztyn, Poland
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27
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Minias P, Pikus E, Whittingham LA, Dunn PO. Evolution of Copy Number at the MHC Varies across the Avian Tree of Life. Genome Biol Evol 2019; 11:17-28. [PMID: 30476037 PMCID: PMC6319602 DOI: 10.1093/gbe/evy253] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2018] [Indexed: 12/24/2022] Open
Abstract
The evolution of the major histocompatibility complex (MHC) is shaped by frequent gene duplications and deletions, which generate extensive variation in the number of loci (gene copies) between different taxa. Here, we collected estimates of copy number at the MHC for over 250 bird species from 68 families. We found contrasting patterns of copy number evolution between MHC class I and class IIB, which encode receptors for intra- and extracellular pathogens, respectively. Across the avian evolutionary tree, there was evidence of accelerated evolution and stabilizing selection acting on copy number at class I, while copy number at class IIB was primarily influenced by fluctuating selection and drift. Reconstruction of MHC copy number variation showed ancestrally low numbers of MHC loci in nonpasserines and evolution toward larger numbers of loci in passerines. Different passerine lineages had the highest duplication rates for MHC class I (Sylvioidea) and class IIB (Muscicapoidea and Passeroidea). We also found support for the correlated evolution of MHC copy number and life-history traits such as lifespan and migratory behavior. These results suggest that MHC copy number evolution in birds has been driven by life histories and differences in exposure to intra- and extracellular pathogens.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Lódz, Poland
| | - Ewa Pikus
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Lódz, Poland
| | - Linda A Whittingham
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee
| | - Peter O Dunn
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Poland.,Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee
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28
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Whittingham LA, Dunn PO, Freeman-Gallant CR, Taff CC, Johnson JA. Major histocompatibility complex variation and blood parasites in resident and migratory populations of the common yellowthroat. J Evol Biol 2018; 31:1544-1557. [DOI: 10.1111/jeb.13349] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 06/12/2018] [Accepted: 06/25/2018] [Indexed: 01/13/2023]
Affiliation(s)
- Linda A. Whittingham
- Behavioral and Molecular Ecology Group; Department of Biological Sciences; University of Wisconsin-Milwaukee; Milwaukee WI USA
| | - Peter O. Dunn
- Behavioral and Molecular Ecology Group; Department of Biological Sciences; University of Wisconsin-Milwaukee; Milwaukee WI USA
| | | | - Conor C. Taff
- Cornell Laboratory of Ornithology; Cornell University; Ithaca NY USA
| | - Jeff A. Johnson
- Department of Biological Sciences; Institute of Applied Sciences; University of North Texas; Denton TX USA
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29
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Hoover B, Alcaide M, Jennings S, Sin SYW, Edwards SV, Nevitt GA. Ecology can inform genetics: Disassortative mating contributes to MHC polymorphism in Leach's storm-petrels (Oceanodroma leucorhoa). Mol Ecol 2018; 27:3371-3385. [PMID: 30010226 DOI: 10.1111/mec.14801] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/31/2018] [Accepted: 06/20/2018] [Indexed: 01/03/2023]
Abstract
Studies of MHC-based mate choice in wild populations often test hypotheses on species exhibiting female choice and male-male competition, which reflects the general prevalence of females as the choosy sex in natural systems. Here, we examined mutual mate-choice patterns in a small burrow-nesting seabird, the Leach's storm-petrel (Oceanodroma leucorhoa), using the major histocompatibility complex (MHC). The life history and ecology of this species are extreme: both partners work together to fledge a single chick during the breeding season, a task that requires regularly travelling hundreds of kilometres to and from foraging grounds over a 6- to 8-week provisioning period. Using a 5-year data set unprecedented for this species (n = 1078 adults and 925 chicks), we found a positive relationship between variation in the likelihood of female reproductive success and heterozygosity at Ocle-DAB2, a MHC class IIB locus. Contrary to previous reports rejecting disassortative mating as a mechanism for maintaining genetic polymorphism in this species, here we show that males make significant disassortative mate-choice decisions. Variability in female reproductive success suggests that the most common homozygous females (Ocle-DAB2*01/Ocle-DAB2*01) may be physiologically disadvantaged and, therefore, less preferred as lifelong partners for choosy males. The results from this study support the role of mate choice in maintaining high levels of MHC variability in a wild seabird species and highlight the need to incorporate a broader ecological framework and sufficient sample sizes into studies of MHC-based mating patterns in wild populations in general.
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Affiliation(s)
- Brian Hoover
- Graduate Group in Ecology, University of California, Davis, California
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Miguel Alcaide
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sarah Jennings
- Graduate Group in Ecology, University of California, Davis, California
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Simon Yung Wa Sin
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
| | - Gabrielle A Nevitt
- Graduate Group in Ecology, University of California, Davis, California
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
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30
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Biedrzycka A, Bielański W, Ćmiel A, Solarz W, Zając T, Migalska M, Sebastian A, Westerdahl H, Radwan J. Blood parasites shape extreme major histocompatibility complex diversity in a migratory passerine. Mol Ecol 2018; 27:2594-2603. [PMID: 29654666 DOI: 10.1111/mec.14592] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 03/14/2018] [Accepted: 03/26/2018] [Indexed: 12/15/2022]
Abstract
Pathogens are one of the main forces driving the evolution and maintenance of the highly polymorphic genes of the vertebrate major histocompatibility complex (MHC). Although MHC proteins are crucial in pathogen recognition, it is still poorly understood how pathogen-mediated selection promotes and maintains MHC diversity, and especially so in host species with highly duplicated MHC genes. Sedge warblers (Acrocephalus schoenobaenus) have highly duplicated MHC genes, and using data from high-throughput MHC genotyping, we were able to investigate to what extent avian malaria parasites explain temporal MHC class I supertype fluctuations in a long-term study population. We investigated infection status and infection intensities of two different strains of Haemoproteus, that is avian malaria parasites that are known to have significant fitness consequences in sedge warblers. We found that prevalence of avian malaria in carriers of specific MHC class I supertypes was a significant predictor of their frequency changes between years. This finding suggests that avian malaria infections partly drive the temporal fluctuations of the MHC class I supertypes. Furthermore, we found that individuals with a large number of different supertypes had higher resistance to avian malaria, but there was no evidence for an optimal MHC class I diversity. Thus, the two studied malaria parasite strains appear to select for a high MHC class I supertype diversity. Such selection may explain the maintenance of the extremely high number of MHC class I gene copies in sedge warblers and possibly also in other passerines where avian malaria is a common disease.
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Affiliation(s)
| | - Wojciech Bielański
- Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
| | - Adam Ćmiel
- Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
| | - Wojciech Solarz
- Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
| | - Tadeusz Zając
- Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
| | - Magdalena Migalska
- Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Alvaro Sebastian
- Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | | | - Jacek Radwan
- Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
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31
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Minias P, Pikus E, Whittingham LA, Dunn PO. A global analysis of selection at the avian MHC. Evolution 2018; 72:1278-1293. [PMID: 29665025 DOI: 10.1111/evo.13490] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/29/2018] [Accepted: 04/09/2018] [Indexed: 12/29/2022]
Abstract
Recent advancements in sequencing technology have resulted in rapid progress in the study of the major histocompatibility complex (MHC) in non-model avian species. Here, we analyze a global dataset of avian MHC class I and class II sequences (ca. 11,000 sequences from over 250 species) to gain insight into the processes that govern macroevolution of MHC genes in birds. Analysis of substitution rates revealed striking differences in the patterns of diversifying selection between passerine and non-passerine birds. Non-passerines showed stronger selection at MHC class II, which is primarily involved in recognition of extracellular pathogens, while passerines showed stronger selection at MHC class I, which is involved in recognition of intracellular pathogens. Positions of positively selected amino-acid residues showed marked discrepancies with peptide-binding residues (PBRs) of human MHC molecules, suggesting that using a human classification of PBRs to assess selection patterns at the avian MHC may be unjustified. Finally, our analysis provided evidence that indel mutations can make a substantial contribution to adaptive variation at the avian MHC.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, 90-237, Poland
| | - Ewa Pikus
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, 90-237, Poland
| | - Linda A Whittingham
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, 53211
| | - Peter O Dunn
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, 90-237, Poland.,Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, 53211
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32
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Sebastian A, Migalska M, Biedrzycka A. AmpliSAS and AmpliHLA: Web Server Tools for MHC Typing of Non-Model Species and Human Using NGS Data. Methods Mol Biol 2018; 1802:249-273. [PMID: 29858815 DOI: 10.1007/978-1-4939-8546-3_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
AmpliSAS and AmpliHLA are web server tools for automatic genotyping of MHC genes from high-throughput sequencing data. AmpliSAS is designed specifically to analyze amplicon sequencing data from non-model species and it is able to perform de-novo genotyping without any previous knowledge of the reference alleles. AmpliHLA is a human-specific version, it performs HLA typing by comparing sequenced variants against human reference alleles from the IMGT/HLA database. Here we describe four genotyping protocols: the first two use amplicon sequencing data to genotype the MHC genes of a passerine bird and human respectively; the third and fourth present the HLA typing of a human cell line starting from RNA and exome sequencing data respectively.
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Affiliation(s)
- Alvaro Sebastian
- Sixth Researcher, Poznan, Poland. .,Instituto Aragonés de Empleo (INAEM), Zaragoza, Spain. .,Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland.
| | - Magdalena Migalska
- Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
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33
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Drews A, Strandh M, Råberg L, Westerdahl H. Expression and phylogenetic analyses reveal paralogous lineages of putatively classical and non-classical MHC-I genes in three sparrow species (Passer). BMC Evol Biol 2017. [PMID: 28651571 PMCID: PMC5485651 DOI: 10.1186/s12862-017-0970-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Major Histocompatibility Complex (MHC) plays a central role in immunity and has been given considerable attention by evolutionary ecologists due to its associations with fitness-related traits. Songbirds have unusually high numbers of MHC class I (MHC-I) genes, but it is not known whether all are expressed and equally important for immune function. Classical MHC-I genes are highly expressed, polymorphic and present peptides to T-cells whereas non-classical MHC-I genes have lower expression, are more monomorphic and do not present peptides to T-cells. To get a better understanding of the highly duplicated MHC genes in songbirds, we studied gene expression in a phylogenetic framework in three species of sparrows (house sparrow, tree sparrow and Spanish sparrow), using high-throughput sequencing. We hypothesize that sparrows could have classical and non-classical genes, as previously indicated though never tested using gene expression. RESULTS The phylogenetic analyses reveal two distinct types of MHC-I alleles among the three sparrow species, one with high and one with low level of polymorphism, thus resembling classical and non-classical genes, respectively. All individuals had both types of alleles, but there was copy number variation both within and among the sparrow species. However, the number of highly polymorphic alleles that were expressed did not vary between species, suggesting that the structural genomic variation is counterbalanced by conserved gene expression. Overall, 50% of the MHC-I alleles were expressed in sparrows. Expression of the highly polymorphic alleles was very variable, whereas the alleles with low polymorphism had uniformly low expression. Interestingly, within an individual only one or two alleles from the polymorphic genes were highly expressed, indicating that only a single copy of these is highly expressed. CONCLUSIONS Taken together, the phylogenetic reconstruction and the analyses of expression suggest that sparrows have both classical and non-classical MHC-I genes, and that the evolutionary origin of these genes predate the split of the three investigated sparrow species 7 million years ago. Because only the classical MHC-I genes are involved in antigen presentation, the function of different MHC-I genes should be considered in future ecological and evolutionary studies of MHC-I in sparrows and other songbirds.
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Affiliation(s)
- Anna Drews
- Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden.
| | - Maria Strandh
- Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden
| | - Lars Råberg
- Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden
| | - Helena Westerdahl
- Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden
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