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Card DC, Van Camp AG, Santonastaso T, Jensen-Seaman MI, Anthony NM, Edwards SV. Structure and evolution of the squamate major histocompatibility complex as revealed by two Anolis lizard genomes. Front Genet 2022; 13:979746. [PMID: 36425073 PMCID: PMC9679377 DOI: 10.3389/fgene.2022.979746] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 10/20/2022] [Indexed: 11/10/2022] Open
Abstract
The major histocompatibility complex (MHC) is an important genomic region for adaptive immunity and has long been studied in ecological and evolutionary contexts, such as disease resistance and mate and kin selection. The MHC has been investigated extensively in mammals and birds but far less so in squamate reptiles, the third major radiation of amniotes. We localized the core MHC genomic region in two squamate species, the green anole (Anolis carolinensis) and brown anole (A. sagrei), and provide the first detailed characterization of the squamate MHC, including the presence and ordering of known MHC genes in these species and comparative assessments of genomic structure and composition in MHC regions. We find that the Anolis MHC, located on chromosome 2 in both species, contains homologs of many previously-identified mammalian MHC genes in a single core MHC region. The repetitive element composition in anole MHC regions was similar to those observed in mammals but had important distinctions, such as higher proportions of DNA transposons. Moreover, longer introns and intergenic regions result in a much larger squamate MHC region (11.7 Mb and 24.6 Mb in the green and brown anole, respectively). Evolutionary analyses of MHC homologs of anoles and other representative amniotes uncovered generally monophyletic relationships between species-specific homologs and a loss of the peptide-binding domain exon 2 in one of two mhc2β gene homologs of each anole species. Signals of diversifying selection in each anole species was evident across codons of mhc1, many of which appear functionally relevant given known structures of this protein from the green anole, chicken, and human. Altogether, our investigation fills a major gap in understanding of amniote MHC diversity and evolution and provides an important foundation for future squamate-specific or vertebrate-wide investigations of the MHC.
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Affiliation(s)
- Daren C. Card
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States
- Museum of Comparative Zoology, Harvard University, Cambridge, MA, United States
- *Correspondence: Daren C. Card,
| | - Andrew G. Van Camp
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States
- Museum of Comparative Zoology, Harvard University, Cambridge, MA, United States
| | - Trenten Santonastaso
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
| | | | - Nicola M. Anthony
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
| | - Scott V. Edwards
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States
- Museum of Comparative Zoology, Harvard University, Cambridge, MA, United States
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2
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Some thoughts about what non-mammalian jawed vertebrates are telling us about antigen processing and peptide loading of MHC molecules. Curr Opin Immunol 2022; 77:102218. [PMID: 35687979 PMCID: PMC9586880 DOI: 10.1016/j.coi.2022.102218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/19/2022] [Accepted: 05/10/2022] [Indexed: 12/11/2022]
Abstract
The major histocompatibility complex (MHC) of mammals encodes highly polymorphic classical class I and class II molecules with crucial roles in immune responses, as well as various nonclassical molecules encoded by the MHC and elsewhere in the genome that have a variety of functions. These MHC molecules are supported by antigen processing and peptide loading pathways which are well-understood in mammals. This review considers what has been learned about the MHC, MHC molecules and the supporting pathways in non-mammalian jawed vertebrates. From the initial understanding from work with the chicken MHC, a great deal of diversity in the structure and function has been found. Are there underlying principles? The genomic organisation of the MHC varies enormously across jawed vertebrates. Total numbers of MHC genes vary among vertebrates, with only a few classical MHC genes. Some nonclassical MHC and classical pathway genes appear earlier than others. Obvious co-evolution within MHC pathways occurs in some species, but not others. The promiscuity of interactions may correlate with differences in genomic organisation.
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3
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Sheppard EC, Martin CA, Armstrong C, González-Quevedo C, Illera JC, Suh A, Spurgin LG, Richardson DS. Genomic associations with poxvirus across divergent island populations in Berthelot's pipit. Mol Ecol 2022; 31:3154-3173. [PMID: 35395699 PMCID: PMC9321574 DOI: 10.1111/mec.16461] [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: 12/03/2021] [Revised: 03/04/2022] [Accepted: 04/04/2022] [Indexed: 11/30/2022]
Abstract
Understanding the mechanisms and genes that enable animal populations to adapt to pathogens is important from an evolutionary, health and conservation perspective. Berthelot's pipit (Anthus berthelotii) experiences extensive and consistent spatial heterogeneity in avian pox infection pressure across its range of island populations, thus providing an excellent system with which to examine how pathogen-mediated selection drives spatial variation in immunogenetic diversity. Here we test for evidence of genetic variation associated with avian pox at both an individual and population-level. At the individual level, we find no evidence that variation in MHC class I and TLR4 (both known to be important in recognising viral infection) was associated with pox infection within two separate populations. However, using genotype-environment association (Bayenv) in conjunction with genome-wide (ddRAD-seq) data, we detected strong associations between population-level avian pox prevalence and allele frequencies of single nucleotide polymorphisms (SNPs) at a number of sites across the genome. These sites were located within genes involved in cellular stress signalling and immune responses, many of which have previously been associated with responses to viral infection in humans and other animals. Consequently, our analyses indicates that pathogen-mediated selection may play a role in shaping genomic variation among relatively recently colonised island bird populations and highlights the utility of genotype-environment associations for identifying candidate genes potentially involved in host-pathogen interactions.
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Affiliation(s)
- Eleanor C Sheppard
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
| | - Claudia A Martin
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
| | - Claire Armstrong
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
| | - Catalina González-Quevedo
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK.,Grupo Ecología y Evolución de Vertebrados, Instituto de Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia
| | - Juan Carlos Illera
- Biodiversity Research Institute (CSIC-Oviedo University-Principality of Asturias), University of Oviedo, Campus of Mieres, Research Building, 5th Floor, c/ Gonzalo Gutiérrez Quirós, s/n, 33600 Mieres, Asturias, Spain
| | - Alexander Suh
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK.,Department of Ecology and Genetics - Evolutionary Biology, Evolutionary Biology Centre (EBC), Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Lewis G Spurgin
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
| | - David S Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norfolk, NR4 7TJ, UK
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4
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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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5
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Abstract
Compared to the major histocompatibility complex (MHC) of typical mammals, the chicken BF/BL region is small and simple, with most of the genes playing central roles in the adaptive immune response. However, some genes of the chicken MHC are almost certainly involved in innate immunity, such as the complement component C4 and the lectin-like receptor/ligand gene pair BNK and Blec. The poorly expressed classical class I molecule BF1 is known to be recognised by natural killer (NK) cells and, analogous to mammalian immune responses, the classical class I molecules BF1 and BF2, the CD1 homologs and the butyrophilin homologs called BG may be recognised by adaptive immune lymphocytes with semi-invariant receptors in a so-called adaptate manner. Moreover, the TRIM and BG regions next to the chicken MHC, along with the genetically unlinked Y and olfactory/scavenger receptor regions on the same chromosome, have multigene families almost certainly involved in innate and adaptate responses. On this chicken microchromosome, the simplicity of the adaptive immune gene systems contrasts with the complexity of the gene systems potentially involved in innate immunity.
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6
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He K, Minias P, Dunn PO. Long-Read Genome Assemblies Reveal Extraordinary Variation in the Number and Structure of MHC Loci in Birds. Genome Biol Evol 2021; 13:evaa270. [PMID: 33367721 PMCID: PMC7875000 DOI: 10.1093/gbe/evaa270] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2020] [Indexed: 12/31/2022] Open
Abstract
Our knowledge of the Major Histocompatibility Complex (MHC) in birds is limited because it often consists of numerous duplicated genes within individuals that are difficult to assemble with short read sequencing technology. Long-read sequencing provides an opportunity to overcome this limitation because it allows the assembly of long regions with repetitive elements. In this study, we used genomes based on long-read sequencing to predict the number and location of MHC loci in a broad range of bird taxa. From the long-read-based genomes of 34 species, we found that there was extremely large variation in the number of MHC loci between species. Overall, there were greater numbers of both class I and II loci in passerines than nonpasserines. The highest numbers of loci (up to 193 class II loci) were found in manakins (Pipridae), which had previously not been studied at the MHC. Our results provide the first direct evidence from passerine genomes of this high level of duplication. We also found different duplication patterns between species. In some species, both MHC class I and II genes were duplicated together, whereas in most species they were duplicated independently. Our study shows that the analysis of long-read-based genomes can dramatically improve our knowledge of MHC structure, although further improvements in chromosome level assembly are needed to understand the evolutionary mechanisms producing the extraordinary interspecific variation in the architecture of the MHC region.
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Affiliation(s)
- Ke He
- College of Animal Science and Technology, College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łodz, Poland
| | - Peter O Dunn
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łodz, Poland
- Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, WI, USA
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7
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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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8
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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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9
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Garamszegi LZ, Zagalska-Neubauer M, Canal D, Blázi G, Laczi M, Nagy G, Szöllősi E, Vaskuti É, Török J, Zsebők S. MHC-mediated sexual selection on birdsong: Generic polymorphism, particular alleles and acoustic signals. Mol Ecol 2018; 27:2620-2633. [PMID: 29693314 DOI: 10.1111/mec.14703] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 04/03/2018] [Accepted: 04/11/2018] [Indexed: 01/06/2023]
Abstract
Several hypotheses predict that the major histocompatibility complex (MHC) drives mating preference in females. Olfactory, colour or morphological traits are often found as reliable signals of the MHC profile, but the role of avian song mediating MHC-based female choice remains largely unexplored. We investigated the relationship between several MHC and acoustic features in the collared flycatcher (Ficedula albicollis), a European passerine with complex songs. We screened a fragment of the class IIB second exon of the MHC molecule, of which individuals harbour 4-15 alleles, while considerable sequence diversity is maintained at the population level. To make statistical inferences from a large number of comparisons, we adopted both null-hypothesis testing and effect size framework in combination with randomization procedures. After controlling for potential confounding factors, neither MHC allelic diversity nor the presence of particular alleles was associated remarkably with the investigated qualitative and quantitative song traits. Furthermore, genetic similarity among males based on MHC sequences was not reflected by the similarity in their song based on syllable content. Overall, these results suggest that the relationship between features of song and the allelic composition and diversity of MHC is not strong in the studied species. However, a biologically motivated analysis revealed that individuals that harbour an MHC allele that impairs survival perform songs with broader frequency range. This finding suggests that certain aspects of the song may bear reliable information concerning the MHC profile of the individuals, which can be used by females to optimize mate choice.
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Affiliation(s)
- László Zsolt Garamszegi
- Department of Evolutionary Ecology, Estación Biológica de Doñana-CSIC, Seville, Spain.,Department of Plant Systematics, Ecology and Theoretical Biology, MTA-ELTE, Theoretical Biology and Evolutionary Ecology Research Group, Eötvös Loránd University, Budapest, Hungary
| | | | - David Canal
- Department of Evolutionary Ecology, Estación Biológica de Doñana-CSIC, Seville, Spain.,Centro para el Estudio y Conservación de las Aves Rapaces en Argentina (CECARA-UNLPam) & Instituto de las Ciencias de la Tierra y Ambientales de La Pampa (INCITAP), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Santa Rosa, Argentina
| | - György Blázi
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
| | - Miklós Laczi
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
| | - Gergely Nagy
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
| | - Eszter Szöllősi
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
| | - Éva Vaskuti
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
| | - János Török
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary.,Ecology Research Group, Hungarian Academy of Sciences, Budapest, Hungary
| | - Sándor Zsebők
- Department of Systematic Zoology and Ecology, Behavioural Ecology Group, Eötvös Loránd University, Budapest, Hungary
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10
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Kaufman J. Unfinished Business: Evolution of the MHC and the Adaptive Immune System of Jawed Vertebrates. Annu Rev Immunol 2018; 36:383-409. [DOI: 10.1146/annurev-immunol-051116-052450] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jim Kaufman
- Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
- Department of Veterinary Medicine, University of Cambridge, Cambridge CB2 0ES, United Kingdom
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11
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Krause ET, Bischof HJ, Engel K, Golüke S, Maraci Ö, Mayer U, Sauer J, Caspers BA. Olfaction in the Zebra Finch ( Taeniopygia guttata ): What Is Known and Further Perspectives. ADVANCES IN THE STUDY OF BEHAVIOR 2018. [DOI: 10.1016/bs.asb.2017.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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12
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Signatures of Crested Ibis MHC Revealed by Recombination Screening and Short-Reads Assembly Strategy. PLoS One 2016; 11:e0168744. [PMID: 27997612 PMCID: PMC5173252 DOI: 10.1371/journal.pone.0168744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 12/06/2016] [Indexed: 02/04/2023] Open
Abstract
Whole-genome shotgun (WGS) sequencing has become a routine method in genome research over the past decade. However, the assembly of highly polymorphic regions in WGS projects remains a challenge, especially for large genomes. Employing BAC library constructing, PCR screening and Sanger sequencing, traditional strategy is laborious and expensive, which hampers research on polymorphic genomic regions. As one of the most highly polymorphic regions, the major histocompatibility complex (MHC) plays a central role in the adaptive immunity of all jawed vertebrates. In this study, we introduced an efficient procedure based on recombination screening and short-reads assembly. With this procedure, we constructed a high quality 488-kb region of crested ibis MHC that consists of 3 superscaffolds and contains 50 genes. Our sequence showed comparable quality (97.29% identity) to traditional Sanger assembly, while the workload was reduced almost 7 times. Comparative study revealed distinctive features of crested ibis by exhibiting the COL11A2-BLA-BLB-BRD2 cluster and presenting both ADPRH and odorant receptor (OR) gene in the MHC region. Furthermore, the conservation of the BF-TAP1-TAP2 structure in crested ibis and other vertebrate lineages is interesting in light of the hypothesis that coevolution of functionally related genes in the primordial MHC is responsible for the appearance of the antigen presentation pathways at the birth of the adaptive immune system.
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13
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Knief U, Forstmeier W. Mapping centromeres of microchromosomes in the zebra finch (Taeniopygia guttata) using half-tetrad analysis. Chromosoma 2016; 125:757-68. [PMID: 26667931 PMCID: PMC5023761 DOI: 10.1007/s00412-015-0560-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 11/12/2015] [Accepted: 11/13/2015] [Indexed: 12/24/2022]
Abstract
Centromeres usually consist of hundreds of kilobases of repetitive sequence which renders them difficult to assemble. As a consequence, centromeres are often missing from assembled genomes and their locations on physical chromosome maps have to be inferred from flanking sequences via fluorescence in situ hybridization (FISH). Alternatively, centromere positions can be mapped using linkage analyses in accidentally triploid individuals formed by half-tetrads (resulting from the inheritance of two chromatids from a single meiosis). The current genome assembly of the zebra finch (Taeniopygia guttata) comprises 32 chromosomes, but only for the ten largest chromosomes centromere positions have been mapped using FISH. We here map the positions of most of the remaining centromeres using half-tetrad analyses. For this purpose, we genotyped 37 zebra finches that were triploid or tetraploid due to inheritance errors (and mostly died as embryos) together with their parents at 64 microsatellite markers (at least two per chromosome). Using the information on centromere positions on the ten largest chromosomes, we were able to identify 12 cases of non-disjunction in maternal meiosis I and 10 cases of non-disjunction in maternal meiosis II. These 22 informative cases allowed us to infer centromere positions on additional 19 microchromosomes in reference to the current genome assembly. This knowledge will be valuable for studies of chromosome evolution, meiotic drive and species divergence in the avian lineage.
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Affiliation(s)
- Ulrich Knief
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
| | - Wolfgang Forstmeier
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany
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14
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Rogers SL, Kaufman J. Location, location, location: the evolutionary history of CD1 genes and the NKR-P1/ligand systems. Immunogenetics 2016; 68:499-513. [PMID: 27457887 PMCID: PMC5002281 DOI: 10.1007/s00251-016-0938-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/04/2016] [Indexed: 01/14/2023]
Abstract
CD1 genes encode cell surface molecules that present lipid antigens to various kinds of T lymphocytes of the immune system. The structures of CD1 genes and molecules are like the major histocompatibility complex (MHC) class I system, the loading of antigen and the tissue distribution for CD1 molecules are like those in the class II system, and phylogenetic analyses place CD1 between class I and class II sequences, altogether leading to the notion that CD1 is a third ancient system of antigen presentation molecules. However, thus far, CD1 genes have only been described in mammals, birds and reptiles, leaving major questions as to their origin and evolution. In this review, we recount a little history of the field so far and then consider what has been learned about the structure and functional attributes of CD1 genes and molecules in marsupials, birds and reptiles. We describe the central conundrum of CD1 evolution, the genomic location of CD1 genes in the MHC and/or MHC paralogous regions in different animals, considering the three models of evolutionary history that have been proposed. We describe the natural killer (NK) receptors NKR-P1 and ligands, also found in different genomic locations for different animals. We discuss the consequence of these three models, one of which includes the repudiation of a guiding principle for the last 20 years, that two rounds of genome-wide duplication at the base of the vertebrates provided the extra MHC genes necessary for the emergence of adaptive immune system of jawed vertebrates.
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Affiliation(s)
- Sally L Rogers
- Department of Biosciences, University of Gloucestershire, Cheltenham, GL50 4AZ, UK
| | - Jim Kaufman
- Department of Pathology, University of Cambridge, Cambridge, CB2 1QP, UK. .,Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES, UK.
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15
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Pauli M, Chakarov N, Rupp O, Kalinowski J, Goesmann A, Sorenson MD, Krüger O, Hoffman JI. De novo assembly of the dual transcriptomes of a polymorphic raptor species and its malarial parasite. BMC Genomics 2015; 16:1038. [PMID: 26645667 PMCID: PMC4673757 DOI: 10.1186/s12864-015-2254-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 11/27/2015] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Studies of non-model species are important for understanding the molecular processes underpinning phenotypic variation under natural ecological conditions. The common buzzard (Buteo buteo; Aves: Accipitriformes) is a widespread and common Eurasian raptor with three distinct plumage morphs that differ in several fitness-related traits, including parasite infestation. To provide a genomic resource for plumage polymorphic birds in general and to search for candidate genes relating to fitness, we generated a transcriptome from a single dead buzzard specimen plus easily accessible, minimally invasive samples from live chicks. RESULTS We not only de novo assembled a near-complete buzzard transcriptome, but also obtained a significant fraction of the transcriptome of its malaria-like parasite, Leucocytozoon buteonis. By identifying melanogenesis-related transcripts that are differentially expressed in light ventral and dark dorsal feathers, but which are also expressed in other regions of the body, we also identified a suite of candidate genes that could be associated with fitness differences among the morphs. These include several immune-related genes, providing a plausible link between melanisation and parasite load. qPCR analysis of a subset of these genes revealed significant differences between ventral and dorsal feathers and an additional effect of morph. CONCLUSION This new resource provides preliminary insights into genes that could be involved in fitness differences between the buzzard colour morphs, and should facilitate future studies of raptors and their malaria-like parasites.
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Affiliation(s)
- Martina Pauli
- Department of Animal Behaviour, Bielefeld University, 33501, Bielefeld, Germany
| | - Nayden Chakarov
- Department of Animal Behaviour, Bielefeld University, 33501, Bielefeld, Germany.
- Present address: Molecular Ecology and Evolution Lab, Lund University, 223 62, Lund, Sweden.
| | - Oliver Rupp
- Bioinformatics and Systems Biology, Justus-Liebig-University, 35390, Giessen, Germany
- Center for Biotechnology, Bielefeld University, 33501, Bielefeld, Germany
| | - Jörn Kalinowski
- Center for Biotechnology, Bielefeld University, 33501, Bielefeld, Germany
| | - Alexander Goesmann
- Bioinformatics and Systems Biology, Justus-Liebig-University, 35390, Giessen, Germany
- Center for Biotechnology, Bielefeld University, 33501, Bielefeld, Germany
| | | | - Oliver Krüger
- Department of Animal Behaviour, Bielefeld University, 33501, Bielefeld, Germany
| | - Joseph Ivan Hoffman
- Department of Animal Behaviour, Bielefeld University, 33501, Bielefeld, Germany
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Newhouse DJ, Balakrishnan CN. High major histocompatibility complex class I polymorphism despite bottlenecks in wild and domesticated populations of the zebra finch (Taeniopygia guttata). BMC Evol Biol 2015; 15:265. [PMID: 26627847 PMCID: PMC4667478 DOI: 10.1186/s12862-015-0546-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/20/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Two subspecies of zebra finch, Taeniopygia guttata castanotis and T. g. guttata are native to Australia and the Lesser Sunda Islands, respectively. The Australian subspecies has been domesticated and is now an important model system for research. Both the Lesser Sundan subspecies and domesticated Australian zebra finches have undergone population bottlenecks in their history, and previous analyses using neutral markers have reported reduced neutral genetic diversity in these populations. Here we characterize patterns of variation in the third exon of the highly variable major histocompatibility complex (MHC) class I α chain. As a benchmark for neutral divergence, we also report the first mitochondrial NADH dehydrogenase 2 (ND2) sequences in this important model system. RESULTS Despite natural and human-mediated population bottlenecks, we find that high MHC class I polymorphism persists across all populations. As expected, we find higher levels of nucleotide diversity in the MHC locus relative to neutral loci, and strong evidence of positive selection acting on important residues forming the peptide-binding region (PBR). Clear population differentiation of MHC allele frequencies is also evident, and this may be due to adaptation to new habitats and associated pathogens and/or genetic drift. Whereas the MHC Class I locus shows broad haplotype sharing across populations, ND2 is the first locus surveyed to date to show reciprocal monophyly of the two subspecies. CONCLUSIONS Despite genetic bottlenecks and genetic drift, all surveyed zebra finch populations have maintained high MHC Class I diversity. The diversity at the MHC Class I locus in the Lesser Sundan subspecies contrasts sharply with the lack of diversity in previously examined neutral loci, and may thus be a result of selection acting to maintain polymorphism. Given uncertainty in historical population demography, however, it is difficult to rule out neutral processes in maintaining the observed diversity. The surveyed populations also differ in MHC Class I allele frequencies, and future studies are needed to assess whether these changes result in functional immune differences.
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Affiliation(s)
- Daniel J Newhouse
- Howell Science Complex, East Carolina University, Greenville, NC, 27858, USA.
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Comparative Analysis and Distribution of Omega-3 lcPUFA Biosynthesis Genes in Marine Molluscs. PLoS One 2015; 10:e0136301. [PMID: 26308548 PMCID: PMC4550275 DOI: 10.1371/journal.pone.0136301] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 08/02/2015] [Indexed: 12/30/2022] Open
Abstract
Recent research has identified marine molluscs as an excellent source of omega-3 long-chain polyunsaturated fatty acids (lcPUFAs), based on their potential for endogenous synthesis of lcPUFAs. In this study we generated a representative list of fatty acyl desaturase (Fad) and elongation of very long-chain fatty acid (Elovl) genes from major orders of Phylum Mollusca, through the interrogation of transcriptome and genome sequences, and various publicly available databases. We have identified novel and uncharacterised Fad and Elovl sequences in the following species: Anadara trapezia, Nerita albicilla, Nerita melanotragus, Crassostrea gigas, Lottia gigantea, Aplysia californica, Loligo pealeii and Chlamys farreri. Based on alignments of translated protein sequences of Fad and Elovl genes, the haeme binding motif and histidine boxes of Fad proteins, and the histidine box and seventeen important amino acids in Elovl proteins, were highly conserved. Phylogenetic analysis of aligned reference sequences was used to reconstruct the evolutionary relationships for Fad and Elovl genes separately. Multiple, well resolved clades for both the Fad and Elovl sequences were observed, suggesting that repeated rounds of gene duplication best explain the distribution of Fad and Elovl proteins across the major orders of molluscs. For Elovl sequences, one clade contained the functionally characterised Elovl5 proteins, while another clade contained proteins hypothesised to have Elovl4 function. Additional well resolved clades consisted only of uncharacterised Elovl sequences. One clade from the Fad phylogeny contained only uncharacterised proteins, while the other clade contained functionally characterised delta-5 desaturase proteins. The discovery of an uncharacterised Fad clade is particularly interesting as these divergent proteins may have novel functions. Overall, this paper presents a number of novel Fad and Elovl genes suggesting that many mollusc groups possess most of the required enzymes for the synthesis of lcPUFAs.
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What chickens would tell you about the evolution of antigen processing and presentation. Curr Opin Immunol 2015; 34:35-42. [DOI: 10.1016/j.coi.2015.01.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 12/30/2014] [Accepted: 01/02/2015] [Indexed: 01/04/2023]
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Major Histocompatibility Complex Genes Map to Two Chromosomes in an Evolutionarily Ancient Reptile, the Tuatara Sphenodon punctatus. G3-GENES GENOMES GENETICS 2015; 5:1439-51. [PMID: 25953959 PMCID: PMC4502378 DOI: 10.1534/g3.115.017467] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Major histocompatibility complex (MHC) genes are a central component of the vertebrate immune system and usually exist in a single genomic region. However, considerable differences in MHC organization and size exist between different vertebrate lineages. Reptiles occupy a key evolutionary position for understanding how variation in MHC structure evolved in vertebrates, but information on the structure of the MHC region in reptiles is limited. In this study, we investigate the organization and cytogenetic location of MHC genes in the tuatara (Sphenodon punctatus), the sole extant representative of the early-diverging reptilian order Rhynchocephalia. Sequencing and mapping of 12 clones containing class I and II MHC genes from a bacterial artificial chromosome library indicated that the core MHC region is located on chromosome 13q. However, duplication and translocation of MHC genes outside of the core region was evident, because additional class I MHC genes were located on chromosome 4p. We found a total of seven class I sequences and 11 class II β sequences, with evidence for duplication and pseudogenization of genes within the tuatara lineage. The tuatara MHC is characterized by high repeat content and low gene density compared with other species and we found no antigen processing or MHC framework genes on the MHC gene-containing clones. Our findings indicate substantial differences in MHC organization in tuatara compared with mammalian and avian MHCs and highlight the dynamic nature of the MHC. Further sequencing and annotation of tuatara and other reptile MHCs will determine if the tuatara MHC is representative of nonavian reptiles in general.
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Taniguchi Y, Matsumoto K, Matsuda H, Yamada T, Sugiyama T, Homma K, Kaneko Y, Yamagishi S, Iwaisaki H. Structure and polymorphism of the major histocompatibility complex class II region in the Japanese Crested Ibis, Nipponia nippon. PLoS One 2014; 9:e108506. [PMID: 25247679 PMCID: PMC4172706 DOI: 10.1371/journal.pone.0108506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 08/21/2014] [Indexed: 12/15/2022] Open
Abstract
The major histocompatibility complex (MHC) is a highly polymorphic genomic region that plays a central role in the immune system. Despite its functional consistency, the genomic structure of the MHC differs substantially among organisms. In birds, the MHC-B structures of Galliformes, including chickens, have been well characterized, but information about other avian MHCs remains sparse. The Japanese Crested Ibis (Nipponia nippon, Pelecaniformes) is an internationally conserved, critically threatened species. The current Japanese population of N. nippon originates from only five founders; thus, understanding the genetic diversity among these founders is critical for effective population management. Because of its high polymorphism and importance for disease resistance and other functions, the MHC has been an important focus in the conservation of endangered species. Here, we report the structure and polymorphism of the Japanese Crested Ibis MHC class II region. Screening of genomic libraries allowed the construction of three contigs representing different haplotypes of MHC class II regions. Characterization of genomic clones revealed that the MHC class II genomic structure of N. nippon was largely different from that of chicken. A pair of MHC-IIA and -IIB genes was arranged head-to-head between the COL11A2 and BRD2 genes. Gene order in N. nippon was more similar to that in humans than to that in chicken. The three haplotypes contained one to three copies of MHC-IIA/IIB gene pairs. Genotyping of the MHC class II region detected only three haplotypes among the five founders, suggesting that the genetic diversity of the current Japanese Crested Ibis population is extremely low. The structure of the MHC class II region presented here provides valuable insight for future studies on the evolution of the avian MHC and for conservation of the Japanese Crested Ibis.
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Affiliation(s)
- Yukio Taniguchi
- Laboratory of Animal Breeding and Genetics, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- * E-mail:
| | - Keisuke Matsumoto
- Laboratory of Animal Breeding and Genetics, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Hirokazu Matsuda
- Laboratory of Animal Breeding and Genetics, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Takahisa Yamada
- Department of Agrobiology, Faculty of Agriculture, Niigata University, Niigata, Japan
| | - Toshie Sugiyama
- Department of Agrobiology, Faculty of Agriculture, Niigata University, Niigata, Japan
| | - Kosuke Homma
- Field Center for Sustainable Agriculture and Forestry, Niigata University, Niigata, Japan
| | | | | | - Hiroaki Iwaisaki
- Laboratory of Animal Breeding and Genetics, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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Jones MR, Cheviron ZA, Carling MD. Variation in positively selected major histocompatibility complex class I loci in rufous-collared sparrows (Zonotrichia capensis). Immunogenetics 2014; 66:693-704. [DOI: 10.1007/s00251-014-0800-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 08/25/2014] [Indexed: 11/25/2022]
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22
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Halley YA, Dowd SE, Decker JE, Seabury PM, Bhattarai E, Johnson CD, Rollins D, Tizard IR, Brightsmith DJ, Peterson MJ, Taylor JF, Seabury CM. A draft de novo genome assembly for the northern bobwhite (Colinus virginianus) reveals evidence for a rapid decline in effective population size beginning in the Late Pleistocene. PLoS One 2014; 9:e90240. [PMID: 24621616 PMCID: PMC3951200 DOI: 10.1371/journal.pone.0090240] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Accepted: 01/27/2014] [Indexed: 11/20/2022] Open
Abstract
Wild populations of northern bobwhites (Colinus virginianus; hereafter bobwhite) have declined across nearly all of their U.S. range, and despite their importance as an experimental wildlife model for ecotoxicology studies, no bobwhite draft genome assembly currently exists. Herein, we present a bobwhite draft de novo genome assembly with annotation, comparative analyses including genome-wide analyses of divergence with the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata) genomes, and coalescent modeling to reconstruct the demographic history of the bobwhite for comparison to other birds currently in decline (i.e., scarlet macaw; Ara macao). More than 90% of the assembled bobwhite genome was captured within <40,000 final scaffolds (N50 = 45.4 Kb) despite evidence for approximately 3.22 heterozygous polymorphisms per Kb, and three annotation analyses produced evidence for >14,000 unique genes and proteins. Bobwhite analyses of divergence with the chicken and zebra finch genomes revealed many extremely conserved gene sequences, and evidence for lineage-specific divergence of noncoding regions. Coalescent models for reconstructing the demographic history of the bobwhite and the scarlet macaw provided evidence for population bottlenecks which were temporally coincident with human colonization of the New World, the late Pleistocene collapse of the megafauna, and the last glacial maximum. Demographic trends predicted for the bobwhite and the scarlet macaw also were concordant with how opposing natural selection strategies (i.e., skewness in the r-/K-selection continuum) would be expected to shape genome diversity and the effective population sizes in these species, which is directly relevant to future conservation efforts.
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Affiliation(s)
- Yvette A. Halley
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas, United States of America
| | - Scot E. Dowd
- Molecular Research LP, Shallowater, Texas, United States of America
| | - Jared E. Decker
- Division of Animal Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Paul M. Seabury
- ElanTech Inc., Greenbelt, Maryland, United States of America
| | - Eric Bhattarai
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas, United States of America
| | - Charles D. Johnson
- Genomics and Bioinformatics Core, Texas A&M AgriLife Research, College Station, Texas, United States of America
| | - Dale Rollins
- Rolling Plains Quail Research Ranch, Rotan, Texas, United States of America
| | - Ian R. Tizard
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas, United States of America
| | - Donald J. Brightsmith
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas, United States of America
| | - Markus J. Peterson
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Jeremy F. Taylor
- Division of Animal Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Christopher M. Seabury
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Characteristics of MHC class I genes in house sparrows Passer domesticus as revealed by long cDNA transcripts and amplicon sequencing. J Mol Evol 2013; 77:8-21. [PMID: 23877344 DOI: 10.1007/s00239-013-9575-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/10/2013] [Indexed: 10/26/2022]
Abstract
In birds the major histocompatibility complex (MHC) organization differs both among and within orders; chickens Gallus gallus of the order Galliformes have a simple arrangement, while many songbirds of the order Passeriformes have a more complex arrangement with larger numbers of MHC class I and II genes. Chicken MHC genes are found at two independent loci, classical MHC-B and non-classical MHC-Y, whereas non-classical MHC genes are yet to be verified in passerines. Here we characterize MHC class I transcripts (α1 to α3 domain) and perform amplicon sequencing using a next-generation sequencing technique on exon 3 from house sparrow Passer domesticus (a passerine) families. Then we use phylogenetic, selection, and segregation analyses to gain a better understanding of the MHC class I organization. Trees based on the α1 and α2 domain revealed a distinct cluster with short terminal branches for transcripts with a 6-bp deletion. Interestingly, this cluster was not seen in the tree based on the α3 domain. 21 exon 3 sequences were verified in a single individual and the average numbers within an individual were nine and five for sequences with and without a 6-bp deletion, respectively. All individuals had exon 3 sequences with and without a 6-bp deletion. The sequences with a 6-bp deletion have many characteristics in common with non-classical MHC, e.g., highly conserved amino acid positions were substituted compared with the other alleles, low nucleotide diversity and just a single site was subject to positive selection. However, these alleles also have characteristics that suggest they could be classical, e.g., complete linkage and absence of a distinct cluster in a tree based on the α3 domain. Thus, we cannot determine for certain whether or not the alleles with a 6-bp deletion are non-classical based on our present data. Further analyses on segregation patterns of these alleles in combination with dating the 6-bp deletion through MHC characterization across the genus Passer may solve this matter in the future.
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Aguilar JRD, Schut E, Merino S, Martínez J, Komdeur J, Westerdahl H. MHC class II B diversity in blue tits: a preliminary study. Ecol Evol 2013; 3:1878-89. [PMID: 23919136 PMCID: PMC3728931 DOI: 10.1002/ece3.598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 04/17/2013] [Indexed: 12/18/2022] Open
Abstract
In this study, we partly characterize major histocompatibility complex (MHC) class II B in the blue tit (Cyanistes caeruleus). A total of 22 individuals from three different European locations: Spain, The Netherlands, and Sweden were screened for MHC allelic diversity. The MHC genes were investigated using both PCR-based methods and unamplified genomic DNA with restriction fragment length polymorphism (RFLP) and southern blots. A total of 13 different exon 2 sequences were obtained independently from DNA and/or RNA, thus confirming gene transcription and likely functionality of the genes. Nine out of 13 alleles were found in more than one country, and two alleles appeared in all countries. Positive selection was detected in the region coding for the peptide binding region (PBR). A maximum of three alleles per individual was detected by sequencing and the RFLP pattern consisted of 4-7 fragments, indicating a minimum number of 2-4 loci per individual. A phylogenetic analysis, demonstrated that the blue tit sequences are divergent compared to sequences from other passerines resembling a different MHC lineage than those possessed by most passerines studied to date.
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Affiliation(s)
- Juan Rivero-de Aguilar
- Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales (CSIC)J. Gutiérrez Abascal 2, E-28006, Madrid, Spain
| | - Elske Schut
- Behavioural Ecology and Self-Organization, The University of GroningenPO Box 11103, 9700 CC, Groningen, The Netherlands
| | - Santiago Merino
- Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales (CSIC)J. Gutiérrez Abascal 2, E-28006, Madrid, Spain
| | - Javier Martínez
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de AlcaláAlcalá de Henares, E-28871, Madrid, Spain
| | - Jan Komdeur
- Behavioural Ecology and Self-Organization, The University of GroningenPO Box 11103, 9700 CC, Groningen, The Netherlands
| | - Helena Westerdahl
- Molecular Ecology and Evolution Lab, Ecology Building, Lund UniversitySölvegatan 37, SE-22362, Lund, Sweden
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Alcaide M, Liu M, Edwards SV. Major histocompatibility complex class I evolution in songbirds: universal primers, rapid evolution and base compositional shifts in exon 3. PeerJ 2013; 1:e86. [PMID: 23781408 PMCID: PMC3685324 DOI: 10.7717/peerj.86] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 05/23/2013] [Indexed: 01/04/2023] Open
Abstract
Genes of the Major Histocompatibility Complex (MHC) have become an important marker for the investigation of adaptive genetic variation in vertebrates because of their critical role in pathogen resistance. However, despite significant advances in the last few years the characterization of MHC variation in non-model species still remains a challenging task due to the redundancy and high variation of this gene complex. Here we report the utility of a single pair of primers for the cross-amplification of the third exon of MHC class I genes, which encodes the more polymorphic half of the peptide-binding region (PBR), in oscine passerines (songbirds; Aves: Passeriformes), a group especially challenging for MHC characterization due to the presence of large and complex MHC multigene families. In our survey, although the primers failed to amplify exon 3 from two suboscine passerine birds, they amplified exon 3 of multiple MHC class I genes in all 16 species of oscine songbirds tested, yielding a total of 120 sequences. The 16 songbird species belong to 14 different families, primarily within the Passerida, but also in the Corvida. Using a conservative approach based on the analysis of cloned amplicons (n = 16) from each species, we found between 3 and 10 MHC sequences per individual. Each allele repertoire was highly divergent, with the overall number of polymorphic sites per species ranging from 33 to 108 (out of 264 sites) and the average number of nucleotide differences between alleles ranging from 14.67 to 43.67. Our survey in songbirds allowed us to compare macroevolutionary dynamics of exon 3 between songbirds and non-passerine birds. We found compelling evidence of positive selection acting specifically upon peptide-binding codons across birds, and we estimate the strength of diversifying selection in songbirds to be about twice that in non-passerines. Analysis using comparative methods suggest weaker evidence for a higher GC content in the 3rd codon position of exon 3 in non-passerine birds, a pattern that contrasts with among-clade GC patterns found in other avian studies and may suggests different mutational mechanisms. Our primers represent a useful tool for the characterization of functional and evolutionarily relevant MHC variation across the hyperdiverse songbirds.
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Affiliation(s)
- Miguel Alcaide
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
| | - Mark Liu
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
| | - Scott V. Edwards
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
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A multi-platform draft de novo genome assembly and comparative analysis for the Scarlet Macaw (Ara macao). PLoS One 2013; 8:e62415. [PMID: 23667475 PMCID: PMC3648530 DOI: 10.1371/journal.pone.0062415] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/21/2013] [Indexed: 12/31/2022] Open
Abstract
Data deposition to NCBI Genomes: This Whole Genome Shotgun project has been deposited at DDBJ/EMBL/GenBank under the accession AMXX00000000 (SMACv1.0, unscaffolded genome assembly). The version described in this paper is the first version (AMXX01000000). The scaffolded assembly (SMACv1.1) has been deposited at DDBJ/EMBL/GenBank under the accession AOUJ00000000, and is also the first version (AOUJ01000000). Strong biological interest in traits such as the acquisition and utilization of speech, cognitive abilities, and longevity catalyzed the utilization of two next-generation sequencing platforms to provide the first-draft de novo genome assembly for the large, new world parrot Ara macao (Scarlet Macaw). Despite the challenges associated with genome assembly for an outbred avian species, including 951,507 high-quality putative single nucleotide polymorphisms, the final genome assembly (>1.035 Gb) includes more than 997 Mb of unambiguous sequence data (excluding N's). Cytogenetic analyses including ZooFISH revealed complex rearrangements associated with two scarlet macaw macrochromosomes (AMA6, AMA7), which supports the hypothesis that translocations, fusions, and intragenomic rearrangements are key factors associated with karyotype evolution among parrots. In silico annotation of the scarlet macaw genome provided robust evidence for 14,405 nuclear gene annotation models, their predicted transcripts and proteins, and a complete mitochondrial genome. Comparative analyses involving the scarlet macaw, chicken, and zebra finch genomes revealed high levels of nucleotide-based conservation as well as evidence for overall genome stability among the three highly divergent species. Application of a new whole-genome analysis of divergence involving all three species yielded prioritized candidate genes and noncoding regions for parrot traits of interest (i.e., speech, intelligence, longevity) which were independently supported by the results of previous human GWAS studies. We also observed evidence for genes and noncoding loci that displayed extreme conservation across the three avian lineages, thereby reflecting their likely biological and developmental importance among birds.
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Follin E, Karlsson M, Lundegaard C, Nielsen M, Wallin S, Paulsson K, Westerdahl H. In silico peptide-binding predictions of passerine MHC class I reveal similarities across distantly related species, suggesting convergence on the level of protein function. Immunogenetics 2013; 65:299-311. [PMID: 23358931 DOI: 10.1007/s00251-012-0676-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 12/24/2012] [Indexed: 11/26/2022]
Abstract
The major histocompatibility complex (MHC) genes are the most polymorphic genes found in the vertebrate genome, and they encode proteins that play an essential role in the adaptive immune response. Many songbirds (passerines) have been shown to have a large number of transcribed MHC class I genes compared to most mammals. To elucidate the reason for this large number of genes, we compared 14 MHC class I alleles (α1-α3 domains), from great reed warbler, house sparrow and tree sparrow, via phylogenetic analysis, homology modelling and in silico peptide-binding predictions to investigate their functional and genetic relationships. We found more pronounced clustering of the MHC class I allomorphs (allele specific proteins) in regards to their function (peptide-binding specificities) compared to their genetic relationships (amino acid sequences), indicating that the high number of alleles is of functional significance. The MHC class I allomorphs from house sparrow and tree sparrow, species that diverged 10 million years ago (MYA), had overlapping peptide-binding specificities, and these similarities across species were also confirmed in phylogenetic analyses based on amino acid sequences. Notably, there were also overlapping peptide-binding specificities in the allomorphs from house sparrow and great reed warbler, although these species diverged 30 MYA. This overlap was not found in a tree based on amino acid sequences. Our interpretation is that convergent evolution on the level of the protein function, possibly driven by selection from shared pathogens, has resulted in allomorphs with similar peptide-binding repertoires, although trans-species evolution in combination with gene conversion cannot be ruled out.
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Affiliation(s)
- Elna Follin
- Immunology Section, BMC-D14, Department of Experimental Medical Sciences, Lund University, 221 84, Lund, Sweden.
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Wutzler R, Foerster K, Kempenaers B. MHC class I variation in a natural blue tit population (Cyanistes caeruleus). Genetica 2012; 140:349-64. [PMID: 23073914 DOI: 10.1007/s10709-012-9679-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 09/03/2012] [Indexed: 12/13/2022]
Abstract
The major histocompatibility complex (MHC) is central to the vertebrate immune system and its highly polymorphic genes are considered to influence several life-history traits of individuals. To characterize the MHC in a natural population of blue tits (Cyanistes caeruleus) we investigated the class I exon 3 diversity of more than 900 individuals. We designed two pairs of motif-specific primers that reliably amplify independent subsets of MHC alleles. Applying denaturing gradient gel electrophoresis (DGGE) we obtained 48 independently inherited units of unique band patterns (DGGE-haplogroups), which were validated in a segregation analysis within 105 families. In a second approach, we extensively sequenced 6 unrelated individuals to confirm that DGGE-haplogroup composition reflects individual allelic variation. The highest number of different DGGE-haplogroups in a single individual corresponded in 19 MHC exon 3 sequences, suggesting a minimum of 10 amplified MHC class I loci in the blue tit. In total, we identified 50 unique functional and 3 non-functional sequences. Functional sequences showed high levels of recombination and strong positive selection in the antigen binding region, whereas nucleotide diversity was comparatively low in the range of all passerine species. Finally, in a phylogenetic comparison of passerine MHC class I exon 3 sequences we discuss conflicting evolutionary signals possibly due to recent gene duplication, recombination events and concerted evolution. Our results indicate that the described method is suitable to effectively explore the MHC diversity and its ecological impacts in blue tits in future studies.
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Affiliation(s)
- R Wutzler
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82305 Seewiesen, Germany.
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Wang B, Ekblom R, Strand TM, Portela-Bens S, Höglund J. Sequencing of the core MHC region of black grouse (Tetrao tetrix) and comparative genomics of the galliform MHC. BMC Genomics 2012; 13:553. [PMID: 23066932 PMCID: PMC3500228 DOI: 10.1186/1471-2164-13-553] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 09/24/2012] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The MHC, which is regarded as the most polymorphic region in the genomes of jawed vertebrates, plays a central role in the immune system by encoding various proteins involved in the immune response. The chicken MHC-B genomic region has a highly streamlined gene content compared to mammalian MHCs. Its core region includes genes encoding Class I and Class IIB molecules but is only ~92Kb in length. Sequences of other galliform MHCs show varying degrees of similarity as that of chicken. The black grouse (Tetrao tetrix) is a wild galliform bird species which is an important model in conservation genetics and ecology. We sequenced the black grouse core MHC-B region and combined this with available data from related species (chicken, turkey, gold pheasant and quail) to perform a comparative genomics study of the galliform MHC. This kind of analysis has previously been severely hampered by the lack of genomic information on avian MHC regions, and the galliformes is still the only bird lineage where such a comparison is possible. RESULTS In this study, we present the complete genomic sequence of the MHC-B locus of black grouse, which is 88,390 bp long and contains 19 genes. It shows the same simplicity as, and almost perfect synteny with, the corresponding genomic region of chicken. We also use 454-transcriptome sequencing to verify expression in 17 of the black grouse MHC-B genes. Multiple sequence inversions of the TAPBP gene and TAP1-TAP2 gene block identify the recombination breakpoints near the BF and BLB genes. Some of the genes in the galliform MHC-B region also seem to have been affected by selective forces, as inferred from deviating phylogenetic signals and elevated rates of non-synonymous nucleotide substitutions. CONCLUSIONS We conclude that there is large synteny between the MHC-B region of the black grouse and that of other galliform birds, but that some duplications and rearrangements have occurred within this lineage. The MHC-B sequence reported here will provide a valuable resource for future studies on the evolution of the avian MHC genes and on links between immunogenetics and ecology of black grouse.
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Affiliation(s)
- Biao Wang
- Population Biology and Conservation Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
| | - Robert Ekblom
- Evolutionary Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
| | - Tanja M Strand
- Population Biology and Conservation Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
- Swedish Institute for Communicable Disease Control, Department of Preparedness, Nobels väg, , 18, Solna, SE-171 82, Sweden
| | - Silvia Portela-Bens
- Population Biology and Conservation Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
| | - Jacob Höglund
- Population Biology and Conservation Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
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Sepil I, Moghadam HK, Huchard E, Sheldon BC. Characterization and 454 pyrosequencing of major histocompatibility complex class I genes in the great tit reveal complexity in a passerine system. BMC Evol Biol 2012; 12:68. [PMID: 22587557 PMCID: PMC3483247 DOI: 10.1186/1471-2148-12-68] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 05/03/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The critical role of Major Histocompatibility Complex (Mhc) genes in disease resistance and their highly polymorphic nature make them exceptional candidates for studies investigating genetic effects on survival, mate choice and conservation. Species that harbor many Mhc loci and high allelic diversity are particularly intriguing as they are potentially under strong selection and studies of such species provide valuable information as to the mechanisms maintaining Mhc diversity. However comprehensive genotyping of complex multilocus systems has been a major challenge to date with the result that little is known about the consequences of this complexity in terms of fitness effects and disease resistance. RESULTS In this study, we genotyped the Mhc class I exon 3 of the great tit (Parus major) from two nest-box breeding populations near Oxford, UK that have been monitored for decades. Characterization of Mhc class I exon 3 was adopted and bidirectional sequencing was carried using the 454 sequencing platform. Full analysis of sequences through a stepwise variant validation procedure allowed reliable typing of more than 800 great tits based on 214,357 reads; from duplicates we estimated the repeatability of typing as 0.94. A total of 862 alleles were detected, and the presence of at least 16 functional loci was shown - the highest number characterized in a wild bird species. Finally, the functional alleles were grouped into 17 supertypes based on their antigen binding affinities. CONCLUSIONS We found extreme complexity at the Mhc class I of the great tit both in terms of allelic diversity and gene number. The presence of many functional loci was shown, together with a pseudogene family and putatively non-functional alleles; there was clear evidence that functional alleles were under strong balancing selection. This study is the first step towards an in-depth analysis of this gene complex in this species, which will help understanding how parasite-mediated and sexual selection shape and maintain host genetic variation in nature. We believe that study systems like ours can make important contributions to the field of evolutionary biology and emphasize the necessity of integrating long-term field-based studies with detailed genetic analysis to unravel complex evolutionary processes.
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Affiliation(s)
- Irem Sepil
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, OX1 3PS, UK.
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