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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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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: 37] [Impact Index Per Article: 7.4] [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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Reed KM, Mendoza KM, Settlage RE. Targeted capture enrichment and sequencing identifies extensive nucleotide variation in the turkey MHC-B. Immunogenetics 2016; 68:219-29. [DOI: 10.1007/s00251-015-0893-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 12/16/2015] [Indexed: 02/08/2023]
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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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