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Hou M, Akhtar MS, Hayashi M, Ashino R, Matsumoto-Oda A, Hayakawa T, Ishida T, Melin AD, Imai H, Kawamura S. Reduction of bitter taste receptor gene family in folivorous colobine primates relative to omnivorous cercopithecine primates. Primates 2024; 65:311-331. [PMID: 38605281 PMCID: PMC11219393 DOI: 10.1007/s10329-024-01124-w] [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: 09/19/2023] [Accepted: 02/26/2024] [Indexed: 04/13/2024]
Abstract
Bitter taste perception is important in preventing animals from ingesting potentially toxic compounds. Whole-genome assembly (WGA) data have revealed that bitter taste receptor genes (TAS2Rs) comprise a multigene family with dozens of intact and disrupted genes in primates. However, publicly available WGA data are often incomplete, especially for multigene families. In this study, we employed a targeted capture (TC) approach specifically probing TAS2Rs for ten species of cercopithecid primates with diverse diets, including eight omnivorous cercopithecine species and two folivorous colobine species. We designed RNA probes for all TAS2Rs that we modeled to be intact in the common ancestor of cercopithecids ("ancestral-cercopithecid TAS2R gene set"). The TC was followed by short-read and high-depth massive-parallel sequencing. TC retrieved more intact TAS2R genes than found in WGA databases. We confirmed a large number of gene "births" at the common ancestor of cercopithecids and found that the colobine common ancestor and the cercopithecine common ancestor had contrasting trajectories: four gene "deaths" and three gene births, respectively. The number of intact TAS2R genes was markedly reduced in colobines (25-28 detected via TC and 20-26 detected via WGA analysis) as compared with cercopithecines (27-36 via TC and 19-30 via WGA). Birth or death events occurred at almost every phylogenetic-tree branch, making the composition of intact genes variable among species. These results show that evolutionary change in intact TAS2R genes is a complex process, refute a simple general prediction that herbivory favors more TAS2R genes, and have implications for understanding dietary adaptations and the evolution of detoxification abilities.
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Affiliation(s)
- Min Hou
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience BLDG Room 502, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | - Muhammad Shoaib Akhtar
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience BLDG Room 502, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | - Masahiro Hayashi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience BLDG Room 502, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | - Ryuichi Ashino
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience BLDG Room 502, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | - Akiko Matsumoto-Oda
- Graduate School of Tourism Sciences, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Takashi Hayakawa
- Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido, Japan
- Japan Monkey Centre, Inuyama, Aichi, Japan
| | - Takafumi Ishida
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Amanda D Melin
- Department of Anthropology and Archaeology, University of Calgary, Alberta, Canada
- Department of Medical Genetics, University of Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Alberta, Canada
| | - Hiroo Imai
- Molecular Biology Section, Center for the Evolutionary Origins of Human Behavior, Kyoto University, Kyoto, Aichi, Japan
| | - Shoji Kawamura
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience BLDG Room 502, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan.
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Jasinska AJ, Apetrei C, Pandrea I. Walk on the wild side: SIV infection in African non-human primate hosts-from the field to the laboratory. Front Immunol 2023; 13:1060985. [PMID: 36713371 PMCID: PMC9878298 DOI: 10.3389/fimmu.2022.1060985] [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: 10/04/2022] [Accepted: 12/15/2022] [Indexed: 01/15/2023] Open
Abstract
HIV emerged following cross-species transmissions of simian immunodeficiency viruses (SIVs) that naturally infect non-human primates (NHPs) from Africa. While HIV replication and CD4+ T-cell depletion lead to increased gut permeability, microbial translocation, chronic immune activation, and systemic inflammation, the natural hosts of SIVs generally avoid these deleterious consequences when infected with their species-specific SIVs and do not progress to AIDS despite persistent lifelong high viremia due to long-term coevolution with their SIV pathogens. The benign course of natural SIV infection in the natural hosts is in stark contrast to the experimental SIV infection of Asian macaques, which progresses to simian AIDS. The mechanisms of non-pathogenic SIV infections are studied mainly in African green monkeys, sooty mangabeys, and mandrills, while progressing SIV infection is experimentally modeled in macaques: rhesus macaques, pigtailed macaques, and cynomolgus macaques. Here, we focus on the distinctive features of SIV infection in natural hosts, particularly (1): the superior healing properties of the intestinal mucosa, which enable them to maintain the integrity of the gut barrier and prevent microbial translocation, thus avoiding excessive/pathologic immune activation and inflammation usually perpetrated by the leaking of the microbial products into the circulation; (2) the gut microbiome, the disruption of which is an important factor in some inflammatory diseases, yet not completely understood in the course of lentiviral infection; (3) cell population shifts resulting in target cell restriction (downregulation of CD4 or CCR5 surface molecules that bind to SIV), control of viral replication in the lymph nodes (expansion of natural killer cells), and anti-inflammatory effects in the gut (NKG2a/c+ CD8+ T cells); and (4) the genes and biological pathways that can shape genetic adaptations to viral pathogens and are associated with the non-pathogenic outcome of the natural SIV infection. Deciphering the protective mechanisms against SIV disease progression to immunodeficiency, which have been established through long-term coevolution between the natural hosts and their species-specific SIVs, may prompt the development of novel therapeutic interventions, such as drugs that can control gut inflammation, enhance gut healing capacities, or modulate the gut microbiome. These developments can go beyond HIV infection and open up large avenues for correcting gut damage, which is common in many diseases.
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Affiliation(s)
- Anna J. Jasinska
- Division of Infectious Diseases, Department of Medicine (DOM), School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Cristian Apetrei
- Division of Infectious Diseases, Department of Medicine (DOM), School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States,Department of Infectious Diseases and Immunology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ivona Pandrea
- Department of Infectious Diseases and Immunology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, United States,Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States,*Correspondence: Ivona Pandrea,
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3
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Eskew EA, Fraser D, Vonhof MJ, Pinsky ML, Maslo B. Host gene expression in wildlife disease: making sense of species-level responses. Mol Ecol 2021; 30:6517-6530. [PMID: 34516689 DOI: 10.1111/mec.16172] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 08/16/2021] [Accepted: 08/31/2021] [Indexed: 12/11/2022]
Abstract
Emerging infectious diseases are significant threats to wildlife conservation, yet the impacts of pathogen exposure and infection can vary widely among host species. As such, conservation biologists and disease ecologists have increasingly aimed to understand species-specific host susceptibility using molecular methods. In particular, comparative gene expression assays have been used to contrast the transcriptomic responses of disease-resistant and disease-susceptible hosts to pathogen exposure. This work usually assumes that the gene expression responses of disease-resistant species will reveal the activation of molecular pathways contributing to host defence. However, results often show that disease-resistant hosts undergo little gene expression change following pathogen challenge. Here, we discuss the mechanistic implications of these "null" findings and offer methodological suggestions for future molecular studies of wildlife disease. First, we highlight that muted transcriptomic responses with minimal immune system recruitment may indeed be protective for nonsusceptible hosts if they limit immunopathology and promote pathogen tolerance in systems where susceptible hosts suffer from genetic dysregulation. Second, we argue that overly narrow investigation of responses to pathogen exposure may overlook important, constitutively active molecular pathways that underlie species-specific defences. Finally, we outline alternative study designs and approaches that complement interspecific transcriptomic comparisons, including intraspecific gene expression studies and genomic methods to detect signatures of selection. Collectively, these insights will help ecologists extract maximal information from conservation-relevant transcriptomic data sets, leading to a deeper understanding of host defences and, ultimately, the implementation of successful conservation interventions.
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Affiliation(s)
- Evan A Eskew
- Department of Ecology, Evolution and Natural Resources, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA.,Department of Biology, Pacific Lutheran University, Tacoma, Washington, USA
| | - Devaughn Fraser
- Wildlife Genetics Research Laboratory, California Department of Fish and Wildlife, Sacramento, California, USA
| | - Maarten J Vonhof
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan, USA
| | - Malin L Pinsky
- Department of Ecology, Evolution and Natural Resources, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - Brooke Maslo
- Department of Ecology, Evolution and Natural Resources, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
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Russell RM, Bibollet-Ruche F, Liu W, Sherrill-Mix S, Li Y, Connell J, Loy DE, Trimboli S, Smith AG, Avitto AN, Gondim MVP, Plenderleith LJ, Wetzel KS, Collman RG, Ayouba A, Esteban A, Peeters M, Kohler WJ, Miller RA, François-Souquiere S, Switzer WM, Hirsch VM, Marx PA, Piel AK, Stewart FA, Georgiev AV, Sommer V, Bertolani P, Hart JA, Hart TB, Shaw GM, Sharp PM, Hahn BH. CD4 receptor diversity represents an ancient protection mechanism against primate lentiviruses. Proc Natl Acad Sci U S A 2021; 118:e2025914118. [PMID: 33771926 PMCID: PMC8020793 DOI: 10.1073/pnas.2025914118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Infection with human and simian immunodeficiency viruses (HIV/SIV) requires binding of the viral envelope glycoprotein (Env) to the host protein CD4 on the surface of immune cells. Although invariant in humans, the Env binding domain of the chimpanzee CD4 is highly polymorphic, with nine coding variants circulating in wild populations. Here, we show that within-species CD4 diversity is not unique to chimpanzees but found in many African primate species. Characterizing the outermost (D1) domain of the CD4 protein in over 500 monkeys and apes, we found polymorphic residues in 24 of 29 primate species, with as many as 11 different coding variants identified within a single species. D1 domain amino acid replacements affected SIV Env-mediated cell entry in a single-round infection assay, restricting infection in a strain- and allele-specific fashion. Several identical CD4 polymorphisms, including the addition of N-linked glycosylation sites, were found in primate species from different genera, providing striking examples of parallel evolution. Moreover, seven different guenons (Cercopithecus spp.) shared multiple distinct D1 domain variants, pointing to long-term trans-specific polymorphism. These data indicate that the HIV/SIV Env binding region of the primate CD4 protein is highly variable, both within and between species, and suggest that this diversity has been maintained by balancing selection for millions of years, at least in part to confer protection against primate lentiviruses. Although long-term SIV-infected species have evolved specific mechanisms to avoid disease progression, primate lentiviruses are intrinsically pathogenic and have left their mark on the host genome.
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Affiliation(s)
- Ronnie M Russell
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | | | - Weimin Liu
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Scott Sherrill-Mix
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Yingying Li
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Jesse Connell
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Dorothy E Loy
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Stephanie Trimboli
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Andrew G Smith
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Alexa N Avitto
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Marcos V P Gondim
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Lindsey J Plenderleith
- Institute of Evolutionary Biology, University of Edinburgh, EH9 3FL Edinburgh, United Kingdom
- Centre for Immunity, Infection, and Evolution, University of Edinburgh, EH9 3FL Edinburgh, United Kingdom
| | - Katherine S Wetzel
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Ronald G Collman
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Ahidjo Ayouba
- Recherche Translationnelle Appliquée au VIH et aux Maladies Infectieuses, Institut de Recherche pour le Développement, University of Montpellier, INSERM, 34090 Montpellier, France
| | - Amandine Esteban
- Recherche Translationnelle Appliquée au VIH et aux Maladies Infectieuses, Institut de Recherche pour le Développement, University of Montpellier, INSERM, 34090 Montpellier, France
| | - Martine Peeters
- Recherche Translationnelle Appliquée au VIH et aux Maladies Infectieuses, Institut de Recherche pour le Développement, University of Montpellier, INSERM, 34090 Montpellier, France
| | - William J Kohler
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109
| | - Richard A Miller
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109
| | | | - William M Switzer
- Laboratory Branch, Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, GA 30329
| | - Vanessa M Hirsch
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892
| | - Preston A Marx
- Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA 70118
- Division of Microbiology, Tulane National Primate Research Center, Covington, LA 70433
| | - Alex K Piel
- Department of Anthropology, University College London, WC1H 0BW London, United Kingdom
| | - Fiona A Stewart
- Department of Anthropology, University College London, WC1H 0BW London, United Kingdom
- School of Biological and Environmental Sciences, Liverpool John Moores University, L3 3AF Liverpool, United Kingdom
| | - Alexander V Georgiev
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138
- School of Biological Sciences, Bangor University, LL57 2UW Bangor, United Kingdom
| | - Volker Sommer
- Department of Anthropology, University College London, WC1H 0BW London, United Kingdom
| | - Paco Bertolani
- Leverhulme Centre for Human Evolutionary Studies, University of Cambridge, CB2 1QH Cambridge, United Kingdom
| | - John A Hart
- Lukuru Wildlife Research Foundation, Tshuapa-Lomami-Lualaba Project, BP 2012, Kinshasa, Democratic Republic of the Congo
| | - Terese B Hart
- Lukuru Wildlife Research Foundation, Tshuapa-Lomami-Lualaba Project, BP 2012, Kinshasa, Democratic Republic of the Congo
| | - George M Shaw
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Paul M Sharp
- Institute of Evolutionary Biology, University of Edinburgh, EH9 3FL Edinburgh, United Kingdom
- Centre for Immunity, Infection, and Evolution, University of Edinburgh, EH9 3FL Edinburgh, United Kingdom
| | - Beatrice H Hahn
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104;
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
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6
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Aunin E, Böhme U, Sanderson T, Simons ND, Goldberg TL, Ting N, Chapman CA, Newbold CI, Berriman M, Reid AJ. Genomic and transcriptomic evidence for descent from Plasmodium and loss of blood schizogony in Hepatocystis parasites from naturally infected red colobus monkeys. PLoS Pathog 2020; 16:e1008717. [PMID: 32745123 PMCID: PMC7425995 DOI: 10.1371/journal.ppat.1008717] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 08/13/2020] [Accepted: 06/19/2020] [Indexed: 12/14/2022] Open
Abstract
Hepatocystis is a genus of single-celled parasites infecting, amongst other hosts, monkeys, bats and squirrels. Although thought to have descended from malaria parasites (Plasmodium spp.), Hepatocystis spp. are thought not to undergo replication in the blood-the part of the Plasmodium life cycle which causes the symptoms of malaria. Furthermore, Hepatocystis is transmitted by biting midges, not mosquitoes. Comparative genomics of Hepatocystis and Plasmodium species therefore presents an opportunity to better understand some of the most important aspects of malaria parasite biology. We were able to generate a draft genome for Hepatocystis sp. using DNA sequencing reads from the blood of a naturally infected red colobus monkey. We provide robust phylogenetic support for Hepatocystis sp. as a sister group to Plasmodium parasites infecting rodents. We show transcriptomic support for a lack of replication in the blood and genomic support for a complete loss of a family of genes involved in red blood cell invasion. Our analyses highlight the rapid evolution of genes involved in parasite vector stages, revealing genes that may be critical for interactions between malaria parasites and mosquitoes.
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Affiliation(s)
- Eerik Aunin
- Parasite Genomics, Wellcome Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Ulrike Böhme
- Parasite Genomics, Wellcome Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Theo Sanderson
- Malaria Biochemistry Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Noah D. Simons
- Department of Anthropology and Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
| | - Tony L. Goldberg
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Nelson Ting
- Department of Anthropology and Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
| | - Colin A. Chapman
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington DC, United States of America
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an, China
- School of Life Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
| | - Chris I. Newbold
- Parasite Genomics, Wellcome Sanger Institute, Hinxton, Cambridge, United Kingdom
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Matthew Berriman
- Parasite Genomics, Wellcome Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Adam J. Reid
- Parasite Genomics, Wellcome Sanger Institute, Hinxton, Cambridge, United Kingdom
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Anderson JA, Vilgalys TP, Tung J. Broadening primate genomics: new insights into the ecology and evolution of primate gene regulation. Curr Opin Genet Dev 2020; 62:16-22. [PMID: 32569794 PMCID: PMC7483836 DOI: 10.1016/j.gde.2020.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/05/2020] [Accepted: 05/06/2020] [Indexed: 12/17/2022]
Abstract
Comparative analyses have played a key role in understanding how gene regulatory evolution contributes to primate phenotypic diversity. Recently, these studies have expanded to include a wider range of species, within-population as well as interspecific analyses, and research on wild as well as captive individuals. This expansion provides context for understanding genetic and environmental effects on gene regulation in humans, including the importance of the pathogen and social environments. Although taxonomic representation remains biased, inclusion of more species has also begun to reveal the evolutionary processes that explain whether and when gene regulation is conserved. Together, this work highlights how studies in other primates contribute to understanding evolution in our own lineage, and we conclude by identifying promising avenues for future work.
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Affiliation(s)
- Jordan A Anderson
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Tauras P Vilgalys
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Department of Medicine, Section of Genetic Medicine, University of Chicago, Chicago, IL, 60637, USA
| | - Jenny Tung
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA; Institute of Primate Research, National Museums of Kenya, Nairobi 00502, Kenya; Duke Population Research Institute, Duke University, Durham, NC 27708, USA.
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Evolution of Host Specificity by Malaria Parasites through Altered Mechanisms Controlling Genome Maintenance. mBio 2020; 11:mBio.03272-19. [PMID: 32184256 PMCID: PMC7078485 DOI: 10.1128/mbio.03272-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Malaria remains one of the most prevalent and deadly infectious diseases of the developing world, causing approximately 228 million clinical cases and nearly half a million deaths annually. The disease is caused by protozoan parasites of the genus Plasmodium, and of the five species capable of infecting humans, infections with P. falciparum are the most severe. In addition to the parasites that infect people, there are hundreds of additional species that infect birds, reptiles, and other mammals, each exquisitely evolved to meet the specific challenges inherent to survival within their respective hosts. By comparing the unique strategies that each species has evolved, key insights into host-parasite interactions can be gained, including discoveries regarding the pathogenesis of human disease. Here, we describe the surprising observation that closely related parasites with different hosts have evolved remarkably different methods for repairing their genomes. This observation has important implications for the ability of parasites to maintain chronic infections and for the development of host immunity. The protozoan parasites that cause malaria infect a wide variety of vertebrate hosts, including birds, reptiles, and mammals, and the evolutionary pressures inherent to the host-parasite relationship have profoundly shaped the genomes of both host and parasite. Here, we report that these selective pressures have resulted in unexpected alterations to one of the most basic aspects of eukaryotic biology, the maintenance of genome integrity through DNA repair. Malaria parasites that infect humans continuously generate genetic diversity within their antigen-encoding gene families through frequent ectopic recombination between gene family members, a process that is a crucial feature of the persistence of malaria globally. The continuous generation of antigen diversity ensures that different parasite isolates are antigenically distinct, thus preventing extensive cross-reactive immunity and enabling parasites to maintain stable transmission within human populations. However, the molecular basis of the recombination between gene family members is not well understood. Through computational analyses of the antigen-encoding, multicopy gene families of different Plasmodium species, we report the unexpected observation that malaria parasites that infect rodents do not display the same degree of antigen diversity as observed in Plasmodium falciparum and appear to undergo significantly less ectopic recombination. Using comparative genomics, we also identify key molecular components of the diversification process, thus shedding new light on how malaria parasites balance the maintenance of genome integrity with the requirement for continuous genetic diversification.
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