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Liu J, Shi F, Zhang Y, Tang X, Wang C, Gao Y, Suo J, Yu Y, Chen L, Zhang N, Sun P, Liu X, Suo X. Evidence of high-efficiency cross fertilization in Eimeria acervulina revealed using two lines of transgenic parasites. Int J Parasitol 2023; 53:81-89. [PMID: 36549444 DOI: 10.1016/j.ijpara.2022.10.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 10/20/2022] [Accepted: 10/22/2022] [Indexed: 12/23/2022]
Abstract
Eimeria species are apicomplexan parasites with a direct life cycle consisting of a replicative phase involving multiple rounds of asexual replication in the intestine or other organs including kidneys, liver, and gallbladder, depending on the species, followed by a sexual phase or gamogony involving the development and fertilization of gametes, an essential process for Eimeria transmission. Recent advances in the genetic manipulation of these parasites made it possible to conduct genetic crosses combined with genomic approaches to elucidate the genetic determinants of Eimeria development, virulence, drug resistance, and immune evasion. Here, we employed genetic techniques to generate two transgenic Eimeria acervulina lines, EaGAM56 and EaHAP2, each expressing two unique fluorescent proteins, with one controlled by a constitutive promotor for cross-efficiency analysis and the other by a male or female gametocyte stage-specific promoter to observe sexual development. The expression of fluorescent proteins in the transgenic lines was analyzed in different developmental stages of the E. acervulina life cycle by immunoblotting and by examination of frozen sections using fluorescence microscopy. The effect of infective doses on cross-fertilization was further investigated by conducting several genetic crosses between the two transgenic lines at different doses and ratios. Two transgenic lines expressing constitutive and gametocyte-specific fluorescence proteins were generated and characterized. These transgenic parasites display synchronous development in chickens, comparable with that of the wild type. Genetic crosses between the two transgenic parasites showed that a high rate of oocysts co-expressing the two reporters could be achieved following inoculation with high doses of infective oocysts. We further showed that the proportion of co-transfected oocysts can be modulated by altering the ratio of the transgenic parental lines. Higher infective doses and similar numbers of functional gametocytes from the parents increase the rate of cross-fertilization. Our data highlight the usefulness of genetic manipulation and fluorescently-labeled transgenic gametocytes as tools to study Eimeria development and to elucidate the factors that modulate sexual development. This work sets the stage for the implementation of novel approaches to investigate other aspects of Eimeria pathogenesis, virulence, and drug susceptibility and resistance.
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Affiliation(s)
- Jie Liu
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Fangyun Shi
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Yuanyuan Zhang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture & Beijing Key Laboratory of Animal Genetic Improvement, China Agricultural University, Beijing 100193 China
| | - Xinming Tang
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Chaoyue Wang
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Yang Gao
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Jingxia Suo
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Ying Yu
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Linlin Chen
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Ning Zhang
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Pei Sun
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Xianyong Liu
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Xun Suo
- National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
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Su XZ, Wu J, Xu F, Pattaradilokrat S. Genetic mapping of determinants in drug resistance, virulence, disease susceptibility, and interaction of host-rodent malaria parasites. Parasitol Int 2022; 91:102637. [PMID: 35926693 PMCID: PMC9452477 DOI: 10.1016/j.parint.2022.102637] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 07/28/2022] [Indexed: 12/31/2022]
Abstract
Genetic mapping has been widely employed to search for genes linked to phenotypes/traits of interest. Because of the ease of maintaining rodent malaria parasites in laboratory mice, many genetic crosses of rodent malaria parasites have been performed to map the parasite genes contributing to malaria parasite development, drug resistance, host immune response, and disease pathogenesis. Drs. Richard Carter, David Walliker, and colleagues at the University of Edinburgh, UK, were the pioneers in developing the systems for genetic mapping of malaria parasite traits, including characterization of genetic markers to follow the inheritance and recombination of parasite chromosomes and performing the first genetic cross using rodent malaria parasites. Additionally, many genetic crosses of inbred mice have been performed to link mouse chromosomal loci to the susceptibility to malaria parasite infections. In this chapter, we review and discuss past and recent advances in genetic marker development, performing genetic crosses, and genetic mapping of both parasite and host genes. Genetic mappings using models of rodent malaria parasites and inbred mice have contributed greatly to our understanding of malaria, including parasite development within their hosts, mechanism of drug resistance, and host-parasite interaction.
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Affiliation(s)
- Xin-Zhuan Su
- Malaria Functional Genomics Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD, USA.
| | - Jian Wu
- Malaria Functional Genomics Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD, USA
| | - Fangzheng Xu
- Malaria Functional Genomics Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD, USA
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Li X, Kumar S, Brenneman KV, Anderson TJC. Bulk segregant linkage mapping for rodent and human malaria parasites. Parasitol Int 2022; 91:102653. [PMID: 36007706 DOI: 10.1016/j.parint.2022.102653] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/18/2022] [Accepted: 08/19/2022] [Indexed: 11/25/2022]
Abstract
In 2005 Richard Carter's group surprised the malaria genetics community with an elegant approach to rapidly mapping the genetic basis of phenotypic traits in rodent malaria parasites. This approach, which he termed "linkage group selection", utilized bulk pools of progeny, rather than individual clones, and exploited simple selection schemes to identify genome regions underlying resistance to drug treatment (or other phenotypes). This work was the first application of "bulk segregant" methodologies for genetic mapping in microbes: this approach is now widely used in yeast, and across multiple recombining pathogens ranging from Aspergillus fungi to Schistosome parasites. Genetic crosses of human malaria parasites (for which Richard Carter was also a pioneer) can now be conducted in humanized mice, providing new opportunities for exploiting bulk segregant approaches for a wide variety of malaria parasite traits. We review the application of bulk segregant approaches to mapping malaria parasite traits and suggest additional developments that may further expand the utility of this powerful approach.
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Affiliation(s)
- Xue Li
- Program in Disease Intervention and Prevention, Texas Biomedical Research Institute, San Antonio, TX, USA.
| | - Sudhir Kumar
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, Washington, USA
| | - Katelyn Vendrely Brenneman
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Tim J C Anderson
- Program in Disease Intervention and Prevention, Texas Biomedical Research Institute, San Antonio, TX, USA.
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Cravo P. On the contribution of the rodent model Plasmodium chabaudi for understanding the genetics of drug resistance in malaria. Parasitol Int 2022; 91:102623. [PMID: 35803536 DOI: 10.1016/j.parint.2022.102623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/22/2022] [Accepted: 06/30/2022] [Indexed: 10/17/2022]
Abstract
Malaria is a devastating disease that still claims over half a million lives every year, mostly in sub-Saharan Africa. One of the main barriers to malaria control is the evolution and propagation of drug-resistant mutant parasites. Knowing the genes and respective mutations responsible for drug resistance facilitates the design of drugs with novel modes of action and allows predicting and monitoring drug resistance in natural parasite populations in real-time. The best way to identify these mutations is to experimentally evolve resistance to the drug in question and then comparing the genomes of the drug-resistant mutants to that of the sensitive progenitor parasites. This simple evolutive concept was the starting point for the development of a paradigm over the years, based on the use of the rodent malaria parasite Plasmodium chabaudi to unravel the genetics of drug resistance in malaria. It involves the use of a cloned parasite isolate (P. chabaudi AS) whose genome is well characterized, to artificially select resistance to given drugs through serial passages in mice under slowly increasing drug pressure. The end resulting parasites are cloned and the genetic mutations are then discovered through Linkage Group Selection, a technique conceived by Prof. Richard Carter and his group, and/or Whole Genome Sequencing. The precise role of these mutations can then be interrogated in malaria parasites of humans through allelic replacement experiments and/or genotype-phenotype association studies in natural parasite populations. Using this paradigm, all the mutations underlying resistance to the most important antimalarial drugs were identified, most of which were pioneering and later shown to also play a role in drug resistance in natural infections of human malaria parasites. This supports the use of P. chabaudi a fast-track predictive model to identify candidate genetic markers of resistance to present and future antimalarial drugs and improving our understanding of the biology of resistance.
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Affiliation(s)
- Pedro Cravo
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, n° 100, 1349-008 Lisboa, Portugal.
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Simwela NV, Waters AP. Current status of experimental models for the study of malaria. Parasitology 2022; 149:1-22. [PMID: 35357277 PMCID: PMC9378029 DOI: 10.1017/s0031182021002134] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 01/09/2023]
Abstract
Infection by malaria parasites (Plasmodium spp.) remains one of the leading causes of morbidity and mortality, especially in tropical regions of the world. Despite the availability of malaria control tools such as integrated vector management and effective therapeutics, these measures have been continuously undermined by the emergence of vector resistance to insecticides or parasite resistance to frontline antimalarial drugs. Whilst the recent pilot implementation of the RTS,S malaria vaccine is indeed a remarkable feat, highly effective vaccines against malaria remain elusive. The barriers to effective vaccines result from the complexity of both the malaria parasite lifecycle and the parasite as an organism itself with consequent major gaps in our understanding of their biology. Historically and due to the practical and ethical difficulties of working with human malaria infections, research into malaria parasite biology has been extensively facilitated by animal models. Animals have been used to study disease pathogenesis, host immune responses and their (dys)regulation and further disease processes such as transmission. Moreover, animal models remain at the forefront of pre-clinical evaluations of antimalarial drugs (drug efficacy, mode of action, mode of resistance) and vaccines. In this review, we discuss commonly used animal models of malaria, the parasite species used and their advantages and limitations which hinder their extrapolation to actual human disease. We also place into this context the most recent developments such as organoid technologies and humanized mice.
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Affiliation(s)
- Nelson V. Simwela
- Institute of Infection, Immunity & Inflammation, Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, UK
| | - Andrew P. Waters
- Institute of Infection, Immunity & Inflammation, Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, UK
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Plasmodium Genomics and Genetics: New Insights into Malaria Pathogenesis, Drug Resistance, Epidemiology, and Evolution. Clin Microbiol Rev 2019; 32:32/4/e00019-19. [PMID: 31366610 DOI: 10.1128/cmr.00019-19] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Protozoan Plasmodium parasites are the causative agents of malaria, a deadly disease that continues to afflict hundreds of millions of people every year. Infections with malaria parasites can be asymptomatic, with mild or severe symptoms, or fatal, depending on many factors such as parasite virulence and host immune status. Malaria can be treated with various drugs, with artemisinin-based combination therapies (ACTs) being the first-line choice. Recent advances in genetics and genomics of malaria parasites have contributed greatly to our understanding of parasite population dynamics, transmission, drug responses, and pathogenesis. However, knowledge gaps in parasite biology and host-parasite interactions still remain. Parasites resistant to multiple antimalarial drugs have emerged, while advanced clinical trials have shown partial efficacy for one available vaccine. Here we discuss genetic and genomic studies of Plasmodium biology, host-parasite interactions, population structures, mosquito infectivity, antigenic variation, and targets for treatment and immunization. Knowledge from these studies will advance our understanding of malaria pathogenesis, epidemiology, and evolution and will support work to discover and develop new medicines and vaccines.
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7
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Abkallo HM, Martinelli A, Inoue M, Ramaprasad A, Xangsayarath P, Gitaka J, Tang J, Yahata K, Zoungrana A, Mitaka H, Acharjee A, Datta PP, Hunt P, Carter R, Kaneko O, Mustonen V, Illingworth CJR, Pain A, Culleton R. Rapid identification of genes controlling virulence and immunity in malaria parasites. PLoS Pathog 2017; 13:e1006447. [PMID: 28704525 PMCID: PMC5507557 DOI: 10.1371/journal.ppat.1006447] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 06/05/2017] [Indexed: 11/20/2022] Open
Abstract
Identifying the genetic determinants of phenotypes that impact disease severity is of fundamental importance for the design of new interventions against malaria. Here we present a rapid genome-wide approach capable of identifying multiple genetic drivers of medically relevant phenotypes within malaria parasites via a single experiment at single gene or allele resolution. In a proof of principle study, we found that a previously undescribed single nucleotide polymorphism in the binding domain of the erythrocyte binding like protein (EBL) conferred a dramatic change in red blood cell invasion in mutant rodent malaria parasites Plasmodium yoelii. In the same experiment, we implicated merozoite surface protein 1 (MSP1) and other polymorphic proteins, as the major targets of strain-specific immunity. Using allelic replacement, we provide functional validation of the substitution in the EBL gene controlling the growth rate in the blood stages of the parasites. Developing a greater understanding of malaria genetics is a key step in combating the threat posed by the disease. Here we use a novel approach to study two important properties of the parasite; the rate at which parasites grow within a single host, and the means by which parasites are affected by the host immune system. Two malaria strains with different biological properties were crossed in mosquitoes to produce a hybrid population, which was then grown in naïve and vaccinated mice. Parasites with genes conveying increased growth or immune evasion are favoured under natural selection, leaving a signature on the genetic composition of the cross population. We describe a novel mathematical approach to interpret this signature, identifying selected genes within the parasite population. We discover new genetic variants conveying increased within-host growth and resistance to host immunity in a mouse malaria strain. Experimental validation highlights the ability of this rapid experimental process for generating insights into malaria biology.
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Affiliation(s)
- Hussein M. Abkallo
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Axel Martinelli
- Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan
- Biological and Environmental Sciences and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Megumi Inoue
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Abhinay Ramaprasad
- Biological and Environmental Sciences and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Phonepadith Xangsayarath
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Protozooolgy, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Jesse Gitaka
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Protozooolgy, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- Centre for Malaria Elimination, School of Medicine, Mount Kenya University, Thika, Kenya
| | - Jianxia Tang
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Jiangsu, China
| | - Kazuhide Yahata
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Protozooolgy, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Augustin Zoungrana
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Hayato Mitaka
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Arita Acharjee
- Indian Institute of Science Education and Research Kolkata, Mohanpur - 741 246, West Bengal, India
| | - Partha P. Datta
- Indian Institute of Science Education and Research Kolkata, Mohanpur - 741 246, West Bengal, India
| | - Paul Hunt
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Richard Carter
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Osamu Kaneko
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Department of Protozooolgy, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Ville Mustonen
- Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Christopher J. R. Illingworth
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (CJRI); (AP); (RC)
| | - Arnab Pain
- Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan
- Biological and Environmental Sciences and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- * E-mail: (CJRI); (AP); (RC)
| | - Richard Culleton
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- * E-mail: (CJRI); (AP); (RC)
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Culleton RL, Abkallo HM. Malaria parasite genetics: doing something useful. Parasitol Int 2014; 64:244-53. [PMID: 25073068 DOI: 10.1016/j.parint.2014.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 07/11/2014] [Indexed: 01/15/2023]
Abstract
Genetics has informed almost every aspect of the study of malaria parasites, and remains a key component of much of the research that aims to reduce the burden of the disease they cause. We describe the history of genetic studies of malaria parasites and give an overview of the utility of the discipline to malariology.
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Affiliation(s)
- Richard L Culleton
- Malaria Unit, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
| | - Hussein M Abkallo
- Malaria Unit, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
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Qi Y, Zhu F, Li J, Fu Y, Pattaradilokrat S, Hong L, Liu S, Huang F, Xu W, Su XZ. Optimized protocols for improving the likelihood of cloning recombinant progeny from Plasmodium yoelii genetic crosses. Exp Parasitol 2012; 133:44-50. [PMID: 23116600 DOI: 10.1016/j.exppara.2012.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 10/16/2012] [Accepted: 10/19/2012] [Indexed: 11/29/2022]
Abstract
Genetic cross is a powerful tool for studying malaria genes contributing to drug resistance, parasite development, and pathogenesis. Cloning and identification of recombinant progeny (RP) is laborious and expensive, especially when a large proportion of progeny derived from self-fertilization are present in the uncloned progeny of a genetic cross. Since the frequency of cross-fertilization affects the number of recombinant progeny in a genetic cross, it is important to optimize the procedure of a genetic cross to maximize the cross-fertilization. Here we investigated the factors that might influence the chances of obtaining RP from a genetic cross and showed that different Plasmodium yoelii strains/subspecies/clones had unique abilities in producing oocysts in a mosquito midgut. When a genetic cross is performed between two parents producing different numbers of functional gametocytes, the ratio of parental parasites must be adjusted to improve the chance of obtaining RP. An optimized parental ratio could be established based on oocyst counts from single infection of each parent before crossing experiments, which may reflect the efficiency of gametocyte production and/or fertilization. The timing of progeny cloning is also important; cloning of genetic cross progeny from mice directly infected with sporozoites (vs. frozen blood after needle passage) at a time when parasitemia is low (usually <1%) could improve the chance of obtaining RP. This study provides an optimized protocol for efficiently cloning RPs from a genetic cross of malaria parasites.
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Affiliation(s)
- Yanwei Qi
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361005, PR China
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10
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Kinga Modrzynska K, Creasey A, Loewe L, Cezard T, Trindade Borges S, Martinelli A, Rodrigues L, Cravo P, Blaxter M, Carter R, Hunt P. Quantitative genome re-sequencing defines multiple mutations conferring chloroquine resistance in rodent malaria. BMC Genomics 2012; 13:106. [PMID: 22435897 PMCID: PMC3362770 DOI: 10.1186/1471-2164-13-106] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 03/21/2012] [Indexed: 01/18/2023] Open
Abstract
Background Drug resistance in the malaria parasite Plasmodium falciparum severely compromises the treatment and control of malaria. A knowledge of the critical mutations conferring resistance to particular drugs is important in understanding modes of drug action and mechanisms of resistances. They are required to design better therapies and limit drug resistance. A mutation in the gene (pfcrt) encoding a membrane transporter has been identified as a principal determinant of chloroquine resistance in P. falciparum, but we lack a full account of higher level chloroquine resistance. Furthermore, the determinants of resistance in the other major human malaria parasite, P. vivax, are not known. To address these questions, we investigated the genetic basis of chloroquine resistance in an isogenic lineage of rodent malaria parasite P. chabaudi in which high level resistance to chloroquine has been progressively selected under laboratory conditions. Results Loci containing the critical genes were mapped by Linkage Group Selection, using a genetic cross between the high-level chloroquine-resistant mutant and a genetically distinct sensitive strain. A novel high-resolution quantitative whole-genome re-sequencing approach was used to reveal three regions of selection on chr11, chr03 and chr02 that appear progressively at increasing drug doses on three chromosomes. Whole-genome sequencing of the chloroquine-resistant parent identified just four point mutations in different genes on these chromosomes. Three mutations are located at the foci of the selection valleys and are therefore predicted to confer different levels of chloroquine resistance. The critical mutation conferring the first level of chloroquine resistance is found in aat1, a putative aminoacid transporter. Conclusions Quantitative trait loci conferring selectable phenotypes, such as drug resistance, can be mapped directly using progressive genome-wide linkage group selection. Quantitative genome-wide short-read genome resequencing can be used to reveal these signatures of drug selection at high resolution. The identities of three genes (and mutations within them) conferring different levels of chloroquine resistance generate insights regarding the genetic architecture and mechanisms of resistance to chloroquine and other drugs. Importantly, their orthologues may now be evaluated for critical or accessory roles in chloroquine resistance in human malarias P. vivax and P. falciparum.
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Anderson T, Nkhoma S, Ecker A, Fidock D. How can we identify parasite genes that underlie antimalarial drug resistance? Pharmacogenomics 2011; 12:59-85. [PMID: 21174623 PMCID: PMC3148835 DOI: 10.2217/pgs.10.165] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
This article outlines genome-scale approaches that can be used to identify mutations in malaria (Plasmodium) parasites that underlie drug resistance and contribute to treatment failure. These approaches include genetic mapping by linkage or genome-wide association studies, drug selection and characterization of resistant mutants, and the identification of genome regions under strong recent selection. While these genomic approaches can identify candidate resistance loci, genetic manipulation is needed to demonstrate causality. We therefore also describe the growing arsenal of available transfection approaches for direct incrimination of mutations suspected to play a role in resistance. Our intention is both to review past progress and highlight promising approaches for future investigations.
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Affiliation(s)
- Tim Anderson
- Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, TX 78245, USA.
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Martinelli A, Henriques G, Cravo P, Hunt P. Whole genome re-sequencing identifies a mutation in an ABC transporter (mdr2) in a Plasmodium chabaudi clone with altered susceptibility to antifolate drugs. Int J Parasitol 2010; 41:165-71. [PMID: 20858498 PMCID: PMC3034870 DOI: 10.1016/j.ijpara.2010.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 07/27/2010] [Accepted: 08/13/2010] [Indexed: 12/16/2022]
Abstract
In malaria parasites, mutations in two genes of folate biosynthesis encoding dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) modify responses to antifolate therapies which target these enzymes. However, the involvement of other genes which modify the availability of exogenous folate, for example, has been proposed. Here, we used short-read whole-genome re-sequencing to determine the mutations in a clone of the rodent malaria parasite, Plasmodium chabaudi, which has altered susceptibility to both sulphadoxine and pyrimethamine. This clone bears a previously identified S106N mutation in dhfr and no mutation in dhps. Instead, three additional point mutations in genes on chromosomes 2, 13 and 14 were identified. The mutated gene on chromosome 13 (mdr2 K392Q) encodes an ABC transporter. Because Quantitative Trait Locus analysis previously indicated an association of genetic markers on chromosome 13 with responses to individual and combined antifolates, MDR2 is proposed to modulate antifolate responses, possibly mediated by the transport of folate intermediates.
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Affiliation(s)
- Axel Martinelli
- Centro de Malaria e Outras Doenças Tropicais/IHMT/UEI Biologia Molecular, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal.
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Afonso A, Neto Z, Castro H, Lopes D, Alves AC, Tomás AM, Rosário VD. Plasmodium chabaudi chabaudi malaria parasites can develop stable resistance to atovaquone with a mutation in the cytochrome b gene. Malar J 2010; 9:135. [PMID: 20492669 PMCID: PMC2881937 DOI: 10.1186/1475-2875-9-135] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 05/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum, has developed resistance to many of the drugs in use. The recommended treatment policy is now to use drug combinations. The atovaquone-proguanil (AP) drug combination, is one of the treatment and prophylaxis options. Atovaquone (ATQ) exerts its action by inhibiting plasmodial mitochondria electron transport at the level of the cytochrome bc1 complex. Plasmodium falciparum in vitro resistance to ATQ has been associated with specific point mutations in the region spanning codons 271-284 of the cytochrome b gene. ATQ -resistant Plasmodium yoelii and Plasmodium berghei lines have been obtained and resistant lines have amino acid mutations in their CYT b protein sequences. Plasmodium chabaudi model for studying drug-responses and drug-resistance selection is a very useful rodent malaria model but no ATQ resistant parasites have been reported so far. The aim of this study was to determine the ATQ sensitivity of the P. chabaudi clones, to select a resistant parasite line and to perform genotypic characterization of the cytb gene of these clones. METHODS To select for ATQ resistance, Plasmodium. chabaudi chabaudi clones were exposed to gradually increasing concentrations of ATQ during several consecutive passages in mice. Plasmodium chabaudi cytb gene was amplified and sequenced. RESULTS ATQ resistance was selected from the clone AS-3CQ. In order to confirm whether an heritable genetic mutation underlies the response of AS-ATQ to ATQ, the stability of the drug resistance phenotype in this clone was evaluated by measuring drug responses after (i) multiple blood passages in the absence of the drug, (ii) freeze/thawing of parasites in liquid nitrogen and (iii) transmission through a mosquito host, Anopheles stephensi. ATQ resistance phenotype of the drug-selected parasite clone kept unaltered. Therefore, ATQ resistance in clone AS-ATQ is genetically encoded. The Minimum Curative Dose of AS-ATQ showed a six-fold increase in MCD to ATQ relative to AS-3CQ. CONCLUSIONS A mutation was found on the P. chabaudi cytb gene from the AS-ATQ sample a substitution at the residue Tyr268 for an Asn, this mutation is homologous to the one found in P. falciparum isolates resistant to ATQ.
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Affiliation(s)
- Ana Afonso
- Unit of Medical Parasitology and Microbiology (UPMM)/IHMT Rua da Junqueira 100, 1349-008 Lisbon, Portugal.
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Su XZ, Jiang H, Yi M, Mu J, Stephens RM. Large-scale genotyping and genetic mapping in Plasmodium parasites. THE KOREAN JOURNAL OF PARASITOLOGY 2009; 47:83-91. [PMID: 19488413 DOI: 10.3347/kjp.2009.47.2.83] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 04/03/2009] [Indexed: 11/23/2022]
Abstract
The completion of many malaria parasite genomes provides great opportunities for genomewide characterization of gene expression and high-throughput genotyping. Substantial progress in malaria genomics and genotyping has been made recently, particularly the development of various microarray platforms for large-scale characterization of the Plasmodium falciparum genome. Microarray has been used for gene expression analysis, detection of single nucleotide polymorphism (SNP) and copy number variation (CNV), characterization of chromatin modifications, and other applications. Here we discuss some recent advances in genetic mapping and genomic studies of malaria parasites, focusing on the use of high-throughput arrays for the detection of SNP and CNV in the P. falciparum genome. Strategies for genetic mapping of malaria traits are also discussed.
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Affiliation(s)
- Xin-Zhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, USA.
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15
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Witkowski B, Berry A, Benoit-Vical F. Resistance to antimalarial compounds: Methods and applications. Drug Resist Updat 2009; 12:42-50. [DOI: 10.1016/j.drup.2009.01.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 01/22/2009] [Accepted: 01/31/2009] [Indexed: 11/29/2022]
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16
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Hunt P, Afonso A, Creasey A, Culleton R, Sidhu ABS, Logan J, Valderramos SG, McNae I, Cheesman S, do Rosario V, Carter R, Fidock DA, Cravo P. Gene encoding a deubiquitinating enzyme is mutated in artesunate- and chloroquine-resistant rodent malaria parasites. Mol Microbiol 2007; 65:27-40. [PMID: 17581118 PMCID: PMC1974797 DOI: 10.1111/j.1365-2958.2007.05753.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Artemisinin- and artesunate-resistant Plasmodium chabaudi mutants, AS-ART and AS-ATN, were previously selected from chloroquine-resistant clones AS-30CQ and AS-15CQ respectively. Now, a genetic cross between AS-ART and the artemisinin-sensitive clone AJ has been analysed by Linkage Group Selection. A genetic linkage group on chromosome 2 was selected under artemisinin treatment. Within this locus, we identified two different mutations in a gene encoding a deubiquitinating enzyme. A distinct mutation occurred in each of the clones AS-30CQ and AS-ATN, relative to their respective progenitors in the AS lineage. The mutations occurred independently in different clones under drug selection with chloroquine (high concentration) or artesunate. Each mutation maps to a critical residue in a homologous human deubiquitinating protein structure. Although one mutation could theoretically account for the resistance of AS-ATN to artemisinin derivates, the other cannot account solely for the resistance of AS-ART, relative to the responses of its sensitive progenitor AS-30CQ. Two lines of Plasmodium falciparum with decreased susceptibility to artemisinin were also selected. Their drug-response phenotype was not genetically stable. No mutations in the UBP-1 gene encoding the P. falciparum orthologue of the deubiquitinating enzyme were observed. The possible significance of these mutations in parasite responses to chloroquine or artemisinin is discussed.
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Affiliation(s)
- Paul Hunt
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratory, Kings Buildings, Edinburgh EH9 3JT, UK.
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17
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Su X, Hayton K, Wellems TE. Genetic linkage and association analyses for trait mapping in Plasmodium falciparum. Nat Rev Genet 2007; 8:497-506. [PMID: 17572690 DOI: 10.1038/nrg2126] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Genetic studies of Plasmodium falciparum laboratory crosses and field isolates have produced valuable insights into determinants of drug responses, antigenic variation, disease virulence, cellular development and population structures of these virulent human malaria parasites. Full-genome sequences and high-resolution haplotype maps of SNPs and microsatellites are now available for all 14 parasite chromosomes. Rapidly increasing genetic and genomic information on Plasmodium parasites, mosquitoes and humans will combine as a rich resource for new advances in our understanding of malaria, its transmission and its manifestations of disease.
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Affiliation(s)
- Xinzhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 9000 Rockville Pike Bethesda, Maryland 20892-8132, USA
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18
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Carter R, Hunt P, Cheesman S. Linkage Group Selection--a fast approach to the genetic analysis of malaria parasites. Int J Parasitol 2006; 37:285-93. [PMID: 17222845 DOI: 10.1016/j.ijpara.2006.11.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 11/06/2006] [Accepted: 11/09/2006] [Indexed: 11/16/2022]
Abstract
Genetic analysis of malaria parasites has shown that the mechanisms of inheritance in these organisms are classically Mendelian. In other words, alleles of genes at different loci recombine, and alleles at the same gene locus segregate, in the progeny of a genetic cross between two genetically distinct lines of malaria parasite. Importantly, such progeny are haploid in the first filial generation following genetic crossing. Consequently, genetic analysis, including linkage analysis, can be done directly upon the cloned cross progeny. Linkage analysis conducted upon the progeny of genetic crosses between malaria parasites can lead to the location of a single gene controlling a specific phenotype, as has been achieved to identify the gene for chloroquine resistance in Plasmodium falciparum. The work involved, however, is extremely labour intensive. It involves the generation of many hundreds, to a thousand or so, of independent recombinant clones from the cross progeny and the biological characterisation, and genetic typing for hundreds of molecular genetic markers of each such clone. We discuss here a fast-track method for identifying genes controlling specific phenotypes, e.g. drug resistance/sensitivity. It involves the mass screening with quantitative molecular genetic markers of the uncloned progeny of a genetic cross following its growth under a selection pressure representing the phenotype of interest. We have called the method Linkage Group Selection.
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Affiliation(s)
- Richard Carter
- University of Edinburgh, Institute of Immunology and Infection Research, School of Biological Sciences, West Mains Road, Edinburgh EH9 3JT, UK.
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19
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van Schalkwyk DA, Egan TJ. Quinoline-resistance reversing agents for the malaria parasite Plasmodium falciparum. Drug Resist Updat 2006; 9:211-26. [PMID: 17064951 DOI: 10.1016/j.drup.2006.09.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Resistance to quinoline antimalarials, especially to chloroquine and mefloquine has had a major impact on the treatment of malaria worldwide. In the period since 2000, significant progress has been made in understanding the origins of chloroquine resistance and to a lesser extent mefloquine resistance in Plasmodium falciparum. Chloroquine resistance correlates directly with mutations in the pfcrt gene of the parasite, while changes in another gene, pfmdr1, may also be related to chloroquine resistance in some strains. Mutations in pfcrt do not appear to correlate with mefloquine resistance, but some studies have implicated pfmdr1 in mefloquine resistance. Its involvement however, has not been definitively demonstrated. The protein products of these genes, PfCRT and Pgh-1 are both located in the food vacuole membrane of the parasite. Current evidence suggests that PfCRT is probably a transporter protein. Chloroquine appears to exit the food vacuole via this transporter in resistant PfCRT mutants. Pgh-1 on the other hand, resembles mammalian multi-drug resistance proteins and appears to be involved in expelling hydrophobic drugs from the food vacuole. Resistance reversing agents are believed to act by inhibiting these proteins. The currently known chloroquine- and mefloquine-resistance reversing agents are discussed in this review. This includes a discussion of structure-activity relationships in these compounds and hypotheses on their possible mechanisms of action. The status of current clinical applications is also briefly discussed.
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Affiliation(s)
- Donelly A van Schalkwyk
- School of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia.
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20
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Abstract
The Eimeria species, causative agents of the disease coccidiosis, are genetically complex protozoan parasites endemic in livestock. Drug resistance remains commonplace among the Eimeria, and alternatives to chemotherapeutic control are being sought. Vaccines based upon live formulations of parasites are effective, but production costs are high, stimulating demand for a recombinant subunit vaccine. The identity of antigens suitable for inclusion in such vaccines remains elusive. Selection of immunoprotective antigens of the Eimeria species as vaccine candidates based upon recognition by the host immune system has been unsuccessful, obscured by the considerable number of molecules that are immunogenic but not immunoprotective. This is a common problem which characterizes work with most eukaryotic parasites. The identification of a selective criterion to directly access genetic loci that encode immunoprotective antigens of Eimeria maxima using a mapping strategy based upon parasite genetics, immune selection and DNA fingerprinting promises to revolutionize the process of antigen discovery. Linkage analyses of DNA markers amplified from populations of recombinant parasites defined by an ability to escape parent-specific deleterious selection by strain-specific immunity and chemotherapy has revealed four discrete regions within the E. maxima genome linked to escape from a protective immune response. These regions now form the basis of detailed study to identify antigens as candidates for inclusion in future vaccination strategies.
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Affiliation(s)
- D P Blake
- Enteric Immunology Group, Institute for Animal Health, Compton, Nr. Newbury, Berkshire, UK.
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21
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Afonso A, Hunt P, Cheesman S, Alves AC, Cunha CV, do Rosário V, Cravo P. Malaria parasites can develop stable resistance to artemisinin but lack mutations in candidate genes atp6 (encoding the sarcoplasmic and endoplasmic reticulum Ca2+ ATPase), tctp, mdr1, and cg10. Antimicrob Agents Chemother 2006; 50:480-9. [PMID: 16436700 PMCID: PMC1366921 DOI: 10.1128/aac.50.2.480-489.2006] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 10/17/2005] [Accepted: 11/15/2005] [Indexed: 11/20/2022] Open
Abstract
Resistance of Plasmodium falciparum to drugs such as chloroquine and sulfadoxine-pyrimethamine is a major problem in malaria control. Artemisinin (ART) derivatives, particularly in combination with other drugs, are thus increasingly used to treat malaria, reducing the probability that parasites resistant to the components will emerge. Although stable resistance to artemisinin has yet to be reported from laboratory or field studies, its emergence would be disastrous because of the lack of alternative treatments. Here, we report for the first time, to our knowledge, genetically stable and transmissible ART and artesunate (ATN)-resistant malaria parasites. Each of two lines of the rodent malaria parasite Plosmodium chabaudi chabaudi, grown in the presence of increasing concentrations of ART or ATN, showed 15-fold and 6-fold increased resistance to ART and ATN, respectively. Resistance remained stable after cloning, freeze-thawing, after passage in the absence of drug, and transmission through mosquitoes. The nucleotide sequences of the possible genetic modulators of ART resistance (mdr1, cg10, tctp, and atp6) of sensitive and resistant parasites were compared. No mutations in these genes were identified. In addition we investigated whether changes in the copy number of these genes could account for resistance but found that resistant parasites retained the same number of copies as their sensitive progenitors. We believe that this is the first report of a malaria parasite with genetically stable and transmissible resistance to artemisinin or its derivatives.
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Affiliation(s)
- A Afonso
- Centro de Malaria e Outras Doenças Tropicais/IHMT/UEI Malaria, Rua da Junqueira 96, 1349-008 Lisbon, Portugal
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22
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Martins TM, Domingos A, Berry C, Wyatt DM. The activity and inhibition of the food vacuole plasmepsin from the rodent malaria parasite Plasmodium chabaudi. Acta Trop 2006; 97:212-8. [PMID: 16329985 DOI: 10.1016/j.actatropica.2005.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 11/04/2005] [Accepted: 11/07/2005] [Indexed: 11/29/2022]
Abstract
The rodent malaria parasite Plasmodium chabaudi encodes one food vacuole plasmepsin-the aspartic proteinases important in haemoglobin degradation. A recombinant form of this enzyme was found to cleave a variety of peptide substrates and was susceptible to a selection of naturally occurring and synthetic inhibitors, displaying an inhibition profile distinct from that of aspartic proteinases from other malaria parasites. In addition, inhibitors of HIV proteinase that kill P. chabaudi in vivo were also inhibitors of this new plasmepsin. P. chabaudi is a widely used model for human malaria species and, therefore, the characterisation of this plasmepsin is an important contribution towards understanding its biology.
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Affiliation(s)
- Tiago M Martins
- Instituto Nacional de Engenharia, Tecnologia e Inovação, Departamento de Biotecnologia, UTPAM, Edifício F, Estrada do Paço do Lumiar, 1649-038 Lisboa, Portugal
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23
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Khan A, Taylor S, Su C, Mackey AJ, Boyle J, Cole R, Glover D, Tang K, Paulsen IT, Berriman M, Boothroyd JC, Pfefferkorn ER, Dubey JP, Ajioka JW, Roos DS, Wootton JC, Sibley LD. Composite genome map and recombination parameters derived from three archetypal lineages of Toxoplasma gondii. Nucleic Acids Res 2005; 33:2980-92. [PMID: 15911631 PMCID: PMC1137028 DOI: 10.1093/nar/gki604] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Toxoplasma gondii is a highly successful protozoan parasite in the phylum Apicomplexa, which contains numerous animal and human pathogens. T.gondii is amenable to cellular, biochemical, molecular and genetic studies, making it a model for the biology of this important group of parasites. To facilitate forward genetic analysis, we have developed a high-resolution genetic linkage map for T.gondii. The genetic map was used to assemble the scaffolds from a 10X shotgun whole genome sequence, thus defining 14 chromosomes with markers spaced at ∼300 kb intervals across the genome. Fourteen chromosomes were identified comprising a total genetic size of ∼592 cM and an average map unit of ∼104 kb/cM. Analysis of the genetic parameters in T.gondii revealed a high frequency of closely adjacent, apparent double crossover events that may represent gene conversions. In addition, we detected large regions of genetic homogeneity among the archetypal clonal lineages, reflecting the relatively few genetic outbreeding events that have occurred since their recent origin. Despite these unusual features, linkage analysis proved to be effective in mapping the loci determining several drug resistances. The resulting genome map provides a framework for analysis of complex traits such as virulence and transmission, and for comparative population genetic studies.
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Affiliation(s)
| | | | | | - Aaron J. Mackey
- Department of Biology and Penn Genomics Institute, University of PennsylvaniaPhiladelphia, PA 19104, USA
| | - Jon Boyle
- Department of Microbiology and Immunology, Stanford University School of MedicineStanford, CA 94305, USA
| | | | | | | | - Ian T. Paulsen
- The Institute for Genomic ResearchRockville, MD 20850, USA
| | - Matt Berriman
- The Wellcome Trust Sanger InstituteHinxton, UK CB10 1SA
| | - John C. Boothroyd
- Department of Microbiology and Immunology, Stanford University School of MedicineStanford, CA 94305, USA
| | - Elmer R. Pfefferkorn
- Department of Microbiology and Immunology, Dartmouth Medical SchoolHanover, NH 03755, USA
| | - J. P. Dubey
- Animal Parasitic Disease Laboratory, ARS, ANRI, USDABeltsville, MD 20705, USA
| | - James W. Ajioka
- Department of Pathology, Cambridge UniversityCambridge, UK CB2 1QP
| | - David S. Roos
- Department of Biology and Penn Genomics Institute, University of PennsylvaniaPhiladelphia, PA 19104, USA
| | - John C. Wootton
- Computational Biology Branch, National Center for Biotechnology Information, National Institutes of HealthBethesda, MD 20894, USA
| | - L. David Sibley
- To whom correspondence should be addressed. Tel: +1 314 362 8873; Fax: +1 314 286 0060;
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Culleton R, Martinelli A, Hunt P, Carter R. Linkage group selection: rapid gene discovery in malaria parasites. Genome Res 2005; 15:92-7. [PMID: 15632093 PMCID: PMC540282 DOI: 10.1101/gr.2866205] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The identification of parasite genes controlling phenotypes such as drug resistance, virulence, immunogenicity, and transmission is vital to malaria research. Classical genetic methods have achieved these goals only rarely and with difficulty. We describe here a novel genetic method, Linkage Group Selection (LGS), which achieves rapid de novo location of genes encoding selectable phenotypes of malaria parasites. A phenotype-specific selection pressure is applied to the uncloned progeny of a genetic cross between two malaria parasites that differ in the relevant phenotype. Selected and unselected progeny are analyzed using genome-wide quantitative genetic markers. Markers of the "sensitive" parent, which are reduced after selection, are sequenced and located in genomic databases. They are expected to be closely linked to gene(s) determining the phenotype under selection. We have validated LGS with the rodent malaria parasite Plasmodium chabaudi chabaudi using a phenotype, pyrimethamine resistance, whose controlling gene, that encoding dihydrofolate reductase (dhfr), is known. We show that molecular markers closely linked to dhfr, and only those linked to this gene, were reduced or removed by pyrimethamine treatment in accordance with the expectations of LGS.
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Affiliation(s)
- Richard Culleton
- Institute of Immunity and Infection Research, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
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Martinelli A, Hunt P, Fawcett R, Cravo PVL, Walliker D, Carter R. An AFLP-based genetic linkage map of Plasmodium chabaudi chabaudi. Malar J 2005; 4:11. [PMID: 15707493 PMCID: PMC550669 DOI: 10.1186/1475-2875-4-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Accepted: 02/11/2005] [Indexed: 11/10/2022] Open
Abstract
Background Plasmodium chabaudi chabaudi can be considered as a rodent model of human malaria parasites in the genetic analysis of important characters such as drug resistance and immunity. Despite the availability of some genome sequence data, an extensive genetic linkage map is needed for mapping the genes involved in certain traits. Methods The inheritance of 672 Amplified Fragment Length Polymorphism (AFLP) markers from two parental clones (AS and AJ) of P. c. chabaudi was determined in 28 independent recombinant progeny clones. These, AFLP markers and 42 previously mapped Restriction Fragment Length Polymorphism (RFLP) markers (used as chromosomal anchors) were organized into linkage groups using Map Manager software. Results 614 AFLP markers formed linkage groups assigned to 10 of 14 chromosomes, and 12 other linkage groups not assigned to known chromosomes. The genetic length of the genome was estimated to be about 1676 centiMorgans (cM). The mean map unit size was estimated to be 13.7 kb/cM. This was slightly less then previous estimates for the human malaria parasite, Plasmodium falciparum Conclusion The P. c. chabaudi genetic linkage map presented here is the most extensive and highly resolved so far available for this species. It can be used in conjunction with the genome databases of P. c chabaudi, P. falciparum and Plasmodium yoelii to identify genes underlying important phenotypes such as drug resistance and strain-specific immunity.
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Affiliation(s)
- Axel Martinelli
- Institute for Immunology and Infection Research, School of Biological Science, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK
- Centro de Malária e Outras Doenças Tropicais/IHMT/UEI Biologia Molecular/UNL, Rua da Junqueira, 96, 1349-008, Lisbon, Portugal
| | - Paul Hunt
- Institute for Immunology and Infection Research, School of Biological Science, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Richard Fawcett
- Institute for Immunology and Infection Research, School of Biological Science, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Pedro VL Cravo
- Centro de Malária e Outras Doenças Tropicais/IHMT/UEI Biologia Molecular/UNL, Rua da Junqueira, 96, 1349-008, Lisbon, Portugal
| | - David Walliker
- Institute for Immunology and Infection Research, School of Biological Science, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Richard Carter
- Institute for Immunology and Infection Research, School of Biological Science, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK
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Hunt P, Martinelli A, Fawcett R, Carlton J, Carter R, Walliker D. Gene synteny and chloroquine resistance in Plasmodium chabaudi. Mol Biochem Parasitol 2004; 136:157-64. [PMID: 15478795 DOI: 10.1016/j.molbiopara.2004.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Chloroquine resistance in the rodent malaria parasite Plasmodium chabaudi has been shown to be caused by a gene on chromosome 11, and is not linked to orthologues of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) or Pgh-1 (pfmdr1) genes. In the current work, the progeny of crosses between chloroquine-resistant and sensitive clones of P. chabaudi have been analysed for the inheritance of 658 AFLP markers. Markers linked to the chloroquine responses of the progeny, including two which are completely linked, have been genetically mapped, sequenced and their homologues, or closely linked loci, identified in P. falciparum. The chromosome 11 markers most closely linked to chloroquine resistance in P. chabaudi map to loci which are also closely linked in P. falciparum, although in two linkage groups on chromosomes 6 and 13 of this species. The P. falciparum orthologue of the gene conferring chloroquine resistance in P. chabaudi is predicted to lie within a 250 kb region of P. falciparum chromosome 6, containing approximately 50 genes. The genetic order of the markers in P. chabaudi is co-linear with the physical linkage represented in the P. falciparum genome database. The findings provide evidence for extensive conservation of synteny between the two species.
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Affiliation(s)
- Paul Hunt
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK.
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Ferreira ID, Nogueira F, Borges ST, do Rosário VE, Cravo P. Is the expression of genes encoding enzymes of glutathione (GSH) metabolism involved in chloroquine resistance in Plasmodium chabaudi parasites? Mol Biochem Parasitol 2004; 136:43-50. [PMID: 15138066 DOI: 10.1016/j.molbiopara.2004.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2003] [Revised: 02/20/2004] [Accepted: 02/20/2004] [Indexed: 10/26/2022]
Abstract
The genes encoding enzymes involved in glutathione (GSH) metabolism may modulate responses to antimalarial drugs, but the role of most of them in antimalarial drug resistance has scarcely been investigated. Using an in silico/PCR combined approach, we have isolated from Plasmodium chabaudi, full sequences of five Plasmodium falciparum gene orthologues involved in GSH metabolism: the gamma-glutamylcysteine synthetase (Pc-gammagcs), glutathione-synthetase (Pc-gs), glutathione peroxidase (Pc-gpx), glutathione reductase (Pc-gr) and glutathione-S-transferase (Pc-gst). DNA sequencing of these genes from drug sensitive parasites, P. chabaudi AS (0CQ), and ones isolated from parasite lines that show genetically stable resistance to chloroquine (CQ) at low, intermediate and high levels, AS (3CQ), AS (15CQ) and AS (30CQ), respectively, revealed no point mutations in the resistant parasites. We used these sequences to design internal oligonucleotide primers to compare relative mRNA amounts of these genes between all P. chabaudi clones, in untreated mice or following CQ treatment with sub-curative doses, by real-time PCR. Analysis of three independent experiments revealed that transcription levels of the Pc-gammagcs, Pc-gs, Pc-gpx, Pc-gr and Pc-gst genes were not changed between chloroquine sensitive and resistant parasite clones, and that treatment with chloroquine did not induce an alteration in the expression of these genes in sensitive or resistant parasites. We concluded that chloroquine resistance in this species is determined by a mechanism that is independent of these genes, and most likely, of GSH metabolism.
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Affiliation(s)
- Isabel D Ferreira
- Centro de Malária e Outras Doenças Tropicais/IHMT/UEI Malária, Rua da Junqueira 96, 1349-008 Lisbon, Portugal
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Ferrer-Rodríguez I, Pérez-Rosado J, Gervais GW, Peters W, Robinson BL, Serrano AE. PLASMODIUM YOELII: IDENTIFICATION AND PARTIAL CHARACTERIZATION OF ANMDR1GENE IN AN ARTEMISININ-RESISTANT LINE. J Parasitol 2004; 90:152-60. [PMID: 15040683 DOI: 10.1645/ge-3225] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The molecular mechanisms by which the malarial parasite has managed to develop resistance to many antimalarial drugs remain to be completely elucidated. Mutations in the pfmdr1 gene of Plasmodium falciparum, as well as an increase in pfmdr1 copy number, have been associated with resistance to the quinoline-containing antimalarial drugs. We investigated the mechanisms of drug resistance in Plasmodium using a collection of P. yoelii lines with different drug resistance profiles. The mdr1 gene of P. yoelii (pymdr1) was identified and characterized. A 2- to 3-fold increase in the pymdr1 gene copy number was observed in the P. yoelii ART line (artemisinin resistant) when compared with the NS parental line. The pymdr1 gene was mapped to a chromosome of 2.1 Mb in all lines analyzed. Reverse transcriptase-polymerase chain reaction and Western blot experiments confirmed the expression of the gene at the RNA and protein levels.
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Affiliation(s)
- Iván Ferrer-Rodríguez
- Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, P.O. Box 365067, San Juan, Puerto Rico
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29
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Cravo PVL, Carlton JMR, Hunt P, Bisoni L, Padua RA, Walliker D. Genetics of mefloquine resistance in the rodent malaria parasite Plasmodium chabaudi. Antimicrob Agents Chemother 2003; 47:709-18. [PMID: 12543682 PMCID: PMC151772 DOI: 10.1128/aac.47.2.709-718.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genetic determinants of resistance to mefloquine in malaria parasites are unclear. Some studies have implied that amplification of, or mutations in, the multidrug resistance gene pfmdr1 in Plasmodium falciparum may be involved. Using the rodent malaria model Plasmodium chabaudi, we investigated the role of the orthologue of this gene, pcmdr1, in a stable mefloquine-resistant mutant, AS(15MF/3), selected from a sensitive clone. pcmdr1 exists as a single copy gene on chromosome 12 of the sensitive clone. In AS(15MF/3), the gene was found to have undergone duplication, with one copy translocating to chromosome 4. mRNA levels of pcmdr1 were higher in the mutant than in the parent sensitive clone. A partial genetic map of the translocation showed that other genes in addition to pcmdr1 had been cotranslocated. The sequences of both copies of pcmdr1 of AS(15MF/3) were identical to that of the parent sensitive clone. A cross was made between AS(15MF/3) and an unrelated mefloquine-sensitive clone, AJ. Phenotypic and molecular analysis of progeny clones showed that duplication and overexpression of the pcmdr1 gene was an important determinant of resistance. However, not all mefloquine-resistant progeny contained the duplicated gene, showing that at least one other gene was involved in resistance.
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Affiliation(s)
- Pedro V L Cravo
- Institute of Cell, Animal, and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
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30
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Hayton K, Ranford-Cartwright LC, Walliker D. Sulfadoxine-pyrimethamine resistance in the rodent malaria parasite Plasmodium chabaudi. Antimicrob Agents Chemother 2002; 46:2482-9. [PMID: 12121922 PMCID: PMC127344 DOI: 10.1128/aac.46.8.2482-2489.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have studied resistance to sulfadoxine-pyrimethamine (S/P) in the rodent malaria parasite Plasmodium chabaudi. A stable S/P-resistant mutant, AS(50S/P), was selected by drug treatment of a clone, AS(PYR), already resistant to pyrimethamine. The sequences of the P. chabaudi dhfr and dhps genes were obtained and found to be identical in AS(50S/P) and AS(PYR), showing that resistance to S/P in AS(50S/P) was not due to additional mutations in either gene. AS(50S/P) was crossed with a drug-sensitive clone, AJ, and 16 independent recombinant progeny were obtained. These clones were phenotyped for their susceptibility to S/P and to sulfadoxine and pyrimethamine separately. Pyrimethamine resistance was invariably associated with S/P resistance, but no correlation was found between resistance to S/P and resistance to sulfadoxine. Quantitative trait locus analysis of the progeny with 31 chromosome-specific markers showed that mutant P. chabaudi dhfr, or one or more genes closely linked to it, was a major determinant of S/P resistance. In addition, the inheritance of genes on chromosomes 5 and 13 from the sensitive parent appeared to contribute to the level of resistance observed. These results demonstrate that the S/P resistance of the AS(50S/P) mutant of P. chabaudi does not involve mutation in dhps and is not due simply to a combination of two genes determining resistance to pyrimethamine and sulfadoxine separately.
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Affiliation(s)
- Karen Hayton
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, Scotland, UK
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31
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Tait A, Masiga D, Ouma J, MacLeod A, Sasse J, Melville S, Lindegard G, McIntosh A, Turner M. Genetic analysis of phenotype in Trypanosoma brucei: a classical approach to potentially complex traits. Philos Trans R Soc Lond B Biol Sci 2002; 357:89-99. [PMID: 11839186 PMCID: PMC1692923 DOI: 10.1098/rstb.2001.1050] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The genome of the African trypanosome, Trypanosoma brucei, is currently being sequenced, raising the question of how the data generated can be used to determine the function of the large number of genes that will be identified. There is a range of possible approaches, and in this paper we discuss the use of a classical genetic approach coupled with positional cloning based on the ability of trypanosomes to undergo genetic exchange. The genetics of these parasites is essentially similar to a conventional diploid Mendelian system with allelic segregation and an independent assortment of markers on different chromosomes. Data are presented showing that recombination occurs between markers on the same chromosome allowing the physical size of the unit of recombination to be determined. Analysis of the available progeny clones from a series of crosses shows that, in principal, large numbers of progeny can readily be isolated from existing cryopreserved products of mating and, taking these findings together, it is clear that genetic mapping of variable phenotypes is feasible. The available phenotypes for analysis are outlined and most are relevant to the transmission and pathogenesis of the parasite. Genetic maps from two crosses are presented based on the use of the technique of AFLP; these maps comprise 146 and 139 markers in 30 and 21 linkage groups respectively. Segregation distortion is exhibited by some of the linkage groups and the possible reasons for this are discussed. The general conclusion, from the results presented, is that a genetic-mapping approach is feasible and will, in the future, allow the genes determining a number of important traits to be identified.
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Affiliation(s)
- Andy Tait
- Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK.
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32
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Abstract
DNA microarrays are a powerful tool for the analysis of RNA and DNA composition on a whole-genome scale. The first applications of this technology in parasitology are in place. This review examines the various approaches to Plasmodium transcript-profiling that are being adopted using DNA microarray analysis and discusses additional strategies for obtaining and collating information relevant to the search for drug and vaccine candidates in malaria.
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Carlton JM, Hayton K, Cravo PV, Walliker D. Of mice and malaria mutants: unravelling the genetics of drug resistance using rodent malaria models. Trends Parasitol 2001; 17:236-42. [PMID: 11323308 DOI: 10.1016/s1471-4922(01)01899-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
It is well recognized that drug resistance is the most significant obstacle to gaining effective malaria control. Despite the enormous advances in the knowledge of the biochemistry and molecular biology of malaria parasites, only a few genes determining resistance to the commonly used drugs have been identified. The idea that rodent malaria parasites should be exploited more widely for such work, in view of the practical problems of studying this subject experimentally in human malaria, is presented.
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Affiliation(s)
- J M Carlton
- National Center for Biotechnology Research, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA.
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34
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Shirley MW, Harvey DA. A genetic linkage map of the apicomplexan protozoan parasite Eimeria tenella. Genome Res 2000; 10:1587-93. [PMID: 11042156 PMCID: PMC310971 DOI: 10.1101/gr.149200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Apicomplexan protozoan parasites have complex life cycles that involve phases of asexual and sexual reproduction. Some genera have intermediate insect hosts, for example, Plasmodium spp. (the cause of malaria), but related genera such as Eimeria spp. (causative agents of coccidiosis in poultry) have a direct life cycle occurring in only a single host. Mechanisms that regulate the life cycles of apicomplexan parasites are unknown, but the intracellular growth of avian Eimeria spp. is easily shortened by serial selection for the first parasites to complete the transition from asexual to sexual reproduction (to yield so-called precocious lines). To investigate the genetic basis of such an abbreviated life cycle, we have used the species E. tenella and analyzed the inheritance of 443 polymorphic DNA markers in 22 recombinant cloned progeny derived from a cross between parents that had selectable phenotypes of precocious development or resistance to an anticoccidial drug. The markers were placed in 16 linkage groups (which defined 12 chromosomes) and a further 57 unlinked groups. Two linkage groups showed an association (P =.0105) with the traits of precocious development or drug-resistance and were mapped to chromosome 2 (ca 1.2 Mbp) and chromosome 1 (ca 1.0 Mbp), respectively. The map provides a framework for further studies on the identification of genetic loci implicated in the regulation of the life cycle of an important protozoan parasite and a representative of a major taxonomic group. [A table with the segregation data is available as an online supplement at http://www.genome.org.]
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Affiliation(s)
- M W Shirley
- Institute for Animal Health, Compton Laboratory, Compton, Near Newbury, Berkshire, RG20 7NN UK.
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Ferdig MT, Su XZ. Microsatellite markers and genetic mapping in Plasmodium falciparum. PARASITOLOGY TODAY (PERSONAL ED.) 2000; 16:307-12. [PMID: 10858651 DOI: 10.1016/s0169-4758(00)01676-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Whole-genome methods are changing the scope of biological questions that can be addressed in malaria research. In the rich context provided by Plasmodium falciparum genome sequencing, genetic mapping is a powerful tool for identifying genes involved in parasite development, invasion, transmission and drug resistance. The recent development of a high-resolution P. falciparum linkage map consisting of hundreds of microsatellite markers will facilitate an integrated genomic approach to understanding the relationship between genetic variations and biological phenotypes. Here, Michael Ferdig and Xin-zhuan Su provide an overview for applying microsatellite markers and genetic maps to gene mapping, parasite typing and studies of parasite population changes.
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Affiliation(s)
- M T Ferdig
- Laboratory of Parasitic Diseases, National Institutes of Health, 4 Center Drive 0425, Bethesda, MD 20892-0425, USA
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36
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Duraisingh MT, Roper C, Walliker D, Warhurst DC. Increased sensitivity to the antimalarials mefloquine and artemisinin is conferred by mutations in the pfmdr1 gene of Plasmodium falciparum. Mol Microbiol 2000; 36:955-61. [PMID: 10844681 DOI: 10.1046/j.1365-2958.2000.01914.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The declining efficacy of chloroquine and pyrimethamine/sulphadoxine in the treatment of human malaria has led to the use of newer antimalarials such as mefloquine and artemisinin. Sequence polymorphisms in the pfmdr1 gene, the gene encoding the plasmodial homologue of mammalian multidrug resistance transporters, have previously been linked to resistance to chloroquine in some, but not all, studies. In this study, we have used a genetic cross between the strains HB3 and 3D7 to study inheritance of sensitivity to the structurally unrelated drugs mefloquine and artemisinin, and to several other antimalarials. We find a complete allelic association between the HB3-like pfmdr1 allele and increased sensitivity to these drugs in the progeny. Different pfmdr1 sequence polymorphisms in other unrelated lines were also associated with increased sensitivity to these drugs. Our results indicate that the pfmdr1 gene is an important determinant of susceptibility to antimalarials, which has major implications for the future development of resistance.
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Affiliation(s)
- M T Duraisingh
- London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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37
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Su X, Carlton JM. Genome display and typing of Plasmodium parasites using anchored PolyA and PolyT oligonucleotides. Exp Parasitol 2000; 94:273-8. [PMID: 10831397 DOI: 10.1006/expr.2000.4492] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- X Su
- Laboratory of Parasitic Diseases, National Institutes of Health, Bethesda, MD 20892-0425, USA.
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38
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Abstract
We have attempted to establish the degree of linkage conservation between different species of the malaria parasite Plasmodium. Initially, the chromosome locations of 42 homologous genes were established in parasites from a rodent malaria species and the human malaria parasite P. falciparum. Of these genes, 26 appeared to be conserved within ten synteny groups between the two genomes. Several synteny groups were analysed further by long-range restriction mapping of digested chromosomes. Finally, a fine restriction map of one of the linkage groups was made from the rodent malaria parasites P. berghei and from P. falciparum and from the simian malaria parasite P. knowlesi. The fine-scale organisation of this linkage group appears to have remained intact among the three species, despite the evolutionary distance between them. This provides the first example of linkage conservation between the rodent, simian and human malaria species, which represent three different branches of the inferred phylogenetic tree of the genus Plasmodium.
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Affiliation(s)
- J M Carlton
- Institute of Cell, Animal and Population Biology, University of Edinburgh, UK.
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