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Fougère A, Jackson AP, Bechtsi DP, Braks JAM, Annoura T, Fonager J, Spaccapelo R, Ramesar J, Chevalley-Maurel S, Klop O, van der Laan AMA, Tanke HJ, Kocken CHM, Pasini EM, Khan SM, Böhme U, van Ooij C, Otto TD, Janse CJ, Franke-Fayard B. Correction: Variant Exported Blood-Stage Proteins Encoded by Plasmodium Multigene Families Are Expressed in Liver Stages Where They Are Exported into the Parasitophorous Vacuole. PLoS Pathog 2017; 13:e1006128. [PMID: 28095481 PMCID: PMC5240906 DOI: 10.1371/journal.ppat.1006128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Fougère A, Jackson AP, Paraskevi Bechtsi D, Braks JAM, Annoura T, Fonager J, Spaccapelo R, Ramesar J, Chevalley-Maurel S, Klop O, van der Laan AMA, Tanke HJ, Kocken CHM, Pasini EM, Khan SM, Böhme U, van Ooij C, Otto TD, Janse CJ, Franke-Fayard B. Correction: Variant Exported Blood-Stage Proteins Encoded by Plasmodium Multigene Families Are Expressed in Liver Stages Where They Are Exported into the Parasitophorous Vacuole. PLoS Pathog 2016; 12:e1006107. [PMID: 27973555 PMCID: PMC5156361 DOI: 10.1371/journal.ppat.1006107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
[This corrects the article DOI: 10.1371/journal.ppat.1005917.].
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Fougère A, Jackson AP, Paraskevi Bechtsi D, Braks JAM, Annoura T, Fonager J, Spaccapelo R, Ramesar J, Chevalley-Maurel S, Klop O, van der Laan AMA, Tanke HJ, Kocken CHM, Pasini EM, Khan SM, Böhme U, van Ooij C, Otto TD, Janse CJ, Franke-Fayard B. Variant Exported Blood-Stage Proteins Encoded by Plasmodium Multigene Families Are Expressed in Liver Stages Where They Are Exported into the Parasitophorous Vacuole. PLoS Pathog 2016; 12:e1005917. [PMID: 27851824 PMCID: PMC5113031 DOI: 10.1371/journal.ppat.1005917] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 09/06/2016] [Indexed: 01/05/2023] Open
Abstract
Many variant proteins encoded by Plasmodium-specific multigene families are exported into red blood cells (RBC). P. falciparum-specific variant proteins encoded by the var, stevor and rifin multigene families are exported onto the surface of infected red blood cells (iRBC) and mediate interactions between iRBC and host cells resulting in tissue sequestration and rosetting. However, the precise function of most other Plasmodium multigene families encoding exported proteins is unknown. To understand the role of RBC-exported proteins of rodent malaria parasites (RMP) we analysed the expression and cellular location by fluorescent-tagging of members of the pir, fam-a and fam-b multigene families. Furthermore, we performed phylogenetic analyses of the fam-a and fam-b multigene families, which indicate that both families have a history of functional differentiation unique to RMP. We demonstrate for all three families that expression of family members in iRBC is not mutually exclusive. Most tagged proteins were transported into the iRBC cytoplasm but not onto the iRBC plasma membrane, indicating that they are unlikely to play a direct role in iRBC-host cell interactions. Unexpectedly, most family members are also expressed during the liver stage, where they are transported into the parasitophorous vacuole. This suggests that these protein families promote parasite development in both the liver and blood, either by supporting parasite development within hepatocytes and erythrocytes and/or by manipulating the host immune response. Indeed, in the case of Fam-A, which have a steroidogenic acute regulatory-related lipid transfer (START) domain, we found that several family members can transfer phosphatidylcholine in vitro. These observations indicate that these proteins may transport (host) phosphatidylcholine for membrane synthesis. This is the first demonstration of a biological function of any exported variant protein family of rodent malaria parasites. Malaria-parasites invade and multiply in hepatocytes and erythrocytes. The human parasite P. falciparum transports proteins encoded by multigene families onto the surface of erythrocytes, mediating interactions between infected red blood cells (iRBCs) and other host-cells and are thought to play a key role in parasite survival during blood-stage development. The function of other exported Plasmodium protein families remains largely unknown. We provide novel insights into expression and cellular location of proteins encoded by three large multigene families of rodent malaria parasites (Fam-a, Fam-b and PIR). Multiple members of the same family are expressed in a single iRBC, unlike P. falciparum PfEMP1 proteins where individual iRBCs express only a single member. Most proteins we examined are located in the RBC cytoplasm and are not transported onto the iRBC surface membrane, indicating that these proteins are unlikely to mediate interactions between iRBCs and host-cells. Unexpectedly, liver stages also express many of these proteins, where they locate to the vacuole surrounding the parasite inside the hepatocyte. In support of a role of these proteins for parasite growth within their host cells we provide evidence that Fam-A proteins have a role in uptake and transport of (host) phosphatidylcholine for parasite-membrane synthesis.
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Affiliation(s)
- Aurélie Fougère
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- Department of Experimental Medicine, University of Perugia, Italy
| | - Andrew P. Jackson
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, UnitedKingdom
| | | | - Joanna A. M. Braks
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Takeshi Annoura
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- Department of Department of Parasitology, National Institute of Infectious Diseases (NIID), Tokyo, Japan
| | - Jannik Fonager
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- Department of Microbiological Diagnostics and Virology, Statens Serum Institute, Copenhagen, Denmark
| | | | - Jai Ramesar
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Séverine Chevalley-Maurel
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Onny Klop
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- Biomedical Primate Research Centre (BPRC), Rijswijk, The Netherlands
| | | | - Hans J. Tanke
- Department of Molecular Cell Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | | | - Erica M. Pasini
- Biomedical Primate Research Centre (BPRC), Rijswijk, The Netherlands
| | - Shahid M. Khan
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Ulrike Böhme
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, UnitedKingdom
| | - Christiaan van Ooij
- The Francis Crick Institute, Mill Hill Laboratory, Mill Hill, London, UnitedKingdom
| | - Thomas D. Otto
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, UnitedKingdom
| | - Chris J. Janse
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Blandine Franke-Fayard
- Leiden Malaria Research Group, Parasitology, Center of infectious Diseases, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- * E-mail:
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Braks JAM, Spiegelberg L, Koljenovic S, Ridwan Y, Keereweer S, Kanaar R, Wolvius EB, Essers J. Optical Imaging of Tumor Response to Hyperbaric Oxygen Treatment and Irradiation in an Orthotopic Mouse Model of Head and Neck Squamous Cell Carcinoma. Mol Imaging Biol 2016; 17:633-42. [PMID: 25724406 PMCID: PMC4768231 DOI: 10.1007/s11307-015-0834-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Purpose Hyperbaric oxygen therapy (HBOT) is used in the treatment of radiation-induced tissue injury but its effect on (residual) tumor tissue is indistinct and therefore investigated in this study. Procedures Orthotopic FaDu tumors were established in mice, and the response of the (irradiated) tumors to HBOT was monitored by bioluminescence imaging. Near infrared fluorescence imaging using AngioSense750 and Hypoxisense680 was applied to detect tumor vascular permeability and hypoxia. Results HBOT treatment resulted in accelerated growth of non-irradiated tumors, but mouse survival was improved. Tumor vascular leakiness and hypoxia were enhanced after HBOT, whereas histological characteristics, epithelial-to-mesenchymal transition markers, and metastatic incidence were not influenced. Conclusions Squamous cell carcinoma responds to HBOT with respect to tumor growth, vascular permeability, and hypoxia, which may have implications for its use in cancer patients. The ability to longitudinally analyze tumor characteristics highlights the versatility and potential of optical imaging methods in oncological research. Electronic supplementary material The online version of this article (doi:10.1007/s11307-015-0834-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Joanna A M Braks
- Department of Oral and Maxillofacial Surgery, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.
| | - Linda Spiegelberg
- Department of Oral and Maxillofacial Surgery, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Senada Koljenovic
- Department of Pathology, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Yanto Ridwan
- Department of Genetics, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Stijn Keereweer
- Department of Otorhinolaryngology and Head & Neck Surgery, Erasmus Medical Center, PO Box 1738, 3015 CE, Rotterdam, Netherlands
| | - Roland Kanaar
- Department of Genetics, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.,Department of Radiation Oncology, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Eppo B Wolvius
- Department of Oral and Maxillofacial Surgery, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Jeroen Essers
- Department of Genetics, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands. .,Department of Radiation Oncology, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands. .,Department of Vascular Surgery, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.
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Silva PAGC, Guerreiro A, Santos JM, Braks JAM, Janse CJ, Mair GR. Translational Control of UIS4 Protein of the Host-Parasite Interface Is Mediated by the RNA Binding Protein Puf2 in Plasmodium berghei Sporozoites. PLoS One 2016; 11:e0147940. [PMID: 26808677 PMCID: PMC4726560 DOI: 10.1371/journal.pone.0147940] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 01/11/2016] [Indexed: 11/19/2022] Open
Abstract
UIS4 is a key protein component of the host-parasite interface in the liver stage of the rodent malaria parasite Plasmodium berghei and required for parasite survival after invasion. In the infectious sporozoite, UIS4 protein has variably been shown to be translated but also been reported to be translationally repressed. Here we show that uis4 mRNA translation is regulated by the P. berghei RNA binding protein Pumilio-2 (PbPuf2 or Puf2 from here on forward) in infectious salivary gland sporozoites in the mosquito vector. Using RNA immunoprecipitation we show that uis4 mRNA is bound by Puf2 in salivary gland sporozoites. In the absence of Puf2, uis4 mRNA translation is de-regulated and UIS4 protein expression upregulated in salivary gland sporozoites. Here, using RNA immunoprecipitation, we reveal the first Puf2-regulated mRNA in this parasite.
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Affiliation(s)
- Patrícia A. G. C. Silva
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649–028, Lisbon, Portugal
| | - Ana Guerreiro
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649–028, Lisbon, Portugal
| | - Jorge M. Santos
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649–028, Lisbon, Portugal
| | | | | | - Gunnar R. Mair
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649–028, Lisbon, Portugal
- Parasitology, Department of Infectious Diseases, University of Heidelberg Medical School, Im Neuenheimer Feld 324, 69120, Heidelberg, Germany
- * E-mail:
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Spiegelberg L, Braks JAM, Djasim UM, Farrell E, van der Wal KGH, Wolvius EB. Effects of hyperbaric oxygen therapy on the viability of irradiated soft head and neck tissues in mice. Oral Dis 2013; 20:e111-9. [DOI: 10.1111/odi.12162] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/14/2013] [Accepted: 06/25/2013] [Indexed: 12/22/2022]
Affiliation(s)
- L Spiegelberg
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
| | - JAM Braks
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
| | - UM Djasim
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
| | - E Farrell
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
| | - KGH van der Wal
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
| | - EB Wolvius
- Department of Oral and Maxillofacial Surgery; Erasmus MC; Rotterdam The Netherlands
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Fonager J, Pasini EM, Braks JAM, Klop O, Ramesar J, Remarque EJ, Vroegrijk IOCM, van Duinen SG, Thomas AW, Khan SM, Mann M, Kocken CHM, Janse CJ, Franke-Fayard BMD. Reduced CD36-dependent tissue sequestration of Plasmodium-infected erythrocytes is detrimental to malaria parasite growth in vivo. ACTA ACUST UNITED AC 2011; 209:93-107. [PMID: 22184632 PMCID: PMC3260870 DOI: 10.1084/jem.20110762] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Adherence of parasite-infected red blood cells (irbc) to the vascular endothelium of organs plays a key role in the pathogenesis of Plasmodium falciparum malaria. The prevailing hypothesis of why irbc adhere and sequester in tissues is that this acts as a mechanism of avoiding spleen-mediated clearance. Irbc of the rodent parasite Plasmodium berghei ANKA sequester in a fashion analogous to P. falciparum by adhering to the host receptor CD36. To experimentally determine the significance of sequestration for parasite growth, we generated a mutant P. berghei ANKA parasite with a reduced CD36-mediated adherence. Although the cognate parasite ligand binding to CD36 is unknown, we show that nonsequestering parasites have reduced growth and we provide evidence that in addition to avoiding spleen removal, other factors related to CD36-mediated sequestration are beneficial for parasite growth. These results reveal for the first time the importance of sequestration to a malaria infection, with implications for the development of strategies aimed at reducing pathology by inhibiting tissue sequestration.
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Affiliation(s)
- Jannik Fonager
- Leiden Malaria Research Group, Department of Parasitology, Leiden University Medical Center, 2333 ZA Leiden, Netherlands
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Braks JAM, Mair GR, Franke-Fayard B, Janse CJ, Waters AP. A conserved U-rich RNA region implicated in regulation of translation in Plasmodium female gametocytes. Nucleic Acids Res 2007; 36:1176-86. [PMID: 18158300 PMCID: PMC2275103 DOI: 10.1093/nar/gkm1142] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Translational repression (TR) plays an important role in post-transcriptional regulation of gene expression and embryonic development in metazoans. TR also regulates the expression of a subset of the cytoplasmic mRNA population during development of fertilized female gametes of the unicellular malaria parasite, Plasmodium spp. which results in the formation of a polar and motile form, the ookinete. We report the conserved and sex-specific regulatory role of either the 3'- or 5'-UTR of a subset of translationally repressed mRNA species as shown by almost complete inhibition of expression of a GFP reporter protein in the female gametocyte. A U-rich, TR-associated element, identified previously in the 3'-UTR of TR-associated transcripts, played an essential role in mediating TR and a similar region could be found in the 5'-UTR shown in this study to be active in TR. The silencing effect of this 5'-UTR was shown to be independent of its position relative to its ORF, as transposition to a location 3' of the ORF did not affect TR. These results demonstrate for the first time in a unicellular organism that the 5' or the 3'-UTR of TR-associated transcripts play an important and conserved role in mediating TR in female gametocytes.
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Affiliation(s)
- Joanna A M Braks
- Department of Parasitology, Centre of Infectious Diseases, Leiden University Medical Centre (LUMC), Leiden, The Netherlands
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Mair GR, Braks JAM, Garver LS, Dimopoulos G, Hall N, Wiegant JC, Dirks RW, Khan SM, Janse CJ, Waters AP. Regulation of sexual development of Plasmodium by translational repression. Science 2006; 313:667-9. [PMID: 16888139 PMCID: PMC1609190 DOI: 10.1126/science.1125129] [Citation(s) in RCA: 347] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Translational repression of messenger RNAs (mRNAs) plays an important role in sexual differentiation and gametogenesis in multicellular eukaryotes. Translational repression and mRNA turnover were shown to influence stage-specific gene expression in the protozoan Plasmodium. The DDX6-class RNA helicase, DOZI (development of zygote inhibited), is found in a complex with mRNA species in cytoplasmic bodies of female, blood-stage gametocytes. These translationally repressed complexes are normally stored for translation after fertilization. Genetic disruption of pbdozi inhibits the formation of the ribonucleoprotein complexes, and instead, at least 370 transcripts are diverted to a degradation pathway.
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Affiliation(s)
- Gunnar R. Mair
- Department of Parasitology, Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands
| | - Joanna A. M. Braks
- Department of Parasitology, Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands
| | - Lindsey S. Garver
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205
| | - George Dimopoulos
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205
| | - Neil Hall
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, Maryland 20850, USA
| | - Joop C.A.G. Wiegant
- Department of Molecular Cell Biology, Leiden University Medical Centre, 2333 AL Leiden, The Netherlands
| | - Roeland W. Dirks
- Department of Molecular Cell Biology, Leiden University Medical Centre, 2333 AL Leiden, The Netherlands
| | - Shahid M. Khan
- Department of Parasitology, Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands
| | - Chris J. Janse
- Department of Parasitology, Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands
| | - Andrew P. Waters
- Department of Parasitology, Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands
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Maier AG, Braks JAM, Waters AP, Cowman AF. Negative selection using yeast cytosine deaminase/uracil phosphoribosyl transferase in Plasmodium falciparum for targeted gene deletion by double crossover recombination. Mol Biochem Parasitol 2006; 150:118-21. [PMID: 16901558 DOI: 10.1016/j.molbiopara.2006.06.014] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 06/29/2006] [Accepted: 06/29/2006] [Indexed: 11/29/2022]
Affiliation(s)
- Alexander G Maier
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
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Braks JAM, Franke-Fayard B, Kroeze H, Janse CJ, Waters AP. Development and application of a positive-negative selectable marker system for use in reverse genetics in Plasmodium. Nucleic Acids Res 2006; 34:e39. [PMID: 16537837 PMCID: PMC1401515 DOI: 10.1093/nar/gnj033] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A limitation of transfection of malaria parasites is the availability of only a low number of positive selectable markers for selection of transformed mutants. This is exacerbated for the rodent parasite Plasmodium berghei as selection of mutants is performed in vivo in laboratory rodents. We here report the development and application of a negative selection system based upon transgenic expression of a bifunctional protein (yFCU) combining yeast cytosine deaminase and uridyl phosphoribosyl transferase (UPRT) activity in P.berghei followed by in vivo selection with the prodrug 5-fluorocytosine (5-FC). The combination of yfcu and a positive selectable marker was used to first achieve positive selection of mutant parasites with a disrupted gene in a conventional manner. Thereafter through negative selection using 5-FC, mutants were selected where the disrupted gene had been restored to its original configuration as a result of the excision of the selectable markers from the genome through homologous recombination. This procedure was carried out for a Plasmodium gene (p48/45) encoding a protein involved in fertilization, the function of which had been previously implied through gene disruption alone. Such reversible recombination can therefore be employed for both the rapid analysis of the phenotype by targeted disruption of a gene and further associate phenotype and function by genotype restoration through the use of a single plasmid and a single positive selectable marker. Furthermore the negative selection system may also be adapted to facilitate other procedures such as ‘Hit and Run’ and ‘vector recycling’ which in principle will allow unlimited manipulation of a single parasite clone. This is the first demonstration of the general use of yFCU in combination with a positive selectable marker in reverse genetics approaches and it should be possible to adapt its use to many other biological systems.
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Affiliation(s)
| | | | | | | | - Andrew P. Waters
- To whom correspondence should be addressed. Tel: +31 71 5265069; Fax: +31 71 5266907;
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