1
|
Young R, Taylor JE, Kurioka A, Becker M, Louis EJ, Rudenko G. Isolation and analysis of the genetic diversity of repertoires of VSG expression site containing telomeres from Trypanosoma brucei gambiense, T. b. brucei and T. equiperdum. BMC Genomics 2008; 9:385. [PMID: 18700033 PMCID: PMC2533676 DOI: 10.1186/1471-2164-9-385] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 08/12/2008] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND African trypanosomes (including Trypanosoma brucei) are unicellular parasites which multiply in the mammalian bloodstream. T. brucei has about twenty telomeric bloodstream form Variant Surface Glycoprotein (VSG) expression sites (BESs), of which one is expressed at a time in a mutually exclusive fashion. BESs are polycistronic transcription units, containing a variety of families of expression site associated genes (ESAGs) in addition to the telomeric VSG. These polymorphic ESAG families are thought to play a role in parasite-host adaptation, and it has been proposed that ESAG diversity might be related to host range. Analysis of the genetic diversity of these telomeric gene families has been confounded by the underrepresentation of telomeric sequences in standard libraries. We have previously developed a method to selectively isolate sets of trypanosome BES containing telomeres using Transformation associated recombination (TAR) cloning in yeast. RESULTS Here we describe the isolation of repertoires of BES containing telomeres from three trypanosome subspecies: Trypanosoma brucei gambiense DAL 972 (causative agent of West-African trypanosomiasis), T. b. brucei EATRO 2340 (a nonhuman infective strain) and T. equiperdum STIB 818 (which causes a sexually transmitted disease in equines). We have sequenced and analysed the genetic diversity at four BES loci (BES promoter region, ESAG6, ESAG5 and ESAG2) from these three trypanosome BES repertoires. CONCLUSION With the exception of ESAG2, the BES sequence repertoires derived from T. b. gambiense are both less diverse than and nearly reciprocally monophyletic relative to those from T. b. brucei and T. equiperdum. Furthermore, although we find evidence for adaptive evolution in all three ESAG repertoires in T. b. brucei and T. equiperdum, only ESAG2 appears to be under diversifying selection in T. b. gambiense. This low level of variation in the T. b. gambiense BES sequence repertoires is consistent both with the relatively narrow host range of this subspecies and its apparent long-term clonality. However, our data does not show a clear correlation between size of trypanosome host range and either number of BESs or extent of ESAG genetic diversity.
Collapse
Affiliation(s)
- Rosanna Young
- Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford, OX1 3SY, UK
| | - Jesse E Taylor
- Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford, OX1 3SY, UK
- Department of Statistics, University of Oxford, 1 South Parks Road, Oxford, OX1 3TG, UK
| | - Ayako Kurioka
- Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford, OX1 3SY, UK
| | - Marion Becker
- Institute of Genetics, Queens Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Edward J Louis
- Institute of Genetics, Queens Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Gloria Rudenko
- Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford, OX1 3SY, UK
| |
Collapse
|
2
|
Becker M, Aitcheson N, Byles E, Wickstead B, Louis E, Rudenko G. Isolation of the repertoire of VSG expression site containing telomeres of Trypanosoma brucei 427 using transformation-associated recombination in yeast. Genome Res 2004; 14:2319-29. [PMID: 15520294 PMCID: PMC525691 DOI: 10.1101/gr.2955304] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 08/14/2004] [Indexed: 11/24/2022]
Abstract
Trypanosoma brucei switches between variant surface glycoproteins (VSGs) allowing immune escape. The active VSG is in one of many telomeric bloodstream form VSG expression sites (BESs), also containing expression site-associated genes (ESAGs) involved in host adaptation. The role of BES sequence diversity in parasite virulence can best be understood through analysis of the full repertoire of BESs from a given T. brucei strain. However, few BESs have been cloned, as telomeres are highly underrepresented in standard libraries. We devised a strategy for isolating the repertoire of T. brucei 427 BES-containing telomeres in Saccaromyces cerevisiae by using transformation-associated recombination (TAR). We isolated 182 T. brucei 427 BES TAR clones, 167 of which could be subdivided into minimally 17 BES groups. This set gives us the first view of the breadth and diversity of BESs from one T. brucei strain. Most BESs ranged between 40 and 70 kb (average, 57 +/- 17 kb) and contained most identified ESAGs. Phylogenetic comparison of the cohort of BES promoter and ESAG6 sequences did not show similar trees, indicating rapid evolution most likely mediated by sequence exchange between BESs. This cloning strategy could be used for any T. brucei strain, facilitating research on the biodiversity of telomeric gene families and host-pathogen interactions.
Collapse
Affiliation(s)
- Marion Becker
- Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, UK
| | | | | | | | | | | |
Collapse
|
3
|
Lan CY, Newport G, Murillo LA, Jones T, Scherer S, Davis RW, Agabian N. Metabolic specialization associated with phenotypic switching in Candidaalbicans. Proc Natl Acad Sci U S A 2002; 99:14907-12. [PMID: 12397174 PMCID: PMC137518 DOI: 10.1073/pnas.232566499] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phase and antigenic variation are mechanisms used by microbial pathogens to stochastically change their cell surface composition. A related property, referred to as phenotypic switching, has been described for some pathogenic fungi. This phenomenon is best studied in Candida albicans, where switch phenotypes vary in morphology, physiology, and pathogenicity in experimental models. In this study, we report an application of a custom Affymetrix GeneChip representative of the entire C. albicans genome and assay the global expression profiles of white and opaque switch phenotypes of the WO-1 strain. Of 13,025 probe sets examined, 373 ORFs demonstrated a greater than twofold difference in expression level between switch phenotypes. Among these, 221 were expressed at a level higher in opaque cells than in white cells; conversely, 152 were more highly expressed in white cells. Affected genes represent functions as diverse as metabolism, adhesion, cell surface composition, stress response, signaling, mating type, and virulence. Approximately one-third of the differences between cell types are related to metabolic pathways, opaque cells expressing a transcriptional profile consistent with oxidative metabolism and white cells expressing a fermentative one. This bias was obtained regardless of carbon source, suggesting a connection between phenotypic switching and metabolic flexibility, where metabolic specialization of switch phenotypes enhances selection in relation to the nutrients available at different anatomical sites. These results extend our understanding of strategies used in microbial phase variation and pathogenesis and further characterize the unanticipated diversity of genes expressed in phenotypic switching.
Collapse
Affiliation(s)
- Chung-Yu Lan
- Department of Stomatology, University of California, San Francisco 94143, USA
| | | | | | | | | | | | | |
Collapse
|
4
|
Mercereau-Puijalon O, Barale JC, Bischoff E. Three multigene families in Plasmodium parasites: facts and questions. Int J Parasitol 2002; 32:1323-44. [PMID: 12350369 DOI: 10.1016/s0020-7519(02)00111-x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Multigene families optimise fitness by providing a set of related genes with possibly different temporal and/or topological expression patterns. We analyse here the structural organisation and sequence diversity of the rDNA, sera and var C Plasmodium falciparum families, and discuss their consequences for parasite biology. The low rDNA copy number, which reduces reshuffling, is probably the corollary of the need for functionally distinct rRNAs in the insect and in the vertebrate host. The unusual intra-genome and population rDNA sequence diversity results in cells equipped with mosaic ribosome sets. The functional constraints are such that ribosome compatibility could influence parasite fitness and contribute to population structuring. Unlike the dispersed rDNA units, the sera family is arranged as a tandem gene cluster, with seven contiguous similar genes, and one more distantly related paralog. We address the question of the inclusion criteria in family definition. We discuss the results concerning the SERA proteins expression and function in the context of the long overlooked multigene family. The var C module is shared by var genes, 'orphan' var C and var C pseudogenes. Analysis of 125 var C deduced protein sequences highlights a well-conserved framework, including putative phosphorylation sites, consistent with the proposed function of mediating interaction with cytoskeletal proteins. The 5' and 3' flanking sequences of the var C pseudogenes are heterogeneous. In contrast, the flanking sequences of the uninterrupted var C modules show remarkable conservation. This is interesting in view of the silencing activity of the var intronic sequence on var expression. The 5' flanking sequence dichotomy reported for internal and sub-telomeric var genes extends to the 3' flanking sequences. This has profound implications for transcription regulation and generation of diversity. The var C family suggests a role for pseudogenes as a diversity reservoir and in genome dynamics by promoting ectopic recombination.
Collapse
Affiliation(s)
- Odile Mercereau-Puijalon
- Unité d'Immunologie Moléculaire des Parasites, Unité de Recherche Associée 1960 du Centre National de la Recherche Scientifique, Institut Pasteur, 25 rue du Dr ROUX, 75015, Paris, France.
| | | | | |
Collapse
|
5
|
Berriman M, Hall N, Sheader K, Bringaud F, Tiwari B, Isobe T, Bowman S, Corton C, Clark L, Cross GAM, Hoek M, Zanders T, Berberof M, Borst P, Rudenko G. The architecture of variant surface glycoprotein gene expression sites in Trypanosoma brucei. Mol Biochem Parasitol 2002; 122:131-40. [PMID: 12106867 DOI: 10.1016/s0166-6851(02)00092-0] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Trypanosoma brucei evades the immune system by switching between Variant Surface Glycoprotein (VSG) genes. The active VSG gene is transcribed in one of approximately 20 telomeric expression sites (ESs). It has been postulated that ES polymorphism plays a role in host adaptation. To gain more insight into ES architecture, we have determined the complete sequence of Bacterial Artificial Chromosomes (BACs) containing DNA from three ESs and their flanking regions. There was variation in the order and number of ES-associated genes (ESAGs). ESAGs 6 and 7, encoding transferrin receptor subunits, are the only ESAGs with functional copies in every ES that has been sequenced until now. A BAC clone containing the VO2 ES sequences comprised approximately half of a 330 kb 'intermediate' chromosome. The extensive similarity between this intermediate chromosome and the left telomere of T. brucei 927 chromosome I, suggests that this previously uncharacterised intermediate size class of chromosomes could have arisen from breakage of megabase chromosomes. Unexpected conservation of sequences, including pseudogenes, indicates that the multiple ESs could have arisen through a relatively recent amplification of a single ES.
Collapse
|
6
|
Meunier L. Clonal variation of gene expression as a source of phenotypic diversity in parasitic protozoa. Trends Parasitol 2001; 17:475-9. [PMID: 11587961 DOI: 10.1016/s1471-4922(01)02017-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Within a cellular clone, individual cells can express different members of a gene family. If the difference in expression is transmitted to daughter cells, 'phenotypic clones' are formed. Such clonal phenotypic variation has evolved independently in phylogenetically distant parasitic protozoa under similar selective pressure: the need for phenotypic diversity at several steps of their life cycle. Here, I review clonal phenotypic variation processes, outline their role in parasite biology and argue that clonal phenotypic variation is complementary to sexual reproduction as a source of phenotypic diversity.
Collapse
Affiliation(s)
- L Meunier
- CEPM, UMR CNRS-IRD 9926, 911 Avenue Agropolis, BP 5045, 34032 Montpellier Cedex 1, France.
| |
Collapse
|
7
|
Palmer RJ, Wakefield AE. Functional glycosylphosphatidylinositol anchor signal sequences in the Pneumocystis carinii PRT1 protease family. Am J Respir Cell Mol Biol 2001; 25:466-73. [PMID: 11694452 DOI: 10.1165/ajrcmb.25.4.4514] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Pneumocystis carinii is fungus which is a frequent cause of severe pneumonia in immunocompromised individuals. The P. carinii genome contains the PRT1 subtelomeric multigene family that encodes a kexin-like serine protease which is expressed on the surface of P. carinii. Analysis of the sequence of the carboxy-terminal sequence of many copies of PRT1 showed that they contained motifs characteristic of a glycosylphosphatidylinositol (GPI) anchor signal sequence. The ability of the C-terminal sequences of PRT1 to direct the addition of a GPI anchor was tested. CD14, a GPI-anchored monocyte glycoprotein antigen, was used as the basis of a heterologous system. CD14 was truncated to remove the carboxy-terminal sequences responsible for GPI-anchor addition. Addition of carboxy-terminal sequences from PRT1 restored high-level surface expression to the truncated CD14. Further, the majority of CD14-PRT1 recombinant protein was removed from the cell membrane by treatment with GPI-specific phospholipase C. These results suggest that the carboxy-terminal residues of most of the members of the PRT1 family of proteases have the potential to form a functional GPI-attachment signal.
Collapse
Affiliation(s)
- R J Palmer
- Molecular Infectious Diseases Group, Department of Pediatrics, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom
| | | |
Collapse
|
8
|
Abstract
The majority of pathogens, including many of medical and veterinary importance, can infect more than one species of host. Population biology has yet to explain why perceived evolutionary advantages of pathogen specialization are, in practice, outweighed by those of generalization. Factors that predispose pathogens to generalism include high levels of genetic diversity and abundant opportunities for cross-species transmission, and the taxonomic distributions of generalists and specialists appear to reflect these factors. Generalism also has consequences for the evolution of virulence and for pathogen epidemiology, making both much less predictable. The evolutionary advantages and disadvantages of generalism are so finely balanced that even closely related pathogens can have very different host range sizes.
Collapse
Affiliation(s)
- M E Woolhouse
- Centre for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK.
| | | | | |
Collapse
|
9
|
Kelly JM, Quack G, Miles MM. In vitro and in vivo activities of aminoadamantane and aminoalkylcyclohexane derivatives against Trypanosoma brucei. Antimicrob Agents Chemother 2001; 45:1360-6. [PMID: 11302796 PMCID: PMC90474 DOI: 10.1128/aac.45.5.1360-1366.2001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We reported recently that the bloodstream form of the African trypanosome, Trypanosoma brucei, is sensitive to the anti-influenza virus drug rimantadine. In the present report we describe the trypanocidal properties of a further 62 aminoadamantane and aminoalkylcyclohexane derivatives. Seventeen of the compounds were found to be more active than rimantadine, with four inhibiting growth in vitro of T. brucei by >90% at concentrations of 1 microM. The most active derivative (1-adamantyl-4-amino-cyclohexane) was about 20 to 25 times more effective than rimantadine. We observed a correlation between structural features of the derivatives and their trypanocidal properties; hydrophobic substitutions to the adamantane or cyclohexane rings generally enhanced activity. As with rimantadine, the activity in vitro varied with the pH. T. brucei was more sensitive in an alkaline environment (including a normal bloodstream pH of 7.4) and less sensitive under acidic conditions. Tests for activity in vivo were carried out with a mouse model of infection with a virulent strain of T. brucei. Although the parasitemia was not eliminated, it could be transiently suppressed by >98% with the most active compounds tested. These results suggest that aminoadamantane derivatives could have potential as a new class of trypanocidal agents.
Collapse
Affiliation(s)
- J M Kelly
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom.
| | | | | |
Collapse
|
10
|
Abstract
This article reviews the molecular genetic data pertaining to the major surface glycoprotein (MSG) gene family of Pneumocystis carinii and its role in surface variation and compares this fungal system to antigenic variation systems in the protozoan Trypanosoma brucei and the bacteria Borrelia spp.
Collapse
Affiliation(s)
- J R Stringer
- Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267, USA.
| | | |
Collapse
|
11
|
Affiliation(s)
- M Hasne
- IBLS, Division of Infection and Immunity, The University of Glasgow, Glasgow, UK
| | | |
Collapse
|
12
|
Abstract
African trypanosomes have plastic genomes with extensive variability at the chromosome ends. The genes encoding the expressed major surface protein of the infective bloodstream form stages of Trypanosoma brucei and are located at telomeres. These telomeric expression-site transcription units are turning out to be surprisingly polymorphic in structure and sequence.
Collapse
Affiliation(s)
- G Rudenko
- Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3FY, UK.
| |
Collapse
|