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

Title: 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
Authors: Young, R
Taylor, JE
Kurioka, A
Becker, M
Louis, EJ
Rudenko, G
Item Type: Journal Article
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 (ESAG s) 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.
Issue Date: 12-Aug-2008
Date of Acceptance: 12-Aug-2008
ISSN: 1471-2164
Publisher: BioMed Central
Journal / Book Title: BMC Genomics
Volume: 9
Issue: 1
Copyright Statement: © 2008 Young et al; licensee BioMed Central Ltd. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Wellcome Trust
Funder's Grant Number: 095161/Z/10/Z
Keywords: Science & Technology
Life Sciences & Biomedicine
Biotechnology & Applied Microbiology
Genetics & Heredity
Amino Acid Sequence
Base Sequence
Cloning, Molecular
DNA, Protozoan
Evolution, Molecular
Gene Expression
Gene Library
Genes, Protozoan
Genetic Variation
Molecular Sequence Data
Recombination, Genetic
Sequence Homology, Amino Acid
Sequence Homology, Nucleic Acid
Species Specificity
Trypanosoma brucei brucei
Trypanosoma brucei gambiense
Variant Surface Glycoproteins, Trypanosoma
06 Biological Sciences
11 Medical And Health Sciences
08 Information And Computing Sciences
Publication Status: Published
Article Number: 385
Online Publication Date: 2008-08-12
Appears in Collections:Department of Medicine
Faculty of Medicine
Faculty of Natural Sciences

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