The DNA sequence of chromosome I of an African trypanosome: gene content, chromosome organisation, recombination and polymorphism.
The African trypanosome, Trypanosoma brucei, causes sleeping sickness in humans in sub-Saharan Africa. Here we report the sequence and analysis of the 1.1 Mb chromosome I, which encodes approximately 400 predicted genes organised into directional clusters, of which more than 100 are located in the largest cluster of 250 kb. A 160-kb region consists primarily of three gene families of unknown function, one of which contains a hotspot for retroelement insertion. We also identify five novel gene families. Indeed, almost 20% of predicted genes are members of families. In some cases, tandemly arrayed genes are 99-100% identical, suggesting an active process of amplification and gene conversion. One end of the chromosome consists of a putative bloodstream-form variant surface glycoprotein (VSG) gene expression site that appears truncated and degenerate. The other chromosome end carries VSG and expression site-associated genes and pseudogenes over 50 kb of subtelomeric sequence where, unusually, the telomere-proximal VSG gene is oriented away from the telomere. Our analysis includes the cataloguing of minor genetic variations between the chromosome I homologues and an estimate of crossing-over frequency during genetic exchange. Genetic polymorphisms are exceptionally rare in sequences located within and around the strand-switches between several gene clusters.
Hall
Neil
N
The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.
Berriman
Matthew
M
Lennard
Nicola J
NJ
Harris
Barbara R
BR
Hertz-Fowler
Christiane
C
Bart-Delabesse
Emmanuelle N
EN
Gerrard
Caroline S
CS
Atkin
Rebecca J
RJ
Barron
Andrew J
AJ
Bowman
Sharen
S
Bray-Allen
Sarah P
SP
Bringaud
Frédéric
F
Clark
Louise N
LN
Corton
Craig H
CH
Cronin
Ann
A
Davies
Robert
R
Doggett
Jonathon
J
Fraser
Audrey
A
Grüter
Eric
E
Hall
Sarah
S
Harper
A David
AD
Kay
Mike P
MP
Leech
Vanessa
V
Mayes
Rebecca
R
Price
Claire
C
Quail
Michael A
MA
Rabbinowitsch
Ester
E
Reitter
Christopher
C
Rutherford
Kim
K
Sasse
Jürgen
J
Sharp
Sarah
S
Shownkeen
Ratna
R
MacLeod
Annette
A
Taylor
Sonya
S
Tweedie
Alison
A
Turner
C Michael R
CM
Tait
Andrew
A
Gull
Keith
K
Barrell
Bart
B
Melville
Sara E
SE
D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics*; D017125:Genes, Protozoan / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000235:genetics
D016054:DNA, Protozoan; D014643:Variant Surface Glycoproteins, Trypanosoma