Fly transmission and mating of Trypanosoma brucei brucei strain 427

Like yeast, Trypanosoma brucei is a model organism and has a published genome sequence. Although T. b. brucei strain 427 is used for studies of trypanosome molecular biology, particularly antigenic variation, in many labs worldwide, this strain was not selected for the genome sequencing project as it is monomorphic and unable to complete development in the insect vector. Instead, the fly transmissible, mating competent strain TREU 927 was used for the genome project, but is not as easily grown or genetically manipulable as strain 427; furthermore, recent findings have spread concern on the potential human infectivity of TREU 927. Here we show that a 40-year-old cryopreserved line of strain 427, Variant 3, is fly transmissible and also able to undergo genetic exchange with another strain of T. b. brucei. Comparison of Variant 3 with lab isolates of 427 shows that all have variant surface glycoprotein genes 117, 121 and 221, and identical alleles for 3 microsatellite loci. Therefore, despite some differences in molecular karyotype, there is no doubt that Variant 3 is an ancestral line of present day 427 lab isolates. Since Variant 3 grows fast both as bloodstream forms and procyclics and is readily genetically manipulable, it may prove useful where a fly transmissible version of 427 is required.