African trypanosomes are unicellular eukaryotic flagellates, causing serious diseases in human and livestock (sleeping sickness, Nagana). The diseases are generally fatal if left untreated. Trypanosoma brucei has an intricate life cycle involving transmission between a mammalian host and an insect vector, the tsetse fly. By undergoing antigenic variation of the Variant cell Surface Glycoprotein (VSG) coat, the bloodstream form trypanosome escapes the host's immune attack. This immune illusiveness has made vaccination against African trypanosome impossible. Even though the molecular bases of antigenic variation have been described over the past 20 years, essential factors and molecular details controlling this immune evasion process in African trypanosomes are largely unknown. This proposal aimed at the identification of factors essential for the control of differential transcription of VSG gene expression sites in T. brucei using the forward genetics approach. The hypothesis is that changing the expression level of factors directly or indirectly involved in the control of VSG expression sites will affect the tightly controlled expression patterns of VSG expression sites. Based on this hypothesis, we will first generate pools of genetic mutants either by randomly knocking down gene expression or randomly up-regulating gene expression. Then we will screen for mutants that are deficient in the control of VSG expression sites. Finally, the causes of the phenotype in selected mutant cell lines will be characterized to reveal factors and mechanisms involved in the VSG expression site control. The ultimate goal of this project is to unravel the molecular details involved in the differential control of surface coat gene expression and essential processes controlling antigenic variation in African trypanosomes. The success of this study may lead to potential targets for therapeutic designs via intervention of essential processes involved in the switching of VSG gene expression. ? ? ?
