Regulation and Function of Surface Glycoproteins of Trypanosomes

Some of the deadliest parasites afflicting humans and their domestic animals are transmitted by insects. These include various sub-species of Trypanosoma brucei which cause sleeping sickness in humans and Nagana in ruminants in large areas of sub-Saharan Africa. These diseases would be even more widespread were it not for the fact that T. brucei is strictly reliant on the tsetse fly for its transmission between mammals. The insect is not a mere "flying syringe" that mechanically transfers parasites from one host to the next as it takes a blood meal.  Instead, there is a complex interaction between the parasite and the tsetse as the trypanosomes differentiate, proliferate and migrate through different tissues before being transmitted to a new host.

Post-transcriptional regulation of gene expression
We are interested in learning how trypanosomes sense their environment and how they regulate gene expression in order to adapt to different hosts, with particular emphasis on genes coding for stage-specific coat proteins.
In many respects, trypanosomes can be regarded as the ultimate control freaks. Unlike many other organisms that regulate expression primarily at the level of the promoter, trypanosomes typically employ multiple levels of post-transcriptional control. We are using several approaches, including biochemical purification of RNA-binding complexes and genome-wide screens with RNAi libraries, and have recently discovered several novel RNA-binding proteins that regulate stage-specific mRNAs.  One of our aims is to identify classes of mRNAs that are co-ordinately regulated by specific ribonucleoprotein complexes and to decipher the sequence and structural motifs that determine binding.

Analysis of the function of parasite proteins in transmission by tsetse
Until recently, extremely little was known about the molecular basis of trypanosome-tsetse interactions. With the advent of transfection systems that allowed gene knockouts in protozoa, it could be shown that a surprising number of parasite surface molecules are not required in culture. Indeed, their functions only become apparent once they are studied within the context of the insect.  For this project we have a long-standing collaboration with Prof. Reto Brun (Swiss Tropical Institute) who runs one of the few Tsetse Laboratories world-wide.

Genome-wide screens for the identification of genes involved in drug-resistance and differentiation
We have recently established procedures that improve the efficiency of genetic manipulation of bloodstream trypanosomes one thousand-fold compared to conventional methods, with the result that large-scale genetic screens now become feasible. This will allow the identification of the genes that confer a particular property, such as drug resistance, by simultaneously screening the entire repertoire rather than by testing candidate genes one at a time.  The same libraries can be screened for genes that either prevent or accelerate differentiation of the parasite to the next stage in its life cycle.