Stable introduction of exogenous DNA into Trypanosoma brucei.

The lack of a homologous transformation system for trypanosomes is a serious handicap to the study of gene expression in these protozoans. Attempts to develop such a system have been complicated by the lack of suitable homologous vectors and ignorance of the requirements for mRNA synthesis which is discontinuous in trypanosomes. We have found that Trypanosoma congolense, a close relative of T. brucei, contains exceptionally small chromosomes, which can be isolated whole and distinguished from those of T. brucei by the presence of a unique satellite DNA. We show here that mini-chromosomes from T. congolense can be introduced into T. brucei by electroporation and detected by hybridisation with T. congolense satellite DNA. The introduced DNA can survive through several generations in the absence of any selective pressure. These results provide the basis for the development of a transformation system for trypanosomes.