Architecture of the Trypanosoma brucei nucleus during interphase and mitosis

The structural basis of mitosis, spindle organisation and chromosome segreg ation, in the unicellular parasite Trypanosoma brucei is poorly understood. Here, using immunocytochemistry, fluorescent in situ hybridisation and ele ctron microscopy, we provide a detailed analysis of mitosis in this parasit e. We describe the organisation of the mitotic spindle during different sta ges of mitosis, the complex ultrastructure of kinetochores and the identifi cation of a potential spindle-organising centre in the mitotic nucleus. We investigate the dynamics of chromosome segregation using telomeric and chro mosome-specific probes. We also discuss the problems involved in chromosome segregation in the light of the fact that the brucei karyotype has 22 chro mosomes in the apparent presence of only eight ultrastructurally defined ki netochores.