Trypanosoma brucei is the flagellated protozoan parasite that causes human sleeping sickness. Its flagellum is required for cell motility, division and morphogenesis, and correct flagellar attachment is crucial for these processes. In trypanosomatids, the flagellum is attached to the cell body through the so-called flagellum attachment zone (FAZ), which is also required for the segregation of the basal body. Only two protein components of this unique cytoskeletal structure have been described so far. Here, Cynthia He and colleagues (p. ) identify the coiled-coil- and C2-domain-containing protein (CC2D) as a new FAZ component that is essential for FAZ assembly and the determination of cell morphology in T. brucei. Using immunofluorescence and immuno-gold labelling, they find that CC2D localises to the FAZ filament, the FAZ-associated ER as well as basal bodies. Depletion of CC2D by using RNAi inhibits FAZ assembly during flagellar duplication and results in detachment of the flagellum. Furthermore, cells that lack CC2D display abnormal basal body segregation during the cell cycle and also morphological defects that include shorter cell length and disruption of the anterior subpellicular microtubule network. Correct FAZ assembly, therefore, is not only important for flagellum attachment but is also essential to determine cell morphology.
