Fig. 3. hMps1 is an essential component of the spindle assembly checkpoint. (A) A schematic illustration of the experimental protocol used for microinjection experiments. (B) Histograms comparing the morphologies of HeLa cells after cytoplasmic injection of non-immune IgG1 or anti-hMps1 antibodies and subsequent incubation in the absence (left panel) or presence of nocodazole (right panel). Open bars indicate the percentage of injected cells with a flattened, interphasic morphology, whereas black bars indicate the proportion of cells with a rounded morphology (i.e. mitotically arrested cells). Approximately 120–150 injected cells were counted for each experiment. Shown are the averages of three independent experiments, with standard deviations. (C and D) Single, widely spaced HeLa cells were injected with control IgG1 or anti-hMps1 antibodies (as indicated), followed by either a 14 h incubation in the absence of nocodazole (C), or a 12 h incubation with nocodazole (D), before fixation with paraformaldehyde solution. Injected cells were visualized using an anti-mouse IgG secondary antibody and DNA was stained by DAPI. Representative examples of injected HeLa cells are shown. Note that the presence of daughter cells indicates successful cell division. Bars = 10 µm.