Fig. 9. Immunolocalization of a spindle checkpoint protein in mast mutant cells. Wild-type (A–C) or mast mutant (D–F) neuroblasts were stained with antibodies against Bub1 (red) and α-tubulin (green). DNA is shown in blue. In wild-type cells, Bub1 accumulates at the centromeres during prophase (A) and prometaphase (B) and is severely reduced as the chromosomes align in the metaphase plate (C). In mast mutant cells, Bub1 shows strong accumulation at the centromeres of chromosomes in monopolar (D and E) and polyploid (F) cells. Bar = 5 µm.