Mitotic spindle pole organization and centrosome structure are normal in cnn1^−/− cells. (A) Spindle pole–organizing proteins, p150^glued (left), and NuMA (right) localize normally in cnn1^−/− and cnn2^−/− cells even when centrosomes fully detach (yellow arrows). (left) Blue, DNA; red, p150; green, TACC3. (right) Blue, DNA; red, NuMA; green, γ-tubulin. Bars, 5 µm. (B) Transmission electron micrographs of serially sectioned prometaphase/metaphase cells. Two sections (i and ii) are shown for a single wt (left) and cnn1^−/− cell (right). (bottom) Microtubules are highlighted in red to aid visualization. Higher magnification of electron micrographs and respective images of whole cells are shown in Fig. S3. Although a large number of microtubules focus in the wt centrosome, microtubules focus outside of the cnn1^−/− centrosome (arrows). Note that these are likely to be spindle microtubules, as they occupy a position between the centrosomes and the chromosomes (see whole-field view in Fig. S3 B). (C) Both wt and cnn1^−/− centrioles are surrounded by an electron-dense matrix. (D) This cnn1^−/− centrosome is close to the cortex and associates with microtubule bundles. Bars, 500 nm.