Figure 4. Live imaging reveals aberrant spindle movement during metaphase/anaphase in Lis1 and cnn mutant neuroblasts.

(A–C) Centrosome positioning and spindle orientation in larval neuroblasts expressing the G147-GFP microtubule-associated protein. Time is given in min:sec relative to onset of prometaphase (0:00).

(A) In wild type neuroblasts, centrosomes were already aligned with the final division axis by NEB (0:00) and spindle orientation remained fixed from prometaphase to telophase (0:00 –13:50; Movie 7).

(B) In cnn^hk21 mutant neuroblasts, bipolar spindle formation was delayed (0:00 – 4:30). Eventually bipolar spindles formed, yet spindles could rotate during metaphase, anaphase, and telophase (4:30 – 11:10; Movie 8).

(C) In Lis1 mutant neuroblasts, centrosome position was abnormal at the onset of prometaphase (0:00) leading to formation of metaphase spindles with aberrant orientation (e.g. 38:40). Misoriented spindles could rotate during metaphase (14:40 – 38:20) and anaphase (63:00 – 66:30; Movie 9). Note the prolonged prometaphase/metaphase interval due to delayed bipolar spindle assembly and defects in mitotic checkpoint silencing.

(D) Representation of centrosome/spindle position in live larval neuroblasts. Depicted is the angular position of the centrosome pair/spindle over time relative to the centrosome pair position at the end of mitosis. Scale bar: 5 μm.