Figure 4.

The absence of intermediate filaments or the disruption of microtubules does not prevent nuclear flattening during cell spreading. (A) Intermediate filaments are not required for nuclear flattening during cell spreading. The nucleus is flattened in vim^−/− cells similar to vim^+/+ cells at 12 h after cell seeding although vim^−/− nuclei are slightly rounded at 1 h into the spreading process. Y-27632 treatment in vim^−/− cells did not prevent nuclear flattening. Scale bar in x-y view is 20 μm and in the x-z view is 5 μm. (B) and (C) show the average aspect ratio and spreading areas; all the differences in aspect ratio can be attributed to the corresponding (inversely related) differences in the degree of cell spreading (^∗p < 0.05, n$\ge$ 30). (D) The effect of nocodazole (0.83 μM) on nuclear flattening and cell spreading, and the effect of colcemid (0.27 μM) on well spread cells. At 6 h, the nocodazole-treated cells were spread and had flattened nuclei, while no microtubules were visible. Likewise, colcemid treatment for 1 h disrupted microtubules in originally well-spread cells but did not alter nuclear height. Collectively the data suggests that microtubules are not required to establish or maintain a flattened nucleus. Measurements of the (E) aspect ratio and (F) spreading area of the cells under various conditions (n$\ge$ 30, ^∗p < 0.05; all comparisons are with untreated control). Scale bar in (E) is 10 μm for x-y view and 5 μm for x-z view. All data are shown as mean $\pm$ SEM.